Synthesis, characterization and electrochemistry of ionically functionalized polyacetylenes with varied ionic density

In order to tailor the properties of cationically and anionically substituted polyacetylene analogues, copolymerization of tetramethylammonium 2-cyclooctatetraenylethanesulfonate and 2-cyclooctatetraenylethyltrimethyl ammonium triflate with eyelooctatetraenyltrimethylsilane were studied. The copolymerization was based on ring opening metathesis polymerization (ROMP) using a Schrock's catalyst, [W=CH (o-C6H 4OMe)(NC6H5)[OCCH3-(CF3)2] 2(THF); THF=tetrahydrofuran]. The choice of this particular catalyst was based on experimental results showing that it was more appropriate for the synthesis of the desired polymers than RuC12(=CHPh)(PCy 3)(ImMesH2) (ImMesH2 = N,N-dimesitylimidazolidine), which is also known to catalyze the ROMP of cyclooctatetraene. Also, the feasibility of using sec-butylcyclooctatetraene in place of cyclooctatetraenyltrimethylsilane was evaluated. Based on the copolymer compositions calculated from experimental results on polymerization rates, sec-butylcyclooctatetraene was deemed unsuitable for making desirable copolymers. The copolymers synthesized were soluble in dimethyl formamide (DMF). They were characterized using UV/Vis, gel permeation chromatography (GPC), multi-angle laser light scattering (MALLS) and nuclear magnetic resonance (NMR).; All of the copolymers synthesized were observed to be electroactive. Their electrochemical properties were studied using cyclic voltammetry. The copolymers exhibited properties similar to the superposition of the properties of the corresponding homopolymers in the cyclic voltammograms (CVs) collected using tetramethylammonium tetrafluoborate (TMABF4) as an electrolyte. It was also observed that when the CV covered both n- and p-doping, the interplay of the two processes accelerated the degradation of the polymers. When CVs were collected using a polyelectrolyte as a supporting electrolyte, all the ionically functionalized copolymers showed self-limited doping (SLD), where the doping level was controlled by the composition of the copolymers, namely the density of ionic functional groups covalently attached to the polymer backbone. Also, the anionically substituted copolymers were shown to be much more stable in polyelectrolyte than in tetrabutylammonium tetrafluoroborate (TBABF4) during the electrochemical process. The SLD behavior of cationically substituted copolymers was shown in electrochemical studies where poly (N, N-dimethyl-3, 5-dimethylene peperidimum) hexfluorophosphate (PDDP) was used as supporting electrolyte. This SLD behavior could potentially pave the way for making polymer based electronic devices where precise control of doping level is necessary.