高密度柱状聚合物刷的合成

Synthesis of Densely Grafted Cylindrical Polymer Brushes

通过铜催化的叠氮-炔偶联反应(CuAAC),利用grafting-onto方法合成每个主链重复单元带有多于一条侧链的高接枝密度的柱状聚合物刷.首先,合成了带有缩酮保护的甲基丙烯酸2,2-双羟甲基丙酯单体(bisMPMA),并通过可逆加成-断裂链转移(RAFT)聚合得到窄分子量分布的线形聚合物.在酸性条件下脱去缩酮保护后,以羟基与戊炔酸酐的酯化反应,得到了每个重复单元带有2个炔基的聚合物主链.之后,利用高效的CuAAC反应,将末端带有叠氮基团的聚环氧乙烷(PEO)或聚苯乙烯(PS)侧链接枝到主链上,用核磁共振氢谱(1H-NMR)和体积排阻色谱(SEC)等对聚合物刷的结构进行表征.

Densely grafted cylindrical polymer brushes with more than one side chains on each repeating unit of backbone were synthesized by copper-catalyzed azide-alkyne cycloaddition （CuAAC） reaction via grafting- onto method. The ketal-protected monomer, 2,2-bis- （hydroxymethyl） propyl methacrylate （bis-MPMA） was prepared and polymerized by reversible addition-fragmentation chain transfer （RAFT） mediated radical polymerization to yield linear polymer backbone with narrow distribution of molecular weight. The polymer backbone with two hydroxyl groups at each repeating unit was obtained after deprotection under acid condition. Then the hydroxyl groups were converted to alkyne groups by reacting with 4-pentynoic anhydride. Azido- terminated poly （ ethylene oxide） （PEO） or polystyrene （ PS）, which were obtained by post-polymerization modification,were coupled with the alkyne groups on the backbone by CuAAC reaction. The grafting ratio and structure of the obtained polymer brushes were characterized by size exclusion chromatography （SEC） and nuclear magnetic resonance （NMR）. The reaction efficiency of PEOn3-N3 and PSts-N3 in CuAAC was 85.1% and 78.0% , and the grafting ratios were 64.7% and 54.6% , respectively. The denseness of the alkyne groups on the polymer backbone or the steric hindrance of the polymer side chains may be holdback of the grafting.