Chemical Polymerization via Sorption of Oxidant

An oxidant-sorption procedure was used by Ojio and Miyata [338] for the fabrication of P(Py)/PVA (Poly(Vinyl Alcohol)) composites. PVA, of M 22,000, was dissolved with FeClj (the oxidant) in water, a film cast from this solution onto a PET film substrate. This oxidant-saturated host-polymer film was then exposed, in a desiccator at low temperature and in a deoxygenated atmosphere, to monomer (pyrrole) and water vapor for 0.5 to 24 h, with the resulting composite films, ca. 2 jam thick, dried in vacuum. Conductivities and transmission values saturated at about 1 h exposure time, to ca. 1 S/cm and 40% ( 550 nm) for a 70 30 w/w ratio PVA/FeClj. Transmission of the film was down to ca. 55% within 0.5 h, (with conductivity ca. 0.1 S/cm) for the same PVA/FeClj ratio. Higher PVA/FeClj ratios (90 10, 95 5) gave not only higher transmissions with minimal conductivity reduction, but also more homogeneous films as evidenced by SEM. 

A similar procedure, using highly viscous liquid complexes formed by FeClj (oxidant) with polymers such as poly(ethylene oxide) (PEO), poly(j3-propiolactone) (PPL) and poly(l,5-di-oxepan-2-one) (PDXO) was employed by Rabek et al [339] to fabricate P(Py) composites. The complexes were first prepared in dry nitro-methane (polymer FeClj ratio 7 3) and cast as films on glass. The films were then exposed to pyrrole vapor in a desiccator, yielding composites of 50 - 200 pm thickness over different reaction times. Excess oxidant and unreacted monomer were removed with a nitromethane wash. Conductivities were ca. 10 S/cm and transmissions below 50% in the mid-Visible region. 

A variant of the above procedures involving sorption of the oxidant is simple addition of monomer into a solution of the host polymer + oxidant, with the solution oxidation potential such that immediate polymerization occurs. The composite is 

Zinger and Kijel [341] described a procedure for preparation of poly(ethylene) (PE) composites with pyrrole, which used initial sorption of poly(styrene sulfonic acid) (PSSA, dopant) in the PE followed by immersion into an Fe(II)/Fe(III) solution, with the Fe(II/III) ratio determining the oxidation potential of the solution. Into this solution, pyrrole was injected, yielding the composite films. The films showed appreciable conductivities and mechanical properties. 

Wiersma et al. [284] described a method for preparation of P(Py) or P(ANi) + polyurethane dispersions which may be applied to textile fibers. Aqueous solutions of pyrrole (or anilinium sulfate) and Fe(N03)3 are added to a dispersion of polyurethane in water. After 20 hrs reaction time, a P(Py) (or P(ANi)) poly-(urethane) dispersion is obtained, which can then be used to fabricate coatings with claimed conductivities up to 10 S/cm. 

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