Chiang Mai Journal of Science

     This study reports the synthesis and characterization of white fluorescent copolyesters through a melt polycondensation-chain extension strategy. Two copolyesters, poly(ethylene glycol succinate-co-ethylene glycol 4-chloro-1,8-naphthalene dicarboxylate) (PESNA) emitting blue fluorescence and poly(butylene glycol isophthalate-co-butylene glycol terephthalate) (PBIT) emitting orange fluorescence, were prepared via melt polycondensation. These copolyesters were then blended at specific mass ratios and further polymerized into block copolymers through chain extension. Characterization techniques demonstrated that the molar ratio of PBIT in the block copolymers could be precisely tuned by adjusting the feed ratio. The resulting block copolymers exhibited a number-average molecular weight exceeding 40000 g/mol with a polydispersity index of 2.2, which is within the typical range for block copolyesters prepared via chain extension. Thermal analysis indicated incompatibility between the two segments, while tensile tests demonstrated an increase in tensile strength along with consistently high elongation at break. Fluorescence spectroscopy revealed that one of the copolymers displayed CIE chromaticity coordinates close to standard white-light coordinates, with tunable fluorescence color. This work provides a feasible approach for preparing white fluorescent copolyesters with tunable optical properties, offering potential applications in optoelectronic devices and advanced materials due to their tunable fluorescence color and balanced mechanical properties (tensile strength up to 35.2 MPa, elongation at break >250%).