Enhancement of T_g of Poly(l‐lactide) by Incorporation of Biobased Mandelic‐Acid‐Derived Phenyl Groups by Polymerization and Polymer Blending

Abstract

A high‐molecular‐weight polyester of poly(mandelate‐co‐lactate) (PML) is prepared by ring‐opening polymerization of stereo‐configuration controlled cyclic diester monomers of methyl‐6‐phenyl‐1,4‐dioxane‐2,5‐dione (MPDD) and lactide. The attained PML shows excellent glassy properties, although the original stereo‐configuration of MPDD is not preserved. The intrinsic high glass transition temperature (Tg) of PML is promising, and it is able to be further enhanced by thermal treatment to as high as 90 °C. Interestingly, the enhanced high Tg is attained by only 15 mol% of mandelate content in the polymer chain which is far lower than the ones suggested by theoretical calculation. The enhancement in Tg is also attained by polymer blending of PML and poly(l‐lactide) (PLLA). The Tg of the polymer blend also reaches 90 °C which is almost 20 °C higher than the ones suggested by theoretical calculations. These results indicate that the rigid mandelate unit consisting of phenyl groups in PML chain effectively interact with PLLA chains in amorphous domain to restrict their chain mobility. The thermal and glassy properties are sufficient to explore new applications in engineering fields.

Sequence‐Controlled Alternating Copolyesters Synthesis via Selective Ring‐Opening Polymerization

“…[24] Therefore, part of the researches focused on incorporating monomers with aromatic groups (such as salicylic acid and mandelic acid) into aliphatic polyesters and studying the properties of the resulting copolymers. [25][26][27][28][29] However, the influence of the sequence structure of the obtained copolymers is not emphasized. In 2019, the regioselective ROP of a cyclic diester of glycolic acid and mandelic acid (3-phenyl-1, 4-dioxane 2, 5-diketone, rac-PDD) initiated by trisphenolate Zr complexes (Zr-1) was reported by Wu and coworkers (Figure 2).…”

High-Tg PLA copolymers via base-catalyzed transesterification of PLA with 2,5,7-trioxabicyclo[2.2.2]octan-6-one

“…[22][23][24][25][26] However, due to its inferior material pro-perties like low glass transition temperature (T g ), brittleness and low elongation at break, it is still necessary to improve the properties of PLA and expand its applications. [27][28][29][30] Among the known chemical and physical methods to improve the material properties of PLLA, [31][32][33][34][35][36][37][38][39][40][41][42][43] the copolymerization of LA with other cyclic ester monomers is simple and versatile. For instance, copolymerization of LA with lactones containing ring structures can greatly enhance the T g of the copolymers and improve their thermal and mechanical properties.…”

Isotactic-Alternating, Heterotactic-Alternating, and ABAA-Type Sequence-Controlled Copolyester Syntheses via Highly Stereoselective and Regioselective Ring-Opening Polymerization of Cyclic Diesters

“…In this work, a regioselective and stereoselective polymerization system was developed to synthesize isotactic-alternating, heterotactic-alternating, and ABAA-type periodic sequence-controlled copolymers of naturally abundant lactic acid and mandelic acid (Scheme D). Besides exploring the methodology for synthesizing complicated sequence-controlled polyesters, an additional motivation of this research is to accurately modulate the properties of polylactide via the regular incorporation of mandelic acid units because the pendant phenyl group of mandelic acid units in the polymer can restrict the flexibility of polymer chains and therefore might improve the T g of polylactide. − Accurate sequence-controlled copolymers with 1:1 and 1:3 ratios of mandelic acid units to lactic acid units were successfully synthesized in this work, and the effects of the sequence on the properties were also demonstrated.…”