Reaction of argon plasma‐treated teflon PFA with aminopropyltriethoxysilane in its n‐hexane solution

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Aspects of argon plasma treatment of tetrafluoroethylene–perfluoropropylvinylether copolymer (PFA) films, followed by air exposure and its subsequent reaction with 3-aminopropyltriethoxy silane (3-APS) have been investigated using XPS and electron spin resonance (ESR) to gain a better understanding about the surface bonding between the modified PFA and 3-APS. The plasma treatment was performed under varying parameters such as radiofrequency power, gas pressure and treatment time. A good correlation was found between the atomic ratios of O/F and Si/F for PFA before and after the reaction with 3-APS. The amount of peroxy radicals before the reaction with 3-APS was also closely related with the atomic ratio of Si/F. By the derivatization reaction of plasma-treated PFA with NaOH it was confirmed that C(O)OH groups exist on the treated PFA surfaces. These observations revealed that the oxygen incorporated at the surface leading to C(O)OH groups plays a substantial role as the reaction site for 3-APS. A similar trend was found between the atomic ratios of Na/F and Si/F after the reactions with NaOH and 3-APS. Based on this observation it is proposed that the surface bonding of 3-APS to the C(O)OH group at the surface occurs through its NH2 group. The analysis of the atomic ratios of O/F, N/F and Si/F after the reaction with 3-APS revealed that a polyaminosiloxane oligomer with a stoichiometry different from that expected for the original 3-APS is formed. The wettability of 3-APS-bound PFA was found to become much greater than that of PFA plasma treated alone. The ageing effect of the wettability of 3-APS-bound PFA was observed, whereas the Si atomic concentration at the surface remained nearly unchanged during ageing. Copyright © 1999 John Wiley & Sons, Ltd.