Synthesis and characterization of carboxymethyl xylan-g-poly(propylene oxide) and its application in films

Carboxymethyl xylan-g-poly(propylene oxide) (CMX-g-PPO) was successfully synthesized by grafting poly(propylene oxide) chains onto xylan from bamboo using the Al(Oi-Pr)3 initiated ring-opening polymerization of propylene oxides, followed by carboxymethylation with sodium chloroacetate under microwave irradiation. The synthesized CMX-g-PPO was well characterized by FT-IR, 13C NMR, and AFM. The AFM imaging showed that the average sizes of xylan were 422.1 × 67.4 × 1.2 nm, while the average sizes of grafting branches PPO were 128.0 × 38.5 × 5.1 nm, which firstly provided an irrefutable and visual evidence for the structure of grafted xylan at single molecular level. Subsequently, a serial of CMX-g-PPO/CS films were prepared without addition of any plasticizers. The surface morphologies, wettability, water vapor barrier properties, mechanical properties, and thermal stabilities of the obtained films were characterized and compared with those of the control films by AFM, contact angle, WVP, tensile testing, and TGA, respectively.