Synthesis and application of styrene/4-hydroxystyrene gradient copolymers made by controlled radical polymerization: Compatibilization of immiscible polymer blends via hydrogen-bonding effects
Synthesis and application of styrene/4-hydroxystyrene gradient copolymers made by controlled radical polymerization: Compatibilization of immiscible polymer blends via hydrogen-bonding effects
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DOI：
10.1016/j.polymer.2006.06.030
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发表时间：
2006-07-26
期刊：
影响因子：
4.6
通讯作者：
Torkelson, John M.
中科院分区：
文献类型：
--
作者：
Kim, Jungki;Zhou, Hongying;Torkelson, John M.
通过水解苯乙烯（S）/4-乙酰氧基苯乙烯（HS）共聚物前体合成S/4-羟基苯乙烯（HS）共聚物;通过半间歇、氮氧自由基介导的受控自由基聚合制备两种梯度共聚物前体，并通过常规自由基聚合制备无规共聚物前体。传统的热曲线从差示扫描量热法表明两个玻璃化转变温度（T（g）的）和广泛的T-g退火59/41摩尔%和25/75摩尔%的S/HS梯度共聚物，分别，这两者都含有短S端嵌段。相比之下，在57/43摩尔%的无规共聚物中观察到窄的Tg。通过溶液混合将每种S/HS共聚物以5重量%添加到80/20重量%聚苯乙烯（PS）/聚己内酯（PCL）共混物中，并测试其在熔融加工期间使共混物相容的能力; HS单元上的羟基可以与PCL酯基团形成氢键。S/HS无规共聚物不能作为增容剂，而两种梯度共聚物都是良好的增容剂。相对于没有共聚物的共混物，具有59/41摩尔% S/HS梯度共聚物的共混物还表现出初始分散相域尺寸和不规则形状域的显著减小，这是急剧减小的界面张力的指标。相比之下，具有25/75摩尔% S/HS梯度共聚物的共混物具有与不含共聚物的共混物相当的平均PCL结构域尺寸和宽的结构域尺寸分布。共混物中S/HS共聚物的存在导致降低的PCL结晶和熔融温度以及降低的结晶和熔融温度，这与共聚物在PCL结构域内部的一些增溶一致。(c)2006爱思唯尔有限公司保留所有权利。
Styrene (S)/4-hydroxystyrene (HS) copolymers are synthesized by hydrolysis of S/4-acetoxystyrene copolymer precursors; two gradient copolymer precursors are made by semi-batch, nitroxide-mediated controlled radical polymerization, and a random copolymer precursor is prepared by conventional free radical polymerization. Conventional heat curves from differential scanning calorimetry indicate two glass transition temperatures (T(g)s) and a broad T-g in well-annealed 59/41 mol% and 25/75 mol% S/HS gradient copolymers, respectively, both of which contain short S end-blocks. In contrast, a narrow Tg is observed in a 57/43 mol% random copolymer. Each S/HS copolymer is added at 5 wt% by solution mixing to an 80/20 wt% polystyrene (PS)/polycaprolactone (PCL) blend and tested for its ability to compatibilize the blend during melt processing; the hydroxyl groups on the HS units can form hydrogen bonds with the PCL ester groups. The S/HS random copolymer fails as a compatibilizer while both gradient copolymers are good compatibilizers. Relative to the blend without copolymer, the blend with 59/41 mol% S/HS gradient copolymer also exhibits a major reduction in initial dispersed-phase domain size and irregularly shaped domains, which are indicators of a sharply reduced interfacial tension. In contrast, the blend with 25/75 mol% S/HS gradient copolymer has an average PCL domain size comparable to the blend without copolymer and a broad domain size distribution. The presence of S/HS copolymers in the blend leads to reduced PCL crystallization and melting temperatures as well as reduced enthalpies of crystallization and melting, consistent with some solubilization of copolymer in the PCL domain interiors. (c) 2006 Elsevier Ltd. All rights reserved.