Interchain effects

The statistical theory of rubber elasticity predicts that isothermal simple elongation and compression at constant pressure must be accompanied by interchain effects resulting from the volume change on deformation. The correct experimental determination of these effects is difficult because of very small absolute values of the volume changes. These studies are, however, important for understanding the molecular mechanisms of rubber elasticity and checking the validity of the postulates of statistical theory. 

The interchain effects in polymer networks are reflected in the thermomechanical inversion at low strains, which arises from a competition of intra- and interchain changes. Calorimetric studies of unidirectional deformation demonstrates this fact very obviously (Fig. 4). The point of elastic inversion of heat (Table 3) is dependent on the energy contribution and the thermal expansion coefficient in an excellent agreement with the prediction of Eq. (45). The value of (AU/W)VjT for the only one point of deformation, i.e. the inversion point, coincides with data obtained by a more general method (Fig. 3). 

Moreover, the ratios Tj/Xj obtained at different temperatures are similar to the values obtained for labell polybutadiene in dilute solution in toluene (= 30). Thus, the surrounding chains seem to affect local dynamics only at the level of the friction coefficient. Intrachain connectivity remains the essential non isotropic constraint on local dynamics in bulk polymers and models for the isolated chain are applicable. This is consistent with the idea that topological interchain effects only act on a... 

Calculations performed on isolated chains appear to be fully consistent with a number of experimental data. However, many recent experimental studies have clearly demonstrated that interchain effects can play an important role [25-32]. In Section 4.4, we report the results of correlated calculations investigating the... 

Other experiments suggest that ID fluctuations may be greatly reduced by interchain effects and that the transition at 54°K is essentially that given by mean field theory. The conductivity at 60°K and above is not so large as to... 

Litmanovich, A. D., Plate, N. A., and Kudryavtsev, Y. V. 2002. Reactions in polymer blends Interchain effects and theoretical problems. Progress in Polymer Science 27 915-970. 

The denominator <5 (Tg — T) accounts actually for the interchain effects (friction between chains) on the yield stress. Thus, the reduced yield stress defined above by Eq. 11.5 should be only a function of an intrachain property, characterized by the chain stiffness (Wu 1990, 1992) ... 

The effects of chain stiflftiess and cohesive forces on the value of Tg are different from each other. The intrachain effect of the stiffness of individual chain segments is generally (hut not always) somewhat more important than the interchain effect of the cohesive (attractive) forces between different chains in determining the value of Tg. 

We then iterate the process m times. The resulting will be defined as the ratio between the average number of monomers in the volume o lco ) and the number of monomers in one subunit g". When is less than 1 we are dealing essentially with a one-chain problem. When > 1, interchain effects become dominant. 

In addition to the well-established molecular relaxations, the TSC spectrum shows a weak / relaxation, ascribed to rotation of trace amounts of absorbed water, and a weak [3 relaxation, a dielectric signal that may correspond to translational mobility of charges, hindered sidechain motions, or even structural relaxation effects [see, e.g., Muzeau et al. (1995) Kalogeras (2004). The a relaxation has a peak at = 110 °C, near the DSC Tg (Kalogeras and Neagu 2004). The intrachain effect of the stiffness of individual chain segments is—at least in the case of PMMA and some other poly(n-alkyl metharylate)s— more important than the interchain effect of the cohesive (attractive) forces... 

With the advent of supercomputers we will soon see tremendous advances in both areas. I expect that effects of impurities and dopants, interchain effects and solid state effects will become amenable to attack using these methods in the near future. 

Interchain effects Organization of polymer chains into a solid and the transport... 

These orientational correlations also play a major role in the orientation process of crosslinked chains. According to the results reported in Fig. 5, it appears clear that most of the orientational anisotropy as manifested by the doublet structure in the H-NMR line is attributed to interchain effects rather than the conventional end-to-end stretching of isolated chains. Indeed, as it seems reasonable to assume that both contributions are operative in elastic network chains we would have anticipated much larger splittings for such chains but this is not borne out by the experiments. From that point of view both kinds of chains, crosslinked and uncrosslinked, appear to be locally indistinguishable. 

Time-resolved fluorescence measurements on unsubstituted thiophene oligomers in solution indicate a sharp increase of the fluorescence quantum yield when the number of thiophene units is increased from two to seven [56, 70] in such experiments, we expect the migration of the excitons towards trapping centers to be minimized due to the finite size of the systems and the absence of interchain effects. The evolution of ( f with chain size has been related to a decrease in nonradiative decay rate /cnr, since the radiative decay constant is observed to be almost unaffected... 

They also show the dependence of the interchain effects on the thermal history. Upon swelling in benzene the scat-... 

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