Synthesis and properties of novel polymers containing triphenylamine (TPA), ethynyl and aromatic moeities

Abstract

Poly (4-ethynyl triphenylamine) (PTPA-AC), poly (4-ethynyl-4``-(2-(9-anthryl)ethynyl) triphenylamine) (PTPA-AN), poly(4-ethylnyl-4``-(2-(4-biphenyl)ethynyl)triphenylamine)(PTPA-BP) were prepared by Pd catalyzed coupling reaction between 4,4``-dibromotriphenylamine(TPA-$Br_2$), 9,10-dibromoanthracene and 4,4``-diiodobiphenyl and 4,4``-diethynyltriphenylamine (TPA-AC2). Polymerization of poly(4,4``-diethynyltriphenylamine) (PTPA-AC2) was carried out by Cu-catalyzed coupling reaction of TPA-AC2 with oxygen bubbling. Although there are no flexible chains in PTPAs, they showed good solubility in common organic solvents. Because spacially twisted TPA moiety prevents the polymer from stacking , PTPAs can not aggregate themselves in solution. These PTPAs show good thermal stability and high glass-transition temperature ($T_g$) range from 130℃ to 220 ℃ demonstrating that the incorporation of structurally rigid moieties(ethynyl, triphenylamine and aryls) improves thermal stability. PTPA-AC and PTPA-AC2 are cross-linked on annealing at ~220℃ and they can be used as a hole-transporting material for multi-layer devices with spin-coating because of insolubility in any solvent. The photoluminescence (PL) spectra were measured with polymers coated on glasses. The PL spectra show shifts similar to those observed in the absorption spectra of the thin film samples. PTPA-AN($λ_{max}$ = 562nm) and PTPA-BP($λ_{max}$ = 493nm) show a bathochromic shift compared to PTPA-AC($λ_{max}$ = 445nm) and PTPA-AC2($λ_{max} = 455nm) because of additional aromatic group elongating π-conjugation. Electroluminescence of PTPAs is relatively weak and shows poor efficiency.