Solution-Crystallization and Related Phenomena in 9,9-Dialkyl-Fluorene Polymers. I. Crystalline Polymer-Solvent Compound Formation for Poly(9,9-dioctylfluorene).
Journal of polymer science. Part B, Polymer physics 53:21 (2015) 1481-1491
Abstract:
Polymer-solvent compound formation, occurring via co-crystallization of polymer chains and selected small-molecular species, is demonstrated for the conjugated polymer poly(9,9-dioctylfluorene) (PFO) and a range of organic solvents. The resulting crystallization and gelation processes in PFO solutions are studied by differential scanning calorimetry, with X-ray diffraction providing additional information on the resulting microstructure. It is shown that PFO-solvent compounds comprise an ultra-regular molecular-level arrangement of the semiconducting polymer host and small-molecular solvent guest. Crystals form following adoption of the planar-zigzag β-phase chain conformation, which, due to its geometry, creates periodic cavities that accommodate the ordered inclusion of solvent molecules of matching volume. The findings are formalized in terms of nonequilibrium temperature-composition phase diagrams. The potential applications of these compounds and the new functionalities that they might enable are also discussed. © 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, 1481-1491.Solution-crystallization and related phenomena in 9,9-dialkyl-fluorene polymers. II. Influence of side-chain structure.
Journal of polymer science. Part B, Polymer physics 53:21 (2015) 1492-1506
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.Multijunction Organic Photovoltaic Cells for Underwater Solar Power
Institute of Electrical and Electronics Engineers (IEEE) (2015) 1-3
A metallic hot carrier photovoltaic cell
Proceedings of SPIE SPIE, the international society for optics and photonics 9358 (2015) 935810-935810-8
High‐Efficiency Organic Photovoltaic Cells Based on the Solution‐Processable Hole Transporting Interlayer Copper Thiocyanate (CuSCN) as a Replacement for PEDOT:PSS
Advanced Energy Materials Wiley 5:3 (2015)