Novel fluorinated block copolymers for the construction of ultra-low energy surfaces and as dispersion stabilizers in solvents with low cohesion energy

Abstract

Block copolymers consisting of polystyrene and a block containing long fluorinated side chains are made by two very effective polymer analogous reactions from commercially available polystyrene-b-polybutadiene block copolymers. Since these polymers consist of two mutually immiscible blocks with hydrophobic and very hydrophobic character they form micelles in a wide range of media down to very hydrophobic solvents, e. g. toluene, tetrahydrofurane (THF), perfluorohexane, perfluoro(methylcyclohexane), hexafluorobenzene and 1,1,2-trichlorotrifluoroethane (Freon 113). First indications that our polymers are useful as effective steric stabilizers in such solvents are given by characterization of some polymer dispersions made in the solvents via precipitation polymerization.

In the solid state, mesophase formation typical for block copolymers is observed and characterized by quantitative small angle X-ray scattering (SAXS). The surface of such films is controlled by the fluorinated block and exhibits an ultra-low surface energy of the order of γ_SV = 15 mN/m, below that of polytetrafluoroethylene (PTFE) or polydimethylsiloxanes (PDMS). Unlike PTFE, the blocky nature of the presented polymer enables thermoplastic processing and dissolution in standard solvents, which is of practical relevance. Gas-permeability measurements on membranes coated with these copolymers exhibit some interesting selectivities.