Synthesis of End-functional and Mid-functional Temperature-responsive Poly (N,N-diethyl-acrylamide) by ATRP
writer：Yue Wang, Nai-pu He*, Zhen-wu
keywords：Atom transfer radical polymerization, Poly(N, N-ethyl-acrylamide), Temperature-responsive
source：期刊
specific source：Acta Polymerica Sinica
Issue time：2017年
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℃. 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.