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Triphenyl ester of boric acid was obtained by esterification of boric acid and phenol in o-xylene with water azeotropic distillation, then it was purified by distillation in vacuo. This substance was used as a model compound for the development of a synthesis method for heat-resistant polymers based on polymethylene esters of phenols and boric acid. Reaction of triphenyl ester of boric acid with 1,3,5-trioxane (paraformaldehyde) gave a new boron-containing oligomer – polymethylene-p-triphenyl ester of boric acid. This oligomer was prepared both in the presence of a solvent and without a solvent in the melt of triphenyl ester of boric acid, since at a temperature of 101 °C it completely passes into a liquid state. The polycondensation reaction was carried out in both cases in an acidic medium. The advantage of the second method is obvious, since for the beginning of the polycondensation reaction, three times less catalyst was required than in the reaction using a solvent. The structure of the synthesized oligomer was confirmed by elemental analysis, IR and 1H, 11B NMR spectroscopy. The modification reactions of polymethylene-p-triphenyl ester of boric acid with sulfur curing system, epoxy resin and urotropine were studied. In the IR spectra of modified materials, bands in the aromatic region, in particular those characteristic of disubstituted benzene, are observed to change bands characteristic of tri- and tetrasubstituted benzenes. Thus, the curing of polymethylene-p-triphenyl ester of boric acid occurs in the o-position of the phenyl ring to form three-dimensional structures. The noted curing reactions allow using polymethylene-p-triphenyl boronic acid ester as an independent thermally stable binder and as additives to composite materials.

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