Submicrometer diameter, light emitting fibers of poly(vinyl alcohol) (PVA) doped with pseudoisocyanine (1,1′-diethyl-2,2′-cyanine bromide, PIC) dye were prepared by electrospinning. A horizontal setup was employed with a stationary collector consisting of two parallel-positioned metal strips separated by a void gap. Formation of uniaxially aligned and randomly deposited fibers in electrospun films was confirmed by microscopy. Photoluminescence (PL) spectroscopy is used to evaluate spectral properties of both types of fibers doped with PIC. While PIC molecules were individually dispersed in PVA solution, they assemble into J-aggregates upon electrospinning when the weight fraction of PIC molecules is above 2.5 wt %. The formation of J-aggregates was observed in both randomly deposited and uniaxially aligned electrospun fibers. Moreover, the fibers aligned uniaxially showed a high degree of polarized emission (PL | /PL ⊥ ) 10), arising from the orientation of J-aggregates along the fiber axis. On the other hand, isotropic emission of J-aggregates was observed from the fibers deposited randomly. As a conclusion, electrospinning was found to be an efficient and a practical method to form highly oriented J-aggregates dispersed into polymer fibers. To the best of our knowledge, it is the first time formation of J-aggregates (a bottom-up approach) and electrospinning (a topdown approach) is successfully combined.

We report molecular aggregate formation of TTBC (1,1′,3,3′-tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine) in submicrometer-sized PVA (poly-(vinyl alcohol)) fibers by electrospinning. The formation of the molecular aggregate is examined by solution and instrumental parameters of electrospinning. The precursor solution of PVA/TTBC, in the range of 0.016−0.065 wt % is subjected to electrospinning under an electrical field ranging from 0.95 to 1.81 kV cm −1 . Both randomly deposited and uniaxially aligned fibers are achieved by using two parallelpositioned metal strips as counter electrode. Photoluminescence and polarized Fourier transform infrared spectroscopies are employed to determine spectral properties of the fibers. H-aggregates are formed within the electrospun fibers, regardless of their alignment, and H-and J-type aggregates coexist in the alternative spin-coated and the cast films. A strongly polarized photoluminescence emission is observed in the direction of uniaxially aligned fibers as a result of the orientation of the H-aggregates along the fiber axis. We demonstrate that electrospinning is a process capable of forming and orienting TTBC aggregates during the structural development of the polymer/dye nanofibers. These fibrous films may potentially find applications in optics and electronics. ■ INTRODUCTIONMolecular aggregates of dyes have attracted remarkable interest because they exhibit collective optical/excitonic properties with various functions. The strong coupling of transition dipoles of the constituent dye molecules which have internal molecular arrangement within the aggregate leads to delocalized excitonic states over a few to several molecules and, accordingly, the enhancement of the optical properties. 1 The aggregation patterns of the dye molecules exhibit red shift (J-type) and blue shift (H-type) in absorption bands. 2,3 TTBC is a twodimensional planar molecule that can form secondary interactions, yielding intriguing supramolecular structure. This cyanine dye undergoes both H-and J-type aggregation by shortrange noncovalent interactions, such as dipole−dipole interactions, π−π stacking, and hydrogen bonding. Aggregation is driven mainly by the presence of a strong transition dipole moment formed by conjugated π-electrons of the polymethine backbone of cyanine dyes. 4 The construction of sophisticated molecular dye assemblies and highly ordered dye aggregates plays a significant role in designing smart materials because their optical properties show alteration depending on the structural organization of the dyes. 5 The understanding of internal organization and controlling the mesoscopic morphology of cyanine aggregates has provided a powerful way of developing techniques for fabrication of functional structures designed for specific purposes. To date, a number of approaches have been demonstrated to form and align the aggregates, such as magnetic field, 6−9 vertical spin coating, 10−12 Langmuir−Blodgett films, 13,14 adsorption on a single crystal surface, 15,16 ...

The novel film structure of corn-zein coated on polypropylene (PP) synthetic film for packaging industry was developed to examine the feasibility of resulting coated films as an alternative water barrier performance for food packaging. The effects of coating formulation (solvent, corn-zein, plasticizer concentration and plasticizer type) on final properties of films were observed. Corn-zein is the most important protein of corn and has good film forming property. Composites structures of PP films coated with corn-zein were obtained through a simple solvent casting method. Polyethylene glycol (PEG) and glycerol (GLY) were used as plasticizer to increase film flexibility. Statistical analysis based on full factorial design was performed to observe coating formulation effects. The high water vapour barriers were obtained for films coated with coating formulation consisting of higher amounts of corn-zein plasticized by GLY. The lower glass transition temperatures (T g ) of films were obtained by plasticization of films and T g decreased by increasing plasticizer content. The statistical analysis defined the key parameters of coating formulation that had major effects on the final properties of coated PP films as corn-zein, plasticizer concentration and plasticizer type. In conclusion, corn-zein coatings could have potential as an alternative to conventional synthetic polymers used in composite multilayer structures for food packaging applications.

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