Zhang Zhenfang, Li Qian, Yesildag Cigdem, Bartsch Christoph, Zhang Xiaoyuan, Liu Wei, Loebus Axel, Su Zhiqiang, Lensen Marga C
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Beijing Key Laboratory of Advanced Functional Polymer Composites, Beijing University of Chemical Technology, Beijing 100029, China.
Polymers (Basel). 2018 Sep 1;10(9):970. doi: 10.3390/polym10090970.
The network structure of hydrogels is a vital factor to determine their physical properties. Two network structures within hydrogels based on eight-arm star-shaped poly(ethylene glycol)(8PEG) have been obtained; the distinction between the two depends on the way in which the macromonomers were crosslinked: either by (i) commonly-used photo-initiated chain-growth polymerization (8PEG⁻UV), or (ii) Michael addition step-growth polymerization (8PEG⁻NH₃). The crystallization of hydrogels is facilitated by a solvent drying process to obtain a thin hydrogel film. Polarized optical microscopy (POM) results reveal that, while in the 8PEG⁻UV hydrogels only nano-scaled crystallites are apparent, the 8PEG⁻NH₃ hydrogels exhibit an assembly of giant crystalline domains with spherulite sizes ranging from 100 to 400 µm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses further confirm these results. A model has been proposed to elucidate the correlations between the polymer network structures and the crystallization behavior of PEG-based hydrogels.
水凝胶的网络结构是决定其物理性质的关键因素。基于八臂星形聚乙二醇（8PEG）的水凝胶内部已获得两种网络结构；两者的区别取决于大分子单体的交联方式：一是通过（i）常用的光引发链增长聚合（8PEG⁻UV），二是通过（ii）迈克尔加成逐步增长聚合（8PEG⁻NH₃）。通过溶剂干燥过程促进水凝胶的结晶，以获得薄水凝胶膜。偏光显微镜（POM）结果表明，在8PEG⁻UV水凝胶中仅出现纳米级微晶，而8PEG⁻NH₃水凝胶则呈现出球晶尺寸范围为100至400 µm的巨型结晶域聚集体。扫描电子显微镜（SEM）和原子力显微镜（AFM）分析进一步证实了这些结果。已提出一个模型来阐明聚合物网络结构与基于PEG的水凝胶结晶行为之间的相关性。
