Synthesis and Comparative Evaluation of Poly(mandelic acid) Prepared by Melt Polycondensation, Azeotropic Polycondensation, and Steglich Polyesterification

Mandelic acid, an aromatic α-hydroxy acid, has become a valuable scaffold in polymer chemistry, providing a rare combination of chemical reactivity and stereochemical control due to its aromatic ring, carboxylic acid group, and stereogenic center. In this work, racpoly(mandelic acid) (PMA) was synthesized via Dean–Stark Azeotropic Polycondensation, Steglich polyesterification with diisopropylcarbodiimide and 4-(dimethylamino)pyridinium p-toluenesulfonate, and a two-stage melt polycondensation. In the melt polycondensation synthesis titanium butoxide, titanium isopropoxide, p-toluenesulfonic acid, and sulfuric acid were investigated as appropriate catalysts. The synthesized samples were characterized using various techniques, such as intrinsic viscosity, Gel Permeation Chromatography, Differential Scanning Calorimetry, Dielectric Relaxation Spectroscopy, Thermogravimetric Analysis, Water Contact Angle measurements as well as enzymatic and aquatic hydrolysis tests. Although PMA has been synthesized before, this work provides the first comprehensive structure–property–degradation map for poly(mandelic acid) synthesized by melt and azeotropic polycondensation and Steglich polyesterification from the L,D-mandelic acid, combining detailed molecular weight analysis, thermal characterization, wettability, hydrolysis and dielectric probing of molecular dynamics.