低催化剂用量ATRP制备丙烯酸酯三嵌段共聚物及性能研究

Studies on Preparation of Acrylate Triblock Copolymers via ATRP with Low Catalyst Concentrations and Their Properties

采用单体摩尔量0.02%的低浓度二价铜盐和廉价配体五甲基二乙烯三胺（PMDETA）络合物为催化剂的ARGET ATRP法,以双官能团引发剂引发丙烯酸丁酯（BA）聚合得到大分子引发剂Br-PBA-Br,研究了温度和催化剂用量对聚合反应速率和可控性的影响.再用氯化铜为催化剂,以Br-PBA-Br引发甲基丙烯酸甲酯（MMA）的ARGET ATRP聚合,得到窄分布的PMMA-b-PBA-b-PMMA三嵌段共聚物,并采用硅藻土对聚合产物进行微量残留铜盐脱除处理,使铜离子含量降到了聚合物质量的0.001%.凝胶渗透色谱（GPC）测得三嵌段共聚物的数均分子量在51000～110000,分布指数低于1.50.核磁共振氢谱（1H-NMR）测得产物共聚组成与GPC结果相近.示差扫描量热仪（DSC）、原子力显微镜（AFM）和动态力学分析（DMA）证明三嵌段共聚物呈现良好的相分离.力学性能测试表明,所得三嵌段共聚物的拉伸强度在2.7～11.7 MPa之间,断裂伸长率在124%～231%之间.采用ARGET ATRP可以合成组成和性能连续可调的PMMA-b-PBA-b-PMMA三嵌段共聚物,同时解决了催化剂用量大,不易脱除的问题。

Macroinitiator Br-PBA-Br was synthesized via atom transfer radical polymerization with activators regenerated by electron transfer（ ARGET ATRP） using the bifunctional initiator and low concentration of complex catalyst composed of inexpensive ligand PMDETA and Cu（ Ⅱ） Br2（ 0. 02% molar fraction of monomer）. The effects of reaction temperature and catalyst dosage on the polymerization rate and controllability were investigated. Then,PMMA-b-PBA-b-PMMA triblock copolymers with narrow polydispersities were prepared via ARGET ATRP initiated by Br-PBA-Br using CuCl2/PMDETA as catalyst. The residual catalyst was separated with cheap diatomite and the residual concentration of cupric ions was reduced to 0. 001%weight fraction to polymer. GPC results showed that the number average molecular weight of the prepared triblock copolymers is in the range of 51000 ～ 110000 and the molecular weight distribution is below 1. 50. The chemical compositions of triblock copolymer determined by1H-NMR were in good agreement with the GPC results. The glass-transition temperatures（ Tg） determined by DSC were around- 47 ℃ and 105 ℃corresponding to PBA and PMMA,respectively. AFM,DSC,and DMA confirmed the obvious phase separation in the triblock copolymers. The tensile strength of the copolymer films were among 2. 7 ～ 11. 7 MPa and the elongation at break were among 124% ～ 231%,which showed that the tensile strength and elongation at break of the triblock copolymers were adjustable by changing copolymerization composition. PMMA-b-PBA-b-PMMA triblock copolymer with adjustable properties can be prepared successfully by ARGET-ATRP and the problems of high dosage of catalyst and difficulty in removal are solved.