Swelling behavior of thermosensitive polyvinyl alcohol-graft-N-isopropylacrylamide copolymer membranes containing carboxyl groups and properties of their polymer solutions

The thermosensitive polyvinyl alcohol-graft-N-isopropylacrylamidemethacryli c acid (PVA-g-NIPAAm-MAc) terpolymer membranes containing carboxyl groups w ere prepared. The swelling ratios of the membranes were measured at various temperatures. The temperature dependence of the swelling ratios of the ter polymer membranes was different from that of PVA-g-NIPAAm copolymer membran es. The swelling ratios of PVA-g-NIPAAm-MAc (5-15) (wt % in feed) increased with increasing temperature up to 35-38 degrees C, then decreased. However , the swelling ratio of PVA-g-NIPAAm-MAc (30-50) terpolymer membranes did n ot depend on temperature in the temperature range of 10-48 degrees C. To cl arify the swelling behavior of the PVA-g-NIPAAm-MAc terpolymer membranes, t he swelling ratios of the PVA-g-NIPAAm-Acrylic acid (AAc) terpolymer membra nes, the viscosity, and optical density of various polymer solutions were m easured. The different swelling behavior of PVA-g-NIPAAm-MAc (or AAc) terpo lymer membranes from that of PVA-NIPAAm copolymer membranes was thought to be due to hydrogen bonding between amide groups in NIPAAm moieties and carb oxyl groups in MAc (or AAc) moieties in the terpolymer membranes and the di fference of swelling behavior between PVA-g-NIPAAm-MAc and PVA-g-NIPAAm-AAc terpolymer membranes was thought to be brought about by hydrophobic intera ction due to methyl groups in PVA-g-NIPAAm-MAc terpolymer membranes. (C) 19 98 John Wiley & Sons, Inc.