Graft Density Dependence of Main Chain Stiffness in Molecular Rod Brushes

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• 作者：Moriya Kikuchi ; Ryo Nakano ; Yuji Jinbo ; Yuta Saito ; Satoshi Ohno ; Daichi Togashi ; Kazushi Enomoto ; Atsushi Narumi ; Osamu Haba ; Seigou Kawaguchi
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：August 25, 2015
• 年：2015
• 卷：48
• 期：16
• 页码：5878-5886
• 全文大小：516K
• ISSN：1520-5835

文摘

The graft density dependence of main chain stiffness in rod brushes composed of a flexible linear polystyrene (PS) main chain and poly(n-hexyl isocyanate) (PHIC) rod side chains has thoroughly been investigated by static light (LS) and small-angle X-ray scattering (SAXS) measurements in tetrahydrofuran (THF) at 25 掳C. A series of statistical graft copolymers having different graft densities (蟽) and graft chain lengths (PS-g-HIC-N_s-l_g, where N_s is the weight-averaged degree of polymerization of HIC and l_g is the average distance (spacing) of the main chain between the side chain joints) were prepared by the nearly azeotrope radical copolymerizations of styrene (M₁) with PHIC macromonomers (M₂) (r₁ = 0.84 卤 0.1 and r₂ = 1.1 卤 0.3) in n-hexane or the bulk at 60 掳C. The compositional heterogeneities of the graft copolymers were carefully characterized by the ratio of the UV to RI signal in the SEC traces and the comparison with those predicted from the theory by Stejskal and Kratochvil [ Macromolecules 1987, 20, 2624], implying that they were sufficiently small enough to allow one to study their dimensional characterizations. The graft density dependence of the root-mean-square cross-section radius of gyration (鉄?i>S_c²鉄?sup>1/2) and the z-averaged root-mean-square radius of gyration (鉄?i>S²鉄?sub>z^1/2) of PS-g-HIC-N_s-l_g was studied and rationalized as the function of 蟽 and N_s. The 蟽-dependence of 鉄?i>S_c²鉄?sup>1/2 could be quantitatively described by the theory for the semiflexible comb whose main and side chains have different chain stiffness. The weight-averaged degree of polymerization of the main chain (N_M) dependence of 鉄?i>S²鉄?sub>z^1/2 was also quantitatively described by the cylindrical wormlike chain model. It was found that the change in the main chain stiffness (位_b^鈥?) resulting from the interactions among the side chains increases in proportion to the scaling law of 位_b^鈥? 鈭?N_s¹蟽¹.