Smart morpholine-functional statistical copolymers synthesized by nitroxide mediated polymerization

Morpholine-functional homopolymers and copolymers (using 4-acryloylmorpholine (4AM), 2-N-morpholinoethyl acrylate (MEA) and 2-N-morpholinoethyl methacrylate (MEMA)) were synthesized by nitroxide mediated polymerization (NMP) and tested for aqueous thermo-responsiveness. MEA homopolymerizations and MEMA/9-(4-vinylbenzyl)-9H-carbazole (VBK) were controlled as evidenced by linear increases in number-average molecular weight, Mn¯, versus conversion (X < 0.75) and relatively low polydispersities Mw¯/Mn¯=1.30−1.60. For MEMA/VBK copolymers, increases in copolymer Mn¯, VBK content in the copolymer and polymer concentration in aqueous solution resulted in a decrease in the cloud point temperature, CPT (typically varied between 33.7 and 47.9 °C). 2-(dimethylamino)ethyl methacrylate (DMAEMA)/4AM copolymerizations were controlled when initial 4AM molar composition f4AM,0 > 0.10; however, the resulting final copolymers exhibited a sharp and completely reversible CPT only when f4AM,0 < 0.20. Poly(MEA) was water-soluble but was not thermo-responsive.