A review on thermally induced phase separation technology in the fabrication of microporous polymer membrane devices for sustained-repellent delivery: Crystallization and morphological studies

This article reports recent advances in thermally induced phase separation technology in fabricating microporous scaffold polymeric membranes as devices suitable for the controlled release of insect repellent. The key aspects, such as the crystallization behavior and morphological study of the polymeric membrane-based repellent, were reported and discussed. Studies demonstrated that trapping of such repellents into microporous polymeric materials can be achieved by spinodal decomposition of the polymer/liquid repellent system. Usually, solubility is enhanced at elevated temperatures. Rapid cooling of such solution below the UCST leads to the formation of cocontinuous phase structures by decomposition. The polymer then forms an open-cell structure with the repellent trapped inside. Approaches to forming such an open-cell polymer structure containing mosquito repellent were successfully performed and confirmed with the SEM and POM techniques. It showed the structure of a polymer and liquid repellent prepared by spinodal decomposition, providing proof that thermally induced spinodal decomposition is a route to trap liquid mosquito repellent into a microporous polymer matrix. Additionally, the effects of polymer type, repellent nature, cooling conditions, and fillers on the morphology and performance of TIPS membranes are also discussed. Finally, challenges in developing microporous polymeric membrane-based repellent using TIPS technology are addressed.