Branched aliphatic polyesters

Tian D, Dubois P, Jerome R, Teyssie P (1994) Macromolecular engineering of polylactones and polylactides. 18. Synthesis of star-branched aliphatic polyesters bearing various functional end-groups. Macromolecules 27 4134 144... 

Hyper-branched aliphatic polyesters are different from linear polyesters because of their unique mechanical and rheological properties, which can easily be tailored by changing the nature of the end group [156-159]. Both dendrimers and hyper-branched macromolecules are prepared from AB2 monomers, using dif-... 

Dong, T., Dubois, P., Jdrdme, R., and Teyssie, P., 1994, Macromolecular Engineering of Polylactones and Polylactides. 18. Synthesis of Star-Branched Aliphatic Polyesters Bearing Various Functional End Groups. Macromolecules, 27 4134... 

Pettersson and Sorensen have described a number of different thermoset resin structures based on hyperbranched aliphatic polyesters [123]. Their results can best be exemplified by a study on hyperbranched alkyd coating resins. A comparative study was performed between an alkyd resin based on a hyperbranched aliphatic polyester and a conventional high solid alkyd, which is a less branched structure. The hyperbranched resin had a substantially lower viscosity than the conventional resin of comparable molecular weight, that is, less solvent was needed to obtain a suitable application viscosity. The hyperbranched resin also exhibited much shorter drying times than the conventional resin, although the oil content was similar. These achievements would not have been possible without a change in architecture of the backbone structure of the resins (Figs. 12,13). 

Yoshikawa Y, Ofuji N, Imaizumi M, Moteki Y, Fujimaki T (1996) Molecular weight distribution and branched structure of biodegradable aliphatic polyesters determined by s.e.c-MALLS. Polymer 37 1281... 

Hyperbranched polymers are formed by polymerization of AB,-monomers as first theoretically discussed by Flory. A wide variety of hyperbranched polymer structures such as aromatic polyethers and polyesters, aliphatic polyesters. polyphenylenes, and aromatic polyamides have been described in the literature. The structure of hyperbranched polymers allows some defects, i.e. the degree of branching (DB) is less than one. The synthesis of hyperbranched polymers can often be simplified compared to the one of dendrimers since it is not necessary to use protection/deprotection steps. The most common synthetic route follows a one-pot procedure " where AB,-monomers are condensated in the presence of a catalyst. Another method using a core molecule and an AB,-monomer has been described. ... 

A versatile way of synthesizing hydroxyfunctional hyperbranched aliphatic polyesters using 2,2-bis(dimethylol)propionic acid together with a polyol core through a pseudo-step-wise procedure has been presented. The polyesters were shown to have a very high degree of branching (-80%), as determined with... 

In our first chapter, we summarize the synthesis of aliphatic polyesters. This includes homopolyesters, random, block, graft, and star- and hyper-branched polyesters. Mainly materials such as PLA and PCL homopolymers have so far been used in most applications. There are, however, many others monomers which one can use as homopolymers or in copolymerization with lactide and caprolactone. Different molecular stuctures give a wider range of physical properties as well as the possibility of regulating the degradation rate. 

Homopolymers of branching multifunctional monomers have also been reported. Aliphatic polyesters were prepared by condensing a polyhydroxy monocarboxylic acid of formula (HO)n-R-COOH, for example, 2,2-di(hydroxymethyl)propionic acid, in either DMF or xylene in the presence of an acid catalyst with azeotropic distillation of water. Since these polymers have a large number of functional groups, they are... 

A number of commercially significant PC copolymers are produced. In addition to the previously discussed branched PCs (for extrusion and blow-molding applications) and copolymers of BPA with tetrabromo-BPA for enhanced flame retardancy, high-Tg polyester carbonate copolymers have been produced for a number of years (Bayer Apec , GE LEXAN PPC Tg approximately 190°C). Polyester carbonate copolymers can be produced via copolymerization of BPA with diacyl chlorides. Aromatic diadds produce high-Tg copolymers, while aliphatic diadds yield lower-Tg copolymers. A lower-Tg PC aliphatic polyester copolymer (GE LEXAN SP resin) exhibits enhanced flow and ductility in comparison to standard PC and is useful for thin-wall injection molding applications requiring ductility and ease of melt processability, such as personal communication devices. GE has recently introduced two new PC copolymers, a PC-siloxane copolymer (LEXAN EXL) and a copolymer of... 

Biodegradable, aliphatic polyesters can be synthesized or produced by bacteria and cyanobacteria. These organisms accumulate poly(3-hydroxy butyrate) (PHB) up to 80 wt% of the dry cellular material. Long branching has been produced by modifying the culture medium [Ramsay et ah, 1991]. PHB is degraded by the enzyme poly(3-hydroxybutyrate depolymerase). 

Alditols polyols are readily renewable, inexpensive and harmless to the environment. By incorporation of polyols into aliphatic polyesters, functional linear or hyperbranched polymers can be prepared with specific biological activities and/or that respond to environmental stimuli. Polyesters with carbohydrate or polyol repeat units in chains have been prepared by chemical methods. " In some cases, the reaction conditions led to hyperbranched polymers (HBPs). The highly branched architecture of HBPs leads to unusual mechanical, rheological and compatibility properties. " These distinguishing characteristics have garnered interest for their use in numerous industrial and biomedical fields. Chemical routes to linear polyol-polyesters require elaborate protection-deprotection steps ". Furthermore, condensation routes to hyperbranched polymers generally require harsh reaction conditions such as temperatures above 150 C and highly acidic catalysts ". ... 

Besides hb poly(ethylene imine) (hbPEI) [vide infra), hb polyesters are a predominating class of hb polymers due to a straightforward synthesis and the success of the commercially available Boltom aliphatic polyesters. Pioneering work was conducted on hb copolyesters ranging from merely aliphatic, aliphatic-aromatic, to aromatic polyesters. Such materials are applied in coating or resins. Long et al. recently reviewed the field of branched polyesters with variation in the DB. ... 

This process is therefore used commercially only for relatively low-molecular-weight, linear, aliphatic polyesters, or for branched or cross-linked alkyd resins. 

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