Light-emitting electrospun (ES) nanofibers with diameters of 250-750 nm were successfully prepared through the binary blends of polyfluorene derivative/poly(methyl methacrylate) (PMMA) using a singlecapillary spinneret. The studied poly(fluorene)s included poly(9,9-dioctylfluoreny-2,7-diyl) (PFO), poly[2,7-(9,9dihexylfluorene)-alt-5,8-quinoxaline] (PFQ), poly[2,7-(9,9-dihexylfluorene)-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT), and poly[2,7-(9,9-dihexylfluorene)-alt-5,7-(thieno[3,4-b]pyrazine)] (PFTP). The transmission electron microscopy (TEM) studies showed that uncontinuous fiberlike structure was obtained at the low PFO/PMMA blend ratio but became a core-shell structure at a high PFO blend ratio. The poorer solubility of PFO in chloroform than that of PMMA probably forced it to be solidified first as the fiber core. Besides, a porous surface structure on the PFO/PMMA blend fibers was observed due to the rapid evaporation of the chloroform solvent. The PFO aggregation domain in the ES fibers was much smaller than that in the spin-coated films and led to higher photoluminescence efficiency. Uniform ES fibers produced from the binary blends of PFO/PMMA, PFQ/PMMA, PFBT/PMMA, and PFTP/PMMA exhibited the following luminescence characteristics (peak maximum (nm); color): 443, blue; 483, green; 539, yellow; 628, red. The present study demonstrates that full color light-emitting ES nanofibers could be produced from the binary blends of polyfluorene derivative/PMMA.

b S Supporting Information ' INTRODUCTION Regioregular poly(3-alkylthiophenes) (P3HT) have attracted extensive scientific interest due to their superior charge-transporting characteristics and favorable processability for optoelectronic device applications, such as photovoltaic cells (PV) 1À4 and organic field-effect transistor (OFET). 5À9 Aligned one-dimensional (1D) structure with nanometer-sized confinement would significantly enhance the orientation of P3HT crystals, which is more favorable for its anisotropic charge transport than the unaligned 1D structure. The charge-carrier mobility of P3HT OFET could be manipulated over a wide range of 4 Â 10 À4 to 3 Â 10 À2 cm 2 /V 3 s through different nanostructure or orientation on crystal domains, such as nanofibers. 10À15 P3HT nanofibers were generally produced via solution selfassembly 11,12 or electrospinning (ES). 13À15 We are particularly interested in producing polymer nanofibers through the ES process because it has the advantages of low cost, flexible morphology tuning, and high-throughput continuous production. 16À20 The strong stretching force and the geometrical confinement associated with the ES process could induce the orientation of polymer chains along the long axis of fiber, 21À23 whose photoelectronic properties were different from that in the spin-coated films. 24À31 In addition, ES aligned nanofibers were easily prepared from several approaches, 32À38 including a scanning tip, 32 a drum rotating at a high speed, 33 a rotating wheel-like bobbin, 34 collector/electrode modification, 22,35,36 and magnetic field-assistance. 37 Liu et al. prepared single P3HT ES nanofiber-based OFET with the mobility as high as 0.03 cm 2 /V 3 s. 14 However, droplets and beaded P3HT nanofibers were occasionally formed due to the rapid evaporation of the solvent and low polymer solubility. Recently, Lee et al. used the coaxial setup to produce continuous and uniform P3HT ES nanofibers with the carrier mobility of 0.017 cm 2 /V 3 s, by continuously providing solvent in the shell to prevent the phase separation of P3HT from the solution at the end

We report the synthesis, morphology, and applications of conjugated rod-coil-coil triblock copolymers, polyfluorene-block-poly(N-isopropylacrylamide)-block-poly(N-methylolacrylamide) (PF-b-PNIPAAm-b-PNMA), prepared by atom transfer radical polymerization first and followed by click coupling reaction. The blocks of PF, PNIPAAm, and PNMA were designed for fluorescent probing, hydrophilic thermo-responsive and chemically cross-linking, respectively. In the following, the electrospun (ES) nanofibers of PF-b-PNIPAAm-b-PNMA were prepared in pure water using a single-capillary spinneret. The SAXS and TEM results suggested the lamellar structure of the PF-b-PNIPAAm-b-PNMA along the fiber axis. These obtained nanofibers showed outstanding wettability and dimension stability in the aqueous solution, and resulted in a reversible on/off transition on photoluminescence as the temperatures varied. Furthermore, the high surface/volume ratio of the ES nanofibers efficiently enhanced the temperature-sensitivity and responsive speed compared to those of the drop-cast film. The results indicated that the ES nanofibers of the conjugated rod-coil block copolymers would have potential applications for multifunctional sensory devices.

Poly(butyl acrylate) (PBA) side chain equipped isoindigobithiophene (II2T) conjugated polymers have been designed and synthesized for stretchable electronic applications. The PBA segment possesses low glass transition temperature and high softness, offering a great opportunity to improve the mechanical property of semiconducting polymer thin films that typically contain lots of rigid conjugated rings. Polymers with 0, 5, 10, 20 and 100% of PBA side chains, named PII2T, PII2T-PBA5, PII2T-PBA10, PII2T-PBA20, and PII2T-PBA100, were explored, and their polymer properties, surface morphology, electrical characteristics, and strain-dependent performance were investigated systematically. The series polymers showed a charge carrier mobility of 0.06−0.8 cm 2 V −1 s −1 with an on/off current ratio over 10 5 dependent on different amounts of PBA chains as probed using a top-contact transistor device. Moreover, we can still achieve a mobility higher than 0.2 cm 2 V −1 s −1 even if 10% of PBA side chains were added (i.e., PII2T-PBA10). Such PII2T-PBA polymers, more attractive, exhibited superior thin film ductility with a low tensile modulus down to 0.12 GPa (PII2T-PBA20) due to the soft PBA side chain. The more PBA segment was incroporated, the lower modulus was reached. The mobility performance, at the same time, remained approximately 0.08 cm 2 V −1 s −1 based on PII2T-PBA10 films even under a 60% strain and could be simultaneously operated over 400 stretching/releasing cycles without significant electrical degradations. The above results suggest that the rational design of soft PBA side chains provides a great potential for next-generation soft and wearable electronic applications.

Highly‐aligned luminescent electrospun nanofibers were successfully prepared from two binary blends of PFO/PMMA and PF+/PMMA. The PFO/PMMA aligned electrospun fibers showed a core/shell structure but the PF+/PMMA fibers exhibited periodic aggregate domains in the fibers. The aligned fibers had polarized steady‐state luminescence with a polarized ratio as high as 4, much higher than the non‐woven electrospun fibers or spin‐coated film. Besides, the PF+/PMMA aligned electrospun fibers showed an enhanced sensitivity to plasmid DNA. Such aligned electrospun fibers could have potential applications in optoelectronic or sensory devices.magnified image