Study of Dielectric Normal Mode Process in Semidilute and Concentrated Solutions of Polymers.

点击翻译按钮获取中文摘要

Generally, the data of dielectric normal mode process provide two informations, i.e. the mean square end-to-end distance < <r^2> > and the relaxation time <tau_n> for fluctuation of the end-to-end vector. Using this technique, we studied the concentration C dependence of < <r^2> > and <tau_n> in semidilute and concentrated solutions of cis-polyisoprene (cis-PI) and compared them with the static and dynamic scaling laws.In a <theta> solvent dioxane, < <r^2> > was found to be independent of concentration as expected, while in a good solvent benzene, we found four concentration regions differing in the C dependence of < <r^2> >, i.e., dilute (I), semidilute (II), semi-concentrated (II') and concentrated (III) regimes. In regime II, < <r^2> > changed in proportion to <C^(-1/5)> in harmony with the scaling theory. In region II', the C dependence of < <r^2> > was explained qualitatively in terms of the Edwards theory. Similar behavior was seen in solutions of cis-PI in n-hexadecane and 1-eicosene having a marginal solvent quality.Relaxation times <tau_n> were reduced to those in an isofriction state <tau_(n zeta)> using the data for solutions of low molecular weight cis-PI. <tau_(n zeta)> in benzene and dioxane were proportional to <C^(1.3)> and <C^(1.6)> , respectively. These dependences can be explained only qualitatively by the dynamic scaling theory proposed by de Gennes. The distribution of the relaxation times was affected little by excluded volume effect and the hydrodynamic effect.