Time-Resolved Fluorescence Spectra in the End-Functionalized Conjugated Triblock Copolymers Consisting of Poly(fluorene vinylene) and Oligo(phenylene vinylene): Proposal of Dynamical Distortion in the Excited State

Abstract

Time-resolved fluorescence study has been explored for end-functionalized conjugated triblock copolymers consisting of poly(9,9-di-n-octylfluorene-2,7-vinylene)s (PFVs, FV repeat units ca. 10 or 20) and oligo(2,5-dialkoxy-1,4-phenylenevinylene)s [OPV, alkoxy = O(CH 2 ) 2 OSi i Pr 3 , 3 or 7 PV repeat unit] as the middle segment. Unit (FV and PV) length dependence of each block on fluorescence was examined. The polymer sample having three PV repeat units as the middle segment with C 6 F 5 end-groups, [10PFV-3PV]F 2 , showed time-dependent fluorescence spectra, in which relative intensities of the vibronic bands increase in later delay time, whereas similar observations were not seen in the other polymer samples containing 7PV as the middle segment even by varying the PFV chain lengths (ca. 20) or the end-group (C 6 F 5 vs C 6 H 5 ). Timeresolved of fluorescence signals for [10PFV-3PV]F 2 can be analyzed by assuming two components: one is a faster decay component and the other is a slower red component, which rises with the time constant of the former one. On the other hand, the other three polymer samples showed single-exponential decays without significant wavelength dependence. Dynamical structural relaxation in the excited state is proposed as the origin of time dependence of the fluorescence spectra in the polymer having 3PV repeat unit on the basis of analysis of time-resolved fluorescence signals as well as viscosity dependence. ■ INTRODUCTIONConjugated polymers are of continuing interest as organic electronics due to their promising applications in optoelectronic and electrochemical devices, 1−5 such as photovoltaic cells, 3b light-emitting diodes, 5c,6 sensors, 5d,7 electrochromics, 8 and field-effect transistors. 5a,b,9 The synthesis of structurally regular, chemically pure polymers by development of new synthetic methods attracts notable attention 1 because their device performances are governed by the structural regularity, chemical purity, and supramolecular order. 2,3 Emerging applications of conjugated polymers require the patterning of materials on the nanometers length scale, and block copolymers made of covalently linked polymers represent an ideal route to control the self-assembly of the nanosized morphologies. Formation of regular one-dimensional conjugated structures on the nanoscale should be thus expected by exploiting the specific assembling properties of rod−coil block copolymers. 10−13 End-group modification of conjugated polymers has also been considered as an attractive topic of investigation because the important properties that have been demonstrated for end-functional conjugated polymers and the significant effect end-groups can have on electronic properties. For example, simple end-capping of conjugated polymers via postpolymerization reactions showed improvement in the performance of bulk heterojunction photovoltaic devices by eliminating traps for charge carriers. 14 Many reports concerning poly(fluorene)s (PFs) containing discrete end-groups (such as triarylamines, perylene mon...

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

“…According to a previous report, 24 PFV prepared by acyclic diene metathesis polymerization 58−75 has been chosen, not only because the approach affords defect-free, stereo-regular (all-trans) materials, 26−28,58−64 but also because the method enables us to afford the π-conjugated polymers with well-defined chain ends (vinyl groups prepared by Ru catalysts) that are suitable for the subsequent end modification by treatment of the vinyl groups with molybdenum-alkylidene catalyst followed by Wittig-type cleavage with aldehyde. 21−28,61,76−78…”

“…Fluorescence quantum yields of samples were obtained as described previously. 25,78 Time-resolved fluorescence measurements were performed with the setup as described previously. 25,78 To obtain florescence anisotropy ratios, excitation was performed with the use of vertically polarized light.…”

“…25,78 Time-resolved fluorescence measurements were performed with the setup as described previously. 25,78 To obtain florescence anisotropy ratios, excitation was performed with the use of vertically polarized light. Emission from the sample solution was collected after passing through a polarizer and then led into the imaging spectrograph, of which the entrance is equipped with a scrambler.…”

Attempt to visualize terminal structure on a specific facet in polymer–metal complex nanocrystals

“…In a similar manner, terminal structure and end-groups oen affect remarkably physicochemical properties in common polymer materials, and their assignment and quantitative analysis should be important in polymer science and engineering. [6][7][8][9][10][11] In addition, PMC in a solid state shows luminescence from metalto-ligand charge transfer (MLCT) excitation states, and the emission energy depends on energy level of p* orbital of ligand. 5 In the previous study, 12 we have fabricated various PMC NCs and changed the luminescence properties by the size effect.…”

High fluorescent ethyl acrylate modified PEDOT‐MeNH2 with enhanced electrochromic performance

“…Fluorescent polymers have drawn significant attentions due to their advantages including structural flexibility, low cost, and feasibility of large area fabrication by solution spin coating or inkjet printing for their potential applications. In fluorescent polymer materials, polyfluorene, polycarbazole, polypyrene are the classical fluorescent scaffolds for the design of various fluorescent materials by judicious molecular modifications, as shown in Chart . These polymers show good performances such as good solubility in common organic solvents, high fluorescence quantum yields and high thermal stability .…”