title: Solution-crystallization and related phenomena in 9,9-dialkyl-fluorene polymers. II. Influence of side-chain structure.
abstract: Solution-crystallization is studied for two polyfluorene polymers possessing different side-chain structures. Thermal analysis and temperature-dependent optical spectroscopy are used to clarify the nature of the crystallization process, while X-ray diffraction and scanning electron microscopy reveal important differences in the resulting microstructures. It is shown that the planar-zigzag chain conformation termed the β-phase, which is observed for certain linear-side-chain polyfluorenes, is necessary for the formation of so-called polymer-solvent compounds for these polymers. Introduction of alternating fluorene repeat units with branched side-chains prevents formation of the β-phase conformation and results in non-solvated, i.e. melt-crystallization-type, polymer crystals. Unlike non-solvated polymer crystals, for which the chain conformation is stabilized by its incorporation into a crystalline lattice, the β-phase conformation is stabilized by complexation with solvent molecules and, therefore, its formation does not require specific inter-chain interactions. The presented results clarify the fundamental differences between the β-phase and other conformational/crystalline forms of polyfluorenes. © 2015 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2015,53, 1492-1506.
authors.affiliation: Department of Physics and Centre for Plastic Electronics Imperial College London London SW7 2AZ United Kingdom.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Perevedentsev
authors.affiliation: Department of Physics and Centre for Plastic Electronics Imperial College London London SW7 2AZ United Kingdom.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Stavrinou
authors.affiliation: Department of Materials Eidgenössische Technische Hochschule (ETH) Zürich Vladimir-Prelog-Weg 5 8093 Zürich Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Smith
authors.affiliation: Department of Physics and Centre for Plastic Electronics Imperial College London London SW7 2AZ United Kingdom.
authors.forename: Donal D C
authors.initials: DD
authors.lastname: Bradley
keywords: conjugated polymers; crystallization; microstructure; polyfluorene; spectroscopy