Polyester branched

In the 1950s poly(ethylene terephthalate) based polyesters branched with glycerine or trimethylolpropane were used for coating copper winding wires [4,5]. The excellent thermal stability of the polyimides was known [6] and also the dif-... 

Thermally Treated Polycarbonate/Polyester (Branching and Cross-Linking)... 

Polyester plasticizers give the best performance in this area, with performance increasing with molecular weight. Additionally, branched esters have somewhat higher volatUities than their linear equivalents. 

Polyester polyols are based on saturated aHphatic or aromatic carboxyHc acids and diols or mixtures of diols. The carboxyHc acid of choice is adipic acid (qv) because of its favorable cost/performance ratio. For elastomers, linear polyester polyols of ca 2000 mol wt are preferred. Branched polyester polyols, formulated from higher functional glycols, are used for foam and coatings appHcations. Phthalates and terephthalates are also used. 

Powder coatings are formulated from the reaction product of trimethylolpropane and IPDI, blocked with caprolactam, and polyester polyols. The saturated polyester polyols are based on aromatic acid diols, neopentyl glycol, and trimellitic anhydride for further branching. To avoid the release of caprolactam in the curing reaction, systems based on IPDI dimer diols are used. 

The polyester resins used in this technology are typically based on terephthaUc acid [100-21 -0] CgH O, or isophthaUc acid [121 -91 -5] CgH O, neopentyl glycol [126-30-7] branched using trimellitic anhydride (38). The most commonly used curing agents are adducts of isophorone... 

If a branched polyol, usually either castor oil or a simple polyester, is heated with an isocyanate but without chain extenders soft and weak rubbery products are obtained with very low resilience. These materials are useful for encapsulation of electronic components and for printer rollers. 

The thermoplastic polyurethane (TPU) adhesives must, of necessity, contain low gel content because they must be processable in an extruder. Most adhesives are relatively linear, with a functionality of 2.0, although small amounts of branching may be introduced, usually at the expense of a lower melt flow. Good physical properties of TPU s are obtained when the thermoplastic urethanes have molecular weights of 100,000 or higher (see p. 56 in [63]). Most TPU adhesives are based on symmetrical polyesters with a fast crystallizing backbone or a backbone slightly modified to increase the open time. 

Additional parameters should be taken into account for polyester networks and hyperbranched polyesters, for example, crosslink density and degree of branching. 

Due to dieir compact, branched structure and to die resulting lack of chain entanglement, dendritic polymers exhibit much lower melt and solution viscosity dian their lineal" counterparts. Low a-values in die Mark-Houwink-Sakurada intrinsic viscosity-molar mass equation have been reported for hyperbranched polyesters.198 199 Dendrimers do not obey diis equation, a maximum being observed in die corresponding log-log viscosity-molar mass curves.200 The lack of chain entanglements, which are responsible for most of the polymer mechanical properties, also explains why hyperbranched polymers cannot be used as diermoplastics for structural applications. Aldiough some crystalline or liquid... 

Alkyd resin synthesis. This synthesis consists of two steps. In the first step, a triglyceride oil is reacted at ca. 250°C with polyols, such as glycerol or pentaery-thritol, in tire presence of a basic catalyst to form a monoglyceride. In the second step, phthalic anhydride, with or without another dibasic acid such as maleic anhydride, is added to the reaction medium and reacted at high temperature. The resulting product is a branched polyester (Scheme 2.56). 

Note Kricheldorf et al.268 synthesized the same polyester by a similar procedure using Ti(OPr)4 as polymerization catalyst. The characteristics of the resulting polymer were inherent viscosity 0.22 dL/g (determined at 20°C in 4/1 CH2C12-trifluoroacetic acid at a concentration of 0.2 g/dL). DSC Tg = 164°C. Degree of branching (DB) 0.48 (determined by H NMR). 

Hyperbranched polyesters, 18, 32, 55-58 bulk synthesis of, 64 synthesis of, 114-118 Hyperbranched polyimides, 307-309 Hyperbranched polymers, 8-10, 348-350, 475-476, 481, 519-520 degree of branching in, 57 Hyperbranched polyphenylquinoxalines, 312-314... 

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

Recently, Brich and coworkers (40) reported the synthesis of lactide/glycolide polymers branched with different polyols. Polyvinyl-alcohol and dextran acetate were used to afford polymers exhibiting degradation profiles significantly different from that of linear poly-lactides. The biphasic release profile often observed with the linear polyesters was smoothened somewhat to a monophasic profile. Further, the overall degradation rate is accelerated. It was speculated that these polymers can potentially afford more uniform drug release kinetics. This potential has not yet been fully demonstrated. 

Brich, Z., Nimmerfall, F., Kissel, T., and Bantle, S., Branched ter-polyesters Synthesis, characterization, in vitro and in vivo degradation behaviors, Proc. Int. Symp. Control. Rel. Bioact. Mater., 15, 95, 1988. 

As early as 1952, Flory [5, 6] pointed out that the polycondensation of AB -type monomers will result in soluble highly branched polymers and he calculated the molecular weight distribution (MWD) and its averages using a statistical derivation. Ill-defined branched polycondensates were reported even earlier [7,8]. In 1972, Baker et al. reported the polycondensation of polyhydrox-ymonocarboxylic acids, (OH)nR-COOH, where n is an integer from two to six [ 9]. In 1982, Kricheldorf et al. [ 10] pubhshed the cocondensation of AB and AB2 monomers to form branched polyesters. However, only after Kim and Webster published the synthesis of pure hyperbranched polyarylenes from an AB2 monomer in 1988 [11-13], this class of polymers became a topic of intensive research by many groups. A multitude of hyperbranched polymers synthesized via polycondensation of AB2 monomers have been reported, and many reviews have been published [1,2,14-16]. 

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