Preparation and Characterization of Temperature and pH-Responsive P(N-vinylcaprolactam-crotonic Acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) Hydrogels

The temperature and pH responsive hydrogels of the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate) and polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl methacrylate) were prepared by free radical polymerization using N-vinylcaprolactam, crotonic acid, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate as raw materials. In the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) hydrogels, N-vinylcaprolactam is the temperature sensitive component, and crotonic acid is pH sensitive component. Six the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) hydrogels with different 2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate contents were prepared. The chemical structure and morphology of the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) hydrogels were characterized by fourier transform infrared spectrum and scanning electron microscopy, respectively. The swelling kinetic curves and equilibrium swelling ratios under different temperature and pH of the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) hydrogels were tested. Mechanical properties of the two hydrogels were determined by compressive testing. Results show that the 2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate content in the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate/2-hydroxyethyl methacrylate) hydrogels affects the pore size, swelling ratio and mechanical properties. Compared with the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl methacrylate) hydrogel, the polymer(N-vinylcaprolactam-crotonic acid-2-hydroxyethyl acrylate) hydrogel has higher swelling properties and mechanical properties due to its uniform network structure.