Littérature scientifique sur le sujet « Coordinative Chain Transfer Polymerization »

The interest in the Coordinative Chain Transfer Polymerization (CCTP) of a family of naturally occurring hydrocarbon monomers, namely terpenes, for the production of high-performance rubbers is increasing year by year. In this work, the synthesis of poly(β-myrcene) via CCTP is introduced, using neodymium versatate (NdV3), diisobutylaluminum hydrade (DIBAH) as the catalytic system and dimethyldichlorosilane (Me2SiCl2) as the activator. A bimodal distribution in the GPC signal reveals the presence of two populations at low conversions, attributable to dormants (arising from reversible chain transfer reactions) and dead chains (arising from termination and irreversible chain transfer reactions); a unimodal distribution is generated at medium and high conversions, corresponding to the dominant species, the dormant chains. Additionally, a mathematical kinetic model was developed based on the Method of Moments to study a set of selected experiments: ([β-myrcene]0:[NdV3]0:[DIBAH]0:[Me2SiCl2]0 = 660:1:2:1, 885:1:2:1, and 533:1:2:1). In order to estimate the kinetic rate constant of the systems, a minimization of the sum of squared errors (SSE) between the model predicted values and the experimental measurements was carried out, resulting in an excellent fit. A set of the Arrhenius parameters were estimated for the ratio [β-myrcene]0:[NdV3]0:[DIBAH]0:[Me2SiCl2]0 = 660:1:2:1 in a temperature range between 50 to 70 °C. While the end-group functionality (EGF) was predominantly preserved as the ratio [β-myrcene]0:[NdV3]0 was decreased, higher catalytic activity was obtained with a high ratio.

The pyridylamido hafnium complex (I) discovered at Dow is a flagship catalyst among postmetallocenes, which are used in the polyolefin industry for PO-chain growth from a chain transfer agent, dialkylzinc. In the present work, with the aim to block a possible deactivation process in prototype compound I, the corresponding derivatives were prepared. A series of pyridylamido Hf complexes were prepared by replacing the 2,6-diisopropylphenylamido part in I with various 2,6-R2C6H3N-moieties (R = cycloheptyl, cyclohexyl, cyclopentyl, 3-pentyl, ethyl, or Ph) or by replacing 2-iPrC6H4C(H)- in I with the simple PhC(H)-moiety. The isopropyl substituent in the 2-iPrC6H4C(H)-moiety influences not only the geometry of the structures (revealed by X-ray crystallography), but also catalytic performance. In the complexes bearing the 2-iPrC6H4C(H)-moiety, the chelation framework forms a plane; however, this framework is distorted in the complexes containing the PhC(H)-moiety. The ability to incorporate α-olefin decreased upon replacing 2-iPrC6H4C(H)-with the PhC(H)-moiety. The complexes carrying the 2,6-di(cycloheptyl)phenylamido or 2,6-di(cyclohexyl)phenylamido moiety (replacing the 2,6-diisopropylphenylamido part in I) showed somewhat higher activity with greater longevity than did prototype catalyst I.

Thesis (Ph. D.)--University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Le nouveau complexe Cp*La(BH4)2(THF)2 a été utilisé en combinaison avec des alkyles magnésiens et aluminiques pour la (co)polymérisation coordinative par transfert de chaîne (CCTP) du styrène et de l’isoprène. En développant ce concept nous avons obtenu la première croissance de chaîne catalysée du styrène et de l’isoprène avec contrôle de la microstructure. L’application de la CCTP à la copolymérisation statistique est une voie nouvelle et originale pour le contrôle de la composition de copolymères.Par ailleurs, une étude mécanistique a été réalisée pour la polymérisation de l’ ε-caprolactone avec des dérivés cationiques de ruthénium [(η5-C5H5)Ru(η6-arène substitué)][PF6]. Nous avons montré que la polymérisation a lieu selon un mécanisme de type monomère activé avec transfert aux alcools, avec modification de l’hapticité du ligand arène
A newly synthesized Cp*La(BH4)2(THF)2 complex in combination with magnesium or aluminum alkyls was used for the coordinative chain transfer (co)polymerization (CCTP) of styrene and isoprene. Using this concept, we have accomplished the first catalyzed chain growth like reaction of styrene and isoprene, with control of the microstructure. The application of CCTP to statistical copolymerization represents a new and original approach to tune the composition of copolymers. In addition, a mechanistic study of the ring-opening polymerization of ε-caprolactone by [(η5-C5H5)Ru(η6-substituted arene)][PF6] complexes shows that the polymerization proceeds via an activated monomer mechanism by transfer to the alcohol with a change of hapticity of the arene ligand

Une série de ligands L1-L11 à base d'iminopyridine/iminoquinoline du type 11-[(Ar)N=C(R)]-R' (Ar = 2,6-Me2-C6H3 ou 2,6-iPr2-C6H3 ou 3,5-(CF3)2-C6H3 ou C6F5, R = H ou Me et R’ = 2-C6H5N ou 2-C6H4N-5-Me ou 2-C9H7N ou 8-C9H7N) et leurs complexes de fer (II) correspondants ont été développés. Les complexes ont été entièrement caractérisés, y compris par diffraction des rayons X pour les nouveaux complexes (6-11), et leurs applications catalytiques ont été étudiées pour la polymérisation coordonnée contrôlée de l'isoprène. La modulation des propriétés stériques et électroniques au sein de cette famille de ligands/complexes s'est avérée influencer la stéréosélectivité et l'activité de la polymérisation de l'isoprène après activation avec divers cocatalyseurs. Les catalyseurs obtenus ont produit des polyisoprènes avec une excellente conversion, une activité élevée et une variété de stéréo-/régio-régularités. Certains de ces catalyseurs ont également été évalués pour la polymérisation coordinative du styrène et ont montré une bonne activité pour la formation de polystyrènes syndiotactiques enrichis. Une autre méthodologie organométallique a été utilisée pour la synthèse de ligands d'aminopyridine (rac-L1H and rac-L2H) et de leurs complexes d'amides de fer correspondants 12 ((L1)2Fe), 13Py et 14Py (LnFe[N(SiMe3)2](Py)) pour leur application dans la (co)polymérisation par ouverture de cycle de L-lactide et ε-caprolactone où les complexes 13Py et 14Py se sont avérés efficaces
A series of iminopyridine-/iminoquinoline-based ligands L1-L11 of type 11-[(Ar)N=C(R)]-R’ (Ar = 2,6-Me2-C6H3 or 2,6-iPr2-C6H3 or 3,5-(CF3)2-C6H3 or C6F5, R = H or Me and R’ = 2-C6H5N or 2-C6H4N-5-Me or 2-C9H7N or 8-C9H7N) and their corresponding iron (II) complexes were developed. The complexes were fully characterized including by X-ray for new complexes (6-11) and their catalytic applications were investigated for the controlled coordinative polymerization of isoprene. The modulation of steric and electronic properties within this family of ligands/complexes has shown to influence the stereo-selectivity and activity of the polymerization of isoprene after activation with various cocatalysts. The resulting catalysts produced polyisoprenes with an excellent conversion, high activity and a variety of stereo-/regio-regularities. Some of these catalysts were also assessed for the coordinative polymerization of styrene and displayed good activity for the formation of syndiotactic enriched polystyrenes. Another organometallic methodology has been utilized for the synthesis of aminopyridine ligands (rac-L1H and rac-L2H) and their corresponding iron amide complexes 12 ((L1)2Fe), 13Py and 14Py (LnFe[N(SiMe3)2](Py)) for their application in the Ring-Opening (Co)polymerizaion of L-lactide and ε-caprolactone where the complexes 13Py and 14Py proved to be effective

Thesis (PhD)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: To comply with the ever growing demands for materials with better properties and complex architectures, polymer chemistry has resorted to the use of living free radical polymerization techniques. Despite the structural control some of these techniques offer, major disadvantages do exist. For example, most require ultra-pure reagents, hence only a small fraction of the monomers used in industry can be polymerized in this way. This rendered these new living techniques less advantageous from a commercial point of view. Recently, a revolutionary new living free radical process, namely the reversible addition-fragmentation chain transfer process, or RAFT process, was developed that combines the control over the polymer produced with the robustness and versatility of a free radical process. However, the RAFT process is not without its problems. In some dithioester mediated polymerizations, significant inhibition and rate retardation effects have been observed. Two main opposing opinions have been proposed in recent literature to explain these phenomena observed. The main point of difference between these two groups is the fate of the formed intermediate RAFT radicals, i.e., slow fragmentation of the formed intermediate radicals together with possible reversible intermediate RAFT radical termination, or fast fragmentation of the formed intermediate radicals together with possible irreversible intermediate RAFT radical termination. Between these opposing two groups, there is a difference of six orders of magnitude for the rate of fragmentation of the formed intermediate RAFT radicals. The work presented in this thesis is an attempt to clarify some of the mysteries, i.e., inhibition and rate retardation observed in some RAFT polymerizations. Experimental evidence to support or contradict the theories of the above mentioned two opposing groups was investigated. The concentration-time evolution of the intermediate radical concentration (cy), for styrene and butyl acrylate polymerizations mediated by cumyl dithiobenzoate (COB) at 70°C and 90 °C, was followed via in situ electron spin resonance spectroscopy (ESR). The concentration-time evolution profiles observed were ascribed to the formation of very short chains during the early stages of the reaction. It was also found that the RAFT process is not particularly sensitive to oxygen. The intermediate and propagating radical (cp) concentrations (and their ratio) for the cumyl dithiobenzoate mediated styrene polymerizations were examined by ESR spectroscopy and kinetics. The system showed strong chain length effects in kinetics, assuming all chains were of similar number average molar mass (Mn). However, unusual behavior with respect to existing mechanistic knowledge was observed in other aspects of the system. The central equilibrium "constant" (Keq) was found to be dependent on both temperature and initial reactant concentrations. The observed intermediate radical concentrations were not consistent with predictions based on existing literature models. It was also found that the time dependence of the intermediate radical concentration varies significantly with the type of RAFT agent used. Unexpectedly, intermediate radicals were detected at very long reaction times in the virtual absence of initiator, enhancing the belief of possible reversible termination reactions involving the intermediate radicals. An extra radical (nonpropagating or intermediate) species was observed (via ESR spectroscopy) to form during some reactions. Its concentration increased with time. The combination of data from several analytical techniques provided evidence for the formation of dead chains by the termination of intermediate radicals in the free radical polymerization of styrene, mediated by a cumyl dithiobenzoate RAFT agent, at 84°C. Experiments done focused on the early stages of the reactions, targeting very low final number average molar mass values, with high initiator concentrations. The formation of these terminated chains did not occur to a significant extent until a large fraction of the chains reached a degree of polymerization greater than unity. This corresponded to the occurrence of a maximum in intermediate radical concentration. In situ 1H nuclear magnetic resonance (NMR) and electron spin resonance spectroscopy was used to directly investigate the processes that occur during the early stages (typically the first few monomer addition steps) of an AIBN-initiated reversible addition fragmentation chain transfer polymerization of styrene, in the presence of a cyanoisopropyl dithiobenzoate and cumyl dithiobenzoate RAFT agent, at 70°C and 84 °C respectively. 1H NMR spectroscopy allowed the investigation of the change in concentration of important dithiobenzoate species as a function of time. Identification and concentrations of the radicals present in the system could be inferred from corresponding ESR spectroscopy data. An apparent "inhibition" effect was observed in both the cyanoisopropyl and cumyl dithiobenzoate mediated polymerizations. This effect could be reduced by increasing the reaction temperature to 84 °C. However, the use of cumyl dithiobenzoate as RAFT agent prolonged this effect. This apparent "inhibition" effect was attributed to selective fragmentation of the formed intermediate radicals during the early stages of the reaction, and to different propagation rate coefficients (kp) of the resulting (different) radicals. A change in the equilibrium coefficient for the systems investigated was ascribed to possible progressively decreasing addition and fragmentation rate coefficients of propagating and intermediate radicals formed during the reaction. The increase in intermediate radical concentration, and thus possible intermediate radical termination, was shown to also be a probable cause of the rate retardation observed in the RAFT mediated systems investigated. To conclude, probable causes of the observed inhibition and rate retardation in some dithiobenzoate mediated systems were investigated. It was found that intermediate RAFT radical termination does occurs, albeit reversibly or irreversibly. A maximum in the intermediate radical concentration, and thus possible intermediate radical termination, was seen to occur during the observed rate retardation. An apparent inhibition effect observed was ascribed to a possible change in termination kinetics, the formation of terminated intermediate radical products and a rapidly changing kp of the propagating radicals.
AFRIKAANSE OPSOMMING: Om te voldoen aan die ewig groeiende aanvraag vir materiale met beter eienskappe en komplekse samestellings, is in die polimeerchemie lewende vry-radikaal polimerisasietegnieke ontwikkel. Ten spyte van die feit dat party van die polimerisasie tegnieke die strukuur van die gevormende polimere kan beheer, bestaan daar tog nadele. Die meeste polimerisasie tegnieke benodig ultra suiwer reagense, dus kan net 'n klein fraksie van die monomere wat deur die industrie gebruik word op so 'n manier gepolimeriseer word. Dus, vanuit 'n komersieële oogpunt, is die nuwe lewende polimerisasietegnieke minder voordelig. Onlangs is 'n revolusionere nuwe lewende vry-radikaal polimerisasieproses, naamlike die RAFT-(eng. reversible addition-fragmentation chain transfer process) proses ontwikkel, wat die beheer oor die geproduseerde polimere, kombineer met die robuustheid en veelsydigheid van 'n vry-radikaalproses. Die RAFT proses is egter nie sonder probleme nie. Beduidende inhibisie en vertraging van die polimerisasie tempo is in sommige dithioester-bemiddelde polimerisasies opgemerk. Daar is hoofsaaklik twee opponerende opinies oor die redes vir die inhibisie en vertragings effekte. Die grootste verskil tussen die twee groepe lê in die lot van die gevormde intermediêre radikaal, m.a.w. stadige fragmentasie van die gevormende intermediêre radikale tesame met moontlike onveranderlike intermediêre radikaalterminasie, of vinnige fragmentasie tesame met moontlike omkeerbare intermediêre radikaalterminasie. Tussen die twee groepe, is daar 'n verskil van ses ordegrotes vir die groote van die tempo van fragmentasie van die gevormende intermediêre radikaal. Die werk wat in die tesis weergee word, is 'n poging om sommige van die geheime van die RAFT proses, m.a.w. inhibisie en vertraging van die polimerisasietempo, op te los. Die ondersoek was gerig op eksperimetele bewyse om die teorieë van die twee opponerede groepe of te bevestig of teen te spreek. Die konsentrasie tyd-verandering van die intermediêre radikaal konsentrasie vir stireen- en butielakrilaatpolimerisasie, bemiddeled deur CDB (eng cumyl dithiobenzoate) by 70 oe and 90 oe, is gevolg deur middel van in situ (lat. vir in die oorspronklike plek, m.a.w. binne-in die ESR masjien) elektronspin-resonans (ESR) spektroskopie. Die vorm van die konsentrasie tyd-profiele is toegeskryf aan die vorming van baie kort polimeerkettings gedurende die vroeë reaksietye. Dit is ook bepaal dat die RAFT-proses nie besonder sensitief was vir suurstof nie. Die intermediêre en die propagerende radikaalkonsentrasie (en hulle verhouding) vir die CDB bemiddelde stireen polimerisasies, is bepaal deur middel van elektronspin-resonans spektroskopie en die kinetika van die sisteem. Die kinetika van die sisteem toon 'n sterk afhanklikheid teenoor die lengte van die polimeerkettings, as aanvaar word dat al die kettings dieselfde numeriese gemiddelde molêre massa het. Des nieteenstaande, is egter onverwagte gedrag in ander aspekte van die sisteem opgemerk. Dit was ook gevind dat die sentrale ewewigs-"konstante" (Keq) afhanklik was van die temperatuur en die oorspronklike reaktant konsentrasie. Die bepaalde intermediêre radikaalkonsentrasie het verskil van voorspelde waardes gebaseer op literatuur modelle. Dit is ook gevind dat die intermediêre radikaalkonsentrasie afhanklik is van die tipe RAFT agent wat in die polimerisasie reaksies gebruik word. Intermediêre radikale is onverwags gevind na baie lang reaksietye, wanner verwag is dat die konsentrasie van die afsetter, en dus ook die intermediêre radikale, baie klein sou wees. Dit het die verwagting dat omkeerbare intermediêre radikaalterminasie kan plaasving, versterk. 'n Ekstra radikale spesie, wat gedurende die reaksie vorm en waarvan die konsentrasie groter word met tyd, is ook deur ESR-spektroskopie geidentifiseer. 'n Kombinasie van verskillende skeikundige tegnieke is gebruik om bewyse te kry vir die vorming van dooie kettings wat ontstaan deur middel van intermediêre radikale terminasiereaksies, in die vry-radikaalpolimerisasie van stireen, wat deur 'n CDB RAFT-agent bemiddeled word by 84°C. Eksperimente is gedoen om die reaksie tydens vroeë reaksietye te ondersoek. Baie hoë afsetter konsentrasies is ook gebruik, wat tot uiters lae numeriese gemiddelde molêre massas van die polimeerkettings gelei het. Beduidende konsentrasies van die dooie kettings is eers gevind nadat 'n graad van polimerisasie van groter as een bereik is. Dit het ooreengestem met 'n maksimum in die konsentrasie van die intermediêre radikale. In situ 1H kern magnetiese-resonans (KMR) en electronspin-resonans spektroskopie was gebruik om 'n RAFT proses, wat gedurende die vroeë reaksie tye (tipies gedurende die eerste paar monomeer toevoegingstappe) te bestudeer, wat deur AIBN (eng azo bis(isobutyronitrile)) afgeset word en bestaan uit stireen en CIDB (eng cyanoisopropyl dithiobenzoate) en CDB RAFT agente onderskeidelik, en by 70°C and 84 °C reageer. 1H KMRspektroskopie was gebruik om die veranderinge in die konsentrasie van die belangrike spesies te bepaal. Die identifikasie en konsentrasie van die radikale kon bepaal word deur middel van ESR data. 'n Skynbare 'inhibisie-effek' is waargeneem in die reaksies wat bemiddeled word deur CIDB en CDB. Die effek is verminder toe die reaksietemperatuur verhoog is na 84°C. Die gebruik van CDB as RAFT agent het egter die effek vergroot. Die skynbare 'inhibisie effek' was toegeskryf aan die selektiewe fragmentasie van die intermediêre radikale gedurende die vroeë reaksietye, en aan verskillende propagasie tempokoëffisiënte (kp) van die verskillende radikale. Die veranderlike sentrale ewewigskoëffisiënte is toegeskryf aan die toevoegings en fragmentasie tempokoëffisiënte van die propagerende en intermediêre radikale wat toenemend afneem. Die is ook getoon dat die toename in die konsentrasie van die intermediêre radikale en dus moontlike intermediêre radikale terminasie, 'n oorsaak kan wees van die vertraging van die polimerisasietempo in die RAFT-bemiddelde reaksies. Ter samevatting, die waarskynlike oorsake vir inhibisie en die polimerisasietempo vertraging opgemerk in sekere dithiobenzoaat-bemiddelde sisteme, is ondersoek. Dit was gevind dat intermediêre radikaalterminasie wel kan gebeur, of dit nou omkeerbaar of onveranderlik gebeur. 'n Maksimum in die konsentrasie van die intermediêre radikale, en dus moontlike intermediêre radikaalterminasie, het voorgekom tesame met 'n vertraging in die polimerisasietempo. Die skynbare inhibisie-effek wat opgemerk was kan toegeskryf word aan 'n moontlike verandering in die terminasie kinetika, die formasie van getermineerde intermediêre radikale en 'n vinnig veranderende propagasie tempokoëffisiënt.

Reversible addition fragmentation chain transfer (RAFT) polymerization is a very versatile way to generate synthetic polymeric materials. Multiblock copolymers have received enormous scientific interest recently due to the ability to mimic the sequence-regulated microstructure of biopolymers. The objective of this thesis was to investigate RAFT polymerization and explore its potential in the synthesis of sequence-controlled multiblock polymeric chains, and their use to tune the micro-structure of the polymers, engineer single chain polymeric nanoparticles, and fabricate functional polymeric nanomaterials. This work firstly addresses the investigation of the enormous ability of sequence-controlled multiblock copolymer to tune the physical properties by altering their microstructure. A series of sequence controlled multiblock copolymers were synthesized by RAFT polymerization using ethylene glycol methyl ether acrylate and tert-butyl acrylate as monomers. These block copolymers were synthesized with an alternating order of the two monomers with a similar total degree of polymerization. The number of blocks was varied by decreasing the length of each block while keeping the ratio of monomers constant. Their microphase separation was studied by investigating the glass transition temperature utilizing differential scanning calorimetry analysis. Small angel X-ray scattering analysis was also applied to investigate the transition of the microphase separation with the variation of the segmentations of these multiblock copolymers. The study found the microstructure was significantly affected by the number of segments of the polymer chain whilst keeping the total length constant. Having demonstrated the enormous potential of sequence controlled multiblock copolymers to access defined microstructures, further studies were focused on mimicking the controlled folding process of the peptide chain to a secondary and tertiary structure using sequence controlled multiblock copolymers. RAFT polymerization was used to produce multiblock copolymers, which are decorated with pendant cross-linkable groups in foldable sections, separated by non-functional spacer blocks in between. An external cross linker was then used to cause the folding of the specific domains. A chain extension-folding sequence was applied to create polymer chains having individual folded subdomains. In order to achieve a further step on the way to copy nature’s ability to synthesize highly defined bio-macromolecules with a distinct three dimensional structure, linear diblock copolymer precursors were synthesized by RAFT polymerization. One block of the precursor with pendant functional groups was folded using an external cross-linker to form tadpole-like single chain nanoparticles (SCNPs). These tadpole-like SCNPs could then self-assemble into a more complex stimuli responsive 3D structure by adaptation to environmental pH changes. The stimuli responsive assemblies were found to be able to dissociate responding to low pH or exposure to glucose.

Polymer Chemistry: A Practical Approach in Chemistry has been designed for both chemists working in and new to the area of polymer synthesis. It contains detailed instructions for preparation of a wide-range of polymers by a wide variety of different techniques, and describes how this synthetic methodology can be applied to the development of new materials. It includes details of well-established techniques, e.g. chain-growth or step-growth processes together with more up-to-date examples using methods such as atom-transfer radical polymerization. Less well-known procedures are also included, e.g. electrochemical synthesis of conducting polymers and the preparation of liquid crystalline elastomers with highly ordered structures. Other topics covered include general polymerization methodology, controlled/"living" polymerization methods, the formation of cyclic oligomers during step-growth polymerization, the synthesis of conducting polymers based on heterocyclic compounds, dendrimers, the preparation of imprinted polymers and liquid crystalline polymers. The main bulk of the text is preceded by an introductory chapter detailing some of the techniques available to the scientist for the characterization of polymers, both in terms of their chemical composition and in terms of their properties as materials. The book is intended not only for the specialist in polymer chemistry, but also for the organic chemist with little experience who requires a practical introduction to the field.

A novel concept is proposed to manipulate droplets without external power sources in this study. The proposed device is a hydrophobic surface containing specific roughness gradients, which is composed of several textured regions with gradually increased structural roughness. Four types of hydrophobic materials, AZ6112, Teflon, Parylene C, and plasma polymerization fluorocarbon film (PPFC), are adopted to fabricate the textured surfaces and tested. Actuating forces come from the different Laplace pressures exerting on a droplet across different hydrophobic surfaces, whereas dragging forces come from the contact angle hysteresis. Two patterns of devices are shown in this article, the chain-shaped and the concentric circular. The former functions as a droplet transporting route and the latter provides both transporting and orientation functions. Theoretical estimation and experimental verification of the droplet motion, including actuation and drag forces, on the device are conducted. Optimal design will be achieved based on accurate estimations of the acting forces. The proposed device provides a simpler fabrication process and shows better biocompatibility for droplet manipulation in microfluidic systems.

Abstract Non-aqueous fluids (NAF) are considered as efficient and reliable drilling fluid systems for challenging wellbore conditions, such as high-temperature drilling operations. NAFs require fluid loss control additives to reduce filtration loss into the formation with minimum filter cake thickness. Polymer developed in this work demonstrated exceptional properties such as high dispersibility, good thermal stability and low plastic viscosity, when compared with traditional natural and synthetic-based fluid loss control additives (e.g., gilsonite). We have utilized a synthetic molecular optimization process to precisely adjust the hydrophilic-lyophilic balance (HLB) by altering the ratio of hydrophilic to hydrophobic monomers. This has allowed us to achieve an HLB that facilitates easy dispersion within NAF formulations. The star polymer was produced using a controlled/radical polymerization technique called Reversible Addition Fragmentation Chain Transfer polymerization (RAFT). The properties of the NAFs, such as rheology, fluid loss, mud cake thickness, and emulsion stability, were evaluated and compared with commercially available fluid loss control additives under simulated downhole pressure and temperature conditions. The chemical structure and thermal stability of the star polymer were analyzed using spectroscopy and thermogravimetric analysis. The spectroscopic studies confirmed the formation of desired polymeric structures and the molecular weight desired. Star-polymer synthesized herein has excellent thermal stability up to 450 °F with great fluid loss control and ultrathin filter cake for NAF systems for mud weight ranging from 10 to 17 lbm/gal. The star polymer also improves emulsion stability. Plastic viscosity (PV) is usually increased with the addition of commercially available fluid loss control additives; however, star-polymer had a negligible effect on PV. Results for both diesel and mineral oil-based mud systems will be presented. High-temperature high-pressure viscometer (Fann 77) was used to study rheological properties at up to 350 °F and 10,000 psi. Our recent work has resulted in the creation of a cutting-edge star polymer (NSP) for use in the industry's next-gen high-performance fluid loss additives. The polymer network can be efficiently synthesized and scaled up for commercial production, providing engineers with an improved solution for drilling high-temperature wells (up to 350°F) with reduced plastic viscosity and increased emulsion stability, while also providing excellent fluid loss control.

Amphiphilic thermoresponsive block copolymers and ABA type PEG-Lipid conjugated macromolecules have been synthesized using microwave-assisted reversible addition-fragmentation chain transfer (RAFT) polymerization and the copper-catalyzed azide-alkyne cycloaddition, commonly termed “click chemistry”, respectively. Characterization of the block copolymers and conjugates has been carried out with the help of 1H-NMR, FTIR and GPC. These copolymers and conjugates were evaluated for the encapsulation and release of drugs. Carbamazepine, an anticonvulsant drug with poor water solubility was selected to be a hydrophobic drug model in the study. The micellization, drug encapsulation and release behavior of macromolecules was investigated by dynamic light scattering (DLS), transmission electron microscope (TEM) and fluorescence spectroscopy. From the results, it has been concluded that the nanoparticles had different average sizes due to different ratio of hydrophilic contents in the block or conjugate backbone. The particle size and structure could be altered by changing the ratio of hydrophilic and hydrophobic contents. The in vitro drug encapsulations highlighted that all the drug-loaded micelles had spherical or near-spherical morphology. In vitro drug release study showed the controlled release of hydrophobic drug over a period of ~70 hours. The results indicate that there is great potential of renewable lipid-based micelle nanoparticles to be used as amphiphilic drug carriers for targeted delivery applications.