| Abstract: | Temperature dependent unperturbed and solvent modified unperturbed dimensions of macromolecules are derived, in a first order approximation, from NMR-data determined on low-molecular-weight analogs in the respective milieu. Because the long range interactions - excluded volume and polymer - polymer interaction - are absent in the conformational balance of those models, the macrodimensions derived in this way are the unperturbed ones, with and without the influence of specific solvent action. Studies on head-to-head vinyl polymers are reported. It is demonstrated that the unperturbed dimensions in virtually non-interacting solvents,<r2>o, may exceed those in thermodynamically good ones, <r2>s, as a consequence of differing conformational balance at segmental level. It is pointed out that those temperature and solvent dependent unperturbed dimensions are effective also in polymer solutions, as long as the molecular weight of the polymer is not exceeding the critical length necessary for occurrence of long range interactions. Capabilities in analyzing the conformational balance in plasticized systems and in compatible polymer blends are discussed. Here the conformation of the second component may be studied in parallel, as a consequence of similar concentrations of both partners in the system. θ-dimensions depend on the type of the pseudoideal solvent. This effect is discussed on the base of NMR studies on the unperturbed conformations at segmental level in the respective θ- milieu. |
