A Versatile Biodegradable Polymer with a Thermo-Reversible/Irreversible Transition

A versatile biodegradable thermoresponsive polymer was developed. The polymer has succinimide and isopropylasparamide segments and exhibits a phase transition with thermoreversibility that can be controlled by changing the polymer composition. With fewer succinimide units, the polymer exhibits the type of thermo-reversible phase transition that is characteristic of poly( N -isopropylacrylamide) (PNIPAAm). The polymer with a higher proportion of succinimide units exhibits a thermo-irreversible phase transition, resulting in the formation of nanospheres that are stable below the transition temperature. The stable nanospheres are generated by dehydration and subsequent conformational stabilization through an interaction between imide rings. This thermoirreversible phase transition in water provides a simple, oil-free preparation of biodegradable nanospheres.