Massimo Scicchitano

New fluorinated thermoplastic elastomers

New fluorinated thermoplastic elastomers (FTE) with perfluoropolyether (PFPE) blocks have been synthesized by reacting a fluorinated macrodiol with aromatic diisocyanates in the presence of a solvent, followed by subsequent chain extension with low molecular weight aliphatic or aromatic diols. Tensile properties measurements and dynamical-mechanical analysis (DMA) have been carried out and the relationship between chemical structure and final properties has been determined. These new thermoplastic fluorinated polyurethanes show an elastomeric behavior over a wide temperature range (between −75 and 100°C), thanks to their multiphase morphology consisting of a continuous fluorinated phase with a very low Tg (−120°C) and a dispersed high melting hydrogenated hard phase, as verified by a calorimetric and dynamic-mechanical analysis. At the same time, some of the outstanding properties of fluorinated oligomers, such as chemical inertness and low surface tension, are retained in the final polymers. Thanks to these characteristics this new class of polymeric materials provides new opportunities for the application of thermoprocessable elastomers in advanced technological fields.

End group chemistry of fluoro-oligomers: Highly selective syntheses of diepoxy, diallyl, and tetraol derivatives

Different synthetic methods for the preparation of polyfunctional fluorinated oligomers were explored and the results compared. Fluoropolyether macromonomers bearing epoxy, allyl, and polyhydroxy end groups were synthesized and spectroscopically characterized. For obtaining a polyol (namely tetraol) functionality, a highly selective route was the reaction of the fluoropolyether macrodiol ZDOL with allylic halides and subsequent oxidation reaction at the CC double bond by means of peroxyacids. This approach made it possible to obtain a segmented structure RH-RF-RH in which the molecular body RF consisted of a perfluoropolyether block endcapped by two hydrogenated segments RH, where RH = − CH2OCH2CH(OH)CH2OH. Unlike other more conventional syntheses, which always produce byproducts and higher molecular weight species such as RH-(RF-RH)n-RF-RH or RH-RF-(RH)n-, the described method offers high yields and selectivity. The fluoropolyether polyfunctional derivatives offer the possibility to prepare a variety of highly crosslinked fluorinated materials and, owing to their well defined regularly segmented structures, they also constitute interesting models for the understanding of basic structure-property relations of fluoro-oligomers and their copolymers.

Chemical approaches toward the definition of new high-solid and high-performance fluorocoatings

Abstract Hydroxy bifunctional fluoropolyether oligomers (ZDOL) are presented suitable for use as resins or for the preparation of polyurethane, polyester and polyether higher OH functionality resins. The synthesis procedures are described and discussed, and the effect of fluorine content and resin structure on glass transition temperature Tg and viscosity of final resin is stressed. It appears that the highly fluorinated polyether type resins, like the tetraolic derivative (TOL) and its mixtures with ZDOL, are characterized by only one, extremely low Tg and minimum viscosity values. Solvent–resin interactions and criteria for obtaining compatibility with polyisocyanate crosslinkers are discussed, pointing out the key role of hydrogen bonding. High solid coatings (solvent content less than 30%) are obtained by curing with blocked aliphatic polyisocyanates, and a preliminary characterization of final materials based on their thermal transitions and mechanical properties is reported.

CYCLIC ACETALS OF FLUORINATED POLYETHER MACRODIOLS

Abstract Telechelic hydroxy terminated perfluoropolyethers were derivatized with dihalomethanes (CH 2 Cl 2 ;CH 2 Br 2 ;CH 2 BrCl) in different stoichiometric ratios. The GPC analysis of the raw reaction product showed a general bimodal molecular weight distribution. Separation of the different fractions was carried out by solvent–non-solvent fractionation procedure or by vacuum distillation. It was proved that the lowest molecular weight product (about 50% of the whole polymer) corresponded to a fluorinated, cyclic monoacetal structure, while the higher MW fractions consisted predominantly of linear, polyacetal polymers. The tendency of fluorinated macrodiols to yield cyclic, instead of linear acetals, is discussed, even in comparison with the behavior of their non-fluorinated analogs. Some physical properties of the new cyclic fluoropolyethers are briefly reported.

Structure-property Relationships of Coatings Based on Perfluoropolyether Macromers

Fluorinated cross-linked polyurethanes can be obtained by the right combination of fluoropolyether macromers with the cyclic trimers of HDI and IPDI.