Design, Synthesis And Properties Of A Novel Photo-/Thermo-Responsive Polymer

With the demand for responsive smart materials increasingly, the development of these flied tends to seek multi-functional responsive polymer materials with good reversibility, high sensitivity, and high controllability. At present, multi-stimuli responsive polymers have been reported in a number of ways, but they are usually obtained by copolymerization of two or more kinds of response monomers. In this paper, through rational molecular design, dual stimuli-responsive polymers with photo-responsive groups of azobenzene and thermo-responsive segments of oligo(ethylene glycol)(OEG) was successfully synthesized, at the same time, the influence factors on photo-responsive or thermo-responsive behaviors were investigated.1, A new dual-responsive monomer(MTEOnAzo, n= 2, 3) containing both thermo-responsive and photo-responsive groups was designed and successfully synthesized. The results show that both of the two monomers have thermo-responsive and reversible photo-isomerization. In addition, the lower critical solution temperature(LCST) of monomer solution increased with increasing of its hydrophilic property. What's more, it is found that, before and after the LCST of monomer solution, the temperature have an affect on its UV-Vis absorption. Meanwhile, by UV irradiation, the LCSTs of monomer solution tend to reduce 3 ~ 6 oC.2, A series of polymers with different length of hydrophilic end groups, PTEO2 Azo and PTEO3 Azo, was obtained by free radical polymerization, and the properties of its aqueous solution was investigated. PTEO2 Azo does not dissolve in water, while PTEO3 Azo has good water solubility with longer hydrophilic end group in room temperature. By the detailed study of PTEO3 Azo aqueous solution, showing that it has photo-responsive and thermo-responsive. The LCST of PTEO3 Azo aqueous solution is 55.8 oC and less dependent on the concentration, but affected by salt species and the degree of its influence is basically consistent with the Hofmeister sequence; On the other hand, it is found that before and after the LCST of polymer aqueous solution, the temperature have an affect on its UV-Vis absorption. At the same time, the LCST of polymer aqueous solution decreased with the increase of the UV irradiation time and tended to be stable and recovered again after visible light irradiation; Therefore, by changing the ultraviolet and visible light, we can well control the LCST of polymer solution.3, Via CPDB as chain transfer agent, a series of polymer(P1~P7) with well-defined molecular weights and narrow molecular weight distribution was successfully synthesized by RAFT polymerization. The characterization of the polymers was performed with 1H NMR, GPC, TGA and UV-Vis. Response studies indicated that all polymers revealed a reversible photo-isomerization properties, and the molecular weight have an effect on the ?-?* electronic transition absorption peak; Meanwhile, the LCST of the polymers solution increases with the increase of polymer molecular weight, and the maximum difference is 17 oC(1 mg mL-1). Furthermore, compared with the UV-Vis absorption spectra of P1 and P7 at different temperatures, it is found that low and high molecular weight polymers have a sensitive response. However, the LCST of the polymers solution reduced to varying degrees after UV irradiation.