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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. © 2006 American Chemical Society. 39 2 678 683 Cited By :51

Four isomeric terpolymers based on benzyl methacrylate (BzMA, nonionic hydrophobic), 2-(dimethylamino)ethyl methacrylate (DMAEMA, ionizable hydrophilic), and methoxyhexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) were synthesized using group transfer polymerization (GTP). The three of the terpolymers were the ABC block sequence isomers, ABC, ACB, and BAC, and the fourth was the statistical terpolymer. Their theoretical molecular weight was 5000 g mol-1, and the theoretical w/w composition was 33% from each monomer. The success of the synthesis was confirmed by gel permeation chromatography (GPC), which showed that the experimental molecular weights were in reasonable agreement with the theoretical ones and the polydispersity indices were low (in most cases Cited By :17

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. 35 7 2506 2513 Cited By :68

Synthesis and characterization of polyampholytic model networks were studied using group transfer polymerization (GTP). The degrees of swelling (DSs) of all the polyampholytic networks were also measured as a function of pH. It was observed that DSs of all networks presented a minimum around the isoelectric point where the net charge is zero, while they increased at alkaline and acidic pHs. 35 6 2252 2260 Cited By :38

43 344 345 Sponsors: 3M Company Air Products and Chemicals, Inc. Ashland Specialty Chemicals Co. Basell Inc. BASF Corporation et al. Conference code: 104817

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. 13 12 4738 4744 Cited By :48

The equilibrium constants of various candidates for the crosslinking reaction between chromium(III) and partly hydrolysed polyacrylamide have been calculated. For this purpose use has been made of a) the crosslinking index in gels to calculate the concentration of crosslinks, b) pH-dependent concentrations of various hydrolysis products of Cr3+ ions and c) pH-dependent concentration of free carboxylic acid anions. The conclusion is that the crosslinks consist of two carboxylic acid anions coordinated with the dimerisation product of the Cr3+ ions. 171 189 200 Cited By :11