Group transfer polymerization (GTP) was used for the preparation of eight amphiphilic networks based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA). Seven of the networks had linear segments of well-defined molecular weight between cross-links; i.e., they were model networks. In the eighth network the lengths of the segments between cross-links had a wide molecular weight distribution (random network) since the cross-linker was copolymerized with the monomers. Five model networks were based on ABA triblocks with polyDMAEMA mid-blocks and polyMMA end-blocks. In these networks the degree of polymerization (DP) of the polyDMAEMA midblock was 20, while the overall DPs were 25, 30, 40, 60, and 120. The sixth model network was based on an equimolar BAB triblock with a polyMMA mid-block and an overall DP ) 40. The seventh model network was based on an equimolar statistical copolymer with a total DP ) 40. The degrees of swelling (DSs) of the networks increased below pH 7. The DSs at low pH increased with the percentage of the hydrophilic monomer. The statistical copolymer-based model network exhibited higher DSs than the isomeric triblock copolymers. Calculations based on a molecular thermodynamic model provided aqueous DSs of ionized networks with the same qualitative trends as the experimental ones, although 30 times higher, reflecting catenation. The model also predicted microphase separation in most ionized ABA triblock-based networks.

Group transfer polymerization was used for the one-pot preparation of a network structure comprising cross-linked star homopolymers. The structure contains many dangling chains (constituting the arms of the primary stars), whose number is approximately equal to the number of the elastic chains. 2-(Dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate were used as the monomer and cross-linker, respectively. The synthesis involved a four-step sequential addition of monomer/cross-linker/monomer/cross-linker, which produced linear polymer, "arm-first" star polymer, "in-out" star polymer, and cross-linked star polymer network, respectively. The products of the first three steps of the synthesis were characterized in terms of their relative molecular weights by gel permeation chromatography, and in terms of their absolute molecular weights by static light scattering, which indicated that the number of arms in the "arm-first" stars is about 50, whereas that in the "in-out" stars is about 100. Seven networks were prepared in total, covering a range of degrees of polymerization of the primary and the secondary arms. The degrees of swelling of all the networks were measured in water and were found to increase by lowering the pH, a result of the ionization of the tertiary amine group of the monomer repeat unit.

ABA triblock copolymers comprising a relative long poly(2-(dimethylamino)ethyl methacrylate) end-capped by short poly(methyl methacrylate) blocks (PMMA-b-PDMAEMA-b-PMMA) were synthesized using group transfer polymerization (GTP), and their aqueous solution properties were explored in aqueous media. At low pH these copolymers behaved as cationic telechelic polyelectrolytes (TP) and were self-organized through hydrophobic interactions among the PMMA blocks (stickers). Two types of associates were observed by atomic force microscopy (AFM) at very low concentrations:  end-to-end linear associates and star like “hairy” loose aggregates where the one end of the TP was located in an irregular hydrophobic core and the other remained as a dangling end (absence of looping chains). By increasing the concentration, finite size clusters (microgels) were formed, the size of which changed continuously, leading eventually to the formation of an infinite transient network. All the structures were visualized by AFM with molecular resolution.