高机械性能的聚(丙烯酸-co-甲基丙烯酸十八酯)疏水缔合凝胶的溶胀行为研究

以丙烯酸(AA)、甲基丙烯酸十八酯(OMA)、十二烷基硫酸钠(SDS)为原料,采用胶束共聚的方法合成了疏水缔合(HA)凝胶.在HA凝胶内部,表面活性剂SDS与疏水单体OMA组成的增溶胶束起到物理交联作用,将亲水的聚合物链交联起来.通过单向拉伸试验证实了该凝胶具有较高的机械性能.此外,也测试了HA凝胶在不同pH值溶液中的溶胀行为.结果显示,HA凝胶具有特殊的溶胀行为,其溶胀过程可以分为凝胶溶蚀、溶胀平衡和凝胶瓦解3个阶段.在强酸性条件下,凝胶的溶胀被抑制,没有出现凝胶瓦解阶段.在强碱性条件下,凝胶的溶胀被促进,溶胀平衡阶段被越过.盐的存在也会抑制HA凝胶的溶胀,但在SDS溶液中,溶液中的SDS会促使凝胶中的疏水改性聚合物溶解到溶液中去,组成新的缔合结构,而使溶液增稠。

STUDIES ON SWELLING BEHAVIOR OF POLY(ACRYLIC ACID-co-OCTADECYL METHACRYLATE) HYDROPHOBIC ASSOCIATION HYDROGELS WITH HIGH MECHANICAL PROPERTIES

The hydrophobic association hydrogels(HA gels) were synthesized through micellar copolymerization of acrylic acid(AA) and a small amount of octadecyl methacrylate(OMA) in solution containing sodium dodecyl sulphate(SDS).The associated micelles consisting of surfactants and hydrophobes acted as physical cross-linking points in the network structure of HA gels.The mechanical properties of HA gels were measured by one-way tensile experiments,and the results confirmed the high toughness of as-obtained hydrogels.The mechanical properties were associated with the effective network chain density and the effective cross-linking point contents.With increasing the content of hydrophilic or hydrophobic monomer in the HA gels,the strength of HA gels all increased while the elongation at break all decreased.Furthermore,the swelling behavior of HA gels in aqueous solutions at different pH values was also investigated.It was found that the HA gels possessed unusual swelling behavior.The swelling process could be divided into three stages:namely,the gel erosion stage,swelling equilibrium stage and gel disruption stage.At strong acidity,the swelling of gel was restrained,and the gel disruption stage did not appear.At strong alkaline condition,the swelling of gels was accelerated so that the swelling equilibrium stage was overpassed.Last,the salt effect restrained the swelling of HA gels,however,in SDS aqueous solutions,the SDS would drag the hydrophobically modified polymers into solution,then new association network was formed,and thus the solution was thickened.