Randomly cross-linked homopolymer networks: synthesis by group transfer polymerization in solution and characterization of the aqueous degree of swelling

Randomly cross-linked homopolymer networks of 2-(dimethylamino)ethyl methacrylate (DMAEMA) of various average degrees of polymerization (DPs) between cross-links were synthesized by group transfer polymerization (GTP) in tetrahydrofuran (THF), using 1-methoxy-1-(trimethylsiloxy)-2-methyl propene (MTS) as the initiator, ethylene glycol dimethacrylate (EGDMA) as the cross-linker (eightfold molar excess with respect to the initiator), and tetrabutylammonium bibenzoate (TBABB) as the catalyst. Networks with monomer-to-initiator molar ratios of 5, 10, 20, 50, 100 and 200 were synthesized successfully, while an attempted synthesis with a monomer-to-initiator molar ratio of 500 did not produce a network. The networks were characterized in terms of their degree of swelling (DS) in water and the effects of DP, pH, salt concentration and temperature were investigated. Moreover, the aqueous degrees of swelling determined in this study of random networks were compared to the aqueous degrees of swelling of model networks also synthesized by GTP and using a similar procedure.