Different Crystallization Behaviors of Poly(vinylidene fluoride) Blended with or Coated with Cetyltrimethylammonium Bromide

Crystallization of poly(vinylidene fluoride) (PVDF) either blended with or coated with cetyltrimethylammonium bromide (CTAB) during isothermal and nonisothermal processes has been studied, which reveals the influence of the interaction way between PVDF and CTAB on the polymorphic behavior of PVDF. The random dispersion of CTAB with limited content in the blend sample leads to three different states of PVDF chains, i.e., intact chains and TGTG′ and TTT chain sequences induced by the ion–dipole interaction. While the intact chains and TGTG′ sequences promote the crystallization of PVDF in the α-phase, the TTT chain sequences cause the crystallization of PVDF in the γ-phase at high temperatures, which endows a full transformation of α into γ′ at the later stage. On the other hand, for the PVDF coated with CTAB, the ion–dipole interaction results in the long TTT sequences, or even all-trans chain segments, at the interface between PVDF and CTAB, which ensure the crystallization of PVDF directly in the γ-phase at high temperatures but in the β-phase during melt-quenching. This provides a simple and effective method for fabricating high-crystallinity (e.g., 47%) electroactive PVDF thin films with a preferential β-phase of ca. 95.3% and a small amount of γ-phase (around 4.7%)

Enhancing the Alpha-To-Gamma Phase Transition of Poly(vinylidene fluoride) via Dehydrofluorination Modification

Due to the high activating energy, it is very difficult to initiate the α-to-γ phase transition of poly(vinylidene fluoride) (PVDF), resulting in an extremely slow transition rate. Here, introducing a small number of double bonds into the PVDF molecular chains through dehydrofluorination is demonstrated to markedly decrease the activating energy and enhance the phase transition efficiency. It is found that the introduced double bonds during the dehydrofluorination reaction accelerate the α-to-γ phase transition, which is reflected by the shortened induction period and increased transition rate. The α-to-γ phase transition in PVDF modified with double bonds occurs mostly from the nuclei of α-spherulites rather than from the scarce boundaries initiated by γ-spherulites as in unmodified PVDF. Comparative analysis reveals that the energy storage performance of γ-PVDF films prepared through the phase transition surpasses that of α-PVDF ones. Compared to α-PVDF, the energy storage density of the modified γ-PVDF exhibits a remarkable enhancement of 181%, while the energy storage efficiency experiences a notable improvement of 124%. Consequently, a molecular modification strategy for the α-to-γ phase transition is introduced, enabling efficient production of γ-PVDF with enhanced energy storage properties and positioning it as an ideal material for driving technological advancements in electronic devices, electric vehicles, and renewable energy sectors

Isolation, Identification, and Bioactivity of Monoterpenoids and Sesquiterpenoids from the Mycelia of Edible Mushroom Pleurotus cornucopiae

Edible mushroom is a profilic source of bioactive metabolites for the development of drugs and nutraceuticals. In this work, four new monoterpenoids (<b>1</b>–<b>4</b>) and one new sesquiterpenoid (<b>6</b>) were isolated from the mycelia of edible mushroom Pleurotus cornucopiae fermented on rice. Their structures were established by nuclear magnetic resonance, mass spectrometry, and circular dichroism (CD) data analysis. Compound <b>1</b> possesses an unusual spiro­[benzofuran-3,2′-oxiran] skeleton. The absolute configuration of the 6,7-diol moieties in compounds <b>1</b>, <b>2</b>, and <b>6</b> was assigned using the <i>in situ</i> dimolybdenum CD method. Compounds <b>1</b>–<b>5</b>, <b>7</b>, and <b>8</b> showed moderate inhibitory activity against nitric oxide production in lipopolysaccaride-activated macrophages, with IC₅₀ values in the range of 60–90 μM. Compounds <b>6</b> and <b>7</b> also exhibited slight cytotoxicity against HeLa and HepG2 cells