China 
Africa 
Explore chapters and articles related to this topic
Role of Different Bioreactor Types and Feeding Regimes in Polyhydroxyalkanoate Production
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Geeta Gahlawat, Sujata Sinha, Guneet Kaur
The dual nutrient limitation feeding regimes during continuous cultivation could help in the synthesis of tailor-made PHA, provided the carbon source is totally consumed by the end of fermentation [59]. This group demonstrated the continuous production of PHA in a one-stage chemostat culture of Pseudomonas putida ATCC 29147. Dual-nutrient (carbon and nitrogen) limiting conditions were applied at a dilution rate of 0.1 h−1. Different mixtures of 5-phenylvalerate, octanoate and 10-decanoate were fed to the culture which resulted in the formation of five new tailor-made copolyesters with varying compositions of aromatic side chains. It was therefore concluded by the group that the steady state in chemostat culture conditions provides a suitable strategy for the production of tailor-made mcl-PHA.
Thermoplastic Elastomers: A Rising Star
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
Marc T. Payne, Charles P. Rader
The useful temperature range of copolyesters is from —55 to 140°C. The temperature range is limited on the upper end due to oxidative degradation of the polymer backbone, and on the lower end by the glass transition temperature of the soft segments. Copolyesters have very good resistance to organic fluids, with the exception of halogenated solvents. They are susceptible to degradation from acids or bases. Copolyesters are hygroscopic and must be dried before processing to prevent degradation during injection molding, extrusion, etc. The specific gravity of copolyesters is higher than that of styrenics, and ranges from 1.1 to 1.3.
Synthesis and Fabrication of Polyesters as Biomaterials
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Philippe Lecomte, Christine Jérôme
A first example is given by star-branched polyesters, which show particular properties such as lower melt viscosities, lower crystallinity, and smaller hydrodynamic volume. Interestingly enough, star-shaped copolyesters contain a higher number of chain-ends compared to linear polymers. Whenever chemists desire to graft a drug, a targeting unit, or a probe, the use of star-shaped polyesters rather than linear polyesters is thus an easy trick to increase their number. Two main techniques allow synthesizing star-shaped copolyesters. In the frame of the arm-first technique, living chains are coupled onto multifunctional (>3) electrophiles (Tian et al. 1994). Conversely, the initiation of the ring-opening polymerization by multifunctional initiators is known as the core-first technique. The most usual conditions are based on the initiation of the polymerization of cyclic esters by polyols in the presence of tin octoate (Trollsas et al. 1998, Lang et al. 2002, Kricheldorf 2004, Choi et al. 2005). Another approach less commonly used relies on the initiation of the polymerization by a spirocyclic initiator (Kricheldorf and Lee 1996, Li et al. 2008). Finally, the arm-first and core-first techniques can be combined to synthesize star-shaped copolymers in order to increase further the range of properties of star-shaped copolymers (Van Butsele et al. 2006, Riva et al. 2011).
Direct synthesis of potentially biodegradable aromatic–aliphatic thermotropic copolyesters with photocrosslinking properties
Published in Liquid Crystals, 2019
Peng Wei, Wei Zhang, Yifeng Zhang, Yanzhi Wang, Zheng Guo, Hongqin Yu, Yumin Xia, Yanping Wang, Yimin Wang
Polyethylene glycol (PEG) as non-toxic, biocompatible and biodegradable polymer has been widely investigated in preparing novel copolymer for application in medical area during the past few decades. The PEG utilisation is mainly reflected in constructing molecular structure of aromatic–aliphatic biodegradable copolyester but not focused on mesophase forming and utilisation of advantages of liquid crystal characteristics [7,14,15]. Chen et al. [16] reported one of the few cases about aromatic–aliphatic thermotropic copolyesters that contained PEG moieties. The copolyesters showed better degradability than that of without PEG units. However, substituent of aromatic monomer disturbed chain regularity seriously and resulted in amorphous structure. Mechanical property and upper limit application temperature of the copolyesters may be confined. Afterward, Liu et al. [17] synthesised a side chain cholesterol-functionalised aliphatic polycarbonate copolymer that contained methoxypolyethylene glycol units. The side cholesterol group endowed the block copolymer smectic mesophase behaviour, but the effect of methoxypolyethylene glycol units on properties of the copolymer was not clarified in detail.