EDTA-assisted hydrothermal synthesis of cubic SrF2 particles and their catalytic performance for the pyrolysis of 1-chloro-1,1-difluoroethane to vinylidene fluoride

Uniform, free-standing and cubic SrF₂ microparticles were fabricated by a facile hydrothermal method with EDTA as the chelating agent.

Inserting –CHCH– into P(VDF-TrFE) by C–F activation mediated with Cu(0) in a controlled atom transfer radical elimination process

A controlled single electron transfer radical elimination (SET-RE) reaction has been successfully developed to introduce CHCH bonds into poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)).

Phase Behavior of Poly(vinylidene fluoride)-graft-poly(diethylene glycol methyl ether methacrylate) in Alcohol-Water System: Coexistence of LCST and UCST

A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted from poly(vinylidene fluoride) (PVDF) backbone by using a combined ATRC and ATRP technique with a high conversion (69%) of the monomer to produce the graft copolymer (PD). It is highly soluble polymer and its solution property is studied by varying polarity in pure solvents (water, methanol, isopropanol) and also in mixed solvents (water-methanol and water-isopropanol) by measuring the hydrodynamic size (Z-average) of the particles by dynamic light scattering (DLS). The variation of Z-average size with temperature of the PD solution (0.2%, w/v) indicates a lower critical solution temperature (LCST)-type phase transition (T(PL)) in aqueous medium, an upper critical solution temperature (UCST)-type phase transition (T(PU)) in isopropanol medium, and no such phase transition for methanol solution. In the mixed solvent (water + isopropanol) at 0-20% (v/v) isopropanol the TPL increases, whereas the T(PU) decreases at 92-100% with isopropanol content. For the mixture 20-90% isopropanol, PD particles having larger sizes (400-750 nm) exhibit neither any break in Z-average size-temperature plot nor any cloudiness, indicating their dispersed swelled state in the medium. In the methanol + water mixture with methanol content of 0-30%, T(PL) increases, and at 40-60% both UCST- and LCST-type phase separations occur simultaneously, but at 70-90% methanol the swelled state of the particles (size 250-375 nm) is noticed. For 50 vol % methanol by varying polymer concentration (0.07-0.2% w/v) we have drawn a quasibinary phase diagram that indicates an approximate inverted hourglass phase diagram where a swelled state exists between two single phase boundary produced from LCST- and UCST-type phase transitions. An attempt is made to understand the phase separation process by temperature-dependent (1)H NMR spectroscopy along with transmission electron microscopy.

Nanoconfinement and Chemical Structure Effects on Permeation Selectivity of Self-Assembling Graft Copolymers

Permeation of small molecule solutes through thin films is typically described by the solution-diffusion model, but this model cannot predict the effects of nanostructure due to self-assembly or additives. Other models focusing on diffusion through isolated nanopores indicate that confining permeation to channels slightly larger than the size of the solute can lead to an increased influence of solute-pore wall interactions on permeation rate. In this study, we analyze how differences in polymer nanostructure affect the relative contributions of solute size and polymer-solute interactions on transport rate. We compared the diffusion rates of several small molecules through two polymer thin films: A cross-linked, homogeneous film of poly(ethylene glycol phenyl ether acrylate) (PEGPEA) and a graft copolymer with a poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) backbone and PEGPEA side chains that self-assemble into continuous ∼1-3 nm PEGPEA domains through which transport occurs. We correlated these rates with the size of each solute and its chemical affinity to PEGPEA, as measured by the difference between their solubility parameters. Diffusion rate through the homogeneous polymer film was controlled by solute size, whereas diffusion rate through the copolymer was strongly controlled by the difference between the solubility parameters. Furthermore, permeation selectivity between two selected molecules was 2.5× higher for the nanostructured copolymer, likely enhanced by the nanoconfinement effects. These initial results indicate that polymer self-assembly is a promising tool for designing polymeric membranes that can differentiate between solutes of similar size but differing chemical structures.

The reaction kinetics and mechanism of crude fluoroelastomer vulcanized by direct fluorination with fluorine/nitrogen gas

The novel vulcanization of fluoroelastomer by fluorination is studied; moreover, the simultaneously accompanied fluorine content increases and tribological property is improved.