两亲性杂侧链聚合物刷的合成及其乳化功能

Synthesis of Amphiphilic Polymer Brushes with Mixed Side Chains and Their Emulsifying Function

报道了一种随机高密度接枝亲水、疏水聚合物侧链的刷形两亲性聚合物.首先,结合可逆加成-断裂链转移(RAFT)聚合和后修饰方法,得到含叠氮侧基的聚甲基丙烯酸缩水甘油酯(PGMA-N3)作为主链;再分别合成端炔基聚苯乙烯(PS)和端炔基聚环氧乙烷(PEO),然后通过铜催化的叠氮-炔环加成反应,将疏水性PS和亲水性PEO同时高效的接到PGMA主链上,制得两亲性杂侧链的聚合物刷.由凝胶渗透色谱(SEC)分析得知,在主链叠氮基团与两侧链总炔基的摩尔投料比为1∶1的条件下,PS和PEO的接枝效率很高,都大于90%.通过调节主链长度和2种侧链的投料比,获得不同组成的聚合物刷.通过等质量的甲苯/水混合体系,考察两亲性聚合物刷的乳化能力,发现主链聚合度为100,PS∶PEO比例为70∶30的聚合物刷表现出最佳的乳化性能.

A series of amphiphilic polymer brushes with a high grafting density as a new polymeric surfactantare developed. A great deal of research on amphiphilic block polymers has been reported to apply as thesurfactants, but the research on polymer brush is still scarce. Nevertheless, amphiphilic polymer brushes would begood surfactants due to their rich surface properties and various morphologies. Therefor, a series of polymerbrushes with mixed hydrophilic and hydrophobic side chains were designed and synthesized via a grafting-ontoapproach. Firstly, a polymeric backbone of poly（glycidyl methacrylate） （PGMA） with pendent azide groups wasprepared by reversible addition-fragmentation chain transfer （RAFT） mediated radical polymerization followed bypost-modification. Two PGMA polymers with degrees of polymerization （DP） of 100 and 390 were obtained bytuning the ratio of the monomer to initiate. Then, an alkynyl-terminated polystyrene （PS, DP = 44） as ahydrophobic side chain was prepared via RAFT polymerization using an alkynyl-containing chain transfer agent,and an alkynyl-terminated poly（ethylene oxide） （PEO, DP = 113） as a hydrophilic side chain was obtained by anucleophilic substitution reaction of PEO with propargyl bromide. Finally, the two types of side chains weresimultaneously coupled onto the PGMA backbone by a copper-catalyzed azide-alkyne cycloaddition （CuAAC）reaction, to yield the PGMA-g-（PSaa-r-PEOl13） polymer brush. The results from size exclusion chromatography（SEC） indicated that the grafting ratios of both PS44 and PEO113 were above 90%, with a molar feeding ratio ofazide to alkynyl group at 11 at 50 ~C in dimethyl formamide. A series of polymer brushes with differentcompositions were obtained by tuning the DP of the backbone and the feeding ratio of the two side chains. Allsamples have narrow molecular weight distributions （Mw/Mn 〈 1.20）. The emulsifying ability of these amphiphilicpolymer brushes in a toluene/water system was characterized. To stabilize toluene/water emulsion, the requiredamount of PGMA100-g-（PSa4-r-PEO113） decreased with an increase in the content of PS44 side chain. A stableemulsion can be formed using PGMAI00-g-[（PSa4）70-r-（PEOlI3）30] at a concentration of as low as 0.002 wt%versus the weight of toluene. In addition, the polymer brush with a long backbone of PGMA390 was not beneficialto emulsion stability. In comparison with the other polymer brushes, the polymer brush with a short backbone ofPGMA100 and a molar ratio of the side chains PSa4：PEOl13 of 70：30 was found to exhibit the most efficientemulsifying ability.