Articles you may be interested inThe role of structure in the nonlinear mechanics of cross-linked semiflexible polymer networks J. Chem. Phys. 136, 065101 (2012); 10.1063/1.3682779Simulation and theory of self-assembly and network formation in reversibly cross-linked equilibrium polymers A model of polymer chain motions is developed which in the limit of long, flexible chains can readily be applied to branched chain and cross-linked systems. The equation governing the motion of a chain takes the form of a differential equation rather than the form of the large set of difference equations that occur in most other treatments. The present model gives essentially the same distribution of relaxation times for linear polymers as previous treatments, and it also gives the same dependence of viscosity upon branching as the theories based on the effective radius of randomly coiled chains.In addition to this information, the theory yields the distribution of relaxation times for branched chain polymers, permitting, for example, the calculation of the energy stored in steady state shear. The relaxation time distribution of several models of a cross-linked polymer is also calculated, and the relationship of this distribution function to that of the uncross-linked materials is discussed.

The intense so-called ``intermolecular charge-transfer spectra'' shown by a large number of molecular complexes in solution are found to exhibit certain regularities in regard to wavelength and intensity. The wavelengths of these transitions show an excellent correlation with the ionization potentials of the electron donor partners of the complexes. The intensities of the charge-transfer transitions are markedly dependent on the electron acceptor partner of the complex. These results are examined in terms of possible theoretical interpretations of the charge-transfer transitions.

No abstract

A simple Brownian motion model is used to discuss thermal diffusion in dilute polymer solutions. The thermal diffusion coefficient is found to be independent of polymer at sufficiently large molecular weights and to be given by DT= -(D.E.)/RT'-where DB is the self-diffusion of the solvent and E. is the activation energy for this diffusion. This suggests that the thermal diffusion ratio a = T DT / Do should show a marked temperature dependence, a molecular weight dependence proportional to M~, and a concentration dependence governed for the most part by that of Do. The results are shown to agree with published data in most respects and are contrasted to the results of other theoretical models. The results indicate that thermal diffusion is not a particularly promising method of fractionating various molecular weight molecules.

The spectra of diglycyl, triglycyl, and glycine anhydride have been extended to 1800A in water solution. The peak observed near 1850A is attributed to an almost additive absorption by the —CONH— groups. The oscillator strength f is 0.27±0.07 per peptide group.