Facile control of system-bath interactions and the formation of crystalline phases of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(9,9-di-{5′-pentanyl}-fluorenyl-2,7-diyl)] in silicone-based polymer hosts

In this paper poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(9,9-di-{5′-pentanyl}-fluorenyl-2,7-diyl)] (PFP) was attached by hydrosilylation reaction to polysiloxanes with lower and higher crosslinking yields. Two types of polysiloxanes were prepared: PDHS-PDVS-l-PFP-X and PDHSS-PDVS-h-PFP-X, with increasing amounts of polyfluorene (X = 4.04 × 10−4 mol (1), 4.04 × 10−5 mol (2) and 4.04 × 10−6 mol (3)), where l and h represent elastomeric and brittle matrices (l = lower crosslinking and h = higher crosslinking yields). Their photophysical properties were studied and compared with the polymer in films, in THF and in two different polysiloxane (poly[(dimethylsiloxane-co-methylvinylsiloxane) dimethylvinylsilyloxyl]-terminated-PDVS and poly[(dimethylsiloxane-co-methylhydrogensiloxane) dimethylhydrogensilyloxy] terminated-PDHS) solutions before the hydrosilylation reactions. Based on the steady-state and dynamical photoluminescence data, the polyfluorene chains are, independent of the polyfluorene amount, disordered in solutions, in films and in PDHS-PDVS-l-PFP-X. Nevertheless, in both PDHSS solutions and in the PDHSS-PDVS-h-PFP-X hybrid, crystalline phases of the polyfluorene were formed. Moreover, aggregates with green emission are also observed with increasing contents of conjugated polymer. Aggregates emitting in longer wavelengths are only formed when other crystalline phases are present in PDHSS-PDVS-h-PFP-X (X = 2 and 3) silicones. The driving force for this formation is probably a combination of π–π interaction between the planar backbone and the hydrophobic interactions of the lateral groups in the poor solvent PDHSS in a more confined environment such as brittle PDHSS-PDVS-h-PFP.