Fast and opposite temperature responsivity in release behavior of cocontinuous hydrogel composites

Abstract

For practical implementation, numerous attempts have been made to improve the mechanical durability and response rate of temperature-responsive hydrogels. In this study, the introduction of a cocontinuous structure with polydimethylsiloxane (PDMS), which successfully improved both the properties, was found to reverse the temperature dependence of release behavior. The cocontinuous composites of poly(N-isopropylacrylamide) (PNIPAm) and PDMS were prepared via directional melt crystallization and subsequent infiltration of PDMS. The compressive moduli of composites were more than 30 times higher than those of PNIPAm. Further, the existence of soft hydrophobic PDMS walls against the PNIPAm phases accelerated the deswelling process, and thus, it was more than 2,000 times faster than that of PNIPAm. The deswelling rate increased as the size of PDMS phases increased. The release rate accelerated above the lower critical solution temperature (LCST) and slowed below the LCST, reversibly, thereby opposing the behavior of PNIPAm. Therefore, the fast volume shrinkage of PNIPAm phases confined between PDMS phases is responsible for the unique release behavior of the composites, and not the molecular diffusion processes through hydrogel mesh structures. Collectively, these findings highlight a versatile tool for engineering the release behavior of smart drug carriers based on temperature-responsive hydrogels. © 2021 The Korean Society of Industrial and Engineering Chemistry