Cellulose/poly (2-hydroxyethyl methacrylate) composites prepared via solution coagulation and subsequent bulk polymerization

Conditions are described for the preparation of eellulose/poly(2-hydroxyethyl methacrylate) (CELL/ PHEMA) composites from solutions of cellulose in dimethylacetamide-lithium chloride (DMAc LiCl) by coagulation with 2-hydroxyethyl methacrylate monomer and subsequent bulk polymerization of the coagulated films. The CELL/PHEMA composites obtained over a wide composition range were characterized mainly through measurements of the temperature dependence of the dynamic storage modulus (E') and loss modulus (E"). For compositions rich in PHEMA (PHEMA > 80 wt%), it was assumed that an original structure of 'as-coagulated' cellulose gels was successfully perpetuated into the PHEMA matrix and, concurrently, an 'IPN'-type organization resulted. These samples gave a Tg value higher than that of PHEMA ( ~ 75°C), and the degree of lowering of their modulus E' in the glass transition region became extremely small with increasing CELL content. The E" versus temperature curves for cellulose-rich compositions (PHEMA < 30 wt%) yielded a single, broad dispersion peak, the maximum position of which was located above 150°C and shifted to the side of higher temperature along with the decrease in PHEMA component. This dispersion was interpreted as due to a molecular relaxation in the abundant amorphous regions of cellulose into which PHEMA constituent was intimately incorporated. Other samples with intermediate CELL/PHEMA compositions showed a dual transition behaviour, due to phase separation into two distinct amorphous mixtures of both polymers.