Precise Synthesis of Poly(fluorene-2,7-vinylene)s Containing Oligo(thiophene)s at the Chain Ends: Unique Emission Properties by the End Functionalization

Star-Shaped ROMP Polymers Coated with Oligothiophenes That Exhibit Unique Emission

A series of oligo(thiophene)-modified "soluble" star-shaped ring-opening metathesis polymerization (ROMP) polymers were prepared by sequential living ROMP of norbornene and a cross-linking agent using a molybdenum-alkylidene catalyst, followed by Wittig-type coupling for termination with oligo(thiophene) carboxaldehydes. The resultant star-shaped ROMP polymers displayed unique emission properties affected by the core size and arm repeat units as well as the kind of oligothiophene coated. The effects of the thiophene groups on photophysical properties of star-shaped/linear polymers were studied via time-resolved fluorescence spectroscopy. Fluorescence lifetimes were determined in THF as 400, 640, 730, and 820 ps for Star 3TPh, Linear 3TPh, Star 4T, and Linear 4T, respectively. A significant enhancement of the nonradiative rate constants k _nr in the star-shaped polymers results in relatively lower fluorescence quantum yields and shorter fluorescence lifetimes compared to the corresponding linear polymers.

Observation of Intramolecular Interaction in Fluorescent Star-Shaped Polymers: Evidence for Energy Hopping between Branch Chains

Time-resolved fluorescence anisotropy measurements were performed on three-branched star-shaped polymers, based on precisely synthesized poly(9,9-di-n-octyl-fluorene vinylene)s containing C₆F₅ end groups. The star-shaped polymers showed identical fluorescence spectra, fluorescence lifetimes, and quantum yields to those of the reference single-chain oligomer. However, a rapid fluorescence anisotropy decay was observed in two kinds of star-shaped polymers, while such decay was not seen in the corresponding single-chain oligomer. On the basis of the analysis using an incoherent hopping model, the observed rapid anisotropy decay is attributable to energy hopping processes between branches within a single polymer species, and its rate was deduced to be ca.100 ps depending upon the core part.

Terthiophene Functionalized Conjugated Triarm Polymers Containing Poly(fluorene-2,7-vinylene) Arms Having Different Cores-Synthesis and Their Unique Optical Properties

Optical properties of three types of terthiophene (3T) functionalized conjugated triarm (star-shaped) polymers consisting of poly(9,9-di-n-octyl-fluorene-2,7-vinylene) (PFV) arms and different [2,4,6-tri(biphenyl)benzene (TBP), 1,3,5-tri(benzyl)benzene (TBB), and triphenylamine (TPA)] cores, prepared by combined olefin metathesis with Wittig coupling, have been studied. Relative intensities [increases in the higher vibronic bands, (0, 1) fluorescence (FL)] of the fully conjugated TPA-core polymers, TPA(PFV-3T)3, in the fluorescence (FL) spectra in tetrahydrofuran (toluene) solution were higher than those in the other triarm polymers, TBP(PFV-3T)3, TBB(PFV-3T)3, whereas no significant differences were observed in their UV-vis spectra; notable temperature dependences were not observed in the UV-vis and FL spectra (at -5, 25, and 55 °C). Remarkable differences were not observed in the spectra in these polymer thin films, whereas λmax values red-shifted due to the formation of J-type aggregates. The observation for the time-resolved study well corresponds to results for the steady-state fluorescence measurements. The observed unique emission by the star-shaped (triarm) polymer containing the TPA core would be assumed to be due to a difference in nature of the core (higher coplanarity) compared to that of the others.

Synthesis and structural analysis of tungsten-carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through pyridine coordination

Synthesis, structural analysis and basic optical properties of tungsten carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through coordination with pyridine have been explored.

Precise one-pot synthesis of fully conjugated end-functionalized star polymers containing poly(fluorene-2,7-vinylene) (PFV) arms

A facile one-pot synthesis of end-functionalized star polymers consisting of PFVs has been achieved by olefin metathesis and Wittig-type coupling.

Precise Synthesis of Poly(fluorene vinylene)s Capped with Chromophores: Efficient Fluorescent Polymers Modified by Conjugation Length and End-Groups

Poly(9,9-di-n-octylfluorene-2,7-vinylene)s containing F-BODIPY [PFV-(F-BODIPY)₂] and Zn(II)-porphyrin have been prepared by olefin metathesis of the vinyl group in the PFV chain ends followed by subsequent Wittig-type coupling. An introduction of tris(2,5-dialkoxy-1,4-phenylene vinylene) into PFV-(F-BODIPY)₂ has also been achieved. The emission properties can be modified by the PFV chain length, chromophore, and the middle segment: PFV-(F-BODIPY)₂ exhibits white-light emission with high quantum efficiency.

Precise Synthesis of Amphiphilic Multiblock Copolymers by Combination of Acyclic Diene Metathesis (ADMET) Polymerization with Atom Transfer Radical Polymerization (ATRP) and Click Chemistry

Various block (graft) copolymers have been prepared by combination of acyclic diene metathesis (ADMET) polymerization of 9,9-dialkyl-2,7-divinyl-fluorene with Cu-catalyzed atom transfer radical polymerization (ATRP) of styrene using macroinitiators prepared by introduction of initiating functionalities into poly(9,9-dialkylfluorene-2,7-vinylene)s (PFVs) chain ends: a precise synthesis of the amphiphilic ABCBA-type block copolymers has also been attained by subsequent combination with click reaction after modification of the chain end with NaN₃.