Synthesis and Properties of pH and Temperature Responsive Copolymer with Pesudorotaxane Structure

pH and temperature responsive copolymers PNAM4VBCB of N-isopropyl acrylamide（NAM） and complex pseudorotaxane monomer N 1-（4-vinylbenzyl）-1,4-diaminobutane dihydrochloride with cucurbit[6]uril（CB[6]） threaded（4VBCB） were prepared via free-radical polymerization in aqueous solution.The copolymers were characterized by 1 H NMR,Fourier transform infrared（FTIR） spectrometry,elemental analysis,and static light scattering.The thermodynamic properties of the copolymers were studied by thermogravimetric analysis（TGA）,and the effects of pH and the concentration of the copolymer on the average hydrodynamic radius（R h） were studied by dynamic light scattering（DLS）.In addition,the thermal sensitivities of the copolymers were studied by DLS and UV-Vis.The experiment data show that CB[6] beads are localized on 1,4-diaminobutane units in the side chains of the copolymer.TGA data show that thermal stability of the copolymers increases with the adding of CB[6] threaded because of the enhanced rigidity and the bulky steric hindrance of 4VBCB in the side chain of PNAM4VBCB.DLS data show that the average hydrodynamic radius of copolymer increases with the increase of the copolymer concentration and has a jump with adjusting pH due to the existing of the small size CB[6] dethreaded from the copolymer with increasing pH.Both pH and electrical conductivity curves of the solution of PNAM4VBCB-4 have a jump because CB[6] could dethread from the copolymers with the addition of NaOH.In addition,the copolymers have thermal sensitivity and their phase-change temperatures could be controlled by adjusting the molar ratio of NAM to 4VBCB in the copolymers.