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Abstract:The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by the structure R H O(CF 2 CF 2 O) n (CF 2 O) m R H have been developed as a new class of environmentally friendly hydrofluoroethers (HFEs) suitable as solvents, long-term refrigerants, cleaning fluids, and heat transfer fluids. Synthetic methodologies for DA-FPEs described here consist of radical-initiated oxypolymerization of olefin, peroxy-elimination reaction in peroxidic perfluoropolyethers (P-PFPEs) and further chemical modification of α,ω-diacylfluoride PFPE. The physical properties of selected α,ω-dimethoxyfluoropolyethers (DM-FPEs) have been evaluated and compared with analogous hydrofluoropolyethers (HFPEs) having -OCF 2 H as end-groups. Atmospheric implications and global warming potentials (GWPs) of selected DA-FPEs are also considered.

Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels. With liquid HF, the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of ≈1.5 mm. A strategy to overcome this limitation would be to perform iterative etching, periodically removing the exhausted products and replenishing the partially etched channel with fresh acid; this procedure is, however, quite cumbersome in the liquid phase. In this paper we present what is to our knowledge the first implementation of the FLICE technique with low-pressure gaseous HF etchant. The use of a gas-phase etchant naturally lends itself to the application of iterative etching techniques, since it is very easy to remove the etchant, by pumping vacuum in the reaction chamber after each etching step. We demonstrate that iterative etching in the gas phase overcomes the limitations of wet etching and allows to achieve nearly constant etching rate for a microchannel length up to ≈3 mm.

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