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·1120·                            精细化工   FINE CHEMICALS                                  第 35 卷

            2.5   P(DEA-co-DMAEMA)/Na 2 WO 4 水凝胶的 pH           重响应性能。通过 Na 2 WO 4 与 DMAEMA 的配位作
                 响应性                                           用,构成物理交联网络,Na 2 WO 4 充当物理交联点。
                 P(DEA-co-DMAEMA)/Na 2 WO 4 水凝胶 同样表            引入 Na 2 WO 4 后的水凝胶孔结构随 Na 2 WO 4 用量的
            现出 pH 敏感性,不同 pH 下 D7∶3Wz 水凝胶的溶                     增加而逐渐减小。由于 Na 2 WO 4 的物理交联作用,
            胀率曲线见图 7。由图 7 可知,D7∶3 的溶胀率曲                        复合水凝胶的力学性能得到显著提升。当 Na 2 WO 4
            线分为两部分:pH<3 时,凝胶的溶胀率随 pH 的增                        质量分数为 3%时,复合水凝胶的储能模量达到了
            大而增大;pH>3 后,凝胶的溶胀率随 pH 的增大而                        2.26 kPa。改变 Na 2 WO 4 用量可以调节水凝胶的温敏
            减小。DMAEMA 是一种弱碱性聚合物单体,结构                           性能,LCST 随 Na 2 WO 4 质量分数的增加呈线性降
            中含有可质子化的叔胺基,其 pKa=7.2               [16] 。当溶液      低,Na 2 WO 4 质量分数为 3%时,复合水凝胶的 LCST
            pH<7.2 时,叔胺基转化为季铵基,此时聚合物带上                         降低至 34.4 ℃。引入 Na 2 WO 4 后,复合水凝胶表现
            正电荷,亲水性增强,由于正电荷之间的静电排斥                             出双重 pH 响应性能。
            作用使得水凝胶的溶胀率增加;当溶液 pH>7.2 后,
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            叔胺基不发生质子化,此时 DMAEMA 的疏水性相
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