氟化单元封端的不同聚合度PBMA甲苯溶液气/液界面结构

Liquid/air interfacial structures of various molecular weights PBMA end-capped with 2-perfluorooctylethyl methacrylate units in toluene solutions

采用ATRP技术合成具有不同聚合度的末端连接甲基丙烯酸全氟辛基乙酯(FMA)单元的聚甲基丙烯酸丁酯(PBMAm-ec-PFMAn).利用和频振动光谱(SFG)和表面张力测定技术研究了各种氟化聚合物溶液的气/液界面结构.发现PBMAm-ec-PFMAn甲苯溶液的表面活性及其气/液界面的结构与两种结构单元数密切相关.当PFMA聚合度(n)大约为4和6时,聚合物溶液的表面张力随着PBMA聚合度的增加从21增加到25mN/m(该值与PBMA均聚物溶液相同).SFG的研究结果表明PBMA段较长时溶液表面被PBMA所占据.PBMA段较短时,PFMA组分吸附在溶液表面,排列比较有序且紧密堆积.当PBMA末端只有1个FMA单元时,其甲苯溶液的表面张力随PBMA段长稍有增加(从22增加到23mN/m),其值介于21与25mN/m之间.研究表明当PBMA段较短时,可能聚合物中的氟化组分吸附在溶液表面,但其排列的有序性较差.随着PBMA聚合度的增加,氟化组分与PBMA组分可能同时占据在溶液表面,这时其表面张力大约为23mN/m.

Various molecular weight poly（butyl methacrylates） （PBMA） end-capped with 2-perfluorooctylethyl methacrylate （FMA） units （PBMAm-ec-FMAn） have been synthesized by atom transfer radical polymerization （ATRP）.The liquid/air interfacial structure of PBMAm-ec-PFMAn in toluene solutions was investigated by surface tension measurement and surface-sensitive sum frequency generation vibrational spectroscopy （SFG）.The results indicate that the surface activity of PBMAm-ec-PFMAn toluene solution is related to the degree of polymerization of PBMA and the number of FMA units at the chain end.When the number of FMA units about 4 and 6,the surface tension of the polymer increases from 21 to 25 mN/m with increasing of PBMA chain length,approaching to the surface tension of pure PBMA solution.SFG results reveal that there is no fluorinated component absorbed at the solution surface for this polymer.When the PBMA chain is short,fluorinated component is absorbed at the solution surface and forms the order of the packing orientation of the perfluoroalkyl side chains,which results in great decrease of the surface tension compared to that of PBMA homopolymer.As to PBMAm-ec-PFMA1,the surface tension of toluene solution increases slightly （from 22 to 23 mN/m） with increasing of the degree of polymerization of PBMA.SFG results reveal that the decrease in surface tension for PBMAm-ec-PFMA1 with short PBMA chain may be attributed to the segregation of fluorinated component with the disorder of the packing orientation of the perfluoroalkyl side chain,that for polymer with longer PBMA chain may be attributed to the segregation of both fluorinated component and ester butyl group in PBMA chain at the solution surface.