Search

The electrospinning technique has been considered an attractive route for processing conjugated polymers in a significant quantity for large-scale applications. The processing-structure-property relationship of the electrospinning process for conjugated polymers is not well understood. Here, we report the electrospinning of poly(3-hexylthiophene) (P3HT) for three different molecular weights of P3HT: 31, 58, and 83 kDa. Chloroform was used as a solvent, and a high molecular weight poly(ethylene oxide) (PEO) was utilized to facilitate the processing of P3HT. The electrospinning was performed on the freshly prepared and 24 h aged spinning solutions. The aging of the spinning solution led to the self-assembly of P3HT chains, particularly with dominant H-aggregation for 83 kDa P3HT. The structure development and properties of the fibers were investigated, including the single-fiber electrical conductivity measured using a custom-built setup. The electrical conductivity has been found to be increasing with increasing molecular weight, and as high as a five-fold enhancement in single fiber electrical conductivity was obtained compared to the fiber from the freshly-prepared solution. Despite a 25% PEO concentration in the fibers, the maximum electrical conductivity of a single fiber was found to be ≈2.7 X 10^(-5) S/cm, similar to the pristine P3HT thin films. Our study provides an additional understanding of P3HT structure development in electrospun fibers as a function of polymer molecular weight and processing steps and relates that to fiber properties.

The development of open-shell organic molecules that magnetically order at room temperature,which can be practically applied, remains a grand challenge in chemistry, physics, and materials science. Despite the exploration of vast chemical space, design paradigms for organic paramagnetic centers generally result in unpaired electron spins that are unstable or isotropic. Here, a high-spin conjugated polymer is demonstrated, which is composed of alternating cyclopentadithiophene and benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole heterocycles, in which macromolecular structure and topology coalesce to promote the spin center generation and intermolecular exchange coupling. Electron paramagnetic resonance (EPR) spectroscopy is consistent with spatially localized spins, while magnetic susceptibility measurements show clear anisotropic spin ordering and exchange interactions that persist at room temperature. The application of long-range π-correlations for spin center generation promotes remarkable stability. This work offers a fundamentally new approach to the implementation of this long-sought-after physical phenomenon within organic materials and the integration of manifold properties within emerging technologies.

Polymer microspheres have been widely investigated because of their applications in areas such as drug delivery, latex diagnostics, and affinity bioseparators. The effect of annealing on polymer microspheres, however, has been rarely studied. In this work, we demonstrate the morphology transformation of polystyrene (PS) microspheres annealed thermally on poly(methyl methacrylate) (PMMA) films. During the annealing process, the PS microspheres gradually sink into the PMMA films and transform into PS hemispheres, driven by the reduction of the surface and interfacial energies. The effect of the film thicknesses on the morphology transformation is also studied. In addition, porous PMMA films or PS hemispheres can be obtained by removing the PS or the PMMA domains of the polymer composites using cyclohexane or acetic acid, respectively.