支链化阳离子和甜菜碱表面活性剂对聚四氟乙烯表面润湿性的影响

Effect of Branched Cationic and Betaine Surfactants on the Wettability of a Poly(tetrafluoroethylene) Surface

利用座滴法研究了支链化阳离子表面活性剂十六烷基羟丙基氯化铵(C16GPC)和两性离子表面活性剂十六烷基羧酸甜菜碱(C16GPB)在聚四氟乙烯(PTFE)表面上的吸附机制和润湿性质,考察了表面活性剂浓度对表面张力、接触角、粘附张力、固液界面张力和粘附功的影响趋势.研究发现,低浓度条件下,表面活性剂疏水支链的多个亚甲基基团与PTFE表面发生相互作用,分子以平躺的方式吸附到固体界面;支链化表面活性剂形成胶束的阻碍较大,浓度大于临界胶束浓度(cmc)时,C16GPC和C16GPB分子在固液界面上继续吸附,与PTFE作用的亚甲基基团减少,分子逐渐直立,固液界面自由能(γsl)明显降低.对于支链化的阳离子和甜菜碱分子,接触角均在浓度高于cmc后大幅度降低.

The adsorption mechanism and wetting properties of aqueous solutions of branched cationic surfactants, hexadecanol glycidyl ether ammonium chloride （C16GPC）, and zwitterionic surfactant, hexadecanol glycidyl ether glycine betaine （C16GPB） on a poly（tetrafluoroethylene） （PTFE） surface were investigated using sessile drop analysis. The influences of surfactant concentration on surface tension, contact angle, adhesional tension, PTFE-solution interfacial tension, and adhesion work were expounded. The results indicate that branched surfactant molecules lie parallel to the PTFE surface through hydrophobic interactions between the multi methylene groups of the alkyl chain and the solid surface below the critical micelle concentration （cmc）. C15GPC and C15GPB molecules still adsorb onto PTFE because of the marked hindrance of branched chains to the formation of micelles above the cmc. The methylene group interactions with PTFE decrease and C16GPC and C16GPB molecules become straightened on the solid surface, which results in a clear decrease in PTFE- solution interfacial tension （ysl）. For branched surfactants, an abrupt decrease in contact angle appears above the cmc.