ATRP技术制备末端和中间功能化的温度敏感性聚N,N-二乙基丙烯酰胺

Synthesis of End-functional and Mid-functional Temperature-responsive Poly(N,N-diethyl-acrylamide) by ATRP

合成了2种含有二硫吡啶结构的原子转移自由基聚合(ATRP)引发剂,ATRP引发剂结构采用核磁共振氢谱(1H-NMR)表征.结果显示,二硫吡啶结构被成功引入引发剂结构末端或链中间.利用2种ATRP引发剂分别制备了链末端功能化和链中间功能化的聚N,N-二乙基丙烯酰胺(pDEAAm).采用1H-NMR和凝胶渗透色谱(GPC)对聚合物结构和分子量进行了表征.1H-NMR结果显示,二硫吡啶基团被引入聚合物链末端或中间.GPC结果表明,末端功能化和中间功能化的聚N,N-二乙基丙烯酰胺(pDEAAm)分子量分布指数分别为1.21和1.23,实现了分子量的可控聚合.并且,具有2个引发位点的引发剂引发单体得到聚合物的分子量较大.采用紫外-可见分光光度法研究了聚合物在溶液中的温度响应性.紫外-可见分光光度法结果说明,pDEAAm溶液在28°C发生相分离,在溶液中表现出温度响应性,且最低临界溶解温度(LCST)为28°C.在末端功能化和中间功能化温敏型pDEAAm可用于嵌段共聚物的合成以及与生物大分子的定位结合.特别对于中间功能化的pDEAAm,有望用于星型聚合物和多臂聚合物的设计和制备.

Two types of atom transfer radical polymerization （ATRP） initiators containing disulfide pyridine structure were synthesized and characterized by ^1H-NMR. The results revealed that disulfide pyridine was successfully introduced to the end or the middle of the ATRP initiator molecule. N,N-diethyl-acrylamide （DEAAm） was initiated by the ATRP initiators using ATRP to prepare the end-functional （end-functional pDEAAm） and the middle-functional poly（N,N-diethyl-acrylamide） （mid-functional pDEAAm）, respectively. Both the end- and mid-functional pDEAAm were characterized by ^1H-NMR and gel permeation chromatography （GPC）. ^1H-NMR results showed that disulfide pyridine was successfully introduced into the end-group of pDEAAm chain to form theend-functional pDEAAm or the middle of the chain of pDAAm to give the mid-functional pDEAAm, respectively. GPC results showed that the molecular weight of the end-functional pDEAAm and the mid-functional pDEAAm with narrow distribution was controlled by ATRP. Polydispersity index （PDI） of the end-functional pDEAAm was 1.21, and that of the mid-functional pDEAAm was 1.23. The molecular weight of the mid-functional pDEAAm was higher than that of the end-functional pDEAAm. The results suggested that ATRP initiator with two initiating sites increased the molecular weight of the pDEAAm. Furthermore, the temperature-responsive behaviors of polymers in the aqueous solutions were tested by UV-visible spectrophotometer. Both types of pDEAAms showed excellent temperature-sensitivity in aqueous solution. The lower critical solution temperature （LCST） of the pDEAAms was identified as 28 ~C. Below the LCST, pDEAAms were completely dissolved in water. In contrast, above the LCST of pDEAAms, phase separation appeared in the polymers aqueous solutions. The position of disulfide pyridine structure in pDEAAms chain did not influence the temperature-responsive behavior of the polymers aqueous solutions. Both pDEAAm are expected to be useful to prepare block copolymers and to bind site-specifically to biomacromolecules. In particular, the mid-functional pDEAAm will be useful to prepare the star-polymers and the multi-armed polymers.