Hydrolytic degradation of cellulose-graft-poly(l-lactide) copolymers.

A series of cellulose- g -poly( l -lactide) (cellulose-g-PLLA) copolymers with 30.65–85.21 % PLLA weight content and the molar substitution of PLLA (MS PLLA ) from 0.99 to 12.73 were synthesized via the homogeneous graft-from reaction in 1-allyl-3-methylimidazolium chloride (AmimCl) with 4-dimethylaminopyridine (DMAP) acting as the catalyst. In common organic solvents, the solubility of obtained graft copolymers was better than cellulose and strongly depended on the MS PLLA . The hydrolytic degradation of cellulose- g -PLLA copolymers was investigated in phosphate buffered solution (PBS, pH 7.4) at 37 °C. Interestingly, it was found that, when the MS PLLA was below 8.83, the hydrolytic degradation rate of cellulose- g -PLLA copolymers was obviously faster than that of both pristine cellulose and PLLA. Moreover, as the MS PLLA decreased, the cellulose- g -PLLA copolymers showed a more rapid weight loss, due to its higher hydrophilicity. Both XPS and 1 H NMR analyses demonstrated the degradation occurred mainly at PLLA segments. The morphological observations indicated that, during the hydrolytic degradation, the graft copolymers firstly experienced a surface erosion process, and then the bulk erosion happened. [ABSTRACT FROM AUTHOR]