Mathur A M, Hammonds K F, Klier J, Scranton A B
Department of Chemical Engineering, Michigan State University, East Lansing 48824, USA.
J Control Release. 1998 Jul 31;54(2):177-84. doi: 10.1016/s0168-3659(97)00186-7.
Responsive hydrogel networks comprising of poly(methacrylic acid) (PMAA) backbone and oligomeric ethylene glycol (PEG) grafts were synthesized by free-radical solution polymerization and their equilibrium swelling properties were characterized in aqueous solutions of a homologous series of alcohols. These hydrogels are known to exhibit swelling transitions in response to external stimuli which lead to formation or disruption of hydrogen-bonded complexes between the backbone and the grafts. Swelling studies performed in aqueous mixtures of methanol, ethanol and propanol revealed that the effectiveness of an alcohol in breaking the PMAA/PEG complexes increased as the aliphatic segment length of the alcohol was increased. These results confirm the importance of hydrophobic interactions for stabilizing the complexes. Studies performed to determine the effect of the synthesis conditions on the equilibrium swelling properties revealed that the equilibrium degree of swelling increased as the solvent fraction during synthesis was increased. Finally, molecular stimulations revealed that it is sterically possible to form complexes with a 1:1 stoichiometry between chains of poly(methacrylic acid) and poly(ethylene glycol) with essentially no additional bond strain.
通过自由基溶液聚合合成了由聚（甲基丙烯酸）（PMAA）主链和低聚乙二醇（PEG）接枝物组成的响应性水凝胶网络，并在一系列同系醇的水溶液中表征了它们的平衡溶胀性能。已知这些水凝胶会响应外部刺激而发生溶胀转变，这会导致主链和接枝物之间氢键复合物的形成或破坏。在甲醇、乙醇和丙醇的水性混合物中进行的溶胀研究表明，随着醇的脂肪族链段长度增加，醇破坏PMAA/PEG复合物的有效性增加。这些结果证实了疏水相互作用对稳定复合物的重要性。为确定合成条件对平衡溶胀性能的影响而进行的研究表明，随着合成过程中溶剂分数的增加，平衡溶胀度增加。最后，分子模拟表明，聚（甲基丙烯酸）链和聚（乙二醇）链之间以1:1化学计量比形成复合物在空间上是可能的，且基本上没有额外的键应变。
