Temperature and Recognition Dual Responsive Poly(N-Isopropylacrylamide) and Poly(N,N-Dimethylacrylamide) with Adamantyl Side Group

A series of copolymers with an adamantyl side group (poly(NIPAM-co-AdMA) and poly(DMAM-co-AdMA)) were prepared by radical copolymerization of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) with a 2-methyl-2-adamantylmethacrylate (AdMA) monomer. The structure and composition of the as-synthesized copolymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance ((1)H NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and elemental analysis. Temperature and recognition dual responsivity of the copolymers was investigated by cloud point (T(cp)) and dynamic light scattering (DLS), respectively. The results show that the as-synthesized copolymers are a kind of temperature-responsive polymer with a lower critical solution temperature (LCST). T(cp) was approximately consistent with the critical temperature of intermolecular copolymer association (T(ass)) from DLS. For these copolymers, T(cp) decreases with increasing content of AdMA unit in the copolymers. After the addition of β-cyclodextrins (β-CD), T(cp) increases, and the increment of T(cp) values gradually became large with increasing content of AdMA in the copolymers. It is host-guest molecular recognition of β-CD and adamantyl groups that endows the as-synthesized copolymers with recognition-tunable thermosensitivity.