Tan Beng H, Gudipati Chakravarthy S, Hussain Hazrat, He Chaobin, Liu Ye, Davis Thomas P
Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore.
Macromol Rapid Commun. 2009 Jun 17;30(12):1002-8. doi: 10.1002/marc.200800799. Epub 2009 Apr 21.
We report the synthesis of a novel pH-responsive amphiphilic block copolymer poly(dimethylaminoethyl methacrylate)-block-poly(pentafluorostyrene) (PDMAEMA-b-PPFS) using RAFT-mediated living radical polymerization. Copolymer micelle formation, in aqueous solution, was investigated using fluorescence spectroscopy, static and dynamic light scattering (SLS and DLS), and transmission electron microscopy (TEM). DLS and SLS measurements revealed that the diblock copolymers form spherical micelles with large aggregation numbers, N(agg) ≈ 30 where the dense PPFS core is surrounded by dangling PDMAEMA chains as the micelle corona. The hydrodynamic radii, R(h) of these micelles is large, at pH 2-5 as the protonated PDMAEMA segments swell the micelle corona. Above pH 5, the PDMAEMA segments are gradually deprotonated, resulting in a lower osmotic pressure and enhanced hydrophobicity within the micelle, thus decreasing the R(h) . However, the radius of gyration, R(g) remains independent of pH as the dense PPFS cores predominate.
我们报道了通过可逆加成-断裂链转移（RAFT）介导的活性自由基聚合反应合成一种新型的pH响应性两亲嵌段共聚物聚（甲基丙烯酸二甲氨基乙酯）-嵌段-聚（五氟苯乙烯）（PDMAEMA-b-PPFS）。利用荧光光谱、静态和动态光散射（SLS和DLS）以及透射电子显微镜（TEM）研究了该共聚物在水溶液中的胶束形成情况。DLS和SLS测量结果表明，二嵌段共聚物形成具有大聚集数的球形胶束，聚集数N(agg) ≈ 30，其中致密的PPFS核被作为胶束冠层的悬垂PDMAEMA链所包围。在pH 2 - 5时，由于质子化的PDMAEMA链段使胶束冠层膨胀，这些胶束的流体力学半径R(h)较大。在pH高于5时，PDMAEMA链段逐渐去质子化，导致胶束内渗透压降低且疏水性增强，从而使R(h)减小。然而，由于致密的PPFS核占主导，回转半径R(g)保持与pH无关。
