Chain geometry, solution aggregation and enhanced dichroism in the liquidcrystalline conjugated polymer poly(9,9-dioctylfluorene)

Abstract

We report on the physical characterization of a dioctyl‐substituted polyfluorene, both in solution and in the solid state. We focus on studies of chain geometry both by molecular modeling and by gel permeation chromatography coupled with light scattering. We determine experimentally a Kuhn segment length, lk = 17.1 ± 2.1 nm and a characteristic ratio C∞ = 21.5 %plusmn; 4.3 indicative of a stiff polymer chain. The effects on absorption and emission spectra of intermolecular interactions that lead to gelation or precipitation from solution are reported. We discuss these results in the context of the strong current interest in the nature of aggregation phenomena and their role in controlling the emissive properties of conjugated polymers. We further show that a markedly enhanced dichroism can be achieved through suitable control of the polymer microstructure.

Polyfluorene based blends for white light emission

“…The LaPPS10 absorption band is broad and centered at k abs = 394 nm, red-shifted by 16 nm compared to the dilute solution. The presence of the low intensity band at k abs = 432 nm is a strong evidence that during the film formation some chains or chains segments are arranged in the b-conformation, a more planar orientation of the backbone [36,[38][39][40][41]. The differences in the emission spectra of the blue emitter LaPPS10 in solution and in film form give further support for the presence of the b phase.…”

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

“…[ 36 ] Polycrystalline polymers such as P3HT, F8BT, and PFO instead typically show a red shift of the absorption edge and/or more structure with vibrational sideband detail in their thin fi lm spectra compared to the good-solvent solution spectra. [ 17,36,47,48,[52][53][54] We additionally recorded the X-ray diffraction (XRD) data ( Figure S1, Supporting Information) of a 330 nm thick fi lm of PFB annealed for 1 h at 150 °C just above the glass transition temperature to encourage any potential crystallite formation (PFMO was not investigated due to limited material availability). Despite a relatively long scan time, the diffractogram showed no diffraction peaks, the spectrum being dominated by the background due to the glass substrate (we note that F8BT fi lms show clear diffraction peaks under the same experimental conditions with the same apparatus (see the Supporting Information of ref.…”

Structure and Dynamics of Nondilute Polyfluorene Solutions

“…In fact, using d ) 1.8 ( 0.5 nm (from SANS), PF molecules can be described as wormlike chains l ) 7 ( 0.5 nm (dashed line in the lower inset of Figure 3), in accord with light scattering data. For a dioctyl-substituted poly(fluorene), a Kuhn segment value of b ) 17 ( 2 nm (l ) 8 ( 1 nm) was reported based 10 only on R g data. Also, the absorption spectra of dihexylsubstituted poly(fluorene) in solution 11 led to a conjugation length of about 12 fluorene units, and hence the persistence length was at least as high as this value (∼10 nm).…”