Synthesis, Characterization, and Properties of Homopolymers Functionalized with Oligothiophene Derivatives in the Side Chain

Abstract

Two novel polynorbornenes 11 and 12 functionalized with electronically active conjugated oligomer units in the side chain were synthesized by the ring-opening metathesis polymerization (ROMP) method. Both polymers showed good optical characteristics, thermal stability, film-forming properties, and interesting electrochemical properties. The photophysical and redox behaviors of 11 and 12 are markedly different due to variation in the structure of the pendant oligomers. Polymer 11 with phenyl end-capped oligothiophene cooligomer in the side chain showed much higher stability toward electrochemical oxidation than 12 with a sexithiophene in the side chain. This was demonstrated by in-situ study of the changes in absorption spectra of the polymer films while varying the potential in electrochemical experiments. During the p-doping process, polymer 11 exhibited highly reversible changes in its absorption peaks when monitored at 430 and 650 nm, and the p-doping/dedoping processes can be repeated many cycles. In sharp contrast, polymer 12 was shown to be electrochemically unstable under the same conditions. Single-layer photovoltaic cells have been fabricated with 11 or 12 as the active organic layer, and their relative performances were compared. These single-layer devices showed relatively large open-circuit voltage and moderate short-circuit current. In addition, the solar cell fabricated from 11 showed better device stability under ambient conditions than that from 12, which can be attributed to the higher stability of phenyl end-capped oligothiophene co-oligomer compared to that of the sexithiophene.

Rodlike Macromolecules through Spatial Overlapping of Thiophene Dendrons

“…The fluorescence band has become somewhat broadened and structureless in contrast to those of linear oligomers. [18,19] The fluorescence quantum yields of 7 and 8 (F F = 8 and 9 %, respectively) are significantly lower than those of linear oligomers, thus suggesting a short length of the p-conjugated system in the dendritic macromonomers. The fluorescence of the dendrtic oligothiophene macromonomers comes from the longest chromophoric a-conjugated unit in a branched structure and the substitution of the thiophene rings at the b-positions induces the twisted conformation of the a-conjugated unit.…”

“…In this context, many oligothiophenes and dendritic thiophenes have been investigated. [11,12,[18][19][20] The electrochemical properties of the macromonomers and dendronized polymers were investigated by using cyclic voltammetry (CV) experiments, which were performed in degassed CH 2 Cl 2 containing Bu 4 NClO 4 as a supporting electrolyte at 100 mV s À1 at room temperature (Table 1). All the potentials were calibrated against a ferrocene/ferrocenium couple, which was used as an internal standard.…”

Progress in side-chain thiophene-containing polymers: synthesis, properties and applications

“…Shortly afterward, two structurally related polymers were reported, which were structurally optimized by elongating the spacer length between the polymer backbone and the co-oligomer unit, one with, while the other without phenyl end-capped groups (Scheme 8(b)) [53]. Both polymers showed interesting electrochemical properties as well as good optical characteristics, thermal stability, and filmforming properties.…”

A Simple Route to Rod‐Coil Block Copolymers of Oligo‐ and Polythiophenes with PMMA and Polystyrene

“…The chloroform fraction was evaporated to afford 150 mg (yield: 20%). 1 H NMR (500 MHz, 6.98 (s, 1H); GPC: M n : 19,300 Da, PDI: 1.24.…”

“…However, no microphase separation was observed in these systems, possibly due to the low molecular weight and small volume fraction of the oligothiophene moieties. Introduction of sexithiophene or phenyl end-capped quaterthiophene as side chains to polynorbornenes has been reported by Ng et al [6] While these polymers showed good optical characteristics, film-forming properties and interesting electrochemical properties, no specific organization of such materials at the nanoscale level was reported. Hayakawa and co-workers [7] reported an interesting semirod-coil diblock copolymer system, poly(styrene)-b-poly-(oligothiophene-isoprene) (PS-b-POTI), which is composed of a styrene block and an isoprene block with pendant oligothiophene side-chains.…”