Temperature-responsive character of acrylic acid and N-isopropylacrylamide binary monomers-grafted celluloses

Abstract

Grafted celluloses with grafted chains consisting of two types of monomer components, acrylic acid (AA) and N-isopropylacrylamide (NIPAAm), were prepared by two photografting methods using periodic acid oxidized cellulose. Dissolving pulp from softwoods was used as the cellulose sample. In the first method (one-step procedure), AA and NIPAAm monomer mixtures were photografted at 50°C on the oxidized sample. With the second method (two-step procedure), AA was first photografted on the oxidized sample and then NIPAAm was further photografted on the AA-grafted sample. The resulting grafted celluloses (one- and two-step samples) prepared by the one- and two-step procedures, respectively, were characterized by the monomer sequence distribution of the grafted chains; that is, the grafted chains of the one-step sample are composed of a random copolymer of AA and NIPAAm, while the monomer sequence of the grafted chains of the two-step sample is of block type with respect to each monomer component. The both grafted celluloses exhibited a temperature-responsive character, in which it swelled and shrank in water at 5°C and 50°C, respectively. The extent of the character was larger for the one-step sample compared to the two-step sample. The temperature-responsive character was considerably improved by treating the grafted celluloses with N, N ′-methylenebisacrylamide, by which a crosslinked structure was introduced into the grafted samples. Moreover, the grafted celluloses were found to have an ability to adsorb cupric ion, the extent of which depended on the preparation methods, such as the one- and two-step procedures.