POLYMERIC PHTHALOCYANINES AND OTHER ELECTRICALLY CONDUCTING POLYMERS FOR ELECTRONIC AND PHOTONIC APPLICATIONS - A REVIEW

Polymers are generally insulators and to exhibit electrical conductivi ty they must have ordered conjugation with extended pi electrons and l arge carrier concentrations. This review summarises the various method s of making conjugated polymers by either addition or condensation rea ctions of monomers by chemical or electrochemical routes. These reacti ons can follow either a direct route or an intermediate precursor rout e, followed by elimination, addition or isomerization reactions. Conju gated polymers are made conductive generally by doping or by thermal t reatment. The doped polymers have limitations like poor stability, poo r processibility and corrosivity. This review lists the various method s adopted for overcoming these drawbacks. The review also gives an acc ount of various types of phthalocyanine polymers that have been prepar ed in our laboratory, and their electrical and magnetic properties. Th e conductivity of these polymers increases by seven orders of magnitud e by thermal treatment. These polymers have suitable structures that f acilitate solitonic, polaronic and bipolaronic conformations leading t o large, ultra-fast nonlinear optical processes. The peripheral functi onal groups can be used for structural modifications to improve proces sibility and allow fabrication of various device structures such as fi lms, channel wave guides, planar wave guides, fibres, etc. The presenc e of macrocyclic structures in these polymers imparts mechanical, ther mal and environmental stabilities. Conjugated polymers, including phth alocyanine polymers, also exhibit nonlinear optical properties because of their response to high intensity radiations like laser. The requir ements of organic molecules and polymers to have x(2) and x(3) propert ies, and the various methods used to study their behaviour as well as techniques employed to improve the nonlinear optical response are also discussed. The various methods that have been used to synthesize ladd er polymers with solubilising groups for processibility have also been discussed.