Semi-aromatic polyester synthesis via alternating ring-opening copolymerization using a chromium complex based on a pentapyridine ligand

Ring-Opening Copolymerization Using a Chromium Complex with a Readily Available Aminotriphenolate Ligand

“…For instance, when using toluene as a solvent, products were obtained with high conversion and selectivity for polyesters. 16 All copolymerization reactions of PA and CHO using 2/ cocatalyst proceeded in a well-controlled manner, showing a low dispersity of 1.10−1.34 even at high conversions (Table 1, entries 1−7). The molecular weights of all products were determined by gel permeation chromatography (GPC) (Figures S8-S12), where traces of bimodal peaks were sometimes observed.…”

“…In agreement with these expectations, poly(NA-alt-CHO) obtained showed a T g of 180 °C (Figure S14), which is considerably high compared to the typical T g (140−208 °C) reported in the literature (Figure 3). 15,16,19,30 Changing the cocatalyst to PPNCl resulted in a very low conversion (2%) and poor selectivity (34% ester content) under the same reaction conditions, probably due to the bulkiness of both NA and PPNCl. When the reaction time was extended, the conversion was slightly improved to 14% in 72 h (entry 2).…”

“…The viscosity of the reaction mixtures and the basicity of the solvent strongly influence the polymerization. For instance, when using toluene as a solvent, products were obtained with high conversion and selectivity for polyesters …”

“…[cocatalyst] of 250:250:1:1. 16,17 However, our previous results using 1 showed that a reduced amount of catalyst and a feed ratio of [PA]:[CHO]: [1]:[cocatalyst] of 800:1600:1:5 were also highly effective for polyester synthesis, achieving 95% conversion in 2 h. 15 Hence, our system generated products with high molecular weights and good thermal properties at a relatively low catalyst loading.…”

“…Recently, our group reported successful ROCOP of epoxides and anhydrides using a five-coordinate Cr complex with a sterically demanding aminotriphenolate ligand ( 1 ), producing fully alternating polyesters selectively and effectively with minimal side reactions . In most binary catalyst/cocatalyst systems for ROCOP, copolymerization of PA and CHO has been performed using a feed ratio of [PA]:[CHO]:[catalyst]:[cocatalyst] of 250:250:1:1. , However, our previous results using 1 showed that a reduced amount of catalyst and a feed ratio of [PA]:[CHO]:[ 1 ]:[cocatalyst] of 800:1600:1:5 were also highly effective for polyester synthesis, achieving 95% conversion in 2 h . Hence, our system generated products with high molecular weights and good thermal properties at a relatively low catalyst loading.…”