Effect of phenolic acids on temperature-sensitive property of self-assembly of ionic pair of poly(ethylene imine)/(phenylthio)acetic acid

Abstract

The ionic pair self-assembly (IPSAM) composed of poly(ethyleneimine) (PEI) and (phenylthio)acetic acid (PTA) was prepared and the effect of phenolic acids (PAs) (e.g. cinnamic acid (CA), hydroxycinnamic acid (HCA), and dihydroxycinnamic acid (DHCA)) on the upper critical solution temperature (UCST) and the temperature-responsive releasing property of IPSAM were investigated. PEI/PTA ionic pair showed a UCST behavior and the PAs decreased the UCST effectively in the order of DHCA > HCA > CA. The PAs were thought to attach to the PEI chain of PEI/PTA ionic pair as pendants. PEI/PTA(3/7) ionic pair was found to be air/water interface-active. CA had little effect on the interfacial activity of the ionic pair. HCA and DHCA significantly decreased the interfacial activity. IPSAM was found as nanoparticles whose diameter was tens of nanometer and PAs had little effect on the shape and the size of IPSAM. The release degree of cargo loaded in IPSAM increased slowly with time lapse when below UCST. Whereas, the release degree increased rapidly with time lapse when above UCST, possibly because of the thermally-induced disintegration of IPSAM.