Crystallization behavior and hydrophobic properties of biodegradable ethyl cellulose-g-poly(3-hydroxybutyrate-co-3-hydroxyvalerate): The influence of the side-chain length and grafting density

The copolymerization of grafting poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) onto ethyl cellulose (EC) was carried out through the homogeneous acylation reaction between EC as a backbone and telechelic OH-terminated PHBV oligomer as side chains in 1,2-dichloroethane by using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent and dibutyltin dilaurate as catalyst. The resulting copolymers were studied by using NMR, FT-IR, WAXD, DSC, and contact angle measurements. It is found that with the increasing of the HDI/PHBV fraction, a transition exhibition occurred on crystallization behavior and hydrophobic properties, which could be modulated through controlling the lengths and grafting densities of PHBV side chains. Compared with those of neat PHBV, the degree of crystallinity for EC-g-PHBV1.8 decreased from 58.1% to 39.1%, the maximum decomposition temperature increased from 259.6 to 266.3 °C, and the contact angle increased from 60.1° to 95.7°.