Synthesis of Alternate-block Copolymers of Poly (2,5-dioctyloxy phenylene vinylene)s with Varying Positional Naphthalene Moieties

Variation of the linking positions of the arylene groups in polyarylene vinyleneblock copolymers can be used as an effective method to fine tune the polymers emissive characteristics. Through Wittig reaction mechanism 2,5-dioctyloxy-1,4-dicarboxaldehyde and varying positional isomers of naphthalene bis(methyl triphenylphosphonium)dibromide gave alternate-block copolymers of poly(2,5-dioctyloxyphenylene vinylene-co-1,4-naphthalene vinylene) (P1), poly(2,5-dioctyloxy phenylenevinylene-co-1,5-naphthalene vinylene) (P2), and poly(2,5-dioctyloxy phenylenevinylene-co-2,6-naphthalene vinylene) (P3). These polymers were highly soluble incommon organic solvents. The chemical and physical characteristics of these polymerswere carried out using TGA, FTIR, 1H NMR, optical absorption and emission spectralmethods. The thermal stabilities of the first two polymers (P1 and P2) were significantlyhigher than the third polymer (P3). The glass transition temperatures of thesepolymers were found to be around 70°C. The first two polymers (P1 and P2) showedabsorption maxima around 360 nm, whereas the last case showed it at 406 nm. As thinfilms, all three polymers exhibited red-shifted absorptions. The photoluminescence (PL)emission maxima of P1, P2 and P3 polymers were 467 nm, 484 nm and 495 nm, in thegiven order. Polymers P1-P3 also showed red-shifted PL emission for their thin films.The differences in the absorption maxima and PL emission maxima of P1 to P3 are dueto the strain force between the vinylene and naphthalene protons. While, P3 polymerexhibited electroluminescence maxima at 540 nm and 555 nm in single layer devicewith a specific configuration (ITO/PEDOT/P3/Al).