Carboxylate-functionalized polymers of intrinsic microporosity (PIMs) are promising materials for gas separation application. However, highly carboxylate-functionalized PIMs (HCPIMs) have not been reported owing to overlooked intermediate products. Herein, we successfully prepared HCPIMs (∼92 mol % of carboxylic acid group) through a prolonged alkaline hydrolysis process (360 h). HCPIMs were found to be soluble in various organic solvents, such as tetrahydrofuran and dimethyl sulfoxide, and then free-standing HCPIM membranes could be prepared by the common solution casting method. The HCPIM membranes were found to have smaller interchain distances and higher CO2 affinity than original PIM-1 films. For example, small gas molecules, such as carbon dioxide, were effectively separated due to the enhanced diffusivity selectivity combined with the smaller cavity size. Further, strong interactions between carbon dioxide and the carboxylic acid groups increased solubility selectivity. These synergetic effects endowed the HCPIM membrane with a selectivity of 53.6 for CO2/N2 separation, the highest among reported chemically modified PIMs.

Hollow polydivinylbenzene@Fe3O4 (h-PDVB@Fe3O4) nanoparticles with a relatively narrow size distribution were prepared by depositing Fe3O4 nanoparticles on h-PDVB. Because of the cavity in the hollow structure, the density of h-PDVB@Fe3O4 (ρ = 1.83 g/cm3) was significantly reduced from that of Fe3O4 (4.52 g/cm3). Deposition of Fe3O4 particles of 10–20 nm size (average particle size ≃14.3 ± 2.5 nm) on the h-PDVB made the h-PDVB@Fe3O4 particle surface quite rough while preserving the spherical shape. The MR suspensions were prepared by dispersing h-PDVB@Fe3O4 in silicone oil medium, and their magnetorheological properties were investigated. The dynamic modulus and the yield stress under magnetic field decreased compared to those of pure Fe3O4 suspension, but the MR behavior of h-PDVB @ Fe3O4 suspension was well preserved. Interestingly, contrasting MR performance of two suspensions (h-PDVB@Fe3O4 (Fe3O4 nanoparticle size ≃14.3 ± 2.5 nm) and foamed PS/Fe3O4 (Fe3O4 nanoparticle size ≃50–100 nm)) with similar densities was observed at high and low magnetic field strength regions due to the particle size difference. The long-term sedimentation stability of the suspensions was investigated with a Turbiscan apparatus. Because of reduced density mismatch between particles and silicon oil medium, the h-PDVB@Fe3O4 suspension exhibited a significantly improved stability compared to that of the pure Fe3O4 suspension, with only 13% of light transmission after 24 h. The MR performance and enhanced long-term sedimentation stability represent a viable application of h-PDVB@Fe3O4 suspensions to microfluidic devices.

Comb-like fluorinated polystyrenes with different side chain interconnecting groups between backbone and side chain, such as ether (PST-O), thioether (PST-S) and sulfone (PST-SO 2 ), were synthesized in order to examine the effect of the interconnecting groups on the surface order and properties. Near edge X-ray absorption fine structure spectroscopy and grazing incidence wide-angle X-ray diffraction showed that PST-SO 2 with very polar sulfone groups exhibited a lower tilt angle of the fluorinated helix to the surface normal as well as higher packing density of fluorinated alkyl side chains than PST-O and PST-S, which have less polar groups. As a result of the ordered structure at the polymer-air interface, PST-SO 2 has a smaller surface energy and better stability in water than PST-O and PST-S. These results suggest that the introduction of polar groups to the side chains of comb-like fluorinated polymers can improve the surface properties including the hydrophobicity and stability of fluorinated surfaces.

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A benzotrithiophene polymer with a new thermally cleavable ketal substituent is reported. It is shown how this functional group can be used to facilitate solvent processing and, subsequently, how it can be removed by a thermal annealing process to generate a structurally ordered and crystalline thin film with significantly improved field-effect transistor properties.

The fabrication of a core–shell structure is an effective method of obtaining a composite film with a high energy density. Herein, we prepared a new type of composite film with high energy density and energy efficiency by using silica-coated core–shells on poly­(vinylidene fluoride) (PVDF) particles that comprised a high proportion of polar phases rather than inorganics with high dielectric constants. We prepared PVDF particles with a high proportion of the β-phase using emulsion polymerization. Subsequently, we prepared PVDF@SiO2 core–shell particles by coating silica using the sol–gel method. The resultant PVDF@SiO2–PVDF exhibited a low reduction in the dielectric constant because of the lower amount of silica than that in other dense silica particles, which was verified through dielectric constant measurements and theoretical calculations. In addition, when the PVDF@SiO2 particle contained 40 wt % silica, a high breakdown strength of 598.95 MV/m was confirmed. Therefore, we verified that the PVDF@SiO2–PVDF composite film has a high discharge energy density of 12.051 J/cm3 when the PVDF@SiO2 is 40 wt %. In addition, the domain size is limited by the silica shell, resulting in a high energy efficiency of 88.22%, which indicated a potential for the utilization of the composite film in energy storage devices. These results offer a novel strategy for the development of polymer-based capacitors with high energy densities and efficiencies.

To control the surface properties of a commonly used polymer, poly(methyl methacrylate) (PMMA), poly(perfluoromethyl methacrylate)s (PFMMAs) with short perfluorinated side groups (i.e., -CF3, -CF2CF3, -(CF3)2, -CF2CF2CF3) were used as blend components because of their good solubility in organic solvents, low surface energies, and high optical transmittance. The surface energies of the blend films of PFMMA with the -CF3 group and PMMA increased continuously with increasing PMMA contents from 17.6 to 26.0 mN/m, whereas those of the other polymer blend films remained at very low levels (10.2-12.6 mN/m), similar to those of pure PFMMAs, even when the blends contained 90 wt %PMMA. Surface morphology and composition measurements revealed that this result originated from the different blend structures, such as lateral and vertical phase separations. We expect that these PFMMAs will be useful in widening the applicable window of PMMA.