温度和pH双重敏感型聚氨酯水凝胶的制备及性能

Synthesis and Characterization of Thermal-and pH-Sensitive Polyurethane Hydrogels

以聚乙二醇(PEG)、4,4’-二苯基甲烷二异氰酸酯(MDI)、三羟甲基丙烷(TMP)为主要原料,分别采用1,4-丁二醇(BDO)、N-甲基二乙醇胺(MDEA)、2,2-二羟甲基丙酸(DMPA)为扩链剂,制备了3种聚氨酯水凝胶Hydrogel(a)、Hydrogel(b)、Hydrogel(c)。通过红外光谱、差示扫描量热分析、X射线衍射和溶胀实验对水凝胶的结构和性能进行了分析。研究结果表明,温度敏感链段(PEG)和pH敏感基团(-N(CH_3)-、-COOH)均成功地引入到了水凝胶分子链中;3种水凝胶的相转变温度分别为55℃、60℃和64℃,且合成后水凝胶中PEG的结晶结构仍然存在;当水溶液温度从45℃上升到60℃时,3种水凝胶的平衡溶胀度均显著减小,显示出温度敏感性;当pH从4.0上升到7.0时,Hydrogel(c)的平衡溶胀度从11.5增大到15.5,当pH从8.5上升到11.5时,Hydrogel(b)的平衡溶胀度从12.9减小到10.0,均显示出pH敏感性;在不同温度(25℃和65℃)和pH(2.5和11.5)的水溶液中反复溶胀,水凝胶Hydrogel(b)和Hydrogel(c)均表现出良好的可逆性和稳定性。

Three types of thermal- and pH-sensitive polyurethane （PU） hydrogels were successfully synthesized via three-step polymerization using polyethylene glycol （PEG）, 4,4’-diphenylmethane diisocyanate （MDI）, 2-ethyl-2-（hydroxymethyl）-1,3-propanediol （TMP） as main raw materials and 1,4-butanediol （BDO）, N-methyldiethanolamine （MDEA）, dimethylolpropionic acid （DMPA） as chain extenders. FT-IR, DSC, XRD, swelling tests, swelling-deswelling tests were used to characterize the structures and properties of the PU hydrogels. FT-IR analysis demonstrate that the thermal-sensitive component （PEG） and pH-sensitive functional groups （-N（CH3）- and -COOH） are successfully incorporated into the PU hydrogels. DSC and XRD analysis reveal that the PEG crystallization in the PU hydrogels is still retained and the phase transition temperatures of the PU hydrogels appeare at 55 ℃, 60 ℃ and 64 ℃, respectively. In addition, the swelling tests show the thermal- and pH-sensitive properties for all PU hydrogels. Concretely, when the temperature increases from 45 ℃ to 60 ℃, the equilibrium swelling ratio （ESR） for the PU hydrogels shows an obvious decrease. Moreover, the ESR for hydrogel （b） sharp decreases from 12.9 to 10.0 in the pH range from 8.5 to 11.5, while the ESR for hydrogel （c） significantly increases from 11.5 to 15.5 in the pH range from 4.0 to 7.0, both of them showing pH-sensitive property. The swelling-deswelling cycles show that Hydrogel （b） and Hydrogel （c） possess good reversibility and stability.