Properties of biodegradable copolyesters of succinic acid-1,4-butanediol/succinic acid-1,4-cyclohexanedimethanol

Effects of Poly(cyclohexanedimethylene terephthalate) on Microstructures, Crystallization Behavior and Properties of the Poly(ester ether) Elastomers

To understand the role of molecular structure on the crystallization behavior of copolyester in thermoplastic poly(ether ester) elastomers (TPEEs), series of poly(butylene-co-1,4-cyclohexanedimethylene terephthalate) (P(BT-co-CT))-b-poly(tetramethylene glycol) (PTMG) are synthesized through molten polycondensation process. The effects of poly(cyclohexanedimethylene terephthalate) (PCT) content on the copolymer are investigated by Fourier transform infrared spectroscopy (FT-IR), ¹H and 13C nuclear magnetic resonance (NMR), gel permeation chromatographs (GPC), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical, and visible light transmittance tests. FT-IR and NMR results confirm the incorporation of PCT onto the copolymer. WAXD and DSC indicate that the crystalline structure of the copolymers changed from α-PBT lattice to trans-PCT lattice when the molar fraction of PCT (MPCT) is above 30%, while both crystallization and melting temperatures reach the minima. An increase in MPCT led to an increase in the number sequence length of PCT, the thermal stability and the visible light transmittance of the copolymer, but to a slight decrease in tensile strength and elastic modulus.

Hydrolysis of Ionic Phthalic Acid Based Polyesters by Wastewater Microorganisms and Their Enzymes

Water-soluble polyesters are used in a range of applications today and enter wastewater treatment plants after product utilization. However, little is known about extracellular enzymes and aquatic microorganisms involved in polyester biodegradation and mineralization. In this study, structurally different ionic phthalic acid based polyesters (the number-average molecular weights (M_n) 1770 to 10 000 g/mol and semi crystalline with crystallinity below 1%) were synthesized in various combinations. Typical wastewater microorganisms like Pseudomonas sp. were chosen for in-silico screening toward polyester hydrolyzing enzymes. Based on the in-silico search, a cutinase from Pseudomonas pseudoalcaligenes (PpCutA) and a putative lipase from Pseudomonas pelagia (PpelaLip) were identified. The enzymes PpCutA and PpelaLip were demonstrated to hydrolyze all structurally different polyesters. Activities on all the polyesters were also confirmed with the strains P. pseudoalcaligenes and P. pelagia. Parameters identified to enhance hydrolysis included increased water solubility and polyester hydrophilicity as well as shorter diol chain lengths. For example, polyesters containing 1,2-ethanediol were hydrolyzed faster than polyesters containing 1,8-octanediol. Interestingly, the same trend was observed in biodegradation experiments. This information is important to gain a better mechanistic understanding of biodegradation processes of polyesters in WWTPs where the extracellular enzymatic hydrolysis seems to be the limiting step.

New Biodegradable Polymers from Renewable Sources – Segmented Copolyesters of Poly(1,3-Propanediol Succinate) and Poly(Ethylene Glycol)

New high-molecular-weight hydrophobic/hydrophilic segmented copolymers of poly(ester-ether-carbonate) structure, containing poly(1,3-propylene succinate) (SP) and poly(ethylene glycol) (PEG) segments in the main chain, were synthesized and characterized. These copolymers were obtained by a two-step chain-extension reaction performed by the thermal polycondensation of αω-dihydroxy-oligo(1,3-propylene succinate) with PEG1000 and PEG2000, respectively. The molecular structure of all the synthesized materials was characterized by 1H-NMR, by SEC for molecular weights, and by DSC for thermal properties. The molecular characterizations were in agreement with the proposed structures. Solubility and swellability tests indicated that the introduction of hydrophilic PEG segments into the high molecular weight poly(1,3-propylene succinate)s imparted amphiphilic character to the new materials. This is expected to influence the biocompatibility and biodegradability of these materials. The new polymers, besides having a degradable backbone, were derived from the monomers, 1,3-propanediol and succinic acid, which are both obtainable from renewable sources. Therefore, they have a potential as environmental friendly materials.

Molecular structure and polymorphism of a cyclohexanediol: trans-1,4-cyclohexanedimethanol

The methoxy substituent intrans-1,4-cyclohexanedimethanol stabilizes equatorial conformations, whose two polymorphs were found and characterized by DSC, FTIR, and XRD.

Toxicity and biodegradation of products from polyester hydrolysis

Toxicity of products from polyester hydrolysis such as succinic acid (SA), adipic acid (AA), mandelic acid (MA), terephthalic acid (TA), 1,4-butanediol (1,4-B), ethylene glycol (EG), styrene glycol (SG) and 1,4-cyclohexane dimethanol (1,4-C) was evaluated by phytotoxicity test on germination of young radish seeds and by cytotoxicity test on HeLa cells. The phytotoxicity test revealed SG > MA > 1,4-C > AA approximately SA > TA approximately EG > 1,4-B in order of decreasing toxicity taking into consideration the growth behavior after germination as well as the percentage of germination. Toxicity on HeLa cells decreased in slightly different order compared to that on young radish seeds, i.e. SG > 1,4-C > MA > TA > SA > AA > EG > 1,4-B. Tests for the phytotoxicity and for cytotoxicity indicated that the aromatic compounds were more harmful than the aliphatic ones. Each group of 4 strains which grew most rapidly on each agar plate containing SA, AA, MA, TA, 1,4-B, EG, SG and 1,4-C respectively as a sole carbon source was identified by the fatty acid methyl esters analysis. The modified Sturm test was carried out using the single isolated strain, an activated sludge or a mixed soil to measure the rate of mineralization of the compounds into carbon dioxide. The aliphatic compounds were mineralized more easily than the aromatic compounds. 1,4-C showed the most exceptionally slow degradation. A scrutiny of residual 1,4-C after degradation is required before polyesters containing 1,4-C could be classified into compostable because 1,4-C has detrimental effects on young radish seeds and HeLa cells and has a tendency to accumulate in the environment due to its slow degradability.