Thermal and physicochemical dissimilarities of biological poly-3-hydroxyalkanoates following graft copolymerization with acrylamide under ultrasonication.

Poly-3-hydroxyalkanoate (PHA) and polyacrylamide (PAM) are potentially copolymerized into a novel hybrid material with distinctive characteristics but scarcely explored. In this study, the copolymerization of semicrystalline and amorphous forms of PHA, designated as scPHA and amPHA, with PAM utilizing ultrasonication and hydrogen peroxide as the initiator under defined conditions were investigated. The effect of varying acrylamide amounts on the yield and properties of graft copolymers (PHA-g-MA) were characterized by molecular weight changes, thermal and spectroscopic properties. Grafting scPHA and amPHA with PAM influenced their initial molecular weights (Mw). Specifically, scPHA's Mw decreased from 140 × 103 to ∼130 × 103 g mol-1, while amPHA's Mw increased from 62 × 103 to ∼68 × 103 g mol-1. Additionally, scPHA and amPHA copolymers showed an increase in thermal decomposition temperature (Td) from 240 °C to 265 °C and 275 °C to 285 °C, respectively. The presence of an amide functional group in the copolymers was authenticated by a Raman peak at 1100 cm-1. Both scPHA and amPHA graft copolymers exhibited unique contrast to their neat counterpart. The scPHA-g-PAMs showed strong crystalline characteristics, evidenced by elevated glass transition and melting temperatures, alterations in crystalline planes and surface morphologies, and a decrease in dielectric constant values. Conversely, amPHA-g-PAMs showed pronounced amorphous characteristics, substantiated by a lowered glass transition and melting temperatures, altered surface morphologies, and increased dielectric constant values. The observations made are attributed to distinct chain packing characteristics between both graft copolymers, which are the consequence of the PHA alkyl side chains length. The biological PHA graft copolymers may offer a diverse array of applications such composite for tissue engineering and biosensor development.