Synthesis and Characterization of Fully Biobased Poly(propylene succinate-ran-propylene adipate). Analysis of the Architecture-Dependent Physicochemical Behavior

Fully biobased aliphatic random poly(1,3-propylene succinate-ran-1,3-propylene adipate) (PPSA) copolyesters with high molar mass were synthesized with different macromolecular architectures based on various succinic acid/adipic acid (SA/AA) molar ratio, by transesterification in melt. Titanium (IV) isopropoxide was used as an effective catalyst. All synthesized copolyesters were fully characterized by different chemical and physicochemical techniques including NMR, size exclusion chromatography, FTIR, wide angle X-ray scattering, differential scanning calorimetry, and thermogravimetric analysis. The final copolyesters molar compositions were identical to the feed ones. The different sequences based on succinate and adipate segments were randomly distributed along the chains. All the corresponding copolyesters showed an excellent thermal stability with a degradation onset temperature higher than 290 degrees C, which increased with the adipate content. According to their compositions and architectures, PPSA copolyesters can exhibit or not a crystalline phase, at room temperature. T-g of copolyesters decreased with the adipate content due to the decrease in the chains mobility, following the Gordon- Taylor relation. PPSA showed a pseudo eutectic melting behavior characteristic of an isodimorphic character. Finally, PPSA copolyesters were not able to crystallize during the cooling or the second heating run, due to the 1,3-propanediol chemical structure, which led to amorphous materials with the exception of the polyester based solely on AA. (C) 2017 Wiley Periodicals, Inc.