直链型与支链型疏水缔合水凝胶的机械性能与溶胀行为

以丙烯酰胺(AM)为亲水单体,脂肪醇聚氧乙烯醚丙烯酸酯(AEO-AC-n-m,n为疏水端烷基链碳的数目,m为亲水端PEG链的长度,n,m=13,5;10,5;13,10)为疏水单体,十二烷基硫酸钠(SDS)为表面活性剂,过硫酸钾(KPS)为引发剂,通过胶束聚合制备了3种聚丙烯酰胺-co-脂肪醇聚氧乙烯醚丙烯酸酯(AM-co-AEO-AC)疏水缔合水凝胶.以疏水烷基链为直链的疏水单体AEO-AC-13-5合成的直链型水凝胶的网络结构均匀且强度高,其形态在水中可维持180 d.而以疏水烷基链为支链的疏水单体AEO-AC-10-5与AEO-AC-13-10合成的支链型水凝胶的机械性能较弱,60 d内即溶解于水中.在相同条件下,直链型水凝胶断裂时的最大应力是支链型水凝胶的4~5倍.利用弹性橡胶理论中的新胡克方程计算了直链型和支链型水凝胶的有效交联密度ν0和有效交联点间的分子量Mc.

Mechanical Strength and Swelling Behavior of Fatty Alcohol Polyoxyethylene Acrylate Hydrophobic Associated Hydrogels

We designed a series of hydrophobic hydrogels( HA-gels) through micellar copolymerization with acrylamide( AM) as hydrophilic monomer, a little amount of fatty alcohol polyoxyethylene acrylate( AEO-AC-n-m:n is the amount of carbon chain, m is the amount of PEG chain, n, m=10, 5;13, 5; 13, 10) as hydrophobic monomer, and potassium thiosulfate( KPS) as initiator in sodium dodecyl sulfate( SDS) aqueous solution. The “straight HA-gels” prepared by AEO-AC-13-5 with straight carbon chain, possess uniform network structure and higher mechanical properties and can maintain their shapes in still water for 180 d. Conversely, the “branched HA-gels” synthesized by AEO-AC-10-5, AEO-AC-13-10 with various branched carbon chains, show relatively weak mechanical properties and degrade in water within 60 d. More specifical-ly, the maximum broken stress of straight HA-gels is almost 4—5 times higher than branched HA-gels under the same constraints. On the basis of the neo-Hookean equation of the rubber elastic theory, the effective network chain density v0 and the molecular weight of the chain length between cross-linking points Mc were evaluated for straight and branched HA-gels.