Hyperbranched polyester copolymers for thermal printing papers: The effects of alkyl chain units in the polymer backbone on developing capability

The demand for a safer alternative to bisphenol A (BPA) developer materials for thermal printing systems has recently grown considerably because of the many potential health effects of exposure to BPA. In this study, we tested the use of hyperbranched polymers as replacements for BPA, and determined the structural features of their polymer backbones that control the developing capability of thermal papers. For this purpose, a novel series of hyperbranched polyester copolymers with linear and terminal phenol groups were prepared via one-pot A2 + B3 reactions of phloroglucinol with various feed ratios of terephthaloyl chloride and adipoyl chloride. The variations with the proportion of alkyl chains in the backbones of the structural, thermal, and color-forming reaction properties of the resultant polymers were investigated. Moreover, the preparation of thermal papers with these polymers was carried out and their developing capabilities were compared to those of BPA–based thermal papers.