Three crosslinkers, poly(ethylene glycol) diacrylate (PEGDA), glycerol ethoxylate triacrylate (GETA) and citric acid-(PEG acrylate)₃ (CA-PEGTA) derived from poly(ethylene glycol) (PEG) were synthesized at first. The three series of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels were prepared by photopolymerization with the crosslinkers and compared with a hydrogel based on commercial crosslinker, N,N′-methylene bis-acrylamide (NMBA). The influence of the crosslinker structures and contents on the swelling behaviour, mechanical properties, and drug release of the hydrogels was investigated. The results showed that the hydrogels based on PEGDA and NMBA exhibited the highest and the lowest swelling ratio, respectively. The content of crosslinker of all hydrogel series showed good thermosensitivity and thermo-reversibility. The critical gel transition temperature (CGTT) appeared at 32 °C for the hydrogel based on NMBA, but appeared at about 34 °C for other hydrogels due to higher hydrophilicity of the crosslinker. In the mechanical properties, three-arms crosslinker GETA and CA-PEGTA led to higher mechanical strength than a linear crosslinker PEGDA. A hydrogel based on GETA (NG6) showed the highest shear modulus of 656.9 kPa and Young’s modulus of 1655.0 kPa. The hydrogels containing higher content of crosslinker revealed lower swelling ratio and higher mechanical strength. In the drug release, the hydrogels with higher swelling ratios showed higher drug absorbed. The highest release percentage of caffeine and vitamin B12 for hydrogel based on PEGDA (NP6) could reach 68.3% and 75.4%, respectively. In addition, the bound water and toxicity of the hydrogels were also investigated.

中文翻译：

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聚乙二醇衍生的交联剂对热敏水凝胶性能的影响

首先合成了三种交联剂：聚（乙二醇）二丙烯酸酯（PEGDA），甘油乙氧基化三丙烯酸酯（GETA）和衍生自聚（乙二醇）（PEG）的柠檬酸-（PEG丙烯酸酯）₃（CA-PEGTA）。通过与交联剂进行光聚合制备了三种系列的聚（N-异丙基丙烯酰胺）（PNIPAAm）水凝胶，并与基于商业交联剂N，N'-亚甲基双的水凝胶进行了比较。-丙烯酰胺（NMBA）。研究了交联剂结构和含量对水凝胶的溶胀行为，机械性能和药物释放的影响。结果表明，基于PEGDA和NMBA的水凝胶分别表现出最高和最低的溶胀率。所有水凝胶系列交联剂的含量均显示出良好的热敏性和热可逆性。基于NMBA的水凝胶的临界凝胶转变温度（CGTT）出现在32°C，而其他水凝胶的临界凝胶转变温度出现在约34°C，这是因为交联剂的亲水性更高。在机械性能方面，三臂交联剂GETA和CA-PEGTA导致的机械强度高于线性交联剂PEGDA。基于GETA（NG6）的水凝胶的最高剪切模量为656.9 kPa，杨氏模量为1655.0 kPa。含有较高交联剂含量的水凝胶显示较低的溶胀率和较高的机械强度。在药物释放中，具有较高溶胀率的水凝胶显示出较高的药物吸收率。基于PEGDA（NP6）的水凝胶中咖啡因和维生素B12的最高释放百分比分别可以达到68.3％和75.4％。另外，还研究了水凝胶的结合水和毒性。