Control of intermolecular cross-linking reaction in free-radical cross-linking monovinyl/divinyl copolymerizations by the aid of amphiphilic nature of primary polymer chains and cross-link units with opposite polarities
Control of intermolecular cross-linking reaction in free-radical cross-linking monovinyl/divinyl copolymerizations by the aid of amphiphilic nature of primary polymer chains and cross-link units with opposite polarities
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DOI：
10.1021/ma0479262
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发表时间：
2005-07-12
期刊：
影响因子：
5.5
通讯作者：
Matsumoto, A
中科院分区：
文献类型：
--
作者：
Doura, M;Naka, Y;Matsumoto, A
借助聚合物主链和交联单元的两亲性，控制自由基交联单乙烯基/二乙烯基共聚反应中的分子间交联反应，得到两亲性网络聚合物。首先，研究了甲基丙烯酸苄酯（BzMA）/二甲基丙烯酸三甘醇酯（PEGDMA-23）（95/5）在1，4-二氧六环（DO）和DO/H2O（85/15）混合溶剂中的共聚反应。聚合物短主链的组装诱导了聚合物自由基的受限运动，从而抑制了聚合物分子量随转化率的增加。第二，研究了甲基丙烯酸2-羟乙酯（HEMA）/二甲基丙烯酸二十一烷二醇酯（PPGDMA-21）（95/5）在DO、DO/H_2O（80/20）和DO/H_2O（70/30）混合溶剂中的共聚反应。非极性交联单元的组装导致了分子间交联反应的增强。此外，由聚（HEMA）在DO中组成的极性初级聚合物链的组装抑制了交联反应，如BzMA/PEGDMA-23（95/5）共聚的情况。然后，通过使用各种溶剂，概括了溶剂对凝胶化的影响。特别是，我们的注意力集中在乙腈（ACN）和N，N-二甲基甲酰胺（DMF）作为溶剂，因为在HEMA/PPGDMA-21（95/5）共聚所得的凝胶在DMF中溶胀，但在ACN中收缩，尽管几乎相同的溶解度参数为两种溶剂。因此，两亲性预聚物的主聚合物链和交联单元都不会在DMF中组装，而具有羟基的主聚合物链将在ACN中组装。短的聚合物主链在丙烯腈中的组装导致分子量随转化率的增加受到抑制，这反映了聚合物自由基的运动受到限制。总之，短的聚合物主链的组装抑制了分子间交联反应的发生，而长的交联单元的组装促进了它。
The control of the intermolecular cross-linking reaction in free-radical cross-linking monovinyl/divinyl copolymerizations resulting in amphiphilic network polymers was attempted by the aid of amphiphilic nature of primary polymer chains and cross-link units with opposite polarities. First, benzyl methacrylate (BzMA)/tricosaethylene glycol dimethacrylate (PEGDMA-23) (95/5) copolymerizations in 1,4-dioxane (DO) and DO/H2O (85/15) mixed solvent were investigated. The assembly of short primary polymer chains induced the restricted motion of propagating polymer radical, leading to a suppressed increment of molecular weight with conversion. Second, 2-hydroxyethyl methacrylate (HEMA)/henicosapropylene glycol dimethacrylate (PPGDMA-21) (95/5) copolymerizations in DO, DO/H2O (80/20) mixture, and DO/H2O (70/30) mixture were explored. The assembly of nonpolar cross-link units led to an enhanced occurrence of intermolecular cross-linking reaction. Moreover, the assembly of polar primary polymer chains consisting of poly(HEMA) in DO suppressed the cross-linking reaction as is the case with BzMA/PEGDMA-23 (95/5) copolymerizations. Then, the solvent effect on gelation was generalized by using various solvents. Especially, our attention was focused on acetonitrile (ACN) and N,N-dimethylformamide (DMF) as solvents because the resulting gel in HEMA/PPGDMA-21 (95/5) copolymerization swelled in DMF but shrank in ACN despite almost the same solubility parameters for both solvents. Thus, both primary polymer chains and cross-link units of amphiphilic prepolymers would not assemble in DMF, whereas primary polymer chains having hydroxyl groups would assemble in ACN. The assembly of short primary polymer chains in ACN led to a suppressed increment of molecular weight with conversion as a reflection of the restricted motion of propagating polymer radical. Conclusively, the assembly of short primary polymer chains suppressed the occurrence of intermolecular cross-linking reaction, whereas the assembly of long cross-link units promoted it.