Erik Gubbels

Carbohydrate-based PBT copolyesters from a cyclic diol derived from naturally occurring tartaric acid: a comparative study regarding melt polycondensation and solid-state modification

2,3-O-Methylene-L-threitol (Thx) is a cyclic carbohydrate-based diol prepared by acetalization and subsequent reduction of the naturally occurring tartaric acid. The structure of Thx consists of a 1,3-dioxolane ring with two attached primary hydroxyl groups. Two series of partially bio-based poly(butylene terephthalate) (PBT) copolyesters were prepared using Thx as a comonomer by melt polycondensation (MP) and solid-state modification (SSM). Fully random copolyesters were obtained after MP using mixtures of Thx and 1,4-butanediol in combination with dimethyl terephthalate. Copolyesters with a unique block-like chemical microstructure were prepared by the incorporation of Thx into the amorphous phase of PBT by SSM. The partial replacement of the 1,4-butanediol units by Thx resulted in satisfactory thermal stabilities and gave rise to an increase of the Tg values, this effect was comparable for copolyesters prepared by MP and SSM. The partially bio-based materials prepared by SSM displayed higher melting points and easier crystallization from the melt, due to the presence of long PBT sequences in the backbone of the copolyester. The incorporation of Thx in the copolyester backbone enhanced the hydrolytic degradation of the materials with respect to the degradation of pure PBT.

Synthesis, kinetics, and characterization of bio-based thermosets obtained through polymerization of a 2,5-furandicarboxylic acid-based bis(2-oxazoline) with sebacic acid

The synthesis of renewable 2,5-furandicarboxylic acid-based cross-linked poly(ester amide)s via the polymerization of a 2,5-furandicarboxylic acid based bis(2-oxazoline) monomer (2,5-bis(4,5-dihydrooxazol-2-yl)furan, 2,5-FDCAox) with sebacic acid is reported in this work. It is demonstrated that the amide groups in the 2,5-furandicarboxamide moiety are susceptible to participation in a branching reaction with 2-oxazoline rings. The corresponding enhanced reaction rate decreases the curing times for the preparation of cross-linked polymers compared to systems containing the isophthalic acid based alternative, 1,3-bis(4,5-dihydrooxazol-2-yl)benzene (IAox). The increased tendency to form branches or cross-links in 2,5-FDCAox based systems is attributed to the occurrence of intra-molecular hydrogen bonding of the 2,5-furandicarboxamide moiety. Such an intra-molecular hydrogen bond increases the nucleophilicity of the furanic amide group and makes it more susceptible to participation in an addition reaction with a 2-oxazoline ring. Furthermore, it is demonstrated that the rate of the branching reaction can be enhanced by the addition of triphenyl phosphite as catalyst, resulting in a further decrease of the curing times of the poly(ester amide)s synthesized in this study. Preliminary coating studies indicate that 2,5-furandicarboxylic acid based cross-linked poly(ester amide)s synthesized via the 2-oxazoline ring opening addition reactions with dicarboxylic acids are good candidates for the development of fully renewable cross-linked poly(ester amide)s.