β-CD聚轮烷嵌段共聚物的制备及其溶致响应性

Preparation of β-Cyclodextrin-based Polyrotaxane Block Copolymers and Their Solvent-responsibily

在20℃水溶液中,选用PMDETA/Cu(Cl)为催化剂,以2-溴代异丁酰基封端的PPO-PEO-PPO三嵌段共聚物与β-环糊精(β-CD)形成的聚准轮烷(PPR)作为引发剂引发丙烯酸羟乙酯(HEA)发生非均相ATRP反应.1H-NMR,GPC,FTIR,WXRD,DSC以及TGA测试表明,PHEA已连接到PPR两端生成了具有管道结晶结构的聚轮烷嵌段共聚物.聚轮烷中β-CD上链量以及PHEA链段聚合度能通过改变其投料摩尔比予以调控.观察到经过用水透析处理后的聚轮烷,β-CD只停留在PPO链段上.而经DMF溶解和无水乙醚沉淀后,大约有1/3的β-CD滑向中间的PEO链段上.表明该聚轮烷嵌段共聚物具有溶致响应性.

A kind of polyrotaxane（ PR）-based block copolymers was synthesized via the atom transfer radical polymerization（ ATRP） of hydroxylethylene acrylate（ HEA） initiated by polypseudorotaxanes（ PPRs） built from a distal 2-bromoisobutyryl end-capped polypropylene glycol-polyethylene glycol- polypropylene glycol（ PPO-PEO-PPO） with a varying amount of β-cyclodextrins（ β-CDs） in the presence of Cu（ I） Cl and N,N,N＇,N＇,N″-pentamethyldiethylenetriamine（ PMDETA） as catalyst at 20 ℃ in aqueous solution. The supramolecular structure of the resulting copolymers was characterized by means of1H-NMR,GPC,FTIR,WXRD,DSC and TGA measurements. It was shown that the PHEA segments were attached to two ends of PPRs to give rise to the PR-based block copolymers featured by a characteristic channel-type crystal structure. The entrapped β-CD number was increased with the feeding molar ratio,but only about one third added β-CDs were retained on the polymer chain after the ATRP process. However,the polymerization degree of PHEA（ DP）segments was well controllable with changing the molar feed ratio. In addition,β-CDs were observed to favourably aggregate around the PPO segments and nearly cannot accommodate with the PEG segments after incubation in water and freeze-drying. However,according to TGA analyses,there were around one-third of the threaded β-CDs enabling to slide to the PEO segments after being treated with DMF and anhydrous ether. The results suggested that these PR-based block copolymers exhibit the solvent-responsibility with the potential to be used as solid smart materials.