Photografting of N-isopropylacrylamide on cellulose and temperature-responsive character of the resulting grafted celluloses

Photografting (lambda > 300 nm) of N-isopropylacrylamide (NIPAAm) on cellulose was investigated at 50 degrees C in water solvent. Fibrous dissolving pulp from softwoods was used as the cellulose sample. Oxidation and swelling treatments of the cellulose sample with aqueous solutions of periodic acid and sodium hydroxide, respectively, were useful for enhancing an ability of the sample to initiate the photografting, where about 80% of NIPAAm monomer used could be introduced into the cellulose sample as grafted chains. The oxidized cellulose sample was also proven to have a high activity for the ceric-salt-initiated grafting of NIPAAm, though a maximum percent grafting was observed at a certain concentration of eerie salt and the value was lower than the percent grafting of the photografting system under the same grafting conditions. The resultant NIPAAm-grafted cellulose samples exhibited a temperature-responsive character, where they swelled and shrank in water at temperatures lower and higher around 30 degrees C, respectively. It was found that the extent of the character is not influenced by the grafting initiation systems, but largely affected by the swelling treatment of cellulose before grafting. That is, the character was smaller for the grafted cellulose samples prepared using swollen sample than those prepared using unswollen sample. (C) 1998 Elsevier Science B.V. All rights reserved.