Synthesis and characterization of anionic amphiphilic model conetworks of 2-butyl-1-octyl-methacrylate and methacrylic acid: effects of polymer composition and architecture.

Seven amphiphilic conetworks of methacrylic acid (MAA) and a new hydrophobic monomer, 2-butyl-1-octyl-methacrylate (BOMA), were synthesized using group transfer polymerization. The MAA units were introduced via the polymerization of tetrahydropyranyl methacrylate (THPMA) followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. Both THPMA and BOMA were in-house synthesized. Ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. Six of the conetworks were model conetworks, containing copolymer chains between cross-links of precise molecular weight and composition. The prepared conetwork series covered a wide range of compositions and architectures. In particular, the MAA content was varied from 67 to 94 mol %, and three different conetwork architectures were constructed: ABA triblock copolymer-based, statistical copolymer-based, and randomly cross-linked. The linear conetwork precursors were analyzed by gel permeation chromatography and 1H NMR spectroscopy in terms of their molecular weight and composition, both of which were found to be close to the theoretically calculated values. The degrees of swelling (DS) of all the amphiphilic conetworks were measured in water and in THF over the whole range of ionization of the MAA units. The DSs in water increased with the degree of ionization (DI) and the content of the hydrophilic MAA units in the conetwork, while the DSs in THF increased with the degree of polymerization of the chains between the cross-links and by reducing the DI of the MAA units. Finally, the nanophase behavior of the conetworks was probed using small-angle neutron scattering and atomic force microscopy.