Synthesis and characterization of novel poly(2-methoxy-(5-(6′-dimethylphosphonate)-hexyloxy)-1,4-phenylenevinylene-ran-2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene)s (MEH-PO-PPVs) and their tunable emission colors

Poly(2-methoxy-(5-(6′-dimethylphosphonate)-hexyloxy)-1,4-phenylenevinylene-ran-2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PO-PPV) was synthesized via Heck coupling reaction of MPOHOB-2Br (1) (1-methoxy-(4-(6-dimethylphosphonate)-hexyloxy)-2,5-dibromobenzene), MEHOB-2Br (2) (1-methoxy-4-(6-bromohexyloxy)-2,5-dibromobenzene), and MEHOB-DV (4) (1-methoxy-4-(2′-ethylhexyloxy)-2,5-divinylbenzene) by varying the molar ratios of monomers. The monomers and their intermediates were characterized by ¹H NMR, FT-IR, and melting point and elemental analyzer, and subsequent polymers by FT-IR, ¹H NMR, GPC, DSC, TGA, and solubility test. The optical (UV-vis, PL) and electrical properties (CV) of polymers were also evaluated. MEH-PO-PPV, containing phosphine oxide groups, exhibited better solubility, lower HOMO and LUMO levels, and larger band gaps. In addition, the PL emission gradually shifted to shorter wavelength, providing 570 (MEH-10PO-PPV), 519 (MEH-30PO-PPV), and of 465 nm (MEH-50PO-PPV) as the PO content increased, compared with 598 nm (MEH-PPV).