Дисертації з теми "Self-Assembly of block copolymers"

Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the “less hydrophilic” barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for “the hydrophobic effect” but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the “hydrophilic effect”.
Blockcopolymere erfahren ein stetig wachsendes Interesse, was an der steigenden Anzahl an Publikationen zu diesem Thema erkennbar ist. Zahlreiche Studien zu amphiphilen Blockcopolymeren haben dabei einige grundlegende Erkenntnisse über deren chemisches und physikalisches Verhalten, vor allem über die Selbstorganisation, hervorgebracht. So können die Größe, die verschiedenen Morphologien und auch die Stabilität der gebildeten Aggregate anhand der relativen und absoluten Blocklängen, die chemischen Struktur der Blöcke, der molekularen Architektur und der Eigenschaften des verwendeten Lösungsmittel erklärt werden. Im speziellen Fall des Wassers als Lösungsmittel bist die Selbstorganisation amphiphiler Blockcopolymere durch den hydrophoben Effekt bedingt. Dieser Arbeit liegt das Interesse an der Selbstorganisation in wässrigem Medium von Blockcopolymeren des Typs A-b-B mit A als hydrophilem Block und B als Block mit variierender Hydrophilie bzw. Hydrophpobie von unlöslich bis vollständig löslich zugrunde. Durch Variation dieser Eigenschaften von Block B soll dessen Einfluss auf das Selbstorganisationsverhalten untersucht werden. Dazu wurden mit Glucose modifizierte Polybutadien-block-Poly(N-Isopropylacrylamid)-Copolymere hergestellt und deren Selbstorganisation in Wasser untersucht. Die Copolymere bilden Vesikel mit einer asymmetrischen Membran, wobei im äußeren Bereich glycolysierte Gruppen und im inneren Bereich Poly(N-Isopropylacrylamid) (PNIPAM) vorliegen. Beim Überschreiten der low critical solution temperature (LCST) kollabiert die vesikuläre Struktur unter Bildung von Mizellen mit einem hydrophoben PNIPAM-Mizellinneren und nach außen gerichteten glycolysierten Blöcken. Diese strukturelle Umwandlung ist reversibel. Die Strukturen zeigten außerdem eine temperaturabhängige Wechselwirkung mit L-Lectin-Proteinen und die Möglichkeit zur Einkapselung organischer Moleküle konnte belegt werden. Des weiteren wurden verschiedene Gruppen von Blockcopolymeren mit zwei hydrophilen Blöcken synthetisiert (double hydrophilic block copolymers – DHBC). Die Blöcke dieser Systeme waren entweder Biopolymere oder Polymerchimäre, die in wässrigen Zwei-Phasen-Trennverfahren eingesetzt werden. Polymere, die auf Dextran- und Poly(ethylenglycol)-Blöcken basieren, zeigen Aggregatbildung in wässriger Phase. Dex6500-b-PEG5500 bildet spontan Vesikel mit PEG als „weniger hydrophilem“ Bestandteil und Dextran als löslichem Block. Die Bildung dieser Vesikel zeigte keine Emfpindlichkeit gegenüber einer Veränderung der Polymerarchitektur und der Konzentration, und nur eine geringe Sensitivität gegenüber Temperaturänderungen. Veränderungen der Blocklängen dagegen beeinflussten die Selbstorganisation und führten zu unterschiedlichen Morphologien. Längere PEG-Blöcke bevorzugten dabei die Bildung eher gekrümmter Aggregate, entgegen dem Trend, der gewöhnlicherweise für amphiphile Blockcopolymere beobachtet wird. Die Verkürzung des Dextran-Blocks fördert die Ausbildung vesikulärer Strukturen, was dem Verhalten der amphiphilen Gegenspieler der DHBC-Systeme entspricht. Die funktionelle Gruppe zur Verbindung der beiden Blöcke hat zwar einen Einfluss auf die Morphologie der gebildeten Aggregate, nicht jedoch auf die eigentliche Fähigkeit der Systeme zur Selbstorganisation. Die Dex6500-b-PEG5500-Vesikel wiesen zudem eine langsame Bildungskinetik in Gegenwart von Con-A-Lectin auf. Des Weiteren waren sowohl Dex6500-b-PEG5500 als auch das quervernetzte Derivate dieses Copolymers in der Lage, Fluoreszenzfarbstoffe einzulagern. Um zu zeigen, dass wässrige Zwei-Phasen-Systeme (aqueous two phase systems – ATPS) eine belastbare Grundlage für die Untersuchung und Entwicklung selbstorganisierender DHBC-Systeme sind, wurden weitere Dextran-basierte Copolymere synthetsisiert: Dextran-b-Poly(vinylalokohol) und Detran-b-Poly(vinylpyrrolidon). In einem zweiten Teil dieser Arbeit wurde das zuvor erarbeitete Prinzip auf auf Polypeptidsysteme ausgeweitet. Dazu wurde ein Poly(N-Hydroxyethylglutamin)-block-Poly(ethylenglycol)-Copolymer hergestellt. Dieses Copolymer, dessen emulgierenden Eigenschaften bereits bekannt waren, wies unmittelbar nach Lösung des Feststoffes in Wasser Vesikelbildung auf. In einem dritten Teil der Studie wurden thermoresponsive Copolymere hergestellt und untersucht: Dextran-b-PNIPAMm. Unterhalb der LCST konnte die Bildung von Aggregaten nachgewiesen werden, deren Struktur nicht zweifelsfrei entschlüsselt werden konnte, wobei jedoch zahlreiche Hinweise auf eine vesikuläre Struktur hindeuten. Oberhalb der LCST wurde durch die Kollabierung der PNIPAM-Ketten die Bildung stabiler Strukturen mit Radien von mehreren hundert Nanometern induziert, deren weitere Entwicklung durch eine weitere Temperaturerhöhung gefördert werden konnte. Durch Rückkühlung in den Temperaturebereich unterhalb der LCST konnten die zuvor beobachteten Aggregate reversibel zurückgebildet werden. Das Selbstorganisationsverhalten von DHBC, unabhängig vom Einfluss des pH-Werts, der Ionenstärke oder der Temperatur are bisher nur in sehr geringem Umfang Gegenstand wissenschaftlicher Veröffentlichungen. Diese Arbeit stellt damit den ersten umfassenden Beitrag zur systematischen Erarbeitung dieses Phänomens dar. Es konnten dabei zwei Ursachen für die beobachteten Selbstorganisationseffekte bestimmt werden: die Inkompatibilität der beiden Polymerblöcke (enthalpischer Effekt) und der Unterschied in deren Löslichkeit (enthalpische und entropische Effekte). Der entropische Beitrag zur positiven Gibbs’schen Freien Mischungsenergie wird dem selben Verlust konformativer Entropie zugeordnet, der auch für den hydrophoben Effekt verantwortlich ist, allerdings angetrieben durch einen Wettbewerb der beiden Polymerblöcke um das Wasser. In diesem Sinne kann man das beobachtete Phänomen als „hydrophilen Effekt“ bezeichnen.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references.
Self-assembly of block copolymers (BCPs) is emerging as a promising route for numerous technological applications to fabricate a variety of nanoscopic structures. The resulting feature sizes range from a few to several hundred nanometers, and are readily tunable by varying the molecular weights of block copolymers. Directed self-assembly of block copolymer is an effective way to pattern periodic arrays of features with long-range order, to generate complex patterns, and to multiplicatively increase the pattern density and resolution that are far beyond the limit of conventional lithography. Despite of the significant progress in the area of directed self-assembly in recent years, critical research problems regarding the dimension scalability toward sub-10-nm regime and large feature sizes on hundreds of nanometers scale as well as the capability of generating complex device-oriented patterns remain challenging. In this thesis, BCP systems, including high-v BCPs that are capable of self-assembling into extreme small and large feature sizes as well as those with more complex block architectures, are identified and studied in order to understand how those materials may be processed and directed selfassembly to bridge the patterning size spectrum between nano- and micro-fabrication. Another focus is placed on the scientific exploration of directed self-assembly of triblock terpolymers and the investigation on the mechanisms that regulate the scaling and geometry of self-assembled patterns. A comprehensive understanding about self-assembly of BCP thin films will enable developing device-oriented geometries, manipulating BCPs phase behavior, and incorporating new functional materials for a wider range of applications. In the meanwhile, optimizing the processing condition of self-assembly of various BCPs is essential to confirm viability of the directed self-assembly of block copolymers process in manufacturing.
by Li-Chen Cheng.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references.
Monolayer patterns of block copolymer (BCP) microdomains have been pursued for applications in below sub-30 nm nanolithography. BCP selfassembly processing is scalable and low cost, and is well-suited for integration with existing semiconductor fabrication techniques. The two critical issues are how to obtain reliable long-range ordering of features with minimum defect densities and how to successfully transfer the patterns into other functional materials. Exceptionally well-ordered and robust nanoscale patterns can be made from poly(styrene-b-dimethylsiloxane) (PS-PDMS) BCPs, which have a very large Flory-Huggins interaction parameter between the blocks compared to other commonly used BCPs. Cylinder- or sphere-forming BCP films were spincoated over silicon substrates patterned with shallow steps using optical lithography or nanoscale posts made by electron-beam lithography, and solvent-annealed to induce ordering. This generates patterns with a correlation length of at least several micrometers. The annealed film was treated with plasma to obtain oxidized PDMS patterns with a lateral dimension of 14 - 18 nm. These can be used as an etch mask or an easily removable template for patterning functional materials. Solvent vapor treatments can tune the pattern dimension and morphology. Different degrees of solvent uptake in BCP films during solvent-annealing can manipulate the interfacial interaction between the two blocks, and a mixed solvent vapor can change the effective volume fraction of each block. The self-assembled patterns can be transferred into various kinds of functional materials.
(cont.) For example, arrays of parallel lines were used as a mask to pattern poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conducting polymer thin films. The resulting PEDOT:PSS nanowire array was used as an chemiresistive-type ethanol-sensing device. Metallic films such as Ti, Pt, Ta, W, and magnetic Co and Ni were structured using a pattern-reversal process. Coercivity enhancements were observed for the fabricated ferromagnetic nanostructures such as wires, rings, and antidots. These functional nanostructures can be utilized for a variety of devices such as high-density and high performance sensor or memory devices.
by Yeon Sik Jung.
Ph.D.

Biocompatible and biodegradable poly(lactide)-2-methacryloyloxyethyl phosphorylcholine (PLA-PMPC) amphiphilic block copolymers were synthesized by a combination of Ring Opening Polymerization (ROP) and Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization techniques. The PLA-macroRAFT agent was synthesized by the derivatization of PLA-OH with RAFT agent 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB) achieving high levels of functionalization and narrow weight distributions (PDI range of 1.02-1.17). PLA-PMPC with varied MPC block lengths were synthesized yielding polymers with a narrow polydispersity PDI = 1.16-1.21. Triblock copolymers PMPC-PLA-PMPC with varying hydrophilic weight ratios were synthesized following an analogous method, the polymerizations were shown to be controlled with PDI’s of 1.24 and 1.36. PLA-PMPC block copolymers with varied compositions were self-assembled using several techniques to target different morphologies. Nanostructures were characterised by DLS and TEM. Block copolymers with a larger PLA block length were shown to generate smaller aggregates i.e. micelles. The morphologies observed for the various block copolymers were consistent amongst different preparative techniques. Vesicle structures were reproducible by the self-assembly of PMPC50-PLA51-PMPC50, however, by preparing nanoparticles by direct dissolution micelles formed. The block copolymers were shown to encapsulate a hydrophobic dye in aqueous media thereby demonstrating its potential drug delivery applications.

Il drug delivery attira molto interesse a causa della necessità di migliorare efficienza e selettività delle terapie farmacologiche. Capsule polimeriche per i farmaci sono una strategia promettente per prolungarne i tempi di circolazione, migliorarne il trasporto nel sangue, e modularne nel tempo il rilascio. In questo ambito, l’organizzazione spontanea dei copolimeri a blocchi (CB) in nanoparticelle (NP) compartimentalizzate in ambiente acquoso è uno strumento potente per la fabbricazione di sistemi per il drug delivery. In questa tesi vengono investigati la sintesi e l’autoassemblaggio (AS) controllati di una serie di CB anfifilici contenenti blocchi idrofilici biocompatibili e biomimetici. Nel Cap. 3 viene presentato un quadro completo del comportamento di AS di PS-b-PDMA in H2O da DMF. E’ stato preparato un set di campioni con pesi molecolari compresi fra 10 kDa e 57 kDa e fPDMA comprese fra 0.06 e 0.75, e le NP sono state caratterizzate con DLS, TEM, CEM, CET, SEM e AFM. Viene proposta una mappa morfologica, dove le morfologie dominanti sono state correlate con la caratteristiche chimiche dei CB. In particolare, quando fPDMA < 0.15, è stata osservata la formazione di particelle porose con diametri fino ad alcuni micron che assumono una fase spugnosa, stabile alla liofilizzazione. Nel Cap. 4, una serie di CB biocompatibili e biodegradabili di PEO-b-PLA sono stati sintetizzati tramite ROP controllata di lattide catalizzata da DBU. Il focus di ricerca era sull’effetto del solvente non selettivo sull’AS: NP ottenute da ACT, DX, THF e DMF sono state analizzate con DLS, CEM e CET. Dimensioni e PDI aumentavano nell’ordine ACT < DX < THF ~ DMF. Le NP sono state classificate in tre cluster: micelle (piccolo raggio, basso PDI), polimersomi (medio raggio, medio PDI), e micelle composte (grande raggio, grande PDI). Mentre ACT e DX portano alla formazione preferenziale di micelle, il THF permette di accedere a uno spazio morfologico molto più ampio. Infine, la DMF favorisce fenomeni di aggregazione di secondo ordine. Nel Cap. 5 vengono valutati la sintesi controllata, la funzionalizzazione terminale e la formazione di di- e triblocchi di polimeri a base di PEtOx biocompatibile tramite una combinazione di ROP e RAFT. Un blocco di PEtOx25 è stato sintetizzato con successo tramite CROP di 2-etil-2-ossazolina con buon controllo; è stato poi usato come macroCTA per la polimerizzazione sequenziale di Sty e t-BA per ottenere il copolimero a tre blocchi PEtOx-b-PS-b-PtBA. Vengono presentati risultati preliminari sul SA in etanolo come solvente selettivo per i blocchi di PEtOx e PtBA, ma non PS. Nel Cap. 6 è stato studiato l’effetto morfogenico di ACT, DX e DMF sul SA di PS-b-PDMA e PEO-b-PLA usando il rotore molecolare AzeNaph-1 come sonda di viscosità per il monitoraggio in situ dell’aggregazione dei CB. L’evoluzione della viscosità in funzione del contenuto di H2O in PS-b-PDMA è simile sia in DMF che DX: all’aggiunta di H2O, le catene di PS collassano rapidamente, formando core prevalentemente vetrosi. Coerentemente, il DLS mostra poca variazione di dimensioni delle NP fra i due solventi. Anche PEO-b-PLA forma domini vetrosi in DMF/H2O, ma non in ACT o DX. Al contrario, la viscosità locale del core è molto minore in ACT e DX che in DMF su tutto il range di frazione di H2O, ed è dipendente dal tempo. Questa aumentata mobilità molecolare promuove la differenziazione delle NP formate. Infine, nel Cap. 7 viene esplorato l’AS indotto da polimerizzazione di CB anfifilici basati su glicopolimeri. Tre campioni di PAGA con DP = 25, 50 e 75 sono stati polimerizzati in H2O/MeOH tramite RAFT, con ottimo controllo. L’ottimizzazione delle condizioni di reazioni ha permesso di usare PAGA25 e PAGA50 come stabilizzanti e macroCTA per l’estensione di catena con BA in H2O/MeOH. Il controllo sulla polimerizzazione è stato basso, ma sono state ottenute NP sferiche, stabili e monodisperse.
Drug delivery is a trending topic in current research due to the need to improve therapeutic efficiency and selectivity. Polymeric encapsulants for drugs are a promising strategy to prolong circulation times, enhance hydrophobic drug transport through the blood stream, and modulate drug release over time. In this field, amphiphilic block copolymers’ (BCs) spontaneous organization in compartimentalized nanoparticles (NPs) in water is a powerful tool for the fabrication of drug delivery systems. In this Doctoral thesis, the controlled synthesis and self-assembly (S-A) of a series of amphiphilic BCs containing biocompatible, stealthy hydrophilic blocks were investigated. Controlled polymerization techniques were employed to prepare copolymers with narrow molecular weight distributions. In Chapter 3, a complete picture of the previously unreported S-A behaviour of PS-b-PDMA in water from DMF is drawn. A comprehensive sample set spanning molecular weights from 10 kDa to 57 kDa and hydrophilic volume fractions fPDMA from 0.06 to 0.75 was prepared by sequential RAFT, and NPs were characterized by DLS, TEM, CEM, CET, SEM, and AFM. A morphology map is proposed, where predominant morphologies were correlated with BC chemical characteristics. In particular, stable hollow particles with diameters up to several microns when fPDMA drops below 0.15 are formed. Micron-large porous particles exhibiting a sponge phase which can withstand lyophilisation were observed. In Chapter 4, a series of biocompatible and biodegradable PEO-b-PLA BCs were synthesized by controlled ROP of lactide catalyzed by non-toxic DBU. The research focus was on the effect of the non-selective solvent on S-A: NPs obtained from ACT, DX, THF, DMF were analyzed by DLS, CEM and CET. Both size and PDI increased in the order ACT < DX < THF ~ DMF. NPs were classified into three clusters, labeled micelles (small size, low PDI), polymersomes (medium size, medium-low PDI) and large compound micelles (large size, large PDI). While ACT and DX yielded mostly micelles, THF allowed to access a much broader morphological space. Finally, DMF favoured second-order aggregation phenomena. In Chapter 5, controlled synthesis, chain-end functionalization and di- and triblock formation of biocompatible PEtOx-based polymers by a combination of ROP and RAFT techniques were evaluated. Biocompatible PEtOx25 blocks were successfully synthesized by CROP of 2-ethyl-2-oxazoline with good control. PEtOx25 was used as a macroCTA for the sequential polymerization of a Sty and tBA to yield a PEtOx25-b-PS50-b-PtBA25 triblock copolymer. Preliminary results on S-A in ethanol as a selective solvent for both PEtOx and PtBA, but not for PS, are presented. In Chapter 6, the morphogenic effect of ACT, DX and DMF on PS-b-PDMA and PEO-b-PLA S-A was studied using molecular rotor AzeNaph-1 as a local viscosity probe for the in situ monitoring of BC aggregation. Evolution of viscosity as a function of water content in PS-b-PDMA was similar both in DMF and DX: upon the addition of H2O, PS chains rapidly collapsed in NP cores, which were largely glassy. Consistently, DLS shows little variation on particle size between the two solvents. PEO113-b-PLAx also formed glassy domains in DMF/H2O, but not in ACT or DX. Contrarily, local core viscosity was much lower in ACT and DX than in DMF over the whole H2O fraction range, and was time-dependent. This increased chain mobility promoted the differentiation of NP formation. Finally, in Chapter 7, polymerization-induced S-A of glycopolymer-based amphiphilic BCs was investigated. Three PAGA samples with DP = 25, 50 and 75 were polymerized in H2O/methanol mixture by RAFT, with remarkable control. Optimization of reaction conditions allowed the use of PAGA25 and PAGA50 as stabilizers and macroCTAs for chain-extension with n-butylacrylate (BA) in methanol/H2O environment. Control on the polymerization was poor, but stable and monodisperse spherical NPs were obtained.

L’objectif de ce travail était de mettre en évidence le potentiel du PDMSBb-PS pour des applications en nanolithographie avancée. Pour cela, nous avons fourni une compréhension du comportement d’auto-assemblage du PDMSB-b-PS en masse et en film mince. Nous avons réalisé l’auto-assemblage de ce copolymère semicristallin en cylindre et gyroïde bien définis avec des périodicités inférieures à 20 nm grâce à un paramètre d’interaction de Flory-Huggins élevé (Chapitre 2). Nous avons par la suite proposé une approche pour obtenir des lamelles perpendiculaires du PDMSB-b-PS en film mince grâce à l’utilisation de sur-couches neutres réticulables. La polyvalence de cette approche a été démontrée à l’aide de CPBs de masses moléculaires différentes et s’est ensuite étendue à la formation d’empilements via un processus d’auto-assemblage itératif (chapitre 3). Enfin, nous avons réticulé la surcouche neutre à l’aide d’agents photo-sensibles ce qui nous a permis d’obtenir un motif par photolithographie au-dessus du film CPB. Ainsi, il a été possible de contrôler l’orientation du CPB à des endroits spécifiques du film (Chapitre 4)
The objective of our work was to highlight the potential of the high-χ PDMSB-b-PS BCP for advanced nanolithography applications. For this purpose, we have demonstrated the ability of our system to self-assemble into well-defined nanostructures in bulk and we have performed the self-assembly of cylinder- and gyroid-forming PDMSB-b-PS BCPs in thin film using industrially-friendly processes (Chapter 2). With the aim of controlling the out-of-plane orientation of lamellar-forming PDMSB-b-PS BCPs in thin film, we have proposed an innovative approach relying on the use of crosslinkable neutral TC layers. The versatility of this approach was demonstrated using BCPs having different macromolecular characteristics and extended to the formation of multi-layer stacks through an iterative self-assembly process (Chapter 3). Taking advantage of the crosslinking ability of our TC material, we have outlined the patterning ability of the TCs using photosensitive crosslinking agents. The patterning of neutral TCs above the lamellar-forming PDMSB-b-PS BCPs further allowed a control of the orientation of the PDMSB-b-PS domains in specific areas of the film (Chapter 4)

La tesi doctoral titulada “Auto-assemblatge de copolímers de bloc per modificació química de la superfície”, presenta com a objectiu principal el desenvolupament, implementació i caracterització d’un mètode de guiatge de copolímers de bloc basat en la modificació química de la superfície. El desenvolupament d’aquest mètode de nanofabricació contribueix a la futura generació de dispositius i circuits nanoelectrònics. Primer de tot, es presenten els aspectes generals sobre l’auto-assemblatge dirigit de copolímers de bloc, així com el seu rol dins del futur de la nanoelectrònica comparat amb altres tecnologies emergents. Després, per tal d’entendre i determinar les interaccions que tenen lloc durant el procés d’auto-assemblatge, es dóna una visió general sobre els processos químics i físics que tenen lloc en les pel·lícules primes de copolímers de bloc. La part principal de la tesi es focalitza en l’estudi, desenvolupament i implementació d’un mètode de guiatge químic per tal de dirigir l’auto-assemblatge de copolímers de bloc. A banda d’estudiar el procés experimental, també es caracteritzen els mecanismes que condueixen l’alineament i s’introdueixen a un model per simular el procés d’auto-assemblatge dirigit. A més, també es presenta la transferència del procés a una línia pilot industrial de fabricació de circuits integrats. La implementació del procés de guiatge químic s’ha provat no únicament amb materials comercials, sinó també amb nous sistemes polimèrics que permeten arribar a mides per sota dels 10 nm. Per aquests sistemes, es defineix un nou mètode de guiatge basat en la combinació de modificacions topogràfiques i químiques. Per tal d’entendre millor el procés, s’estudien tècniques específiques de metrologia. En particular, mitjançant tècniques d’alta energia de rajos X, es descriuen les principals diferències entre patrons químics de guiatge. D’altra banda, les propietats nanomecàniques dels diferents dominis del copolímer es determinen mitjançant el mode peak force tapping de la microscòpia de força atòmica. Finalment, es mostra un mètode per transferir els motius del copolímer al substrat. Aquest es basa en la infiltració d’un domini del copolímer. La infiltració canvia les propietats del material i el fa més resistiu al gravat amb oxigen. D’altra banda, i com a aplicació final, es presenta un procés de fabricació de ressonadors nanomecànics, basats en el procés d’auto-assemblatge de copolímers de bloc amb infiltració.
The thesis entitled “Directed self-assembly of block copolymers on chemically nano-patterned surfaces”, aboard the challenge of the development, implementation and characterization of a chemical epitaxy process to direct self-assemble block copolymers. The development of this nanofabrication method contributes to the next generation of nanoelectronic devices and circuits. Firstly, the main aspects of directed self-assembly of block copolymers and its role and status in the future of nanoelectronics is presented, and compared with other powerful technologies. Then, a general overview about the physics and chemistry involved in block copolymer thin films is presented, in order to understand and determine the interactions taking place during the DSA process. The main part of the thesis is focused on the study, development and implementation of a chemical epitaxy approach to guide the self-assembly of block copolymers. Apart from the process development, the mechanisms which drive the block copolymer alignment are characterized and simulated into a DSA model. Moreover, the process transfer to a more industrial pilot line is presented. The implementation of the chemical epitaxy process is addressed not only with commercial block copolymers, but also with new polymer systems which allow getting sub- 10 nm resolution. For these systems, a new guiding method is presented based on the combination of a chemical and graphoepitaxy approach. To better understand the DSA process, dedicated metrology methods are also studied. In particular, by using high-energy X-ray techniques it is possible to describe the main characteristics of the chemical guiding patterns. On the other hand, the nanomechanical properties of block copolymer domains are studied by using the peak force tapping mode in atomic force microscopy. A reliable method to pattern transfer the block copolymer features into the substrate is showed. It is based on infiltrating one block copolymer domain and enhancing thus, its resistivity to plasma etching. Finally, as a final application, a novel fabrication process of a nanowire mechanical resonator by means of DSA and infiltration is presented.

In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.
Die Selbstorganisation von mehrfach thermisch schaltbaren Blockcopolymeren in verdünnter wässriger Lösung wurde mittels Trübungsphotometer, dynamischer Lichtstreuung, TEM Messungen, NMR sowie Fluoreszenzspektroskopie untersucht. Die schrittweise Überführung eines hydrophilen in ein hydrophobes Blockcopolymer beinhaltet ein oder mehr amphiphile Zwischenstufen mit einstellbarem hydrophilen zu lipophilen Anteil (HLB). Dies führt dazu, dass die Selbstorganisation solcher Polymere in Lösung nicht nur einem Alles-oder-nichts-Prinzip folgt sondern ein mehrstufiges Aggregationsverhalten beobachtet wird. Die Synthese von doppelt thermisch schaltbaren Diblockcopolymeren und dreifach thermisch schaltbaren Triblockcopolymeren wurde durch sequenzielle RAFT Polymerisation realisiert. Dazu wurden zweifach TMS-markierte RAFT Agentien verwendet, welche die Bestimmung der molaren Masse sowie der verbliebenen Endgruppenfunktionalität direkt aus einem Protonen NMR Spektrum erlauben. Mit diesen RAFT Agentien wurde zunächst eine Serie von doppelt thermisch schaltbaren Diblockcopolymeren aus Poly(N-n-propylacrylamid)-b-Poly(N-ethylacrylamid), welche sich lediglich durch die relativen Blocklängen unterscheiden, hergestellt. In Abhängigkeit von der relativen Blocklänge wurde ein unterschiedliches Aggregationsverhalten der Diblockcopolymere in verdünnter wässriger Lösung beobachtet. Des Weiteren wirken die komplementär TMS-markierten Endgruppen als NMR-Sonden während der schrittweisen Aggregation dieser Polymere. Reversible, temperaturabhängige Peakaufspaltung der TMS-Signale in der NMR Spektroskopie spricht für eine Aggregation in gemischte stern-/blumenartige Mizellen, in denen ein Teil der hydrophoben Endgruppen in den hyrophoben Kern zurückfaltet. Obendrein wurden dreifach thermisch schaltbare Triblockcopolymere aus Poly(N-n-propylacrylamid) (A), Poly(methoxydiethylen glycol acrylat) (B) und Poly(N-ethylacrylamid) (C) in allen möglichen Blocksequenzen (ABC, BAC, ACB) durch schrittweisen Aufbau mittels RAFT Polymerisation erhalten. Das Aggregationsverhalten dieser Polymere in verdünnter wässriger Lösung war relativ komplex und hing stark von der Position der einzelnen Blöcke in den Triblockcopolymeren ab. Besonders die Position des Blocks mit der niedrigsten LCST (A) war ausschlaggebend für die resultierenden Aggregate. So wurde oberhalb der ersten Phasenübergangstemperatur nur Aggregation der Triblockcopolymere beobachtet, wenn der A Block an einem der beiden Enden der Polymere lokalisiert war. Wurde der A Block hingegen in der Mitte der Polymere positioniert, entstanden unimere Mizellen zwischen der ersten und zweiten Phasenübergangstemperatur, welche erst aggregierten, nachdem der zweite Block (B) seinen Phasenübergang durchlief. Die Transportereigenschaften dieser Triblockcopolymere wurden mittels Fluoreszenzspektroskopie getestet. Dazu wurde die Einlagerung eines hydrophoben, solvatochromen Fluoreszenzfarbstoffes, Nilrot, in Abhängigkeit der Temperatur untersucht. Im Gegensatz zu den Polymeren mit der Blocksequenz ABC oder ACB, zeigten die Polymere mit der Sequenz BAC eine verminderte Aufnahmefähigkeit des hydrophoben Farbstoffes oberhalb des ersten Phasenübergangs, was auf die fehlende Aggregation und die damit verbundenen relativ kleinen hydrophoben Domänen der unimolekularen Mizellen zwischen der ersten und zweiten Phasenübergangstemperatur zurückzuführen ist. Aufgrund des zunehmenden Verlustes von funktionellen Endgruppen während der RAFT Synthese von Triblockcopolymeren wurde ein neuartiges Konzept zur Einschrittsynthese von mehrfach schaltbaren Blockcopolymeren entwickelt. Dieses erlaubt die Synthese von mehrfach schaltbaren Diblock- und Triblockcopoylmeren in einem einzelnen Reaktionsschritt. Die Copolymeriation von verschiedenen N-substituierten Maleimiden mit einem thermisch schaltbaren Styrolderivat (4-Vinylbenzylmethoxytetrakis(oxyethylene) ether) ergab alternierende Copolymere mit variabler LCST. Die Verwendung eines Überschusses dieses styrolbasierten Monomers erlaubt ferner die Synthese von Gradientenblockcopolymeren in einem einzelnen Polymerisationsschritt.

Incorporation of peptide or mesogenic units into block copolymers enables hierarchical order, whereby an interplay between microphase separation and peptide secondary structure formation or liquid crystal ordering occurs. This thesis concerns the self-assembly process and dynamics in block copolymers with hierarchical order. The second and third chapters discuss peptide-based poly(γ-benzyl-Lglutamate)-poly(ethylene glycol)-poly(γ-benzyl-L-glutamate) triblock copolymers and side-group liquid crystal polystyrene-poly [2-(((3-cholesteryl)-oxy)carbonyl)decyl methacrylate)] diblock copolymers. In the first case, the morphology was revealed and the peptide secondary structure was probed by a combination of scattering and microscopy techniques.

Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Marcus Weck; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Jones, Christopher; Committee Member: Payne, Christine

Les monomères d'un copolymère statistique sont aléatoirement mélangés, tandis que ceux d'un copolymère à bloc sont nettement séparés en sections de compositions différentes. Entre ces deux structures modèles existent des copolymères asymétriques, qui sont définis comme une distribution de monomères au sein de la chaîne qui n'est ni complètement ségrégée comme pour un copolymère à bloc ni statistiquement distribuée de manière indépendante de la position au long de la chaîne comme dans le cas des copolymères statistiques. Ainsi, les propriétés des copolymères asymétriques devraient combiner les caractéristiques des structures à bloc et statistiques. Dans cette étude, des copolymères d'acide acrylique-(acrylate de n-butyle) (AA-n-BA) et diméthylacrylamide-N-isopropylacrylamide (DMA-NIPAM), avec des masses molaires ciblés de 10 kg mol-1 et 20 kg mol-1 , ont été obtenus par polymérisation RAFT en utilisant une synthèse forcée et par étapes. Les deux systèmes de copolymères sont des polymères sensibles aux stimuli : des macromolécules qui subissent des transitions de phase lorsqu'elles subissent de subtils changements des conditions environnementales. Les copolymères P(AA-n-BA) réagissent au pH et les copolymères P(DMA-NIPAM) sont thermosensibles. Lors de cette étude, la composition des copolymères a été fixée (50% AA ou 50% NIPAM), mais la distribution des unités de monomères au sein de la chaîne varie. En effet, des structures à blocs, statistiques, à gradient, asymétriques dibloc et tribloc ont été obtenues dans le but de comparer leurs propriétés physiques et d'auto-assemblage. Les caractéristiques macromoléculaires des copolymères ont été obtenues par spectroscopie de résonance magnétique nucléaire (1H RMN) et chromatographie d'exclusion stérique (SEC). Les copolymères P(AA-n-BA) en solution à différents pH ont été étudiés par diffusion dynamique de la lumière (DLS), microscopie électronique à transmission cryogénique (cryo-TEM) et diffusion de neutrons aux petits angles (SANS) et il a été possible de démontrer les changements de taille et de comportement d'auto-assemblage en fonction du pH des différentes solutions de copolymères. Les résultats ont montré que les copolymères asymétriques P(AA-n-BA) forment des agrégats de morphologie différente selon le pH, par exemple des vésicules à pH 4 ou des micelles et des micelles vermiculaires à pH 5. D'autre part, la morphologie des copolymères à bloc de même composition, n'est pas influencée par les changements de pH. Les copolymères de P(DMA-NIPAM) ont été analysés en solution par DLS, SANS et 1H RMN en fonction de la température. L'évolution de la taille hydrodynamique en fonction de la température a pu être suivie par DLS. La micellisation induite par le changement de température a été analysée par SANS. Enfin, l'effondrement de la structure induit par la température et la perte de mobilité résultante des chaînes polymères ont été suivis à un niveau moléculaire par 1H RMN. Des résultats intéressants ont été obtenus, car les copolymères à bloc de faible masse molaire (Mn = 10 kg mol-1) présentent un comportement similaire au copolymère à gradient de masse molaire plus élevé (Mn = 20 kg mol-1). Ce phénomène a été observé par SANS et 1H RMN, et il a été attribué à la faible longueur du copolymère à bloc : une fraction significative des unités NIPAM dans le copolymère à bloc peuvent être en contact avec le DMA du bloc adjacent, conduisant à un changement progressif de la composition effective du polymère en fonction de la longueur de la chaîne
Block copolymers are made from polymer chains of different chemical composition that are covalently joined via their respective end groups. On the other hand, there are statistical copolymers whose monomers are randomly copolymerized together. Between these structures exist asymmetric copolymers, which are defined as a distribution of monomers within the chain which is neither completely segregated as for a block copolymer nor statistically distributed in a manner that is independent of the position along the chain as in the case of statistical copolymers. Based on the latter, the properties of asymmetric copolymers are expected to combine characteristics of block and statistical structures. In this investigation, acrylic acid-(n-butyl acrylate) (AA-n-BA) copolymers and dimethylacrylamide-N-isopropylacrylamide (DMA-NIPAM) copolymers, with targeted molecular weights of 10 kg mol-1 and 20 kg mol-1, were obtained by RAFT polymerization using forced and stepwise synthesis. Both copolymer systems are stimuli-responsive polymers: macromolecules which undergo phase transitions when they experience subtle changes in the environmental conditions. P(AA-n-BA) copolymers are pH-responsive and P(DMA-NIPAM) copolymers are thermosensitive. The composition of the copolymers was always the same (50% AA or 50% NIPAM), but the distribution of the monomer units within the chain was different. Block, statistical, gradient, asymmetric diblock and triblock structures were obtained with the aim to compare their physical and self-assembly properties. The macromolecular characteristics of copolymers were obtained by nuclear magnetic resonance spectroscopy (1H NMR) and size exclusion chromatography (SEC). P(AA-nBA) copolymers in solution at different pH were studied by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS) and it was possible to demonstrate the changes in size and self-assembly behavior as a function of pH of the copolymers solutions. The results showed that the P(AA-nBA) asymmetric copolymers form aggregates of different morphology depending on the pH, for example vesicles at pH 4 or micelles and worms at pH 5. On the other hand, the morphology of block copolymers with the same composition, is not influenced by changes in pH. P(DMA-NIPAM) copolymers in solutions were analyzed by DLS, SANS and 1H NMR as a function of temperature. The evolution of hydrodynamic size as a function of temperature could be followed by DLS and the temperature-induced micellization was analyzed by SANS whereas by 1H NMR, the temperature-induced collapse and resulting loss of mobility of the polymer chains could be followed at a molecular level. Interesting results were obtained, since low molar mass block copolymers (Mn = 10 kg mol-1) displayed similar behavior to the corresponding to high molar mass gradient copolymer (Mn = 20 kg mol-1). This phenomenon was observed by SANS and 1H NMR, and it was attributed to the short length scale of the block copolymer, in which the chain is short enough that a significant fraction of the NIPAM units in the block copolymer are strongly affected by the DMA of the adjoining block, leading to a gradual change in the effective composition of the polymer as a function of chain length

It is known that А-В and А-В-А block copolymers with interacting blocks are related to the class of in-tramolecular polycomplexes. Such block copolymers form a stable micellar structures in dilute aqueous so-lutions due to hydrophobic interactions between non-polar bound segments of the blocks. Given micellar structures have attracted a considerable attention due to their possible applications as different templates, drug delivery systems, nanoreactors. Here we presented peculiarities of a template synthesis of the block copolymers consisting interacting poly(ethylene oxide) and poly(acrylic acid) blocks and also its self-assembly to micelles in acidic aqueous solutions, which was confirmed by Transmission Electron Microsco-py (TEM). When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35608

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.
Includes bibliographical references (leaves 28-29).
This research focused on methods for regulating arrangement of self-assembled block copolymers by understanding fabrication conditions and their effects on the polymers on flat and patterned substrates. Block copolymer self-assembly is a simple and low cost process for creating lithographic masks with features under 100nm in dimension. These patterns can be transferred to more permanent materials for applications in electronics, magnetic devices, as well as sensors and filters. Polystyrene-poly(ferrocenyldimethylsilane) block copolymer thin films were characterized in terms of their spin curves, PSF spherical domain cross sectional area distributions, and correlation distances. Optimal fabrication conditions were selected from studying polymer behavior on flat substrates and then used for templated substrate studies. Substrates that were templated with grooves produced quantized numbers of rows of spherical domains ranging from 4 to 7. Behavior in these grooves was characterized in terms of groove width constraints, cross sectional domain area distributions, and row ordering. For all templated arrays, the lengths of ordered regions were more than 2 fold higher than the diameters of ordered regions of arrays on flat substrates. The characterization accomplished in this work will be used to compare block copolymers with similar volume fractions of the blocks that allow sphere microdomain formation but of different molecular weights. The ultimate goals are to establish how the molecular weight of this block copolymer affects its self assembly on templated and on flat substrates and to use this factor as well as fabrication conditions and template geometries to engineer arrays with desirable properties.
by Marianna Shnayderman.
S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.
Vita.
Includes bibliographical references.
Linear-dendritic block copolymers consisting of a poly(styrene) linear block and poly(amidoamine) dendrimer block were synthesized and examined for their ability to self-assemble in both aqueous environments and organic/aqueous mixtures. These polymers were shown to assemble into vesicle structures under a variety of conditions. Furthermore, size measurements of the dendritic portion were taken by means of Langmuir-Blodgett isotherms, demonstrating both the steric area, as well as the electrostatic area occupied by the dendrimer in a monolayer. Further studies into the rapid synthesis of such systems were also undertaken, with a particular interest in use of the so-called "click" reaction to be used as a facile means toward block copolymer synthesis.
by Kristoffer Keith Stokes.
Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Engineering enzymes and other proteins into biocatalysts or bioelectronic devices has the potential to lead to a new generation of energy-generating and energy conversion technologies. Controlling the hierarchical structure of protein materials from the nanoscale single molecule level up to the microscale material morphology is critical to improving their function. Lithographic patterning methods such as electron beam lithography, dip-pen nanolithography, and nanograftin allow proteins to be patterned with nanoscale resolution, but parallelization to increase throughput remains a significant challenge. While templated self-assembly enables patterning in three dimensions, maximizing protein loading and controlling orientation are challenges that remain to be addressed. Self-assembly provides a low-cost method to nanopattern proteins for biofunctional devices with high operational efficiency through control over three-dimensional spatial arrangement and orientation. Complementary experimental techniques were used to investigate the phase behaviors of globular protein-polymer block copolymers and provide insight into the relevant physics and thermodynamics governing their self-assembly. In particular, methodical permutations were made to the protein block to understand the relationship between protein interactions and protein-polymer block copolymer selfassembly. Order-disorder and order-order transitions were demonstrated for the first time within a rich window of phase space of hexagonal, lamellar, perforated lamellar, and micellar phases that were dependent on coil fraction. Protein-polymer net repulsive interactions were discovered to be important for self-assembly. The type of nanostructures formed at a given coil fraction are different between globular-coil and coil-coil systems due to the anisotropy between protein and coil shape and interactions and minor differences in solvent selectivity. A set of structurally homologous proteins in which the chemical composition and surface interaction potential were varied globally throughout the entire sequence and locally through single point mutations demonstrated highly similar phase behavior, revealing that coarse-grained properties such as the protein shape, size, solubility, surface charge, and virial coefficient can capture the general shape of the phase diagram in nonselective solvents. Engineering greater changes in protein electrostatic interactions and virial coefficient demonstrated that the electrostatic environment of proteins may be designed to tune the morphologies of protein-polymer blok copolymers, both enhancing and suppressing formation of nanostructures through attractive and repulsive interactions, respectively. A combination of small-angle neutron scattering experiments, theory, and coarse-grained modeling and simulation was used to elucidate the shape of protein-polymer block copolymers in dilute solution and quantify their interactions. Modeling protein-polymer interactions using repulsive Weeks-Chandler- Andersen potentials showed that the polymer exists as a relatively unperturbed coil extended away from the protein. The coarse-grained representation additionally provides a simple way to model the conformation of protein-polymer conjugates with strong interactions that result in the polymer wrapping around the protein in a shroud-like configuration.
by Christopher N. Lam.
Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Unconventional computation is a paradigm of computation that uses novel information tokens from natural systems to perform information processing. Using the complexity of physical systems, unconventional computing systems can efficiently solve problems that are difficult to solve classically. In this thesis, we use block copolymer self-assembly, a well-studied phenomenon in polymer science, to develop a new approach to computing by applying directed self-assembly to implement Ising-model-based computing systems in materials. In the first part of the thesis, we investigate directed self-assembly of block copolymer thin films within templates of different polygonal shapes. We define a two-state system based on the two degenerate alignment orientations of the ladder-shaped block copolymer structures formed inside square confinements, and study properties of the two-state system. In the second part of the thesis, we demonstrate an Ising lattice setup for directed self-assembly of block copolymers defined on two-dimensional arrays of posts. We develop an Ising-model-based simulation method that can perform block copolymer pattern prediction and template design. Finally, we design simple Boolean logic gates as a proof-of-concept demonstration of computation.
by Hyung Wan Do.
Ph. D.

El principal objectiu d'aquesta tesi, titulada "autoensamblatge dirigit de copolímers de bloc per a la fabricació d'estructures nanomecàniques", és demostrar la possibilitat de fabricar estructures nanomecàniques funcionals mitjançant el autoensamblatge dirigit (DSA) de copolímers de bloc (BCPs) com a tècnica de nanoestructuració . El DSA és una tècnica de nanolitografía bottom-up basada en la capacitat que tenen els BCPs de segregar en dominis d'escala micro / nanomètrica. Gràcies a la seva alta resolució, alt rendiment i baix cost, aquesta tècnica ha estat molt estudiada per la indústria de semiconductors per nanoelectrònica, però també ha estat aplicada en altres camps que requereixen d'una alta densitat d'elements a escala nanomètrica. En aquesta tesi presentem un procés innovador basat en DSA que demostra ser apte per a la fabricació de sistemes nanomecànics. Vam demostrar la fabricació de membranes de silici suspeses ancorades per matrius de gran nombre de nanofils de silici emprant la grafoepitaxia de poliestirè-b-polimetilmetacrilat (PS-b-PMMA), un dels BCP més estesos. Els dispositius obtinguts poden desenvolupar-se per construir sensors de massa d'alta sensibilitat basats en ressonadors nanomecànics.
El principal objetivo de esta tesis, titulada "Autoensamblaje dirigido de copolímeros de bloque para la fabricación de estructuras nanomecánicas", es demostrar la posibilidad de fabricar estructuras nanomecánicas funcionales mediante el autoensamblaje dirigido (DSA) de copolímeros de bloque (BCPs) como técnica de nanoestructuración. El DSA es una técnica de nanolitografía bottom-up basada en la capacidad que tienen los BCPs de segregarse en dominios de escala micro/nanométrica. Gracias a su alta resolución, alto rendimiento y bajo coste, esta técnica ha sido muy estudiada por la industria de semiconductores para nanoelectrónica, pero también ha sido aplicada en otros campos que requieren de una alta densidad de elementos a escala nanométrica. En esta tesis presentamos un proceso novedoso basado en DSA que demuestra ser apto para la fabricación de sistemas nanomecánicos. Demostramos la fabricación de membranas de silicio suspendidas ancladas por matrices de gran número de nanohilos de silicio empleando la grafoepitaxia de poliestireno-b-polimetilmetacrilato (PS-b-PMMA), uno de los BCP más extendidos. Los dispositivos obtenidos pueden desarrollarse para construir sensores de masa de alta sensibilidad basados en resonadores nanomecánicos.
The main goal of this dissertation, entitled "irected self-assembly of block copolymers for the fabrication of nanomechanical structures", is to demonstrate the possibility of fabricating nanomechanical functional structures by employing the directed self-assembly (DSA) of block copolymers (BCPs) as a nanopatterning tool. DSA is a bottom-up nanolithography technique based on the ability of BCPs to segregate into domains at the micro/nanoscale, and it has attracted high interest due to its inherent simplicity, high throughput, low cost and potential for sub-10 nm resolution. Thanks to these characteristics, the technique has been heavily studied by the semiconductor industry for nanoelectronics, and also applied to alternate fields that might require from the definition of high-density nanoscale features. In this thesis we present a novel fabrication route based on DSA that proves to be suitable for the fabrication of nanomechanical systems. Here, we demonstrate the fabrication of suspended silicon membranes clamped by high-density arrays of silicon nanowires by using a DSA approach based on the graphoepitaxy of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), a well-known diblock copolymer. Obtained devices can be further developed for building up high-sensitive mass sensors based on nanomechanical resonators.
Universitat Autònoma de Barcelona. Programa de Doctorat en Enginyeria Electrònica i de Telecomunicació

Ce travail a porté sur la préparation de copolymères à blocs et l’étude de leur assemblage supramoléculaire basé sur des liaisons hydrogènes entre les motifs homocomplémentaires ou hétérocomplémentaires. La stratégie de synthèse était basée sur la combinaison de la polymérisation radicalaire contrôlée de type RAFT et de la chimie supramoléculaire. Dans le chapitre 2, nous avons développé une stratégie s'appuyant sur la conception d'agents RAFT portant des groupements de type thymine / diaminopyridine (DAP) capables de générer des copolymères en étoile de type « miktoarm » bien définis. Pour élargir le champ d’application de ces agents RAFT capables d’établir des liaisons H, nous avons également étudié, dans le chapitre 3, la préparation d’agents RAFT fonctionnalisés par des motifs présentant de très hautes constantes de liaison. Le couple Hamilton / barbiturate (log (K) ≈ 4-5) a été sélectionné pour générer de plus stables copolymères à blocs supramoléculaires. Afin d’élaborer des macromolécules originales aux hautes propriétés d’association et de simplifier la stratégie de la synthèse, nous avons finalement exploré la préparation de copolymères tribloc ABC supramoléculaires à base de PA11 (oligomères OPA11) dans le chapitre 4. L’introduction d'un groupe dithiobenzoate pertinemment choisi sur les oligomères conduit à l’obtention de macroagents RAFT qui permettent la préparation de copolymères tribloc ABC supramoléculaires, où A est semi-cristallin, B à l'état caoutchouteux et C à l'état vitreux. Les études sur l'incorporation de tels copolymères dans les réseaux époxy sont en cours
This work dealt with the preparation and the study of supramolecular block copolymers based on hydrogen-bonding between homocomplementary or heterocomplementary stickers. The synthetic strategy was based on the combination of RAFT-mediated controlled radical polymerization and supramolecular chemistry. In the Chapter 2, we developed a strategy relying on the design of RAFT agents bearing thymine/diaminopyridine (DAP) recognition pairs and capable to grow well-defined miktoarm star supramolecular copolymers. To further extend the scope of H-bonding RAFT agents, in the Chapter 3, we also investigated the preparation of RAFT agents functionalized with motifs exhibiting very high binding constants. The Hamilton/barbiturate couple (log(K)≈4-5) was selected to generate more stable supramolecular block copolymers. Aiming at elaborating original associating macromolecules and at simplifying the strategy of synthesis, we finally explored the preparation ABC triblock supramolecular copolymers based on PA11 oligomers (OPA11) in Chapter 4. Ligation of a relevant dithiobenzoate group on the oligomers afforded oligomeric RAFT agents that allow for the preparation of ABC triblock supramolecular copolymers, where A is semi-crystalline, B in rubbery state and C in glassy state. Studies on the incorporation of such copolymers in epoxy networks are under progress

It’s becoming more and more difficult to make smaller, denser, and faster computer chips. There’s an increasing demand to design new materials to be applied in current lithographic process to get higher patterning performance. In this work, the aqueous developable single molecule resists were introduced, synthesized and patterned. A new group of epoxide other than glycidyl ether, cyclohexene oxide was introduced to functionalize a molecular core and 15 nm resolution was obtained. The directed self-assembly (DSA) of block copolymers as an alternative lithographic technique has received growing interest in the last several years for performing higher levels of pitch subdivision. A 3-step simplified process for DSA by using a photodefinable substrate was introduced by using a functionalized polyphenol with an energy switchable group and a crosslinkable group. Two high χ block copolymers PS-b-PAA and PS-b-PHEMA were successfully designed and synthesized via ATRP with controlled Mw and PDI. The size of the same PS-b-PAA polymer was tunable by varying the thermal annealing time. PS-b-PHEMA shows to be a suitable block polymer for the industry-friendly thermal annealing process. A self-complementary hydrogen-bonding urea group as a center group was used to facilitate the self-assembly of polymers. “Click” chemistry is promising for synthesis of PS-Urea-Urea-PMMA.

The presented thesis entitled “High-resolution guiding patterns for the directed self-assembly of block copolymers” investigates strategies to introduce long-range order into block copolymer thin films for nanopatterning applications. Structures defined by top-down lithography that enable the introduction of long-range order into an otherwise disordered thin film of block copolymers are referred to as guiding patterns. This thesis explores and develops different techniques that enable the fabrication of guiding patterns with a particular focus on methods capable of providing high-resolution and high-accuracy, because they are at the prospect of playing a crucial role in the directed self-assembly of very low-pitch block copolymer materials. We demonstrate the directed self-assembly of an 11.7 nm full-pitch PS-b-PMMA block copolymer with guiding patterns fabricated by means of five different top-down lithography techniques. One strategy to fabricate guiding patterns consists in the generation of topographic structures, which is referred to as graphoepitaxy. In this case, we have used extreme-ultraviolet interference lithography to fabricate trenches with nanometer precision to study the self-assembly behavior of block copolymers under nanoconfinement with high accuracy. This system has allowed us to develop a free energy model to predict for which guiding pattern dimensions the defect-free directed self-assembly can be expected. Moreover, we have used electron beam lithography for the fabrication of sub-10 nm wide topographical guiding patterns and study the directed self-assembly of block copolymers in structures with feature sizes close to the material’s half-pitch. Another strategy to fabricate guiding pattern consists of chemical surface modification to create areas that are selectively affine to one of the blocks. We have presented a novel approach based on thermal scanning probe lithography and adjust the patterning conditions for the fabrication of chemical guiding patterns with 10 nm line width. Due to the absence of the proximity and diffraction effects, thermal scanning probe lithography is ideal for the fabrication of dense high-resolution chemical patterns. As a third strategy to align block copolymers, we use grain boundaries in block copolymer thin films as order-inducing surfaces. A surface modification is used to trap a grain of vertically oriented block copolymers between two grains of horizontally oriented block copolymer domains in a controlled manner. We call the developed technique “grain-boundary induced alignment”. To demonstrate its working principle we employ mechanical AFM and electron beam direct writing, and show the ordering of block copolymers on length scales of various hundreds of nanometers. The presented thesis is complemented with the development of a probe-based imaging technique to study the thermal conductivity of polymer materials with sub-10 nm lateral resolution. The dissipation of heat into a sample is determined at each measurement point by means of an electrical circuit that is integrated into the cantilever. We study the thermal conductivity of PS-b-PMMA block copolymers with different pitches and different orientations. This technique represents an advance in the investigation of polymeric surfaces due to its high resolution and good material sensitivity.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Includes bibliographical references.
There is significant interest from both the academic and industrial communities for understanding and controlling the self-assembly behavior of complex macromolecular systems and has been an active area of research in recent years. Such systems can be designed to result in a wide range of nanoscale morphologies and greater functionality can be introduced with increasing complexity.This thesis focuses on the synthesis and characterization of a class of side chain liquid crystalline block copolymers (SCLCBCPs) that are based on a low glass transition temperature (Tg) siloxane backbone. Moieties that self-assemble into smectic liquid crystalline (LC) phases are covalently attached to the polystyrene-polyvinylmethylsiloxane (PS-PVMS) block copolymer backbone. Precise control over the functionalization of the LCs onto the functional siloxane backbone allows for unique control over the self-assembly and the resulting properties of the system. The LC content significantly affects the stability of the smectic mesophase and subsequently the interactions with the inter-material dividing surface (IMDS) with the PS domains. A strong preference for homogenous anchoring of the LC moieties relative to the IMDS is observed, and increasing the LC content intensifies the preference for this arrangement. Utilizing the effects of LC anchoring to alter the self-assembly behavior is a reoccurring theme throughout this work. Additionally, the mechanical properties of these materials can be precisely manipulated over several orders of magnitude through variations in LC content and the block copolymer backbone architecture.Several methods can be used to manipulate the morphologies of these materials once synthesized including, thermal annealing and mechanical deformation.
(cont.) Thermal annealing provides additional mobility for self-assembly often resulting in morphological rearrangements. Mechanical deformation can be used to orient the self-assembled structures relative to an applied shear flow. Additionally, the self-assembled morphologies of spin cast into thin films were investigated. The presence of the substrate has significant effects upon the orientation of the morphologies; thermal annealing and variations liquid crystal content are shown to be useful tools for achieving a wide range of thin film morphologies.
by Eric Anton Verploegen.
Ph.D.

This thesis explores the fabrication processes and the optical characterization of a metamaterials made by block copolymer self-assembly. Optical metamaterials are artificial systems designed to produce optical properties that may not be found in nature. They gain their properties not from their chemical composition but rather from their desig structure that affects the interaction with electromagnetic waves, producing an optical response different from the constituent material. The structural features have sub-wavelength size so that the metamaterial is perceived homogeneous by the incident waves and the electromagnetic response is expressed in terms of homogenized material parameters. In this work such structural features will be fabricated well below optical wavelengths by metal replica of a gyroid morphology generated by block copolymer self-assembly. Block copolymers consist of two or more chemically different polymers that are covalently tethered. Self-assembly in such systems is driven by enthalpy reduction through microphase separation that minimizes unfavourable interfaces, leading to a range of potential morphologies. The gyroid morphology consists of a continuous three dimensional structure with constant mean curvature and chiral directions. The gold gyroid effectively behaves as a metamaterial with its own distinct optical characteristics: a reduced plasma frequency and highly enhanced transmission, an hall mark of optical metamaterials. The optical characterization discussed in this dissertation showed good agreement with infinite difference time domain (FDTD) calculations and analytical models. The optical properties of the fabricated metamaterials were successfully tuned by modifying the structural dimensions and the surrounding mediums. The transmission efficiency was, then, further enhanced by fabricating an hollow gyroid structure with increased surface area. The hollow gyroid enabled also the fabrication of composite metamaterial employing the combination of different metals in the 3D continuous structure. Next, exible and stretchable metamaterial were fabricated by infiltrating an elastomer around the gyroid network, paving the way for practical applications. Finally, the gyroid metamaterial was used as vapour sensor, exploiting the regular pore size and the variation of the optical response with surrounding media.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Block copolymers microphase separate to form periodic patterns with period of a few nm and above without the need for lithographic guidance. These self-assembled nanostructures have a variety of bulk geometries (alternating lamellae, gyroids, cylinder or sphere arrays, tiling patterns, core-shell structures) depending on the molecular architecture of the polymer and the volume fraction of its blocks. And in thin films, surface interaction and commensurability effect influence the self-assembly and result in more diverse morphologies including hexagonal-packed perforated lamellae, square array of holes. The progress of self-assembly can be tracked in situ using Grazing Incidence Small Angle X-ray Scattering, and the annealed morphology can be revealed in 3D using TEM tomography. Moreover, non-bulk morphologies can be produced, the ordering of the microdomains can be improved and their locations directed using various templates and processing strategies. The blocks can themselves constitute a functional material, such as a photonic crystal, or they can be used as a mask to pattern other functional materials, functionalized directly by various chemical approaches, or used as a scaffold to assemble nanoparticles or other nanostructures. Block copolymers therefore offer tremendous flexibility in creating nanostructured materials with a range of applications in microelectronics, photovoltaics, filtration membranes and other devices.
by Wubin Bai.
Ph. D.

Ce travail de thèse propose une nouvelle approche pour la préparation de membranes à matrice mixte basée sur l’utilisation de copolymères à blocs et de nanoparticules inorganiques disposant de propriétés magnétiques. Des aggrégats de copolymères ont été préparés avec une morphologie variée (sphères, cylindres et vésicules) à partir du copolymère poly(acide méthacrylique)-b-poly(méthacrylate de méthyle). Ce dernier a été synthétisé par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) dans l’éthanol à 70°C. Des particules d’oxyde de fer ont, quant à elles, été préparées en présence de différents stabilisants à température variée pour permettre d’atteindre la charge de surface et les propriétés magnétiques recherchées. La structure des copolymères à bloc a permis d’obtenir à la fois des membranes hydrophobes via le procédé de séparation de phase induite par un non-solvant, ainsi que des membranes hydrophiles lorsque que la technique de spin-coating était appliquée aux aggrégats formés par auto-assemblage induit lors de la polymérisation. Grâce à l’étude détaillée des propriétés de filtration des membranes obtenues, la relation structure-propriété a été discutée sous l’action d’un champ magnétique externe. Enfin, la sensibilité au colmatage a été vérifiée via la filtration de solutions de protéines. Il a ainsi été démontré une diminution notable du colmatage sous champ magnétique, ouvrant de belles perspectives pour ces nouvelles membranes
This thesis presents a new approach to produce mix matrix membranes using block copolymers and inorganic nanoparticles having magnetic properties. The polymeric nanoparticle with different morphologies (linear, Spheres, worms, and vesicles), from poly (methacrylic acid)-b-(methyl methacrylate) diblock copolymer, were synthesized using Reversible addition−fragmentation chain transfer polymerization (RAFT) in ethanol at 70 ֠C. The inorganic counterpart, iron oxide nanoparticles were prepared using different stabilizers at various temperatures to acquire the necessary surface charge and magnetic properties. The chemistry of the particles leads to form both hydrophobic membranes using non-solvent induced phase separation as well as a hydrophilic membrane by using the simple spin coating technique with the particles from polymerization induced self-assembly. By a detailed experimental study of the membrane filtration, the influence of different parameters on the process performance has been investigated with and without magnetic field. Finally, membrane fouling has been studied using protein solution. Also, the membrane performance was examined under magnetic field revealing the successful reduction in the fouling phenomenon making them new performant membranes in the area of membrane technology

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Includes bibliographical references (leaves 88-93).
As device size decreases, conventional lithographic methods are finding it increasingly hard to keep up. Introduction of newer method such as E-beam, X-ray lithography etc. has demonstrated possibility of scaling to lower dimensions. However most of these methods are too expensive, too complex or too slow. Hence a method is required which can provide high resolutions at low cost, is easy to implement and can be integrated with current processing technologies. Block copolymer self assembly promises to do just that. An immiscible block copolymer will microphase separate into individual domains due to unfavorable mixing enthalpy. These microphase-separated blocks can have domain sizes of very low dimensions, to the order of 15-20 nms. By careful preparation, microphase-separated thin films of immiscible block copolymers can act as nanomasks for a variety of applications in electronic, optoelectronic and storage media fields. One such application is patterned media. With ever increasing areal densities, there is a limit to which the grain size within a bit can be decreased, for a conventional thin film media. Beyond a certain limit, which is dictated by the superparamagnetic effect, these grains will spontaneously reverse, resulting in undesired data loss. Patterned media has been proposed as an alternative to surpass this thermal instability criterion. In patterned media, lithographically defined nano-scale magnetic elements form single bits onto which the data is stored. Due to its unique structure in which each magnetic dots act as a single magnetic domain it can postpone the arrival of superparamagnetic effect beyond densities much higher than 10 Terabits/inch². However, very high resolutions and strict positioning control is required for its fabrication so as to attain a marketable 1Tb/inch² advantage.
(cont.) Block Copolymer self assembly holds great promise in fabrication of such devices requiring periodic, high resolution pattern generation. If issues such as long range order, pattern uniformity and placement accuracy of magnetic dots can be effectively resolved, block copolymer self assembly enabled lithography can quickly become the main stay of the multimillion dollar hard disk industry.
by Anay Chaube.
M.Eng.

The work presented in this Thesis focuses on the solution-phase self-assembly behaviour of a series of di- and triblock copolymers with semicrystalline, π-conjugated segments, namely poly(3-alkylthiophene) (P3AT) and poly(3-alkylselenophene) (P3ASe) derivatives. Our group has shown that crystallisation-driven self-assembly (CDSA) of P3AT and P3ASe block copolymers (BCPs) in block-selective solvents allows access to colloidally-stable nanofibers with π-conjugated cores. In this thesis, we demonstrate that the contour length of P3ASe nanofibers can be controlled using a seeded-growth technique. Furthermore, we show that hierarchical nanostructures can be accessed from the coassembly of P3ATs and P3ASes using sequential CDSA. This "bottom-up" methodology could be employed as a facile route to nanomaterials with controlled dimensions, interesting optoelectronic properties and potential applications in polymer-based devices.

Block copolymer (BCP) thin film patterns, generated using directed self-assembly (DSA) of diblock copolymers, have shown excellent promise as templates for semiconductor device manufacturing since they have the potential to produce feature pitches and sizes well below 20 nm and 10 nm, respectively, using current 193 nm optical lithography. The goal of this work is to explore block copolymers with sufficient thermodynamics driving force (as described by the Flory Huggins interaction parameter, χ) for phase separation at these smallest lengths scales. Here, poly(styrene)-b-poly(hydroxystyrene) is investigated since the PHOST domain is known to form extensive hydrogen bond networks resulting in increased χ due to this strong enthalpic interaction. In this work, nitroxide mediated polymerization (NMP) techniques were utilized to produce PS-b-PHOST diblock copolymers with a range of molecular weights (5000-30000) with low PDI approaching 1.2. The phase separation of low molecular weight PS-b-PHOST on neutral underlayer substrates via solvent annealing provided thin film vertical lamellae with 13 nm pitch. These results illustrate the improved resolution of PS-b-PHOST compared with the current industry standard of PS-b-PMMA (with 20 nm pitch). The directed self assembly of lamellar PS-b-PHOST patterns with 18 nm pitch via graphoepitaxy is demonstrated. Also, a highly selective atomic layer deposition (ALD) and etch technique was investigated which provided selective block removal of (PS-b-PHOST) block copolymer patterns which initially exhibited no inherent etch contrast. In this process, the PS domain is removed leaving a high fidelity etch relief pattern of the original block copolymer template. Finally, an alternative system is presented, namely Poly(trimethylsilylstyrene)-block-poly(hydroxystyrene) (PTMSS-b-PHOST), which utilizes silicon containing functionality in one of the blocks, providing high etch contrast. PTMSS-b-PHOST patterns were also exposed to oxygen plasma allowing selective block removal of the PS domain without the need for additional ALD processing steps.

The research presented in this thesis involves the development of a variety of synthetic routes which have enabled the preparation of a library of novel polymeric materials, primarily block copolymers containing a polyferrocenylsilane metalloblock. A large emphasis has been placed on the subsequent investigations into the self-assembly of these materials, where they have been found to form a variety of interesting nanostructures, making them candidates for use in a number of different scientific fields. An introduction to the principal areas of research of this thesis is given in Chapter 1. Block copolymer (BCP) self-assembly in the bulk is discussed, highlighting the interest in studying BCP systems exhibiting greater complexity. This is followed by a similar discussion concerning block copolymer self-assembly in the solution phase. The synthesis and selfassembly of BCPs containing polyferrocenylsilane is introduced. The final sections of the introduction are dedicated to block copolymer lithography and bit-patterned media. Miktoarm star terpolymers represent a class of BCPs which are comprised of three chemically distinct polymeric blocks joined at a single junction point. Previous studies into their bulk self-assembly have shown them to self-assemble into a large number of complex morphologies, including a range of Archimedean tiling patterns which aren't obtainable through the self-assembly of their linear triblock terpolymer counterparts. These materials could be utilised for block copolymer lithography, facilitating the fabrication of features ~xhibiting greater complexity than simpler diblock copolymer. In Chapter 2, the synthesis of a range of polystyrene-arm-polyisoprene-arm-poly(ferrocenylethylmethylsilane) miktoarm star terpolymers ()..t-SIF) is discussed; two synthetic routes were pursued, a chlorosilane route and a core-first route. In total, 5 j.l-SIFs were prepared. Their bulk self-assembly was investigated by transmission electron microscopy (TEM) and three different morphologies were obtained - two Archimedean tiling patterns ([8.8.4] and [12.6.4]) and a lamellae + cylinder morphology. Additionally, the thin film self-assembly and pattern transfer of one of the [8.8.4] Archimedean-tiling-pattern-forming j.l-SIFs is presented, demonstrating the applicability of these materials for use in block copolymer lithography. In addition to the structures formed by the self-assembly of block copolymers in the bulk and thin film, a wide variety of colloidally stable nanoscale architectures have been shown to be accessible through the solution self-assembly of block copolymers. The solution self-assembly of two j.l-SIF terpolymers is described in Chapter 3, one bearing a crystallisable poly(ferrocenyldimethylsilane) block (j.l-SIFc) and the other bearing an amorphous, non-crystallisable poly(ferrocenylethylmethylsilane) block (j.l-SIFa). The selfassembly of these materials was studied by TEM, atomic force microscopy (AFM) and dynamic light scattering (DLS), whereupon it was shown that the solvent and the 1 crystallisable nature of the PFS block have a profound influence on the micelle architectures formed. Spheres bearing phase-mixed cores and distorted spheres bearing phase-separated cores were obtained for j.l-SIFa in different solvents. For j.l-SIFc, a transition from distorted spherical micelles bearing a phase-separated core to elongated fibres bearing a phaseseparated core was observed. Additionally, cylindrical micelles with a phase-separated corona were obtained for Il-SIFc in another solvent. Finally, successful seeded growth studies with the crystallisable j.l-SIFc terpolymer were demonstrated, yielding B-A-B block co-micelles.

The continuous demand for small portable electronics is pushing the semiconductor industry to develop novel lithographic methods to fabricate the elementary structures for microelectronics devices with dimensions reduced size. Self-Assembly of Block copolymers is extremely appealing due to its excellent compatibility with conventional photolithographic processes, high-resolution patterns and low process costs. This thesis work will focus on the Self-Assembly of cylinderforming Block copolymers as promising next-generation technology for the fabrication of sub-20 nm structures. Two different BCPs were investigated: polystyrene-b- polymethylmethacrylate (PSb-PMMA) and Polystyrene-block- poly(dimethylsiloxane-random-vinylmethylsiloxane) (PS-b-P(DMS-r-VMS)).

Nanofabrication has been long characterized by a top-down approach for the definition of small features starting from large pieces of material. In this contest the process of size scaling in microelectronics devices is based on photolithography that is an advanced top-down technology. In order to design integrated circuits with small features with characteristic dimension below 20 nm, a new kind of approach is needed such as the bottom-up one of self-assembly systems. Indeed symmetric block copolymers are able to spontaneously phase separate into ordered nanoscale lamellar pattern, which can be fruitfully implemented into the fabrication of next generation of microelectronics devices. This thesis offers a systematic study of the thermodynamics and kinetics of the self-assembly process of lamellae forming block copolymers in view of their possible exploitation as lithographic materials.

In the present work we have synthesized two-component block copolymers MOPEO-b-PААm and PААm-b-PЕО-b-PААm comprised methoxypoly(ethylene oxide), poly(ethylene oxide) and chemically complementary polyacrylamide. These copolymers we used as special matrices in the process of borohydride reduction of Ag+ ions. It was established the influence of chemical nature, molecular architecture and concentration of the matrices and the content of silver nitrate on some reaction parameters, size and stability of Ag-nanoparticles in aqueous solutions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34965

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Block copolymer (BCP) self-assembly is attractive because it provides nanoscale long-range ordered structures in a massive quantity. The capability of generating features with size as low as 5 nm is of particular interest in semiconductor fabrication since current photolithography has reached its resolution limitation and the other competing technologies are either too slow such as e-beam lithography or too expensive such as EUV system. In this thesis, BCP lithography is utilized to fabricate magnetic nanostructure and the corresponding magnetic properties are explored. The polystyrene- b-polydimethylsiloxane (PS-b-PDMS) diblock copolymer with different molecule weight is used to generate various sizes of robust silica pattern after solvent annealing and reactive ion etching. Pattern transfer methods are developed to convert the silica pattern into functional materials, including magnetic materials like cobalt, Co/Pd, FePt and CoFeB magnetic tunnel junctions (MTJ), and MoS2 monolayers. For magnetic nanowire arrays, the interactions between neighboring wires are investigated. For perpendicular MTJ nanopillar arrays, the size-dependent switching behavior and magnetostatic effects between two layers are analyzed. MoS 2 monolayers are patterned into features such as nanodots, nanorods and nanomeshs and the corresponding photoluminescence are characterized. Finally, machine learning and deep learning algorithms are the first-time ever demonstrated to model the BCP self-assembly process. The built model is able to recognize different BCP patterns and predicting the resulting morphology and pattern quality based on experimental process parameters. With this model, the BCP self-assembly can be further optimized toward industrial-grade production.
by Kun-Hua Tu.
Ph. D.

博士
國立清華大學
化學工程學系
96
The self-assembly of synthetic supramolecules has been inspired by using the secondary interactions, and has already created a large number of nanoscale architectures. Among self-assembled architectures, helical morphology is probably the most fascinating morphologies in nature. Chirality of compounds has been referred to one of the main origins for the formation of helical textures. For the self-assembly of block copolymers (BCPs), one-, two-, or three-dimensional periodic nanostructures can be easily tailored by molecular engineering of synthetic BCPs. By taking the advantage of the BCP self-assembly and the specific configuration of chirality, chiral block copolymers (BCP*), poly(styrene)-block-poly(L-lactide) (PS-PLLA), containing both achiral PS and chiral PLLA blocks was designed for self-assembly. A unique transmission electron microscopy observation and small-angle X-ray scattering pattern for the self-assembled PS-PLLA nanostructure revealed the novel morphology of a hexagonally packed nanohelical phase. On the basis of the geometric features, the space group of the new nanohelical phase was identified as P622. The formation of the nanohelical phase from the BCP* self-assembly is thus referred to the contribution of chiral entities and might provide a new concept for design of the helical morphology in bulk. Because of large-size polymeric chains, the molecular chain dynamics is critical for the formation of stable and equilibrium morphology. Thermally induced transitions between the microphase-separeated morphologies are well known such as a HEX to BCC, a HPL to gyriod and a gyroid to HEX phase by varying the Flory interaction parameter x (a function of 1/T) at fixed block copolymer composition. In this study, to finely control formation of the helical morphology, metastability and order-disorder transition temperature for the nanohelical phase was examined by using time-resolved small-angle X-ray scattering and corresponding transmission electron microscopy. The phase transition of PS-PLLA after solution casting from a HPL to nanohelix was obtained by thermal annealing. With substantial time for annealing, the formed nanohelical phase might transform to a HEX phase; suggesting that the nanohelix is a metastable phase. Also, molecular weight effect on the formation of the nanohelical morphology was examined at a constant composition. The appearance of a gyriod instead of nanohelical phase for low-molecular-weight PS-PLLA indicates the formation of nanohelical phase is dependent upon segregation strength. To manipulate the three-dimensionally packed nanohelical morphology from BCP* in bulk, various stimuli were applied such as crystallization and shear stress. The self-assembled nanohelices can transform into crystallization- and shear-induced cylinders. The stress-induced cylinders (stretched nanohelices) were found thermally reversible upon annealing through undulation. As a result, the hexagonally packed PLLA nanohelices in PS matrix of chiral PS-PLLA block copolymers appear as spring-like behavior in response to the applied stimuli. This unique phase behavior thus creates a possible way for manipulating switchable nanohelical structures in practical applications. Since the crystallization-induced cylinder from nanohelical phase can be achieved by control of crystallization temperature, comprehension of the crystalline details within the nanohelical microdomain is critical. Various crystalline PS-PLLA nanostructures were obtained by controlling the crystallization temperatures of PLLA (Tc,PLLA) at which crystalline nanohelices (PLLA crystallization directed by helical confined microdomain) and crystalline cylinders (stretching of helical nanostructure dictated by crystallization) occur while Tc,PLLA