Synthesis and characterization of electroactive styrenic polymers with pyrrole pendant groups

Abstract

Four styrenic monomers containing 3-substituted pendant pyrrole ring with ester or amide spacer were synthesized. Their homopolymers were prepared by free-radical polymerization. They were soluble in organic solvent such as dimethylformamide (DMF) and hexafluoro-2-propanol (HF-2PrOH). Their electroactive characteristics were examined by cyclic voltammogram (CV). The chemical oxidation was accomplished by adding iron (III) chloride $(FeCl_3)$ into a solution of styrenic polymers dissolved in 1:1 mixture of DMF and acetonitrile (ACN) to give conducting properties. The electrical conductivities of the oxidized powders, measured by four-point probe techniques, were in the order of $10^{-10}~10^{-9} S/cm$. To give high conductivity, pyrrole was copolymerized with pyrrole unit of poly(1-(p-vinylbenzyl)-4-(3-pyrrolyl)oxobutyrate (PPVBPOB) via oxidative polymerization with $FeCl_3$ in DMF solution. The oxidized copolymer, PVBPOB-ox-Py were totally insoluble in any organic solvent. The electrical conductivity of the PVBPOB-ox-Py was $10^{-6} S/cm$. Poly(styrene-co-(1-(p-vinylbenzyl)-4-(3-pyrrolyl)-4-oxobutyrate) (PSt-PVBPOB) containing 16.7 mol% 1-(p-vinylbenzyl)-4-(3-pyrrolyl)-4 -oxobutyrate (PVBPOB) was synthesized by emulsion polymerization. Pyrrole was copolymerized with pyrrole moiety of PSt-PVBPOB via oxidative polymerization by using $FeCl_3$. Two kinds of conducting polymers were prepared. PSt-PVBPOB-ox-Py (E) was obtained in the emulsion, however, PSt-PVBPOB-ox-Py (S) was prepared in the THF solution. The conductivity of PSt-PVBPOB-ox-Py (E) (1.590 S/Cm) was much higher than that of PSt-PVBPOB-ox-Py (S) (0.022 S/Cm). The proposed mechanisms of conductivity enhancement in the oxidized copolymer prepared in the emulsion is disscused. Upon the scanning electron micrograph (SEM), a clusters of polypyrrole (PPy) moiety distributed uniformly throught the particle of PSt-PVBPOB-ox-Py (S). On the other hand, a squashed PPy moiety is located mainly on the surface of th...