STATICS AND DYNAMICS OF OMEGA-FUNCTIONALIZED BLOCK-COPOLYMERS OF STYRENE AND ISOPRENE
STATICS AND DYNAMICS OF OMEGA-FUNCTIONALIZED BLOCK-COPOLYMERS OF STYRENE AND ISOPRENE
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DOI：
10.1021/ma00118a045
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发表时间：
1995-07
期刊：
影响因子：
5.5
通讯作者：
G. Floudas;G. Fytas;S. Pispas;N. Hadjichristidis;T. Pakuła;A. Khokhlov
中科院分区：
文献类型：
--
作者：
G. Floudas;G. Fytas;S. Pispas;N. Hadjichristidis;T. Pakuła;A. Khokhlov
用小角X射线散射、流变学和介电谱研究了ω功能化的苯乙烯和异戊二烯两嵌段共聚物的静力学和动力学。不对称两嵌段共聚物(ωPS 30%)的链两端均含有二甲氨基或两性离子基团，分子量在(0.6 2~2.44)×10 4之间。根据温度的不同，SAXS结果显示了两种不同程度的微相分离，一种是形成微区结构的聚苯乙烯(PS)和聚异戊二烯(PI)之间的微相分离，另一种是离子和非离子材料之间的微相分离。后一个过程产生了足够的对比，尽管两性离子基团很少。当两性离子连接到PI链端时，在低温下在PI相中形成聚集体。这些聚集体分别在流变学和介电谱中表现出来，具有扩展的橡胶平台和与限制等电点分段松弛相关的新的介电过程。当两性离子位于PS链端时，在高温下，PS相中会发生缔合作用，并将新的微区稳定到非常高的温度。与中性嵌段相比，ω功能化的两嵌段共聚物构成了一类新的材料，它可以通过在链的一端引入少量的极性基团来改变相行为。
The statics and dynamics of ω-functionalized diblock copolymers of styrene and isoprene have been studied with small-angle X-ray scattering (SAXS) and with rheology and dielectric spectroscopy. The asymmetric diblock copolymers (ω PS 30%) had a dimethylamino or zwitterion group at either end of the chain, and the molecular weights were in the range (0.62-2.44) x 10 4 . Depending on the temperature, the SAXS results revealed two separate levels of microphase separation, one between the polystyrene (PS) and polyisoprene (PI) blocks forming the microdomain structure and another one between ionic and nonionic material. The latter process creates sufficient contrast notwithstanding the small fraction of the zwitterionic groups. When the zwitterion is linked to the PI chain end, aggregates are formed at low temperatures within the PI phase. These aggregates manifest themselves both in rheology and in dielectric spectroscopy, respectively, with an extended rubbery plateau and with a new dielectric process associated with restricted PI segmental relaxation. When the zwitterion is located on the PS chain end, association takes place, at high temperatures, within the PS phase and acts to stabilize the new microdomain up to very high temperatures. When compared with neutral diblocks, the ω-functionalized diblock copolymers constitute a new class of materials which provide the possibility of altering the phase behavior by introducing a small amount of a polar group at one chain end.