Bell C L, Peppas N A
School of Chemical Engineering, Purdue University, West Lafayette, IN 47907-1283, USA.
J Biomater Sci Polym Ed. 1996;7(8):671-83. doi: 10.1163/156856296x00444.
Grafted poly(methacrylic acid-g-ethylene glycol) (P(MAA-g-EG)) copolymers were synthesized and their pH sensitivity investigated as a function of copolymer composition and PEG graft molecular weight. Interpolymer complexation occurred by hydrogen bonding between carboxylic groups on poly(methacrylic acid) (PMAA) and ether groups on poly(ethylene glycol) (PEG). This complexation was sensitive to the surrounding environment as complexes formed at pH levels low enough to insure substantial protonation of PMAA acid groups. At high pH, the acid groups became neutralized and did not form complexes. P(MAA-g-EG) membranes showed pH-sensitivity due to complex formation and dissociation. Uncomplexed equilibrium swelling ratios were much higher than those of the complexed states and varied according to copolymer composition and PEG graft length. Mesh sizes in the two states were determined. Swelling under oscillatory pH conditions and constant ionic strength revealed the dynamic sensitivity of P(MAA-g-EG) membranes. Under changing pH conditions, network syneresis (complexation) occurred more rapidly than network expansion (decomplexation) because of the rates of diffusion of specific ions causing the responses. No distinct water fronts were observed. Instead, water transport was continuous through the gel. These gels show great promise for a number of biomedical applications where fast biomaterial response is necessary.
合成了接枝聚（甲基丙烯酸 - g - 乙二醇）（P(MAA - g - EG)）共聚物，并研究了其pH敏感性与共聚物组成和聚乙二醇接枝分子量的关系。聚合物间的络合作用是通过聚（甲基丙烯酸）（PMAA）上的羧基与聚（乙二醇）（PEG）上的醚基之间的氢键形成的。这种络合作用对周围环境敏感，因为在足够低的pH值下形成络合物，以确保PMAA酸基团大量质子化。在高pH值下，酸基团被中和，不形成络合物。P(MAA - g - EG)膜由于络合物的形成和解离而表现出pH敏感性。未络合的平衡溶胀率远高于络合状态的溶胀率，并根据共聚物组成和PEG接枝长度而变化。测定了两种状态下的网孔尺寸。在振荡pH条件和恒定离子强度下的溶胀揭示了P(MAA - g - EG)膜的动态敏感性。在变化的pH条件下，由于引起响应的特定离子的扩散速率，网络脱水收缩（络合）比网络膨胀（解络合）发生得更快。未观察到明显的水前沿。相反，水通过凝胶持续传输。这些凝胶在许多需要快速生物材料响应的生物医学应用中显示出巨大的潜力。
