Journal of Polymer Science Part A: Polymer Chemistry, Vol.54, No.11, 1560-1572, 2016
Vinyl Phenylboronic Acid Controlling Co-Monomer for Nitroxide Mediated Synthesis of Thermoresponsive Poly(2-N Morpholinoethyl Methacrylate)
Low concentrations of 4-vinylphenylboronic acid (VPBA) were copolymerized with 2-N-morpholinoethyl methacrylate (MEMA) by nitroxide mediated polymerization using BlocBuilder (TM) unimolecular initiator at 80 to 90 degrees C. The MEMA/VPBA copolymerizations were performed at initial feed compositions (f(VPBA, 0)) of 0.05 to 0.10 VPBA, with f(VPBA, 0)=0.10 using dimethylacetamide (DMAc) solvent being most effective, as seen by a linear increase in number average molecular weight, M-n, versus conversion and low dispersity, (D < 1.40. The copolymers were further chain-extended with a second batch of VPBA, resulting in a block copolymer with monomodal molecular weight distribution and D = 1.66. For MEMA/VPBA copolymers, increases in VPBA composition and polymer solution concentration resulted in decreases in the cloud point temperature (CPT, typically varied between 27.4-37.8 degrees C) and CPT increased from 31.2 to 33.8 degrees C to about 88 degrees C with decreases in pH from 7 to 4. Rheological tests with small angle light scattering (SALS) confirmed CPTs measured by UV-Vis and DLS. These copolymers were targeted as models to combine possible glucose-sensing boronic acid functionality the thermoresponsiveness provided by MEMA groups. (C) 2015 Wiley Periodicals, Inc.
Keywords:copolymerization;block copolymers;nitroxide-mediated polymerization;water-soluble polymers;stimuli-sensitive polymers