Concentration Dependence of Loop Fraction in Styrene−Isoprene−Styrene Triblock Copolymer Solutions and Corresponding Changes in Equilibrium Elasticity
Concentration Dependence of Loop Fraction in Styrene−Isoprene−Styrene Triblock Copolymer Solutions and Corresponding Changes in Equilibrium Elasticity
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苯乙烯-异戊二烯-苯乙烯三嵌段共聚物溶液中环分数的浓度依赖性以及相应的平衡弹性变化
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
K. Osaki
中科院分区：
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作者：
H. Watanabe;Tomohiro Sato;K. Osaki
研究了苯乙烯-异戊二烯-苯乙烯(SIIS)三嵌段和SI两嵌段共聚物溶液在I-选择性溶剂正十四烷(C14)中的介电行为。SI共聚物在I嵌段具有不倒置的A型偶极，而SIIS共聚物是SI的头偶联二聚体，在I嵌段具有一次倒置的偶极。在低温(5℃)下，S块形成玻璃状的球形微区，SiIS的I块具有桥式或环状构型。这些I块中的回路分数φL是根据SiIS和SI溶液在低频下的介电损耗估算的。随着硅胶浓度的降低(从50wt%增加到20wt%)，L的φ从0.6wt%增加到0.8wt%。φL的这种增加归因于稀释时桥构型的伸展和失稳。根据φL的值和SiIS/C14浓缩液的流变数据估算的桥梁和悬垂回路的平衡弹性在量级上是相似的。这个标志..。
Dielectric behavior was examined for solutions of a styrene-isoprene-styrene (SIIS) triblock and SI diblock copolymers in an I-selective solvent, n-tetradecane (C14). The SI copolymer had noninverted type-A dipoles in the I block while the SIIS copolymer, a head-to-head coupled dimer of SI, had once-inverted dipoles in the I block. At a low temperature (5 °C) where the S blocks formed glassy, spherical microdomains, the I blocks of SIIS had either the bridge or loop configurations. The loop fraction φl in these I blocks was estimated from the dielectric losses of the SIIS and SI solutions at low frequencies. The φl was found to increase (from 0.6 to 0.8) with decreasing SIIS concentration (from 50 to 20 wt %). This increase of φl was attributed to stretching and destabilization of the bridge configuration on dilution. The equilibrium elasticities of the bridge and dangling loop, estimated from the φl values and rheological data of the concentrated SIIS/C14 solutions, were comparable in magnitude. This sig...