TECHNOLOGY FOCUS - ELECTRONICS - Preferred Electrode: The electrode further comprises at least one binder.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst layer comprises (pbw): a catalyst, the polymer (P1) (0.1-65), and further comprises a binder (0.1-50). The catalyst is platinum (Pt); metal-Pt alloy including Pt and at least one metal selected from gold(Au), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), tin (Sn), molybdenum (Mo), cobalt (Co) and/or chromium (Cr); or mixture of Pt and the metal. The catalyst is a catalyst metal or support catalyst in which the catalyst metal is loaded on a carbonaceous support. The catalyst layer further comprises at least one proton conductor selected from a phosphoric acid or 1-20C organic phosphonic acid.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (disclosed): Preparation of the monomer (I) (where R1-R3 are -O-T1) involves heating a mixture of phosphoric acid tris-(4-hydroxy-phenyl) ester, amine of formula 3H2NR3 and p-formaldehyde, optionally in solvent, refluxing the mixture, and performing a work-up process of the resultant.    TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: In the polymer (P1), the amount of the crosslinkable compound is 5-95 parts by weight (pbw) based on 100 pbw of the monomer (I). The electrolyte membrane further comprises at least one proton conductor selected from a phosphoric acid and 1-20C organic phosphonic acid. Preferred Components: The crosslinkable compound is at least one compound selected from polybenzimidazole (PBI), polybenzimidazole-base complex, polybenzthiazole, polybenzoxazole, or polyimide. The binder is poly(vinylidene fluoride), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer, fluorinated ethylene propylene (FEP), styrene butadiene rubber (SBR) and polyurethane. Preferred Definitions:    R1 and R2=-O-T1, -O-phenyl, phenyl, -CH2CH2CH3;    R3=phenyl, 3-trifluoromethyl-phenyl, 4-fluoro-phenyl, 2,4-difluoro-phenyl, 3,4-difluoro-phenyl, 2,4,6-trifluoro-phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, or pyrimidin-2-yl.    SPECIFIC COMPOUNDS - 7 Compounds are specifically claimed as the monomer (I) e.g. phosphoric acid tris-(3-(3,4-difluoro-phenyl)-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl) ester (I'); phenyl-phosphonic acid bis-(3-pyridin-3-yl-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl) ester; phosphoric acid 3-(3,4-difluoro-phenyl)-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl ester diphenyl ester; phosphoric acid bis-(3-(4-fluoro-phenyl)-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl) ester phenyl ester; and phosphoric acid diphenyl ester 3-pyridin-2-yl-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl ester.    EXAMPLE - Tris(4-hydroxyphenyl)phosphate (3 g), p-formaldehyde (1.68 g) and 3,4-difluoroaniline (3.41 g) were added to a flask and mixed in an oil bath at 90 degrees C. After 30 minutes, the reaction was quenched using tetrahydrofuran, and then the mixture was cooled to room temperature. After work-up phosphoric acid tris-(3-(3,4-difluoro-phenyl)-3,4-dihydro-2H-benzo(e)(1,3)oxazin-6-yl) ester was obtained.