Counterion effect on the rheology and morphology of tailored poly(dimethylsiloxane) ionomers
Counterion effect on the rheology and morphology of tailored poly(dimethylsiloxane) ionomers
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DOI：
10.1021/ma052275a
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发表时间：
2006-02-21
期刊：
影响因子：
5.5
通讯作者：
Winey, KI
中科院分区：
文献类型：
--
作者：
Batra, A;Cohen, C;Winey, KI
我们对聚二甲基硅氧烷(PDMS)离聚体随时间变化的流变性和形态进行了系统的研究，其中离子之间的单体数目和链上的离子数目是阳离子的函数。用小角X射线散射(SAXS)和扫描电子显微镜(STEM)对样品的结构进行了分析。非平衡新沉淀离聚体的流动行为从流动的液体到弱网络不等。流动的低摩尔%锌和钴离聚体在STEM图像中不显示聚集体，而以凝胶形式沉淀的镓、钡和高摩尔%锌离聚体显示不同范围的聚集体。所有离聚体在室温下达到平衡状态的速度非常慢，在高温下达到平衡状态的速度更快，并且是一个物理上与阳离子无关的交联网络。对于不同的阳离子，观察到非常不同的形貌。低摩尔%(约1摩尔%)的离聚体有棒状和球状离子聚集体；镓离聚体有不均匀分布的高度分散的球形聚集体；低摩尔%(约1摩尔%)的锌和钴离聚体没有聚集体，而高摩尔%(约7.4mol%)的锌离聚体则有球形和棒状聚集体。阳离子的性质对平衡样品的弹性模量影响不大。
We have carried out a systematic study of the time-dependent rheology and morphology of poly(dimethylsiloxane) (PDMS) ionomers with tailored number of monomers between ions and number of ions per chain as a function of the cation. Small-angle X-ray scattering (SAXS) and scanning transmission electron microscopy (STEM) were used to examine the structure of the samples. The flow behavior of nonequilibrated freshly precipitated ionomers varies from flowing liquids to weak networks. Low mol % zinc and cobalt ionomers that flow do not show aggregates in STEM images whereas gallium, barium, and high mol % zinc ionomers that precipitate as gels show a diverse range of aggregates. The equilibrium state of all ionomers is reached very slowly at room temperature or more rapidly at high temperatures and is a physically cross-linked network irrespective of the cation. Very different morphologies were observed for different cations. Low mol % (similar to 1 mol %) barium ionomers have rod-shaped and spherical ionic aggregates; gallium ionomers have inhomogeneously distributed highly polydisperse spherical aggregates; and low mol % zinc and cobalt ionomers have no aggregates whereas high mol % (similar to 7.4 mol %) zinc ionomers have spherical and rodlike aggregates. The nature of the cation has little influence on the elastic modulus of the equilibrated samples.