Kinetics of chain collapse in dilute polymer solutions: Molecular weight and solvent dependences

フォーマット:

論文

責任表示:

Maki, Yasuyuki ; Dobashi, Toshiaki ; Nakata, Mitsuo

言語:

英語

出版情報:

American Institute of Physics, 2007-04-02

著者名:

• Maki, Yasuyuki
• Dobashi, Toshiaki
• Nakata, Mitsuo

掲載情報:

The Journal of Chemical Physics

ISSN:

0021-9606    

巻:

126

通号:

13

開始ページ:

134901

終了ページ:

134907

バージョン:

VoR

概要:

application/pdf<br />Journal Article<br />The molecular weight and solvent dependences of the characteristic time of chain collapse were studied for poly(methyl methacrylate) (PMMA) of the molecular weight Mw =6.4× 106 and 1.14× 107 in pure acetonitrile (AcN) and in the mixed solvent of AcN+water (10 vol %). The size of PMMA chains was measured as a function of the time after the quench by static light scattering and the chain collapse … processes were expressed by the plot of the expansion factor α2 vs ln t. The chain collapse in the mixed solvent AcN+water (10 vol %) was found to occur much faster than that in pure AcN, though the measurement of the former collapse process required several hours. In order to make a comparison between the rates of chain collapses, the fast chain collapse process was superposed on the slow one by scaling the time of the fast process as γt. The scale factor γ was determined by comparing the chain collapse processes of nearly the same equilibrium expansion factor with each other. Accordingly, the superposition of the collapse for Mw =6.4× 106 on that for Mw =1.14× 107 yielded γm =4.0±0.6 for the process in AcN+water and 5.5±0.6 in AcN. The superposition of the chain collapse process in AcN+water on that in AcN yielded γs =9.5±1.4 for Mw =6.4× 106 and 12.0±1.8 for Mw =1.14× 107. This analysis suggests that γm and γs are constant independent of each other. Thus, by assuming the molecular weight dependence of γm ∼ Mz, the characteristic time τexp of chain collapse was conjectured as τexp ∼κ Mz, where κ reflects the nature of solvent species. The ratio of κ for PMMA in AcN to that in AcN+water is given by γs. The exponent was estimated to be z=2.4±0.7 for AcN+water and 3.0±0.7 for AcN. These values are compatible with the theoretical prediction z=3 based on a phenomenological model, though the observed characteristic times are longer by several orders of magnitude than those of the theoretical prediction. 続きを見る