Synthesis and characterization of greenish‐blue emitting vinyl copolymer containing pyrene and triarylamine moieties

Two fluorescent monomers N-phenyl-N-(4-vinylphenyl)pyren-1-amine (vinyl-PyPA) and 1-vinyl pyrene (VPy) were synthesized in good yields. A series of soluble conductive vinyl copolymers P(PyPA-co-VPy) containing vinyl-PyPA and VPy moieties in different composition ratios were prepared by free radical solution polymerization. These copolymers showed high Tg (190−201 °C) and good thermal stability. The photoluminescence emission maxima of the copolymers were all in the range 474.5−478.5 nm, which was similar to the poly(N-phenyl-N-(4-vinylphenyl)pyren-1-amine) (P(PyPA)) (475 nm) but blue shifted compared with poly(1-vinyl pyrene) (PVPy) (490.5 nm). The lifetime of the copolymers increased from 10.2 to 29.7 ns with an increase in pyrene content. The copolymers had higher quantum yields (0.51) than those of the homopolymers of P(PyPA) (0.48) and PVPy (0.13). The highest occupied molecular orbital of the copolymers remained relatively unchanged from P(PyPA), while the lowest unoccupied molecular orbital varied from −2.41 eV to −2.51 eV with an increase in pyrene ratio in the copolymers. The energy bandgaps of the copolymers (from 2.70 eV to 2.81 eV) were smaller than those of P(PyPA) (2.82 eV) and PVPy (3.47 eV). Two polymer light-emitting diode (PLED) series were attempted including indium tin oxide (ITO) (fluorocarbon (CFx) treated)/P(PyPA-co-VPy)/LiF/Al and ITO(CFx treated)/P(PyPA-co-VPy)/1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi)/LiF/Al. The results suggested that the PyPA moiety is hole conducting and the PLEDs can achieve high luminance from 650 to 1150 cd m−2 (at 100 mA cm−2) only when an electron injecting layer TPBi is employed. © 2013 Society of Chemical Industry