@misc{knaapila_control_over_2008, 
author={Knaapila, M.,Stepanyan, R.,Torkkeli, M.,Haramus, V.M.,Galbrecht, F.,Nehls, B.S.,Preis, E.,Scherf, U.,Monkman, A.P.},
title={Control over phase behavior and solution structure of hairy-rod polyfluorene by means of side-chain length and branching},
year={2008},
howpublished = {journal article},
doi = {https://doi.org/10.1103/PhysRevE.77.051803},
abstract = {We present guidelines on how the solution structure of pi-conjugated hairy-rod polyfluorenes is controlled by the side-chain length and branching. First, the semiquantitative mean-field theory is formulated to predict the phase behavior of the system as a function of side-chain beads (N). The phase transition at N=N* separates a lyotropic phase with solvent coexistence (N<N*) and a metastable membrane phase (N>N*). The membrane phase transforms into the isotropic phase of dissolved rodlike polymers at the temperature T<sub>mem</sub><sup>*</sup>(N), which decreases both with N and with the degree of side-chain branching. This picture is complemented by polymer demixing with the transition temperature T<sub>IN</sub><sup>*</sup>(N), which decreases with N. For N<N*, the lyotropic phase turns isotropic with increasing T at T<sub>IN</sub><sup>*</sup>. For N>N*, stable membranes are predicted for T<sub>IN</sub><sup>*</sup><T<T<sub>mem</sub><sup>*</sup> and metastable membranes with nematic coexistence for T<T<sub>IN</sub><sup>*</sup>. Second, in experiment, samples of poly(9,9-dialkylfluorene) with N=6–10 were mixed in methylcyclohexane. For N=8 the side-chain branching was controlled by (9,9-dioctylfluorene)/(9,9-bis(2-ethylhexyl)fluorene) (F8/F2/6) random copolymers. The proportion of F8 to F2/6 repeat units was 100:0, 95:5, 90:10, 50:50, and 0:100. In accordance with the theory, lyotropic, membrane, and isotropic phases with the corresponding phase transitions were observed. For N<N*~6 only the lyotropic phase is present for attainable temperatures. The membrane and isotropic phases are present for N>N*. T<sub>mem</sub><sup>*</sup>(N) decreases from 340 K to 280 K for N>=8. For copolymers, the membrane phase is found when the fraction of F8 units is at least 90%, T<sub>mem</sub><sup>*</sup> decreasing with this fraction. The membrane phase contains three material types: loose sheets of two polymer layers, a better packed beta phase, and dissolved polymer. For N>=7 and T<T<sub>mem</sub><sup>*</sup> the tendency for membrane formation becomes stronger with increasing temperature.},
note = {Online available at: \url{https://doi.org/10.1103/PhysRevE.77.051803} (DOI). Knaapila, M.; Stepanyan, R.; Torkkeli, M.; Haramus, V.; Galbrecht, F.; Nehls, B.; Preis, E.; Scherf, U.; Monkman, A.: Control over phase behavior and solution structure of hairy-rod polyfluorene by means of side-chain length and branching. Physical Review  E. 2008. vol. 77, no. 5, 051803. DOI: 10.1103/PhysRevE.77.051803}}