PREPARATION OF PHTHALONITRILE MONOMER WITH LOW MELTING POINT

Abstract

This article presents the results of the synthesis of para – and meta-hydroxyphenoxyphalonitrile,phosphorus-containing chlorangidrides with various substituents in phosphorus and 4-(3-propargyloxyphenoxy)phthalonitrile, the introduction of which into the binder, allowed to achieve the necessary viscosity indicators withoutloss of heat resistance. At the first stage, it was proposed to obtain a monomer with a phenoxy group in phosphorus.For this purpose, we proposed the use of dimethylacetamide (DMAA) with K2CO3, but the product washydrolytically unstable in the main medium, so it was impossible to isolate the desired monomer. To solve thisproblem, we conducted a number of experiments on the selection of synthesis conditions using various solvents.Comparing the Tgt of the obtained monomers, we found higher values for para-oriented phthalonitriles, which isprobably due to higher structure symmetry, as well as an increase in glass transition temperature (Tgt) forphosphonate-based monomers. Due to the equally high thermal properties of the cured matrices, we decided to use4-(3-hydroxyphenoxy) phthalonitrile as the main precursor, as well as phosphate chlorangidrides. Based on thecalculated data, a pattern was identified that consists in a decrease in the Tgt of phosphorus-containing phthalonitrileswhen switching to aliphatic substituents in phosphorus. A decrease in the Tgt of monomers was found with anincrease in the size of the aliphatic substituent. As a result of the experiment, we obtained 9 new phosphoruscontaining phthalonitrile monomers with high yield that are resistant to hydrolysis, which is confirmed by the factthat the products were isolated by flash chromatography on silica gel, as well as two-dimensional TLC. Thesynthesized substances were glassy masses with Tgt = - 5-58 °C. The consistency of the approach involving theintroduction of phosphate bridges into the structure of phthalonitriles was shown.