High-sensitivity stimuli-responsive polysiloxane synthesized via catalyst-free aza-Michael addition for ibuprofen loading and controlled release

Abstract

Herein, we report a strategy to synthesize a series of high-sensitivity stimuli-responsive polysiloxanes (SPSis) via a facile, highly efficient, catalyst-free aza-Michael addition of poly(aminopropylmethylsiloxane) (PAPMS) with N-isopropylacrylamide. The SPSis structures are systematically characterized using FT-IR, ¹H NMR and ¹³C NMR. The effects of N-isopropyl amide group (NIPAs) content in PAPMS, pH, and salinity on the responsive properties of SPSis are examinated in detail. The as-prepared SPSis show high sensitive respond to three changes of thermo-, pH-, and salinity, where the phase separation occurred within 0.3 °C due to their flexible Si–O–Si backbone, and lower critical phase separation (LCST) changed from 14.7 °C to 57.0 °C at varied NIPAs contents. Surprisingly, the SPSis exhibit effectively hydrogen bond-derived loading (up to 74 wt%) and temperature-dependent release of hydrophobic drugs (ibuprofen). The present methodology may open a route for developing high-sensitive multi-stimuli-responsive polymers.