Lower LCST Research Articles

Effect of HPC on the Thermo-Sensitive and Hydrophilicity of PAN Films

In this paper, a series of blending films were prepared based on Polyacrylonitrile (PAN) and hydroxypropylcellulose (HPC). The phase transition temperature of these blend films was investigated by warming UV-vis spectrophotometer and Differential Thermal Scanning Calorimetry (DSC). The results showed that the phase transition temperature of HPC/PAN blend films was lower than that of HPC when adding PAN into HPC and the more PAN contents the lower LCST of blend films. The contact angle and surface image of HPC/APN blend films were studied. It was indicated that HPC could endow PAN film with not only thermo-sensitive property but also great hydrophilicity.

Self-oscillating gel composed of thermosensitive polymer exhibiting higher LCST

We have developed self-oscillating polymers and gels as novel biomimetic materials by utilizing an oscillating reaction, known as the Belousov–Zhabotinsky (BZ) reaction. The self-oscillating polymer gel is composed of a poly(N-isopropylacrylamide) (PNIPAAm) network in which the catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the gel undergoes spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli. In order to induce self-oscillation while maintaining a larger amplitude at higher temperatures and around body temperature for potential applications to biomaterials, etc., here we prepared a self-oscillating gel composed of a thermosensitive N,N′-ethylmethylacrylamide (EMAAm) polymer exhibiting a higher LCST than that of the NIPAAm polymer. The self-oscillating behavior of the poly(EMAAm-co-Ru(bpy)3) gel was investigated by comparing against gels composed of a thermosensitive NIPAAm polymer with a lower LCST or non-thermosensitive N,N′-dimethylacrylamide (DMAAm) polymer. The design concept of self-oscillation at higher temperatures without a decrease in swelling–deswelling amplitude was demonstrated by utilizing a thermosensitive polymer exhibiting a higher LCST.

Effect of time on the hydration and temperature-induced phase separation in aqueous polymer solutions. 1H NMR study

Dehydration during temperature-induced phase separation in D 2O solutions of poly(vinyl methyl ether) (PVME), poly( N-isopropylmethacrylamide) (PIPMAm) and poly( N-isopropylacrylamide) (PIPAAm) was followed from time dependences of NMR spin–spin relaxation times T 2 of HDO. Both the time characterizing the exclusion of the water from mesoglobules (manifested by the increase in T 2 values) and the induction period which precedes the increase in T 2 values, increased in the order PVME < PIPMAm < PIPAAm. For D 2O solutions of PIPMAm/PVME (or PIPMAm/PIPAAm) mixtures a direct connection between the state of the mesoglobules (hydrated or dehydrated) formed by the component with lower LCST (PVME, PIPAAm) and the temperatures of the phase transition of the PIPMAm component was established by NMR spectroscopy.