POTENTIAL-DEPENDENT NUCLEOPHILICITY OF POLYANILINE

The reaction of electrode-confined polyaniline with trifluoroacetic an hydride in acidified acetonitrile giving insulating and electroinactiv e trifluoroacetylated polyaniline has been studied by electrochemistry , reflectance IR, and microelectrochemistry. Variation of electrochemi cal. potential from 0.2 V (reduced, most reactive) to 0.6 V (oxidized by 0.5 electron per repeat unit, unreactive) vs SCE allows control of the reaction rate. Reaction of trifluoroacetic anhydride with aniline oligomers N-phenylphenylenediamine and N,N'-diphenylphenylenediamine g ave N-trifluoroacetylation products exclusively, exhibiting positive s hifts in oligomer oxidation potential of >0.5 V, with terminal amines reacting considerably faster than internal amines. Reflectance IR foll owing the potential-dependent growth of CO and CS peaks for macroelect rode films of polyaniline treated with trifluoroacetic anhydride showe d similar potential dependence of reactivity as conductivity measureme nts during trifluoroacetylation of polyaniline-derivatized microelectr ode arrays. Polyaniline trifluoroacetylation was accompanied by narrow ing but no shifting of the potential window of electroactivity and con ductivity, and eventual elimination of all conductivity. Trifluoroacet ylation of polyaniline terminal amines, rapid at all potentials, does not detectably affect conductivity. Also examined by electrochemistry were the reactions of polyaniline with other anhydrides resulting in t he reactivity order (F3CCO)(2)O > (Cl3CCO)(2)O > (H2ClCCO)(2)O > (HCl2 CCO)(2)O >> (H3CCO)(2)O. IR through polyaniline electrodeposited onto optically transparent Au electrodes shows that essentially complete lo ss of polyaniline electroactivity occurs when approximate to 25% of ni trogens are trifluoroacetylated. Electroactivity and conductivity of t rifluoroacetylated polyaniline may be recovered by hydrolysis in K2CO3 /CH3OH/O-2 solution to regenerate polyaniline. Use of the reversible t rifluoroacetylation of polyaniline provides a proof-of-concept for a n ew approach to an erasable-programmable-read-only-memory device.