In recent years, poly(3-hexylthiophene) (P3HT) nanowires have attracted great interest because of their unique physical and electronic properties. The annealing effects on the properties and morphologies of P3HT nanowires, however, are still not fully understood. In this work, the effects of thermal annealing and solvent annealing on the morphologies and crystallinities of P3HT nanowires prepared by the whisker method are studied. P3HT is fi rst dissolved in heated p -xylene, followed by a cooling process to room temperature, and P3HT nanowires are formed by self-assembly. The crystallinities of the P3HT nanowires are observed to increase by both thermal annealing and solvent annealing, as confi rmed by differential scanning calorimetry and X-ray diffraction. The device performances of organic fi eld-effect transistors based on the annealed nanowires are also examined. After annealing, an enhancement of the charge mobility by one order is observed.

Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self-assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.

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. P olymer microspheres have attracted significant attention because of their applications in areas such as drug delivery, latex diagnostics, and affinity bioseparators. 1−4 Many fabrication methods have been developed to prepare polymer microspheres such as emulsion polymerization, dispersion polymerization, spray-drying, and distillation precipitation polymerization. 3,5,6 For controlling the morphologies and properties of polymer materials, annealing techniques such as thermal annealing or solvent annealing are commonly used. 7−11 The annealing effects on the morphologies and properties of polymer microspheres, however, have been rarely investigated.In this work, we report the effect of thermal annealing on polystyrene (PS) microspheres deposited on poly(methyl methacrylate) (PMMA) films. After thermal annealing, the microspheres gradually sink into the PMMA films and transform into hemispheres to minimize the surface and interfacial energies of the polymers. As a result, composites of PS hemispheres encapsulated in PMMA films are obtained. The effect of the PMMA film thicknesses on the morphology transformation is also studied.To confirm the compositions and morphologies of the PS/ PMMA composities, a selective removal technique is applied. 12−14 The PS domains can be removed selectively using cyclohexane, and porous PMMA films can be obtained, where the pore sizes are controlled by the original sizes of the PS microspheres. Besides, the PMMA films can be removed selectively using acetic acid, and PS hemispheres can be released.This work provides a simple and feasible approach to prepare heterogeneous polymer surfaces with well-defined regions, which could be applied to selective patterning in biomedical applications. In addition, the polymer composites can be used to prepare hemispheres and porous polymer films, which can not be easily prepared by other means.The experimental scheme to fabricate the PS/PMMA composites is illustrated in Figure 1. PMMA films with different thicknesses are first prepared by blade-coating on glass substrates, followed by an annealing process at 120°C for 3 h to reduce the roughness of the films. Subsequently, PS microspheres with an average diameter of...

Poly­(3-hexylthiophene) (P3HT) films have been usually prepared by spin-coating for the applications of electronic devices such as organic photovoltaic devices (OPV) and organic field-effect transistors (OFETs). The wetting and dewetting behaviors of the swollen P3HT films during the spin-coating processes, however, are still poorly understood. In this work, we investigate the dewetting behaviors of P3HT thin films and the formation of ring structures during the spin-coating process by controlling the spin rates and the solution temperatures. Quantitative studies of the dewetting phenomena are conducted by measuring the sizes of the ring structures of the dewetting patterns. It is observed that the sizes of the ring structures are larger at lower spin rates because of the longer dewetting times allowed during the spin-coating processes. More importantly, the dewetting behaviors of the P3HT films are discovered to be affected by the formation of the P3HT nanowhiskers (nanowires). This work offers a deeper understanding of the dewetting behaviors of swollen P3HT films during the spin-coating processes, which is crucial for the development of P3HT-based optoelectronic devices.

This article examines the thermal conductivity of a single P3HT nanowire with a cross-section of 5 nm by 15 nm.