Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties.

Leakage and accumulation of highly stable commercial plastics has led to substantial contamination of the environment. Highly isotactic poly(propylene oxide) (PPO) was investigated as a potential high-strength thermoplastic with greater susceptibility toward degradation under ambient conditions. Various stereoregular forms of PPO including enantiopure, enantioenriched, racemic, and stereoblock were synthesized with a single catalyst architecture in the presence of chain transfer agents. These materials were found to possess the same approximate ultimate tensile strength (UTS) via uniaxial tensile elongation analysis (∼75 MPa). A serrated tensile response corresponding to stress oscillations was observed in all forms of PPO. An investigation on strain rate dependence showed that an increase in strain rate results in the decay and disappearance of the serrated response. Further evaluation of PPO revealed its dramatic strain hardening afforded an UTS comparable to that of nylon-6,6. Exposing PPO to UVA light (365 nm) resulted in photolytic degradation. Following 30 days of continuous exposure at 250 μW cm, the decreased from 93 kDa to 21 kDa, while samples not exposed to UVA light remained unchanged. Through selective stabilization with antioxidant additives, we believe PPO could be a suitable replacement for nylon-6,6 in environmentally susceptible applications.