New rod-coil diblock and coil-rod-coil triblock copolymers containing conjugated poly[2,7-(9,9-dihexylfluorene)] (PF) and coil-like poly(2-vinylpyridine) (P2VP) were synthesized by combining coupling reaction and living anionic polymerization. Scanning force microscopy (SFM), transmission electron microscopy (TEM), cryo-transmission electron microscopy (cryoTEM), and dynamic light scattering (DLS) were used to obtain the morphologies of the aggregates in selective solvents of different methanol(MeOH)/tetrahydrofuran (THF) compositions. The effects of micellar morphologies on the photophysical properties were studied by optical absorption and photoluminescence (PL). The experimental results showed that the diblock PF-b-P2VP (di-PFPVP) maintained spherical micellar aggregates as the MeOH content increased. However, the triblock PF-b-P2VP(tri-PFPVP) were found to readily aggregate in elongated cylinders due to its symmetric structure. Consequently, tri-PFPVP polymer chains could stack together favorably and have stronger π-π interchain stacking compared with di-PFPVP, leading to the higher absorption wavelength maximum. The quantum efficiencies were gradually quenched with increasing the MeOH content for both copolymers. Moreover, for di-PFPVP, the increase of the MeOH content induced a blue shift in both absorption and PL spectra, suggesting an "H-type" aggregation. However, tri-PFPVP exhibited a blue shift in absorption but a red shift in PL by increasing the MeOH content, which reflected a different type of aggregation. The present study revealed the effects of polymer chain architecture and the aggregated structures of the rod-coil block copolymers on the photophysical properties.

The anionic polymerization of styrene monomers para-substituted with π-conjugated mono-, di-, and tri(9,9-dihexylfluorene) moieties, St-Fl, St-Fl 2 , and St-Fl 3 , was examined under the conditions either in THF at -78°C or in tert-butylbenzene at 20°C with sec-BuLi as an initiator. The polymerization of both St-F l and St-Fl 2 was found to proceed in a living manner to quantitatively afford the corresponding polymers with predictable molecular weights and narrow molecular weight distributions (M w /M n < 1.08). The anionic polymerization of St-Fl 3 was also indicative to proceed in a living manner but with an unpredictable molecular weight. Both AB and BA diblock copolymers with the well-defined and expected structures could be successfully prepared by the sequential addition of St-Fl or St-Fl 2 followed by styrene and vice versa. The block copolymerization results clearly indicate the living nature of the anionic polymerization of St-Fl and St-Fl 2 and the almost same anionic polymerization behaviors of both monomers as styrene in reactivities of monomer(s) and propagating chain-end anion(s). Solubilities, intrinsic viscosities, and glass transition temperatures of the poly(St-Fl) and poly(St-Fl 2 ) herein prepared were measured. The optical absorption and luminescence spectra of the studied polymer films showed well-resolved vibronic structures and the peak maxima was progressively increased as the fluorene chain length increased. The luminescence spectra also showed reduced aggregation/excimer emission in comparison with that of parent polyfluorene. The present study suggests that living anionic polymerization could be employed to polymerize other styrene derivatives with π-conjugated moieties in a controlled manner and such polymers may exhibit precisely defined physical properties.

New luminescent electrospun (ES) fibers for pH-tunable colorimetric sensors were prepared from binary blends of poly(phenylquinoline)-block-polystyrene (PPQ-b-PS)/polystyrene (PS) with a single-capillary spinneret. The PPQ-b-PS aggregated domain sizes in the ES fibers prepared from dichloromethane (CH(2) Cl(2) ), chlorobenzene (CB) and chloroform (CHCl(3) ) were 1.5 ± 0.5, 2.2 ± 0.4 and 4.1 ± 1.1 µm, respectively. Such variation on the aggregation size led to the red-shifting photoluminescence spectra changing from green, to yellow, and orange. ES fibers prepared from CH(2) Cl(2) exhibited pH-tunable photoluminescence and the emission maximum varied from 532 to 560 nm as the pH value changed from 7 to 1. The study demonstrated that the ES fibers prepared could have potential applications for sensory devices.

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