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.

Synthesis and Characterization of pH-Responsive Block Copolymers with Primary Amine Groups

A new pH-responsive block copolymer, methoxy poly（ethylene glycol）-b-poly[5-methacrylamido- pentylamine hydrochloride]（mPEG-b-PMAAPA） was synthesized and characterized in this paper. The monomer 5-methacrylamido-pentylamine hydrochloride（MAAPA） and the macroinitiator（mPEG-ACVA） were synthesized, re- spectively, and mPEG-b-PMAAPA was then obtained by free radical polymerization. The structure and molecular weight of mPEG-b-PMAAPA were cont]rmed by hydrogen nuclear magnetic resonance（~H NMR） spectroscopy and gel permeation chromatography with multiangle laser light scattering（GPC-MALLS） measurements. At a low pH, it is hydrophilic due to the protonation of the primary amine groups. With increasing pH value, deprotonation occurs and the hydrophobicity of PMAAPA block increases. This molecular feature leads to interesting aggregation behavior of mPEG-b-PMAAPA in aqueous solutions at different pH values as revealed by dynamic light scattering（DLS） measurements, transmission electron microscopy（TEM） observations and resonance light scattering（RLS） measure- ments.

SYNTHESIS AND PROPERTIES OF COPOLYMERS CONTAINING CUCURBIT[6]URIL-BASED PSEUDOROTAXANE STRUCTURE

Novel copolymers based on acrylamide （AM） and complex pseudorotaxane monomer N＇-（3-vinylbenzyl）-l,4- diaminobutane dihydrochloride with cucurbit[6]uril （CB[6]） （3VBCB） were prepared via free-radical polymerization in aqueous solution, and characterized by XH-NMR, FT-IR, elemental analysis and static light scattering. The compositions of the copolymers （PAM3VBCB） with pseudorotaxane units were determined by 1H-NMR and elemental analysis. Thermal properties of the copolymers were studied by TGA, and the effects of the copolymer concentration and pH on the average hydrodynamic radius （Rh） of the copolymer molecules were studied by dynamic light scattering （DLS）. The experiment data show that CB[6] beads are localized on 1,4-diaminobutane units in side chains of the copolymers. TGA results show that thermal stability of the copolymer increases with increasing the content of pseudorotaxane unit because of the enhanced rigidity and the bulky steric hindrance of 3VBCB in side chains of PAM3VBCB. DLS data show that the average hydrodynamic radius of copolymer molecules increases with the increase in the copolymer concentration, and both the pH and electrical conductivity of PAM3VBCB solutions demonstrate an acute change with addition of NaOH because of CB[6] dethreading from the side chains of PAM3VBCB. CB[6] threading and dethreading of PAM3VBCB could be controlled by addition of BaC12 and Na2SO4.