Temperature induced structural evolution of a fluorene‐thiophene copolymer on rubbed surfaces

Abstract

The thermal alignment of the liquid crystalline fluorene-thiophene copolymer (F8T2) on rubbed polyimide surfaces is investigated by ex-situ and in-situ X-ray scattering experiments. The ex-situ characterization allows an assignment of the observed diffraction peaks to distances between polymer backbones (1.6 nm), distances between the flexible side groups of the polymer chains (0.43 nm), and intramolecular distances of adjacent ring units (0.5 nm). The in-situ characterization allows a temperature dependent observation of the polymer chain alignment. A gradual alignment process of the polymer backbones is observed for temperatures up to 563 K. Decreasing temperature after the polymer chain alignment is accompanied by a glass transition of the side chains at 380 K.

Strongly Photosensitive and Fluorescent F8T2 Electrospun Fibers

“…Indeed the optical micrograph obtained with crossed polarizers (Figure 2b) clearly shows birefringence of fibers, which is not observed in the F8T2 films (Figure 2c). These results agree with the recent report of Werzer et al18 about the self‐alignment of F8T2 polymer. They found that the polymer backbones gradually align themselves (along the rubbing direction) with the increasing temperature (up to 290 °C).…”

“…They found that the polymer backbones gradually align themselves (along the rubbing direction) with the increasing temperature (up to 290 °C). Above that temperature, the alignment of the polymer backbones is still present but less significant 18. The production of a fiber by ES involves an extrusion process which is responsible for the alignment of the polymer backbone and consequently for the birefringence observed in the fibers.…”

Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

“…[ 38,45 ] This is very different from that of polycrystalline polymers such as P3HT, poly(9,9-dioctylfl uorene) (PFO), poly(9,9-dioctylfl uorene-alt -benzothiadiazole) (F8BT), and poly(9,9-dioctylfl uorene-alt -bithiophene), which can have rich and complex DSC spectra showing multiple peaks from glass, crystallization, and melting transitions. [ 36,[46][47][48][49][50][51] The thin fi lm optical absorption spectra of PFB and PFMO (Figure 2 resemble the solution spectra using a good solvent in which the chains are in the random-coil conformation. This is exactly as for TFB, being an expected characteristic of an amorphous semiconducting polymer.…”