Research articles

An immiscible blend of isotactic polypropylene (PP) and ethylene-butene-1 copolymer (EB) containing a small amount of N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide as a nucleating agent to generate β-form crystals was prepared by T-die extrusion. We successfully prepared an extruded sheet in which the orientation of the PP molecules is perpendicular to the deformation of the EB particles. It is suggested that EB barely affects the crystalline form and orientation of PP. Since this sheet containing a large amount of β-form crystals exhibits an extraordinary structure, unique mechanical anisotropy is obtained.

To synthesize CO₂-derived polycarbonates with high T_g values, epoxides having rigid and bulky 2-norbornyl or 1-adamantyl substituents were selected as comonomers. The alternating copolymer obtained from 1-adamantylethylene oxide showed a T_g above 150 °C. This is the highest T_g among those observed for alternating copolymers obtained from CO₂ and a terminal epoxide.

An efficient method to decrease dielectric constant (ɛ) of poly(2,6-dihydroxy-1,5-naphthylene) (PDHN) by introducing bulky alkyl side chains was reported. Poly(2,6-dialkoxy-1,5-naphthylene)s (PDANs) were prepared by the O-alkylation of PDHN with alkyl halides. The ɛ values of PDANs at 10 GHz decreased as the length and size of side chains increased. Especially, PDCHMN exhibited the lowest dielectric constant (ɛ = 2.29). The ε value results were also supported by refractive index measurement.

By simply coating a thin layer of 4,4’-diphenylmethane diisocyanate, polyacrylic acid and borax on the surface of PET film, a transparent PET film with extremely low gas vapor barrier value can be obtained. The oxygen transmission rate can be dramatically decreased to the detection limit of commercial instrumentation (<0.005 cc/m²/day).

Synthesis and properties of borafluorene-containing conjugated polymers with various comonomers are presented. From the comparison with the gallafluorene copolymers, higher luminescent quantum yields were obtained from the borafluorene copolymers. Additionally, from the electrochemical measurements, it was shown that the electron-withdrawing property of the boron atoms led to the stabilization of LUMOs of the borafluorene copolymers. In the X-ray diffraction profiles, the significant peaks originated from π−π stacking and assembly of the side chains were observed. The borafluorene copolymers were more crystalline materials relative to the gallafluorene polymers.

The thermoresponsive copolymer P(MEO₂MA-co-OEGMA₅₀₀) was successfully prepared using a novel photopolymerization procedure. The synthesis was carried out using a user-friendly method with a few ppm of a photoredox iridium-based catalyst. Monomer conversions higher than 50% were achieved in less than 1 h of synthesis showing a faster polymerization rate when compared to the traditional Cu-based ATRP synthesis. The photochemically controlled method here described provides true control over polymer structure, architecture, and properties. Furthermore, the polymer showed no toxicity on four mammalian cell lines at the highest concentration tested (0.4 mg/ml).