Synthesis, Characterization and Optical Properties of Poly(4,4-dioctyloxy-3,3-biphenylene vinylene)Copolymers

Alternating block copolymers of poly(4,4 -dioctyloxy-3,3 -biphenylene vinylene)- alt-(1,4-naphthalene vinylene) (P1), poly(4,4 -dioctyloxy-3,3 -biphenylene vinylene)-alt-(1,5-naphthalene vinylene) (P2), poly(4,4 -dioctyloxy-3,3 -biphenylene vinylene)-alt-(2,6-naphthalene vinylene) (P3), poly(4,4 -dioctyloxy-3,3 -biphenylene vinylene)-alt-(9,9 -dioctyl-2,7-fluorenylene vinylene) (P4), and poly[(4,4 -dioctyloxy- 3,3 -biphenylene vinylene)-alt-(1,2-bis(2-thienylethylene)-5,5 -vinylene)] (P5) were synthesized through Wittig polycondensation of aryl bis(methyl triphenylphosphonium) dibromide with aryl dialdehyde. The effect of positional isomers was studied using three naphthalene isomers, viz., 1,4, 1,5 and 2,6 linking positions, respectively. All the alternating copolymers showed good solubility in organic solvents. The synthesized polymers were characterized by GPC, 1H NMR, FTIR and TGA. Thermal analysis of the polymers showed that they have thermal stability up to 250°C and their glass transition temperatures are around 50-70°C. The optical properties of the polymers both in solution and films were investigated. Optical studies of the polymers revealed that all the polymers except P5 had absorption maxima between 347 nm and 360 nm and emission maxima in the range 430-460 nm in solution whereas polymer P5 had absorption maxima at 452 nm and emission maxima at 515 nm. 4,4 -Dioctyloxy-3,3 - biphenylene in the polymer backbone caused blue shift in optical properties compared with polymers having either of phenylene or 4,4 -biphenylene backbones. Optical properties of the polymers showed they are promising materials for opto-electronic devices, as well