TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Mixture: The mixture also contains conductive salt(s) selected from lithium hexafluorophosphate, LiPF6; perchlorate, LiClO4; trifluoromethanesulfonate, LiCF3SO3; hexafluoroarsenate, LiAsF6; tetrachloroaluminate, LiAlCl4; hexafluorosilicate, LiSiF6; lithium hexafluoroantimonate, LiSbF6; carbide and nitride derivatives of the formulae LiC(CF3SO2)3, LiN(SO2F)2, LiN(CF3SO2)2 and LiN(CF3CF2SO2)2; and especially lithium tetrafluoroborate, LiBF4.    TECHNOLOGY FOCUS - POLYMERS - Preferred Process: Polymer (IX) is obtained by polymerizing (b1) 5-75 wt.% compound capable of free radical polymerization, other than (VII), and (b2) 25-95 wt.% (VIII).Preferred Polymer: (V) is a condensation product of (i) a polyol (VI) with a main chain containing carbon and oxygen atoms and (ii) not less than 1 mole/mole (VI) of an alpha,beta-unsaturated carboxylic acid (VII). Preferred Definitions:    R1, R2, R3, R4 = (-CH2-CH2-O)n-CH3;    n = 1 or 2; especially    R1, R2, R3, R4 = -CH2-CH2-O-CH3    SPECIFIC COMPOUNDS - The ester is tris(2-methoxyethyl)boron, tris(2-methoxyethyl)phosphate, 2-methoxyethyl (2-methoxyethoxy)methanoate, bis(2-methoxyethyl)sulfate and/or silicon tetra(2-methoxyethoxide).    EXAMPLE - 75 g wollastonite hydrophobized with epoxysilane (Tremin 800 EST; RTM; average particle size 3 mum; pH 8.5 in aqueous suspension) were dispersed in 300 g toluene and 5 g tris(2-methoxyethyl) phosphate. Then 12.5 g polyethylene oxide (Mn = 2000000; Polyox; RTM), 12.5 g methacrylic acid diester of a propylene oxide-ethylene oxide block polymer (Pluriol PE600; RTM) and 0.02 g ultraviolet photoinitiator (Lucirin BDK; RTM) were added. The mixture was spread on siliconized paper, in a thickness of 300 microns, at 60C, then freed from diluent (5 minutes) and peeled off, giving a 40 microns thick film, which was photocured (10 minutes exposure under argon with superactinic fluorescent tubes, 5 cm away) (film A). A control (B) was made from a solution of 12.5 g polyethylene oxide, 12.5 g methacrylate diester and 0.02 g photoinitiator in 200 g tetrahydrofuran (i.e. without wollastonite and tris(2-methoxyethyl) phosphate). Both films were flexible, had excellent flexural strength and even tolerated bending through a radius well below 1 mm without breaking. After 2 weeks at room temperature, both were free from spherolitic polyethylene oxide crystals and had (A) good, (B) satisfactory resistance to swelling in organic electrolytes containing one of the cited conductive salts. This type of electrolyte diffused into the film spontaneously within a few minutes. With (A), the increase in weight was less than 50 wt.% and the swollen film had good strength. With (B), the increase in weight was under 150 wt.%, there was a considerable change in the size and thickness of the film and the strength was significantly lower than that of (A).