Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8685, Japan.
Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Soft Matter. 2023 Feb 22;19(8):1653-1663. doi: 10.1039/d2sm01036d.
Polymer crystallization drastically changes the physical properties of polymeric materials. However, the crystallization in polymer networks has been little explored. This study investigated the crystallization behavior of a series of poly(ethylene glycol) (PEG) networks consisting of well-defined branched precursors. The PEG networks were prepared by drying gels synthesized at various conditions. The PEG networks showed slower crystallization with lower final crystallinity than uncrosslinked PEGs with amine end groups. Surprisingly, the effect of network formation was not as significant as that of the relatively bulky end-groups introduced in the uncrosslinked polymer. The molecular weight of the precursor PEG, or equivalently the chain length between neighboring junctions, was the primary parameter that affected the crystallization of the PEG networks. Shorter network chains led to lower crystallization rates and final crystallinity. This effect became less significant as the network chain length increased. On the other hand, the spatial and topological defects formed in the gel synthesis process did not affect the crystallization in the polymer networks at all. The crystallization in the polymer networks seems insensitive to these mesoscopic defects and can be solely controlled by the chain length between junctions.
聚合物结晶会极大地改变聚合材料的物理性质。然而，聚合物网络中的结晶却鲜有研究。本研究探究了一系列聚（乙二醇）（PEG）网络的结晶行为，这些网络由结构明确的支化前体制备。PEG 网络是通过干燥在不同条件下合成的凝胶制备的。PEG 网络的结晶速度较慢，最终结晶度低于具有胺端基的未交联 PEG。令人惊讶的是，网络形成的影响并不像在未交联聚合物中引入相对较大的端基那样显著。前体 PEG 的分子量，或者等效于相邻连接点之间的链长，是影响 PEG 网络结晶的主要参数。较短的网络链导致较低的结晶速率和最终结晶度。随着网络链长的增加，这种影响变得不那么显著。另一方面，在凝胶合成过程中形成的空间和拓扑缺陷对聚合物网络中的结晶没有任何影响。聚合物网络中的结晶似乎对这些介观缺陷不敏感，并且可以仅通过连接点之间的链长来控制。
