Regular Mixing Thermodynamics of Hydrogenated Styrene鈥揑soprene Block鈥揜andom Copolymers

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• 作者：Bryan S. Beckingham ; Richard A. Register
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：April 23, 2013
• 年：2013
• 卷：46
• 期：8
• 页码：3084-3091
• 全文大小：391K
• 年卷期：v.46,no.8(April 23, 2013)
• ISSN：1520-5835

文摘

Random copolymerization of A and B monomers represents a versatile method to tune interaction strengths between polymers, as ArB random copolymers will exhibit a smaller effective Flory interaction parameter 蠂 (or interaction energy density X) upon mixing with A or B homopolymers than upon mixing A and B homopolymers with each other, and the ArB composition can be tuned continuously. This approach can also be used to tune the segregation strength in A鈥揂rB 鈥渂lock鈥搑andom鈥?copolymers. Simple models of polymer mixing thermodynamics suggest that the effective interaction energy density in such block鈥搑andom copolymers should follow X_A鈥揂rB = f_B²X_A鈥揃, but this prediction has not been tested quantitatively. The present work systematically assesses the validity of this rule for thermally stable hydrogenated derivatives of styrene鈥搃soprene block copolymers, through measurements of the order鈥揹isorder transition (ODT) temperature on near-symmetric diblock and diblock鈥搑andom copolymers of varying composition and suitable molecular weight (M). Both hydrogenated derivatives wherein the styrene aromaticity is retained, and derivatives wherein the styrene units are saturated to vinylcyclohexane, are examined, and both are found to closely obey the X_A鈥揂rB = f_B²X_A鈥揃 prediction, thereby confirming the utility of this simple relationship in designing block copolymers with targeted interaction strengths using only these two common monomers. The reduction in X_A鈥揂rB over X_A鈥揃 permits the synthesis of polymers having much larger M and domain spacing d while maintaining a thermally accessible ODT; measured domain spacings are found to closely follow the expected scaling, d X^1/6M^2/3.