Vol. 7, Issue 2, Part A (2025)

Two novel dihydroxy monomers 3,5-dihydroxy-N-(naphthalen-8-yl)benzamide (Monomer A) and 3,5-dihydroxy-N-(naphthalen-7-yl)benzamide (Monomer B) were synthesized and polymerized with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC) by interfacial polycondensation to yield two series of polyesters (PE-1 to PE-5 from Monomer A, and PE-6 to PE-10 from Monomer B). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to compare thermal stability and glass transition behavior. All polyesters show decomposition onset above 150 °C. The A-series shows the highest char yield (up to 52.69% in one composition) while the B-series exhibits generally higher glass transition temperatures (TG). These differences are discussed in terms of the positional substitution of the naphthyl unit and its effect on chain packing and rigidity.