Synthesis and shape memory effects of Si–O–Si cross-linked hybrid polyurethanes
Synthesis and shape memory effects of Si–O–Si cross-linked hybrid polyurethanes
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DOI：
10.1016/j.polymer.2005.11.035
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发表时间：
2006-01
期刊：
影响因子：
4.6
通讯作者：
Jianwen Xu;W. Shi;W. Pang
中科院分区：
文献类型：
--
作者：
Jianwen Xu;W. Shi;W. Pang
以异佛尔酮二异氰酸酯（IPDI）、聚环氧乙烷（PEO）和一种新合成的含可水解Si-OEt基团的杂化二元醇（HD）为原料，合成了一系列具有形状记忆效应的Si-O-Si交联有机/无机杂化聚氨酯（HYPUs）。采用广角X射线散射（WAXS）、差示扫描量热法（DSC）、动态力学分析（DMA）和形状恢复测试等方法对Si-OEt水解缩合后的薄膜进行表征，研究了形状记忆行为与聚合物结构之间的关系。随着Si-O-Si交联度的增加，杂化聚氨酯的玻璃化转变温度（Tg）和储能模量增加。当加热温度高于Tg 25 ° C时，杂化聚氨酯在大气中和水中分别在40 s和10 s内几乎完全恢复到其原始形状。形状记忆机制是由于非晶态分子链的微布朗运动在低温下的冻结和在高温下的激活，因为恢复曲率发生最急剧变化的温度范围被发现在它们的玻璃化转变范围附近。在TgDMA以下和TgDMA以上的储能模量的高比率解释了在低温下的暂时形状固定。具有更多Si-O-Si交联的样品在高温下具有更高的储能模量，导致更快的形状恢复速度但更低的临时形状固定。
A series of novel Si–O–Si cross-linked organic/inorganic hybrid polyurethanes (HYPUs) with shape memory effect were prepared from isophorone diisocyanate (IPDI), poly(ethylene oxide) (PEO), and a newly synthesized hybrid diol (HD) containing hydrolysable Si–OEt groups. After hydrolyzation and condensation of Si–OEt groups, the resulted films were characterized using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and shape recovery test to get the insight into the relationship between shape memory behaviors and polymeric structures. The glass transition temperatures (Tg) and storage modulus increased with Si–O–Si cross-linking increasing in the hybrid polyurethanes. The hybrid polyurethanes can recover to their original shapes almost completely in less than 40s in atmosphere and in less than 10s in water, respectively, when heated at 25°C above Tg. The shape memory mechanism is coming from the freezing at low temperature and activation at high temperature of micro-Brownian movement of amorphous molecular chains since the temperature ranges at which the sharpest changes of recovered curvature happened are found to be around their glass transition range. The high ratio of storage modulus below and above TgDMAaccounted for the temporary shape fixing at low temperature. The samples with more Si–O–Si cross-linking have higher storage modulus at high temperature, resulting in faster shape recovery speed but lower temporary shape fixing.