Combination of polymerization and polycondensation in the synthesis, chemical modification, and cure of rolivsan thermosetting resins

Abstract

Rolivsan thermosetting resins (ROLs) attract constant attention due to their epoxy-like high processability; at the same time, their high-temperature performance is much better than that of epoxy resins and bismaleimides. Development of these materials involves a nontrivial approach to synthesis of thermostable resins; this approach is based on introducing a new structure-forming tool, that is, 1-arylethanol group. The present article demonstrates the important role of polycondensation in rolivsan chemistry. ROLs consist of (di)vinylaromatic ethers and thermosensitive monomeric and oligomeric (di)methacrylates, which are formed after a series of acid-catalyzed reactions between di-secondary aliphatic-aromatic diols, such as bis-[4-( α-hydroxyethyl)phenyl] ether, and unsaturated carboxylic acids, such as methacrylic acid. The process of ROL cure is a combination of polymerization and polycondensation. In the course of this process, in the temperature range from 140°С to 170°С, the initial densely cross-linked ROL-copolymer is formed as a result of three-dimensional radical copolymerization of highly unsaturated components. Post-cure of ROLs in the 200–300°С temperature interval leads to structural rearrangement (polycondensation). Cured ROLs demonstrate morphology typical of thermosets; they consist of highly cross-linked spherical microdomains that are weakly bound by less densely cross-linked polymer interlayers. Thermocatalytic transformations of rolivsans modified by small amounts of additives (epoxies and aromatic diamines) were used in the development of a new approach to synthesis of heat-resistant thermosetting resins via high-temperature polycondensation in interdomain layers (which are used as a peculiar kind of microreactors).