Fabrication and characterization of poly (bisphenol A borate) with high thermal stability

Highlights: • PBAB with excellent thermal resistance and high char yield was synthesized. • The chemical reaction of BPA with BA, and chemical structure of PBAB were studied. • PBAB show excellent thermal resistance in N₂ and air atmospheres. • The thermal stability of PBAB is greatly influenced by boron content. • Boron oxide and boron carbide are formed during the pyrolysis of PBAB. - Abstract: In this work, poly (bisphenol A borate) (PBAB), which has excellent thermal resistance and a high char yield, was synthesized via a convenient A₂ + B₃ strategy by using bisphenol A (BPA) and boric acid (BA). The chemical reaction between BPA and BA and the chemical structure of PBAB were investigated. The results demonstrate that PBAB consists of aromatic, Ph–O–B and B–O–B structures, as well as a small number of boron hydroxyl groups and phenolic hydroxyl groups. The thermal properties of PBAB were studied by DMA and TGA. The results indicate that the glass transition temperature and char yield are gradually enhanced by increasing the boron content, where the char yield of PBAB at 800 °C in nitrogen (N₂) reaches up to 71.3%. It is of particular importance that PBAB show excellent thermal resistance in N₂ and air atmospheres. By analysing the pyrolysis of PBAB, the high char yield of PBAB can be attributed to the formation of boron oxide and boron carbide at high temperatures, which reduced the release of volatile carbon dioxide and improved the thermal stability of the carbonization products. This study provides a new perspective on the design of novel boron-containing polymers and possesses significant potential for the improvement of the comprehensive performance of thermosetting resins to broaden their applicability in the field of advanced composites.