Polymer Chain Deformation in Stretched and Swollen Elastomers

1986 ◽  
Vol 79 ◽  
Author(s):  
Robert Ullman
Keyword(s):  
Free Energy ◽  
Polymer Chain ◽  
Small Angle Neutron Scattering ◽  
Experimental Information ◽  
Rubber Elasticity ◽  
Polymer Chains ◽  
New Developments ◽  
Dimensional Changes ◽  
The Mean ◽  
Actual Relation

AbstractIn the early theories of rubber elasticity, the retractive force and change in free energy of a stretched specimen were calculated from the deformation of the polymer chains of which the rubber network was formed. The mean chain deformation was presumed to be the same as that of the macroscopic specimen, an assumption which seemed reasonable, but could not be confirmed experimentally. Small angle neutron scattering (SANS) made measurement of chain dimensions possible, and it was soon discovered [1], [2] that the actual relation between dimensional changes of the polymer chain and deformation of the specimen was not at all what had been assumed.SANS studies of carefully prepared elastomeric networks provide the most direct experimental information required for a molecular theory of rubber elasticity, and have stimulated many new developments.

scholarly journals Elucidating the Energetics and Effects of Solvents on Cellulose Hydrolysis Using a Polymeric Acid Catalyst

2018 ◽  
Vol 8 (10) ◽  
pp. 1767 ◽  
Author(s):  
Xiaoquan Sun ◽  
Xianghong Qian
Keyword(s):  
Free Energy ◽  
Catalytic Activity ◽  
Polymer Chain ◽  
Critical Role ◽  
Acid Catalyst ◽  
Cellulose Hydrolysis ◽  
Polymer Chains ◽  
Biomass Hydrolysis ◽  
Imidazolium Chloride ◽  
Polymeric Acid

A novel polymeric acid catalyst immobilized on a membrane substrate was found to possess superior catalytic activity and selectivity for biomass hydrolysis. The catalyst consists of two polymer chains, a poly(styrene sulfonic acid) (PSSA) polymer chain for catalyzing carbohydrate substrate, and a neighboring poly(vinyl imidazolium chloride) ionic liquid (PIL) polymer chain for promoting the solvation of the PSSA chain to enhance the catalytic activity. In order to elucidate the mechanism and determine the energetics of biomass catalytic processing using this unique catalyst, classical molecular dynamics (MD) coupled with metadynamics (MTD) simulations were conducted to determine the free energy surfaces (FES) of cellulose hydrolysis. The critical role that PIL plays in the catalytic conversion is elucidated. The solvation free energy and the interactions between PSSA, PIL, and cellulose chains are found to be significantly affected by the solvent.

PATH INTEGRAL APPROACH TO A SINGLE POLYMER CHAIN WITH RANDOM MEDIA

2004 ◽  
Vol 18 (10n11) ◽  
pp. 1465-1478 ◽  
Author(s):  
CH. KUNSOMBAT ◽  
V. SA-YAKANIT
Keyword(s):  
Polymer Chain ◽  
Path Integral ◽  
Random Media ◽  
Feynman Path Integral ◽  
Feynman Path ◽  
Short Range Correlation ◽  
Range Correlation ◽  
End Distance ◽  
Non Local ◽  
The Mean

In this paper we consider the problem of a polymer chain in random media with finite correlation. We show that the mean square end-to-end distance of a polymer chain can be obtained using the Feynman path integral developed by Feynman for treating the polaron problem and successfuly applied to the theory of heavily doped semiconductor. We show that for short-range correlation or the white Gaussian model we derive the results obtained by Edwards and Muthukumar using the replica method and for long-range correlation we obtain the result of Yohannes Shiferaw and Yadin Y. Goldschimidt. The main idea of this paper is to generalize the model proposed by Edwards and Muthukumar for short-range correlation to finite correlation. Instead of using a replica method, we employ the Feynman path integral by modeling the polymer Hamiltonian as a model of non-local quadratic trial Hamiltonian. This non-local trial Hamiltonian is essential as it will reflect the translation invariant of the original Hamiltonian. The calculation is proceeded by considering the differences between the polymer propagator and the trial propagator as the first cumulant approximation. The variational principle is used to find the optimal values of the variational parameters and the mean square end-to-end distance is obtained. Several asymptotic limits are considered and a comparison between this approaches and replica approach will be discussed.

Effect on Polymer Chain Structure Caused by the Molar Fraction of 4-Hydroxybutyrate in Poly(3-hydroxybutyrate- co -4-hydroxybutyrate)

2012 ◽  
Vol 602-604 ◽  
pp. 776-780
Author(s):  
Zhi Qiang Li ◽  
Mei Li ◽  
Wei Jia Fan
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Polymer Chain ◽  
Molar Fraction ◽  
Chain Structure ◽  
The Other ◽  
Mean Square ◽  
Polarizing Microscope ◽  
Other Hand ◽  
The Mean

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)copolymer [P(3HB-co-4HB)] is a kind of biodegradable high molecular polymer produced by bioaccumulation. Because of the good biodegradability and biocompatibility, P(3HB-co-4HB)s have attracted wide attention . At first, the intrinsic viscosity[η] in good solvent of P(3HB-co-4HB) s with varying contents of 4HB was investigated in different temperature. Second, observed the changes of crystallization gathered state caused by the varying contents of 4HB by polarizing microscope. The results show that to the P(3HB-co-4HB)s in same molecular weight, the intrinsic viscosity[η] in good solvent barely changes when the mole fractions of 4HB increase. On the other hand, the mean square end to end distances[0] of macromolecular flexible chains increase with the mole fractions of 4HB. At the same time, the states of aggregation change from spherulites to dendrites. In this investigation, we discuss the reasons of the differences in depth.

Autocorrelation function of the spin misalignment in magnetic small-angle neutron scattering: application to nanocrystalline metals

2013 ◽  
Vol 46 (3) ◽  
pp. 788-790 ◽  
Author(s):  
Andreas Michels ◽  
Jens-Peter Bick
Keyword(s):  
Neutron Scattering ◽  
Autocorrelation Function ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Anisotropy Field ◽  
Real Space ◽  
Scattering Data ◽  
Stiffness Constant ◽  
The Mean ◽  
Cobalt And Nickel

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010).Phys. Rev. B,82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic `anisotropy-field' radius.

scholarly journals The Effects of Chemical Disinfection on Dimensional Stability among Different Type of Impression Addition Silicon Materials

2020 ◽  
Vol 5 (12) ◽  
pp. 645-649
Author(s):  
Salah A. Yousief ◽  
Khames T. Alzahrani ◽  
Suha M. Alhuwairini ◽  
Fai Y. Alharbi ◽  
Dalal A. Eissa ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Epoxy Resin ◽  
Dimensional Stability ◽  
Control Group ◽  
P Value ◽  
Impression Material ◽  
Dimensional Changes ◽  
The Mean ◽  
Master Model ◽  
The Cross

Introduction: Saliva and blood contaminated impressions are often a source of cross contamination between the clinic and dental laboratory. Explicit communication and observance of an infection control protocol for handling of dental impressions must exist among the office staff as well as between office and dental laboratories. Though disinfection of impression is routinely followed, autoclaving elastomeric impression is an effective method of sterilization them. Objectives: The purpose of this study was to evaluate dimensional stability and detail reproduction of a new addition silicon impression material after disinfection. Methods: In this study, a total of twenty impressions for the master model using heat resistant plastic stock trays. The twenty impressions were divided into two groups according to disinfection technique: (Table 2) Group 1: (n=10) Control group, untreated impressions. (C.G) Group 2: (n=10) Impressions were chemically disinfected. (D.G). after all impressions treatment, they were poured with extra hard stone (type IV) to get stone casts. Dimensional accuracy and detail reproduction of the impression material were evaluated indirectly through the recovered improved stone casts from impressions of the master model using the travelling microscope. Results: Cross arch distance (A): Epoxy resin master model cross arch distance measurement (A) was (41.36 mm). 1.1 Measurements of the cross-arch distance of stone casts Control group (C.G): The mean and standard deviation values of distance (A) in stone models obtained from C.G. were 41.553 ± 0.170 mm. Disinfection group (D.G): The mean and standard deviation values of distance (A) in stone models obtained from D.G were 41.368 ± 0.083 mm. ANOVA test showed that there was a statistically difference shrinkage between the groups (P-value = 0.006). 1.2 Measurement of the dimensional changes in the cross-arch distance of the different groups. The mean and standard deviation values of cross arch distance changes in stone models of C.G. were 0.191 ± 0.170 mm. while dimensional changes in stone models obtained from D.G. were 0.006 ± 0.082 mm. Conclusion: The purpose of this study was to evaluate dimensional stability and detail reproduction of a new addition silicon impression material after disinfection. In this study an epoxy resin master model was duplicated from a modified dentate mandibular model. Within the limitations of this study, it could be concluded that Chemical disinfectant of polyvinyl siloxane impression material can be successfully used in making fixed partial dentures.

scholarly journals Collapse of a polymer chain in a melt of incompatible polymer chains

1981 ◽  
Vol 42 (8) ◽  
pp. 1145-1150 ◽  
Author(s):  
J.F. Joanny ◽  
F. Brochard
Keyword(s):  
Polymer Chain ◽  
Polymer Chains
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