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Bibliografias temáticas / Polymer chain conformation

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Literatura científica selecionada sobre o tema "Polymer chain conformation"

Autor: Grafiati

Publicado: 8 de fevereiro de 2025

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Artigos de revistas sobre o assunto "Polymer chain conformation"

1

Qin, Linlin, Linling Li, Ye Sha, Ziyu Wang, Dongshan Zhou, Wei Chen e Gi Xue. "Conformational Transitions of Polymer Chains in Solutions Characterized by Fluorescence Resonance Energy Transfer". Polymers 10, n.º 9 (10 de setembro de 2018): 1007. http://dx.doi.org/10.3390/polym10091007.

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The critical overlap concentration C* is an important concept in polymer solutions and is defined as the boundary between dilute and semidilute regimes. In this study, the chain conformational changes of polystyrene (PS) with both high (Mn = 200,000 Da) and low (Mn = 13,000 Da) molecular weights in cis-decalin were compared by intrachain fluorescence resonance energy transfer (FRET). The random labeling of donor and acceptor chromophores strategy was employed for long PS chains, whereas chain-end labeling was used for short PS chains. By monitoring the spectroscopic intensity ratio between acceptor and donor, the concentration dependence on chain conformation from dilute to semidilute solutions was determined. Both long and short chains exhibit a conformational transition concentration, above which the polymer chains begin to collapse with concentration significantly. Interestingly, for randomly labeled polymer long chains, such concentration is consistent with C* determined from the viscosity result, below which only slight conformational change of polymer chain takes place. However, for the chain-end labeled short chain, the conformational transition concentration takes place earlier than C*, below which no significant polymer conformation change is observed.

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Qiu, Xing, Cunliang Hu, Jingqing Li, Dinghai Huang e Shichun Jiang. "Role of conformation in crystal formation and transition of polybutene-1". CrystEngComm 21, n.º 29 (2019): 4243–49. http://dx.doi.org/10.1039/c9ce00576e.

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Polymer conformation is the molecular basis underlying essentially all physical properties of polymers, and chain conformation and conformational energy play central roles in crystalline structure formations and structure transitions of polymers.

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Kugimoto, Daisuke, Aoi Taniguchi, Masaki Kinoshita e Isamu Akiba. "Effect of Molecular Architecture on Associating Behavior of Star-Like Amphiphilic Polymers Consisting of Plural Poly(ethylene oxide) and One Alkyl Chain". Polymers 13, n.º 3 (31 de janeiro de 2021): 460. http://dx.doi.org/10.3390/polym13030460.

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Associating behavior of star-like amphiphilic polymers consisting of two or three poly(ethylene oxide) (PEO) chains and one stearyl chain (C18) was investigated. Although the aggregation number (Nagg) of linear analogue of amphiphilic polymers monotonically decreased with increasing number-average molecular weight of PEO (Mn,PEO), the Nagg of micelles of star-like amphiphilic polymers with Mn,PEO = 550 g/mol was smaller than that with Mn,PEO = 750 g/mol, whereas that with Mn,PEO ≥ 750 g/mol showed general Mn,PEO dependence. Small-angle X-ray scattering analyses revealed that the occupied area of one PEO chain on the interface between hydrophobic core and corona layer in the micelles of star-like polymers was much narrower than that in the linear amphiphilic polymers. This result indica ted the PEO chains of star-like polymers partially took unfavorable conformation near the core–corona interface in polymer micelles. The effect of local conformation of PEO chains near the interface on the associating behavior became significant as Mn,PEO decreased. Therefore, in polymer micelles of star-like amphiphilic polymers containing PEO with Mn,PEO = 550 g/mol, the enlargement of occupied area of PEO on the core–corona interface should be caused to avoid the formation of unfavorable conformations of partial PEO chains, resulting in a decrease in Naggs.

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Guo, Yingying, e Linqing Bai. "Dissipative Particle Dynamics Simulation for the Self-Assembly of Symmetric Pentablock Terpolymers Melts under 1D Confinements". Polymers 15, n.º 19 (3 de outubro de 2023): 3982. http://dx.doi.org/10.3390/polym15193982.

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The phase behavior of CBABC pentablock terpolymers confined in thin films is investigated using the Dissipative Particle Dynamic method. Phase diagrams are constructed and used to reveal how chain length (i-block length), block composition and wall selectivity influence the self-assembly structures. Under neutral walls, four categories of morphologies, i.e., perpendicular lamellae, core–shell types of microstructures, complex networks, and half-domain morphologies, are identified with the change in i-block length. Ordered structures are more common at weak polymer–polymer interaction strengths. For polymers of a consistent chain length, when one of the three components has a relatively smaller length, the morphologies transition is sensitive to block composition. With selective walls, parallel lamellae structures are prevalent. Wall selectivity also impacts chain conformations. While a large portion of chains form loop conformations under A-selective walls, more chains adopt bridge conformation when the wall prefers C-blocks. These findings offer insights for designing nanopatterns using symmetric pentablock terpolymers.

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Hu, Zhongjian, Ryan T. Haws, Zhuping Fei, Pierre Boufflet, Martin Heeney, Peter J. Rossky e David A. Vanden Bout. "Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes". Proceedings of the National Academy of Sciences 114, n.º 20 (2 de maio de 2017): 5113–18. http://dx.doi.org/10.1073/pnas.1620722114.

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Fluorination represents an important strategy in developing high-performance conjugated polymers for photovoltaic applications. Here, we use regioregular poly(3-ethylhexylthiophene) (P3EHT) and poly(3-ethylhexyl-4-fluorothiophene) (F-P3EHT) as simplified model materials, using single-molecule/aggregate spectroscopy and molecular dynamic simulations, to elucidate the impacts of backbone fluorination on morphology and excitonic coupling on the molecular scale. Despite its high regioregularity, regioregular P3EHT exhibits a rather broad distribution in polymer chain conformation due to the strong steric hindrance of bulky ethylhexyl side chains. This conformational variability results in disordered interchain morphology even between a few chains, prohibiting long-range effective interchain coupling. In stark contrast, the experimental and molecular dynamic calculations reveal that backbone fluorination of F-P3EHT leads to an extended rod-like single-chain conformation and hence highly ordered interchain packing in aggregates. Surprisingly, the ordered and close interchain packing in F-P3EHT does not lead to strong excitonic coupling between the chains but rather to dominant intrachain excitonic coupling that greatly reduces the molecular energetic heterogeneity.

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Sikorski, Andrzej. "Diffusion of Confined Polymer Chains". Defect and Diffusion Forum 237-240 (abril de 2005): 169–74. http://dx.doi.org/10.4028/www.scientific.net/ddf.237-240.169.

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Simple lattice model of polymer systems was developed and studied using the Monte Carlo method. The model chains were star-branched with f = 3 arms and rings. The number of polymer segments in a chain was varied up to 800. The chains were built on a simple cubic lattice with the excluded volume interactions only (the athermal system). The polymers were confined between two parallel impenetrable walls with a set of irregular obstacles what can be treated as porous media. A Metropolis-like sampling algorithm employing local changes of chain conformation was used. The dynamic properties of the model system were studied. The differences in the mobility of chains with different internal architectures were shown and discussed. The possible mechanisms of motions were presented.

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Kobayashi, Masamichi, e Takehito Kozasa. "Conformational Ordering Process on Physical Gelation of Syndiotactic Polystyrene/Solvent Systems Revealed by Time-Resolved Infrared Spectroscopy". Applied Spectroscopy 47, n.º 9 (setembro de 1993): 1417–24. http://dx.doi.org/10.1366/0003702934067450.

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Syndiotactic polystyrene (SPS) dissolved in various organic solvents forms stable gels. Infrared spectroscopic research shows that SPS molecules assume highly ordered TTGG conformation in gels, giving rise to many infrared bands characteristic of the regular TTGG sequences. The behavior of the conformational ordering is strongly dependent on the solvent and the temperature. The time evolution of the conformational order on gelation has been investigated for SPS/CHCl3 systems at various polymer concentrations and temperatures by time-resolved infrared spectroscopy. By the analysis of the rate of formation of the ordered conformation derived from the time-resolved intensity measurement of the conformation-sensitive band at 572 cm−1, the number of the chain segments that contribute to the formation of clusters having ordered TTGG conformation has been evaluated as a function of temperature. The results indicate that at a temperature around 10°C the conformation ordering proceeds through clustering of five chain segments. The number decreases with lowering temperature and becomes unity below a certain temperature, suggesting that the ordering proceeds via self-organization within one chain. Such a crossover between the two mechanisms is found for other solvents, although the crossover temperature depends on the solvent. It has been concluded that strong interactions between polymer and solvent molecules play important roles in controlling the gelation behavior of SPS/solvent systems.

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Tanaka, Fumihiko, e Hideharu Ushiki. "Chain conformation in ternary polymer solutions". Macromolecules 21, n.º 4 (julho de 1988): 1041–46. http://dx.doi.org/10.1021/ma00182a033.

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Jones, Ronald L., Sanat K. Kumar, Derek L. Ho, Robert M. Briber e Thomas P. Russell. "Chain conformation in ultrathin polymer films". Nature 400, n.º 6740 (julho de 1999): 146–49. http://dx.doi.org/10.1038/22080.

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Cotton, J. P. "Conformation of a polymer chain in liquid crystalline polymers". Neutron News 1, n.º 3 (janeiro de 1990): 22–23. http://dx.doi.org/10.1080/10448639008202040.

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Teses / dissertações sobre o assunto "Polymer chain conformation"

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Arrighi, Valeria. "Chain conformation of a main-chain thermotropic liquid crystalline polymer". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46651.

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2

Ube, Toru. "Orientation and Conformation of Single Polymer Chain Studied by Scanning Near-Field Optical Microscopy". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142243.

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3

Nasreddine, Victor Fuad. "Solid state nuclear magnetic resonance spectroscopy of polymer thin films : chain conformation, dynamics, and morphology". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83081.

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This dissertation presents solid-state NMR studies of the chain conformation, dynamics and morphology of three adsorbed polymer systems: two random semi-crystalline copolymers, poly(ethylene-co-acrylic acid) (PEA) and poly(propylene-co-acrylic acid) (PPA), and an amorphous homopolymer, poly(n-butyl methacrylate) (PnBMA). Zirconia (ZrO2) was chosen as the substrate for all three polymers since the binding of carboxylic acids to this metal oxide is well understood. The choice of polymers was based on their particular bulk conformational and dynamic properties as well as their common use in polymer coatings. These studies are motivated by the general lack of a microscopic picture of adsorbed polymers, which can be provided by NMR, and the relevance of chain conformation and dynamics to important polymer film properties such as adhesion.
First the chain conformation and surface binding of adsorbed PEA as a function of acrylic acid content are characterized by 13C cross polarization - magic angle spinning (CP-MAS), 2D 1H- 13C wideline separation (WISE) and 1H spin diffusion NMR experiments and FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) measurements. The most important finding is that the chain conformation of adsorbed PEA is determined primarily by the sticker group density rather than the surface coverage. The second study of PEA concerns the chain dynamics in the bulk and adsorbed states. Variable temperature NMR experiments provide evidence that ethylene segments of adsorbed PEA form partially folded loops rather than flat extended trains. Finally 129Xe NMR studies, used to probe the morphology of adsorbed PEA, show a bulk-like signal only for the highest loadings.
The second system investigated, PPA, is another semi-crystalline random copolymer which binds to zirconia via carboxylate linkages. The 13 C CP-MAS NMR spectra of adsorbed PPAC unexpectedly show splittings normally associated with chain-chain packing in the crystalline regions of bulk polypropylene (PP). The splittings in the spectra of adsorbed PPAC, which are more resolved than in bulk PPA, are proposed to arise from recrystallization of the PP segments between sticker groups.
Finally the interfacial properties of an amorphous homopolymer, PnBMA were studied using 13C and 129Xe NMR to characterize adsorbed and filled samples. PnBMA binds to zirconia via the partial hydrolysis of the ester side chains. The remaining ester chains of adsorbed PnBMA are found to segregate to the polymer/air interface. Both adsorbed and ZrO 2-filled PnBMA show enhanced local segmental mobility. However, the 129Xe NMR measurements of the filled samples are consistent with restricted motion on a larger length scale which may be due to particle bridging.

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Zhao, Yiqiang. "Thermodynamic and Dynamic Behaviors of Self-Organizing Polymeric Systems". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1094190642.

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Zhang, Qiang. "Chain conformation of cellulose, a sustainable biopolymer, and its derivatives in ionic liquid studied by small-angle neutron and X-ray scattering". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF075.

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La cellulose, un biopolymère renouvelable, peut remplacer les matériaux non biodégradables dans les applications industrielles. Elle est d'abord dissoute, puis transformée (par exemple en fibres) et enfin « régénérée » (recristallisation par ajout d'eau). Cependant, la dissolution de la structure cristalline très stable nécessite des solvants agressifs et polluants, au contraire des liquides ioniques (IL). Cette thèse étudie le processus de dissolution et l'état dissous pour deux liquides ioniques sélectionnés comme solvants efficaces. Nous étudions la structure et la conformation des chaînes de cellulose par la diffusion des rayons X et des neutrons. Les signaux sont très faibles (< 1 cm⁻¹), en raison de la forme fine des bâtonnets, du faible contraste et de la difficulté à mesurer en raison de la grande sensibilité à l'eau. Le chapitre 1 résume l'état de l'art sur les solutions dans des solvants industriels et dans les liquides ioniques, et sur les études de diffusion, de la lumière, des rayons X et des neutrons, montrant des situations diverses. Le chapitre 2 présente la préparation des échantillons et les techniques. Le chapitre 3 présente des études de Diffusion des rayons X aux Petits Angles (DXPA), réalisées à l'aide de spectromètres sur synchrotron, à flux élevé et à faisceau étroit. Nous avons d'abord étudié la cellulose microcristalline (MCC, degré de polymérisation DP = 200 unités) dans deux IL à base de butyl-méthyl-imidazolium : acétate (BmimAc) ou chlorure (BmimCl). Différents régimes sont attendus à partir d'études rhéologiques. - Dans le régime dilué (0,005 - 0,02 g/g). La diffusion est ajustée au facteur de forme P(q) d'une chaîne en forme de bâtonnet, entourée d'une coquille de densité différente de celle du solvant, avec éventuellement une grande longueur de persistance (> 7 nm). - Pour des concentrations plus importantes, dans des cas encore bien dissous, un facteur de structure révèle des répulsions inter-chaînes faibles, sans alignement fort. - A des concentrations plus élevées, la diffusion suggère une séparation de phase liquide-liquide. - Enfin, aux concentrations les plus élevées, des cristaux non dissous sont détectés à grand q (WAXS), un grand avantage de notre technique. La coexistence avec les cristaux a été étudiée pendant le gonflement de films ou de fibres de cristaux de nanocellulose, par balayage en faisceau étroit d'un gradient de concentration. L'effet d'un faible pourcentage d'eau ajoutée a été testé, les Il bons solvants étant assez hygroscopiques. Au-delà de quelques pour cent d'eau, une diffusion beaucoup plus forte suggère de fortes fluctuations de concentration, ou une structure biphasique, utile pour comprendre les premières étapes de la « régénération » (recristallisation) par ajout d'eau. Les courbes de diffusion de cellulose d'autre origine et de poids moléculaire également faible (rayonne, nanocristaux - CNC) sont similaires à celles du MCC. Celle de la cellulose bactérienne montre aussi une identité complète à l'échelle locale, mais avec des agrégats indépendants visibles aux moyens q. Le chapitre 4 présente les mesures : - de Diffusion des Neutrons aux Petits Angles (DNPA) aux faibles concentrations, le profil de DNPA est celui de la DXPA, ce qui permet une évaluation complémentaire des densités de longueur de diffusion. Par extrapolation à la fraction zéro de cellulose deutérée, nous avons tenté d'extraire la fonction intra-chaîne S₁(q)~P(q), et la fonction inter-chaîne S₂(q). Des difficultés sont apparues à faible q en raison de la forte remontée de la cellulose deutériée bactérienne. A q élevé il y a accord avec la DXPA. - de Diffusion de Neutrons aux Grands Angles (DNGA) suit les corrélations à courte échelle. Nous avons effectué différentes deutériations : soit le cation Bmim, soit l'anion Ac, soit les deux. Par comparaison nous discutons de l'absorption possible des anions acétate sur les chaînes
Cellulose, a renewable bio-polymer, can replace non-biodegradable materials in various technological applications. Industrially, it is first dissolved, then processed (e.g. by spinning), and finally “regenerated” (recrystallization by adding water). However, dissolution from the very stable crystal structure requires harsh, pollutant solvents for individual chains to stay in solution. Ionic liquids (ILs) have emerged as non - polluting effective solvents. This thesis aims at the dissolution process and dissolved state checking how the two selected ILs are successful solvents, which is controversial. Our approach is to study structure and conformation of cellulose chains by X-Ray and neutron scattering, which are very weak (< 1 cm⁻¹), due to the small volume of the thin rod, the low contrast and difficult to measure due to high sensitivity to water. Chapter 1 summarizes the state of the art on solutions of cellulose in different widely industrially used solvents, in ionic liquids, and in scattering studies, light, X-rays and neutrons, showing various states of dispersion. Chapter 2 presents the preparation of the samples and the techniques. Chapter 3 reports Small Angle X rays Scattering (SAXS) studies, using high flux and narrow beam synchrotron spectrometers. We first monitored MicroCrystalline Cellulose (MCC, Degree of Polymerisation DP ≈ 200 units) in two Butyl-methyl-imidazolium based ILs: acetate (BmimAc), or Chloride (BmimCl). Different regimes are assumed from rheological studies. -In the dilute regime (0.005 – 0.02 g/g). Scattering is fitted to the form factor P(q) of a rod-like chain, surrounded by a shell of density different from the one of the solvent, with possibly a large persistence length (> 7 nm). -For larger concentrations, in yet well dissolved cases, a structure factor unveils soft interchain repulsions, without strong alignment. -At higher concentration, the scattering suggests a liquid-liquid phase separation -Finally, at the highest concentrations, non-dissolved crystals are detected at large q (WAXS), a great advantage of our technique. The coexistence with crystals was also investigated during swelling in nanocellulose crystals films or fibers, through narrow beam scanning of a concentration gradient. The effect of a small percentage of added water was tested, the IL good solvents for cellulose being quite hygroscopic. Above a few per cent of water, much stronger scattering suggests strong concentration fluctuations, or biphasic structure, useful to understand the first stages of the “regeneration” (recrystallization) step performed by adding water, to obtain the final products. Cellulose of other origin and similarly small molecular weights (in rayon, and CNC), superimpose their scattering on the one of MCC. Bacterial cellulose scattering superposes only at large q (hence a complete identity at local scale), but shows an additional strong low q upturn, due to independent aggregates. This opens the way to neutron scattering experiments using deuteriated cellulose, which is available only in a bacterial form. Chapter 4 reports the measurements of: -Small Angle Neutron Scattering (SANS) shows for low concentrations a profile similar to SAXS, allowing a complementary evaluation of the Scattering Length Density of cellulose. Using extrapolation at Zero Deuteriated Cellulose Fraction, we attempted the extraction of the intrachain function S₁(q)~P(q), the interchain function S₂(q). Difficulties appeared at low q due to the strong upturn, while high q showed agreement with the SAXS measurement of the form factor below c*. -Wide Angle Neutron Scattering (WANS) was used to track the correlations at short scale. Different solvents were used in which either the Bmim cation, or the anion Ac, or both, were deuteriated using our own synthesis processes. Comparisons enable us to discuss about possible absorption of the acetate anions on the cellulose chains

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Ecker, Christof. "Conformations of single polymer chains on surfaces". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2005. http://dx.doi.org/10.18452/15324.

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In dieser Arbeit wurden auf Substratoberflächen adsorbierte Polymermoleküle mit Rasterkraftmikroskopie (RKM) untersucht. Dabei war die Form der Moleküle (Konformation) von besonderem Interesse. Sie ist von zentralerer Bedeutung in der Polymerphysik und wird üblicherweise in Lösung und mit Streumethoden untersucht. Polymerkonformationen auf Oberflächen sind heutzutage noch wenig untersucht. Üblicherweise wird das Verhalten nach dem so genannten Wormlike-Chain Modell angenommen. Es basiert auf der Annahme, dass die Kettenbiegung nur aus thermischen Fluktuationen resultiert, so dass sich die Kettenform durch statistische Mechanik beschreiben lässt. Es wurden für verschiedene Modellsystem einzelne Moleküle hochaufgelöst abgebildet und die Konformation aus den Bildern bestimmt. Es hat sich gezeigt, dass die idealisierte Vorstellung des Wormlike-Chain Modells tatsächlich nur für wenige der untersuchten Systeme erfüllt ist. Abweichende Konformationen sind oft auffallend regelmäßig: entweder sinusartig mäandrierte oder spiralförmig gedrehte. Beide Charakteristika lassen sich aus dem Prozess der Adsorption erklären, was zeigt, dass die Moleküle auf dem Substrat immobil sind, so dass eine thermische Relaxation der Konformation verhindert ist. Konformtionen lassen sich mit RKM nicht nur beobachten, sondern auch gezielt verändern (Nanomanipulation). Für dendronisierte Polymere konnte so gezeigt werden, dass es einen glasartigen Zustand für das einzelne Molekül gibt. In diesem Zustand verhält sich das Molekül nicht mehr wie eine bewegliche Kette, sondern formstabil, ähnlich einem makroskopischen festen Körper.
In this work single polymer molecules adsorbed onto substrate surfaces were investigated by scanning force microscopy (SFM). The focus was on the shape (conformation) of the molecules, which is of central importance in polymer physics. It is commonly investigated in solutions and with scattering methods. Conformations on surfaces are only little investigated thus far. Often a behavior according to the so-called worm-like chain model is assumed. It is based on the assumption that chain bending results entirely from thermal fluctuations so that the overall chain shape can be described by statistical mechanics. For several model systems single molecules were imaged and the conformation was determined from the images. It was found that the idealistic wormlike chain behavior is only valid for a few systems. Deviations are often remarkable regular: either sine-like undulated or spiral wound. Both characteristics can be explained from the process of adsorption, indicating that molecules are immobile on the substrate so that thermal relaxation is inhibited. Conformations can not only be imaged using the SFM, but also changed in a defined way (nanomanipulation). Manipulation experiments with dendronized polymers the existence of a glassy state for the single polymer. In this state the molecule no longer behaves as a flexible chain but remains its shape, similar to a macroscopic solid body.

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Qian, Hong. "Conformation and dynamics of main-chain liquid crystalline polymers". Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/245.

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Sakaue, Takahiro. "Conformational transition of a semiflexible polymer chain : effect of chain length, stiffness and electrostatics". 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147792.

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Zuber, Mohammad. "Main chain liquid crystalline polyethers based on conformational isomerism". Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056133548.

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Nam, Sunghyun. "Dynamics of Cyclic and Linear Poly(oxyethylene) and Threading Conformation in Their Blends". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14135.

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Chemically identical but topologically different cyclic and linear polymers not only result in marked differences in dynamics, but also lead to unique transport properties of their blends, where cyclic polymers have chances to be threaded onto the linear polymers. This dissertation addresses the effect of ring architecture on dynamics using different time/length scale techniques: self-diffusion coefficients, NMR spin-spin relaxation time (T2) and bulk viscosity. In deuterated water, synthesized cyclic poly(oxyethylene) (CPOE) (400-1500 g/mol) diffused faster than corresponding linear POE (LPOE) and linear POE dimethyl ether (LPOEDE). However, the self-diffusion coefficients in melts were arranged in the following manner: LPOEDE > CPOE > LPOE, in excellent agreement with T2 and viscosity data, showing topological and chain end effects. Compared to LPOEDE, both CPOE and LPOE had higher activation energies for viscosity with less dependence on the molecular weight. In the blends of CPOE and LPOE for 900 and 1500 g/mol, the diffusion coefficient and viscosity in melts were higher and lower than the values predicted by a binary mixing rule, respectively. These deviations were attributed to the threading conformation, and the weight fraction of the threaded chains for 1500 g/mol was estimated by a three-term mixing rule. This threading conformation also appeared to influence such important bulk properties as the glass transition and spherulitic growth rate of the blends.

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Mais fontes

Livros sobre o assunto "Polymer chain conformation"

1

Torres, F. G. Polymer and polymer composite flows: Modelling of molecular chain conformations and reinforcing fibre orientations. Manchester: UMIST, 1997.

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Capítulos de livros sobre o assunto "Polymer chain conformation"

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Gafurov, Ulmas. "Conformation Regroupings in Deformation Process at Various Temperatures of the Oriented Flexible-Chain Linear Crystalline Polymer". In Functional Materials, 362–66. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607420.ch61.

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Gedde, Ulf W. "Chain Conformations in Polymers". In Polymer Physics, 19–38. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-0543-9_2.

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3

Strobl, Gert R. "Single Chain Conformations". In The Physics of Polymers, 13–61. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-662-03243-5_2.

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Strobl, Gert R. "Single Chain Conformations". In The Physics of Polymers, 13–61. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-662-03488-0_2.

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5

Tonelli, Alan, e Jialong Shen. "Determining the Microstructural Dependent Conformational Preferences of Polymer Chains". In Conformations, 19–55. Boca Raton : CRC Press, [2020]: CRC Press, 2020. http://dx.doi.org/10.1201/b22496-3.

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Tonelli, Alan, e Jialong Shen. "Connecting the Behaviors/Properties of Polymer Solids to the Microstructural Dependent Conformational Preferences of Their Individual Polymer Chains". In Conformations, 123–78. Boca Raton : CRC Press, [2020]: CRC Press, 2020. http://dx.doi.org/10.1201/b22496-6.

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7

Hu, Wenbing. "Scaling Analysis of Real-Chain Conformations". In Polymer Physics, 43–74. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-0670-9_4.

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Tonelli, Alan, e Jialong Shen. "Connecting the Behaviors/Properties of Polymer Solutions and Liquids to the Microstructural Dependent Conformational Preferences of Their Polymer Chains". In Conformations, 109–21. Boca Raton : CRC Press, [2020]: CRC Press, 2020. http://dx.doi.org/10.1201/b22496-5.

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9

Liu, Guangming, e Guangzhao Zhang. "Conformational Change of Grafted Polymer Chains". In SpringerBriefs in Molecular Science, 9–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-39790-5_2.

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De Rosa, Claudio. "Chain Conformation, Crystal Structures, and Structural Disorder in Stereoregular Polymers". In Materials-Chirality, 71–155. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2004. http://dx.doi.org/10.1002/0471471895.ch2.

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Trabalhos de conferências sobre o assunto "Polymer chain conformation"

1

Jones, Ronald L., Christopher L. Soles, Francis W. Starr, Eric K. Lin, Joseph L. Lenhart, Wen-li Wu, Dario L. Goldfarb e Marie Angelopoulos. "Chain conformation in ultrathin polymer films". In SPIE's 27th Annual International Symposium on Microlithography, editado por Theodore H. Fedynyshyn. SPIE, 2002. http://dx.doi.org/10.1117/12.474232.

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2

chen, yunzhi, Tianyi Guan, Yujing Wang e Tianyi Zong. "Conformation simulation of polymer chain with SAW module". In International Conference on Statistics, Applied Mathematics, and Computing Science (CSAMCS 2021), editado por Ke Chen, Nan Lin, Romeo Meštrović, Teresa A. Oliveira, Fengjie Cen e Hong-Ming Yin. SPIE, 2022. http://dx.doi.org/10.1117/12.2628094.

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3

Lee, Jeong Yong, Bo Kyung Ryu, Joo Sung Lee, Hyun Wook Jung, Jae Chun Hyun, Albert Co, Gary L. Leal, Ralph H. Colby e A. Jeffrey Giacomin. "Dynamics and Conformation of Single Polymer Chain in a Slot Coating Flow". In THE XV INTERNATIONAL CONGRESS ON RHEOLOGY: The Society of Rheology 80th Annual Meeting. AIP, 2008. http://dx.doi.org/10.1063/1.2964654.

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4

Prasad, Paras N., e Jacek Swiatkiewicz. "Organic crystals and polymers as nonlinear optical materials". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tum1.

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Organic molecular and polymeric systems have emerged as an important class of nonlinear optical materials for various uses. The advantage of a molecular material is the tremendous flexibility it offers to modify its chemical structure and conformation and consequently to tune its nonlinear optical properties. In addition the molecular, specially polymeric materials are also easily conformable to guided wave device structures. In our research, both second-and third-order nonlinearities have been investigated. Efficient second harmonic generation has been observed in several new classes of molecular crystal. Electrooptic effect in the surface plasmon geometry has been investigated for the Langmuir-Blodgett films of side-chain liquid crystalline polymers. Third-order optical nonlinearity in conjugated polymers has been investigated by femtosecond degenerate four-wave mixing. The anisotropy of χ(3) in stretch-oriented polymer has been studied. We have also investigated third-order nonlinear optical processes in polymeric waveguides.

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5

Weiland, Lisa Mauck, Emily K. Lada, Ralph C. Smith e Donald J. Leo. "Application of Monte Carlo Simulations to Hydrated Nafion Stiffness Predictions". In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80396.

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Application of Rotational Isomeric State (RIS) theory to the prediction of Young’s modulus of a solvated ionomer is considered. RIS theory directly addresses polymer chain conformation as it relates to mechanical response trends. Successful adaptation of this methodology to the prediction of elastic moduli would thus provide a powerful tool for guiding ionomer fabrication. The Mark-Curro Monte Carlo methodology is applied to generate a statistically valid number of end-to-end chain lengths via RIS theory for a solvated Nafion case. The distribution of chain lengths is then fitted to a Probability Density Function by the Johnson Bounded distribution method. The fitting parameters, as they relate to the model predictions and physical structure of the polymer, are studied so that a means to extend RIS theory to the reliable prediction of ionomer stiffness may be identified.

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6

Zangrilli, Ursula T., e Lisa M. Weiland. "Multiscale Modeling of Nafion Mechanical Properties". In ASME 2009 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2009. http://dx.doi.org/10.1115/smasis2009-1331.

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Multiscale modeling is used to investigate the mechanical characteristics of ionic polymers with the intent of ultimately expanding understanding of the interplay between multiscale stiffness and electromechanical response. Strategies for manipulating electromechanical transduction of ionic polymers include, but are not limited to: variation of hydration and/or the equivalent weight. In general, variations resulting in increased electroactive response also result in decreased mechanical stiffness and can decrease to the point of limiting mechanical integrity. This effort begins with the supposition that a better understanding of the ionic polymer multiscale material stiffness will enable bypass of this perceived trade-off. Rotational Isomeric State (RIS) theory is used to predict the conformation of a typical polymer hydrophobic backbone for a fully hydrated, sodium exchanged, Nafion 1200 EW case. The RIS method generates a large number of crosslink-to-crosslink chain lengths. The distribution is assessed via Johnson distributions and in turn, employed in a Boltzmann statistical thermodynamics framework to assess mechanical stiffness. The approach explores the impact of morphology on stiffness via imposing as assumed morphology a priori.

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Shiba, E., J. N. Lindon, L. Kushner, B. Kudryk e E. W. Salzman. "DETECTION BY MONOCLONAL ANTIBODIES OF CONFORMATIONAL CHANGE IN FIBRINOGEN ADSORBED ON ARTIFICIAL SURFACES". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642921.

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Adsorption of fibrinogen (Fg) appears to be an important precusor of platelet reactivity with artificial surfaces. We have reported that, contrary to the prevailing view, platelet reactivity is less well correlated with the total concentration of adsorbed Fg on the surface than with the concentration of adsorbed Fg detectable by labelled anti-Fg polyclonal antibodies ("native" Fg), and therefore presumably recognizable by the platelet's Fg receptors. To clarify the nature of the conformational change in Fg implied by these findings, we measured Fg adsorbed on a series of polyalkyl methacrylates, using a solid phase RIA in methacrylate-coated microtiter wells with monoclonal antibodies (MoAb) directed against a variety of Fg epitopes. Total Fg adsorption (125I-Fg) was the same on polymethyl methacrylate (PMMA, single carbon side chain) as on polybutyl methacrylate (PBMA, 4 carbon side chain), but platelet reactivity in a bead column was greater on PBMA than on PMMA. Adsorbed "native" Fg increased with the length of the alkyl side chain when assessed by MoAb against Fg fragment D or E, whole Fg, or γ/γγ chain at the saturated concentration of adsorbed Fg (0.3 ug/cm2) and was significantly greater on PBMA than on PMMA. Adsorbed "native" Fg decreased with length of the alkyl side chain at a lower concentration of Fg (<0.08 ug/cm2) measured with these MoAb. Platelet retention in a polymer bead column was blocked by Fab fragments of these MoAb. These results indicate that Fg molecules adsorbed to some artificial surfaces assume a specfic orientation and conformation that may be important in subsequent interaction of the surface with platelets.

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Nishioka, Toshikatsu. "Two-dimensional infrared correlation spectroscopy studies of polymer blends 1: Chain conformation and bonding in atactic polystyrene-poly(2,6-dimethyl-1,4-phenylene ether) blends". In International symposium on two-dimensional correlation spectroscopy. AIP, 2000. http://dx.doi.org/10.1063/1.1302871.

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Matveev, N., V. Lisitsin, Natal'ya Evsikova, Nina Kamalova e S. Vnukova. "Matrix method of averaging squares of vector quantities of complex polymers". In PHYSICAL BASIS OF MODERN SCIENCE-INTENSIVE TECHNOLOGIES. FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov, 2022. http://dx.doi.org/10.34220/pfmsit2022_12-16.

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In the article, within the framework of the conformational approach, the problem of averaging the square of vector quantities of complex polymers is presented. This approach is based on determining the average values of the square of the dipole moment for the µ-th monomeric unit of the chain, which is a unique parameter of the supramolecular structure of the polymer, depending on the product of the rotation matrices. A generalization of the matrix method of averaging the product of several tensor quantities over possible conformations within the entire macromolecule is considered.

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10

Henschen, A., e E. Müller. "ON THE FACTOR XIIIa-INDUCED CROSSLINKING OF HUMAN FIBRIN α-CHAINS". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644649.

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Factor XIIIa catalysis the formation of isopeptide bonds Between γ-carbamoyl groups of peptide-bound glutamines and ε-amino groups of lysines or lysine analogues. During fibrin crosslinking two such bonds are rapidly formed between the C-termini of two γ-chains in adjacent molecules and then several bonds are more slowly formed between several α-chains. The crosslinking sites in the γ-chain were identified already 15 years ago, those in the α-chain are still only tentatively or partially identified,, However, by determining the incorporation of lysine analogues in the α-chain it could be shown that the glutamines in positions 328, 366 and possibly also 237 may participate in crosslinking reactions. Analyses of cyanogen bromide fragments isolated from crosslinked fibrin indicated the segments 271-776 and 518-587 to contain the primary crosslinking sites.In the present study factor XHI-containing fibrinogen was incubated over night with thrombin in presence of calcium ions and cysteine or, as a control, in presence of EDTA. The fibrin material was cleaved with cyanogen bromide, mercaptolysed, pyri-dylethylated and then subjected to Sephacryl S-300 chromatography. The early protein fractions were tested by reversed-phase high-performance liquid chromatography (HPLC) using fibrinogen fragments as reference. In the control sample Aa-chain fragment 271-776 eluted first but in the crosslinked sample it was missing and instead a heterogeneous mixture of higher-molecular weight components was observed. N-Terminal sequence analysis showed the mixture to contain not only the expected fragments 241-476 and 518-584,but in fact all glutamine- or lysine-containing Aα-chain fragments between positions 208 and 611. In the corresponding 6 fragments a total of 6 glutamines and 21 lysines as potential crosslinking sites are present. Two fragments contain only one each of these residues which therefore must be true crosslinking sites. Remaining sites and the actual linkages were identified after reversed-phase HPLC of the tryptic peptide mixture by N-terminal sequence and total amino acid analyses.The linkage pattern will provide information about the localisation and conformation of the C-terminal part of the α-chain and its contribution to the fibrin polymer structure.

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