端糖基化聚(N-异丙基丙烯酰胺)的合成及其温敏性表征

制备了两种糖基引发剂(AcCDBr和AcG-lABr),以CuBr/三-(N,N-二甲基氨基乙基)胺(Me6TREN)为催化体系,应用原子转移自由基聚合方法,在60℃下引发N-异丙基丙烯酰胺聚合,脱去乙酰基保护后得到末端分别带有β-环糊精和2-氨基葡萄糖基团的线形聚(N-异丙基丙烯酰胺)(CD-PAM和GlA-PAM)。对产物的结构进行了表征,凝胶渗透色谱(GPC)测得聚合物分子量分布较窄(PDI=1.12～1.20)。采用紫外-可见吸收光谱仪(UV-Vis)和示差扫描量热仪(DSC)对聚合物水溶液的相转变行为进行了测试,结果表明末端引入糖类结构使得PNIPAM的最低临界溶解温度(LCST)升高,并随着分子量的增大而降低,而且相同聚合度的GlA-PAM的LCST比CD-PAM的高3.7℃左右。

Synthesis and thermo-responsive property of end-functionalized poly(N-isopropylacrylamide) with two saccharide groups

Two kinds of derived carbohydrates(AcCDBr and AcGlABr) were synthesized as the initiators for atom transfer radical polymerization(ATRP) of N-isopropylacrylamide.The polymerizations of end-functionalized poly(N-isopropylacrylamide) with different saccharide groups(CD-PAM and GlA-PAM for short) were carried out using CuBr/tris(2-dimethylaminoethyl)amine(Me6TREN) as the catalyst system with the feed ratio of nmonomer]0∶ninitiator]0∶n0∶nMe6TREN]0 = 50∶1∶1∶1 in DMF/water at 60℃.The structures of the initiators and the polymers were characterized by means of FT-IR and NMR.Low polydispersity indices(PDI = 1.12-1.20) were obtained by gel permeation chromatography(GPC).Ultraviolet-visible spectroscopy(UV-vis) and differential scanning calorimetry(DSC) were employed to measure the lower critical solution temperature(LCST) of the end-functionalized PNIPAMs.The results showed the LCSTs of end-functionalized PNIPAM were increased due to the hydrophilicity of the saccharide groups,and the LCST of GlA-PAM was about 3.7℃ higher than that of CD-PAM.Furthermore,the end-functionalized PNIPAM showed an inverse molecular weight dependence of their cloud points.