Photophysical characterizations of 2-(4-biphenylyl)-5 phenyl-1,3,4-oxadiazole in restricted geometry

Abstract

Langmuir and Langmuir-Blodgett (LB) films of non-amphiphilic 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (abbreviated as PBD) mixed with stearic acid (SA) as well as with the inert polymer matrix poly(methyl methacrylate) (PMMA) have been studied. Surface pressure versus area per molecule (p-A) isotherm studies suggest that PBD molecules very likely stand vertically on the air-water interface and this arrangement allows the PBD molecules to form stacks and remain sandwiched between SA/PMMA molecules. At lower surface pressure, phase separation between PBD and matrix molecules occurs due to repulsive interaction. However, at higher surface pressure, PBD molecules form aggregates. The UV-vis absorption and steady-state fluorescence spectroscopic studies of the mixed LB films of PBD reveal the nature of the aggregates. H-type aggregate predominates in the mixed LB films, whereas I-type aggregate predominates in the PBD-PMMA spin-coated films. The degree of deformation produced in the electronic levels are largely affected by the film thickness and the surface pressure of lifting. r 2007 Published by Elsevier B.V.

Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

“…For example, in D1, the band with a maximum at 299 nm is characteristic of the CAB absorption [37], also consistent with the strongest absorption peak of PYCAB (a pyrene-cored polyphenylene dendrimer with CAB in the periphery, see Supplementary Materials) [24]. The band with a maximum at 319 nm can be assigned to the absorption of PBD [38], similar to that of PYPBD (a pyrene-cored polyphenylene dendrimer with PBDs in the periphery, see Scheme S1). The other band (λ max : 392 nm, ε:~50,000 L·mol −1 ·cm −1 ) is much sharper and originates from π-π* transitions of the pyrene core [24,40,41].…”

“…One with characteristic shape and significant intensity (ε: 230,000-250,000 L·mol −1 ·cm −1 ) is attributed to the energy transitions of PCs and polyphenylenes [37][38][39]. For example, in D1, the band with a maximum at 299 nm is characteristic of the CAB absorption [37], also consistent with the strongest absorption peak of PYCAB (a pyrene-cored polyphenylene dendrimer with CAB in the periphery, see Supplementary Materials) [24].…”

“…In addition, a TPA-and PBD-functionalized dendrimer D2 was prepared for comparison. The emission of CAB [37], PBD [38] and TPA [39] show good overlaps with the absorption of the core, i.e., 1,3,6,8-tetraphenylpyrene [40,41], for efficient surface-to-core energy transfers. For this purpose, shape-persistent polyphenylene dendrimers enable generation-by-generation (core-shell-surface) functionalization and OLEDs utilizing efficient surface-to-core energy transfers of pyrene-cored polyphenylene dendrimers have been reported [22][23][24].…”

“…In addition, a TPA-and PBD-functionalized dendrimer D2 was prepared for comparison. The emission of CAB [37], PBD [38] and TPA [39] show good overlaps with the absorption of the core, i.e., 1,3,6,8-tetraphenylpyrene [40,41], for efficient surface-to-core energy transfers. To summarize, in this contribution a new method to make polyphenylene dendrimers with donor-acceptor periphery is introduced.…”

Nano Dimensional Hybrid Organo-clay Langmuir-Blodgett Films

“…Langmuir-Blodgett (LB) films are known for a high degree of organization of organic molecules [2][3][4][5][6][7][8][9][10]. Recently, LB technique has been extended to the preparation of hybrid organo-clay mono-and multilayers [11][12][13][14][15].…”