Polyesters derivatives

Plasticizers. About 2.5% of U.S. adipic acid consumed in 1988 was used in two basic types of adipic ester based plasticizers (195). Simple adipate esters prepared from Cg—alcohols are used especially as PVC plasticizers (qv). Eor special appHcations requiring low volatility or extraction resistance, polyester derivatives of diols or polyols are preferred. 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Poly(L-malic acid) denotes a family of polyesters derived from L-malic acid as the building unit. By chemical synthesis, three kinds of poly(L-malic acid) have been obtained, depending on the molecular position of the ester bond the a-type(I) [1], the j8-type(II) [2], and the a,j8-mixed-type(III) [3). 

Shellac [124,125] is a natural resin used in very old times for varnishes and moulding compounds. The resin secreted by the lac insect, Kerriar paca, is collected by scraping the shellac-encrusted trees found in southern parts of Asia. It consists of a complex mixture of cross-linked polyesters derived from hydroxy acids, principally aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). From a structural point of view, it appears that this material can be used as a crosslinking agent and/or as a monomer for developing dentrite-like polymers. The question is whether it is possible to produce this material from shellac by controlled hydrolysis. 

In order to make polymers behave as liquid crystals it is necessary to introduce some structural rigidity. A typical polymer which has the required rigidity is poly(phenylenetetraphthalamide) (10.7). This material belongs to a class of polymer known as the aramids. Other liquid crystalline polymers are the thermotropic polyesters derived from /7-hydroxybenzoic acid, p, p -biphenol and terephthalic acid (10.8). 

There has in the past been some confusion in the use of the term alkyd, which is said to have been derived from alcohol plus acid. The definition offered by Kienle [1], discussed later, is broad enough to include all polyesters derived essentially from diols and dicarboxylic acids, and consequently linear polyesters were initially included in this class of polymer. On the other hand, Bjorksten et al. [2], in their 1956 compilation of published information about polyesters, restrict the term polyester to the polycondensation products of dicarboxylic acids with dihydroxy alcohols, and say that this definition does not include materials commonly known as alkyds . At the present time, there are still problems of nomenclature in the fibre field arising from the use of polyester as a generic term to cover fibres containing only a very restricted range of chemical groups. 

Turner et al. [71, 72] also report on hyperbranched polyesters derived from 3,5-bis(trimethylsiloxy)benzoyl chloride and from 3,5-diacetoxybenzoic acid, which both yield phenolic polyesters after hydrolysis of the end groups. The same group investigated the hyperbranched polyesters obtained in the melt condensation of 5-acetoxyisophthalic acid and 5-(2-hydroxy)-ethoxyisophthalic acid respectively. The latter yields a soluble product while the former results in an insoluble polymer due to formation of anhydride bridges. 

Fierier I, Le Borgne A, Spassky N (1990) Synthesis of functional polyesters derived from serine. Polym Bull 24 349-353... 

Yu X-h, Feng J, Zhuo RX (2005) Preparation of hyperbranched aliphatic polyester derived from functionalized l,4-dioxan-2-one. Macromolecules 38 6244—6247... 

The probable mechanism for conductance in selected polymers is related to the difficulty of delocalizing electrons. Carraher and colleagues found that antimony polyesters derived from aliphatic diacids are weak semiconductors with bulk specific resistivities in the range of 10"10 ohm cm, whereas analogous polyesters derived from aromatic diacids are good semiconductors with bulk resistivities of about 10"4 ohm cm. The difference in electron conductivity is believed to be due to a difference in ability of the material to delocalize electrons the aromatic polyesters possess the ability to delocalize electrons throughout the polymer chain and thus are more conductive (lower resistivities). 

Polyarylates (PAr) are wholly aromatic polyesters derived from aromatic dicarboxylic acids and diphenols or their derivatives. They are amorphous in nature with good injection moldability. Figure 7 shows the typical formula structure of PAr. 

The different polyesters derived from sebacic acid show widely different viscosities which have no great influence on the yield curve. Therefore, the general opinion that the efficiency of a plasticizer depends only on its viscosity is not justified. The polyesters derived from sebacic acid do not have the same good behavior... 

THE SYNTHESIS AND CHARACTERIZATION OF POLYESTERS DERIVED FROM L-LACTIDE AND VARIABLY-SIZED POLY(CAPROLACTONE)... 

Several review articles on biodegradable polymers and polyesters have appeared in the literature [12-22]. Extensive studies have been carried out by Al-bertsson and coworkers developing biodegradable polymers such as polyesters, polyanhydrides, polycarbonates, etc., and relating the structure and properties of aliphatic polyesters prepared by ROP and polycondensation techniques. In the present paper, the current status of aliphatic polyesters and copolyesters (block, random, and star-shaped), their synthesis and characterization, properties, degradation, and applications are described. Emphasis is placed primarily on aliphatic polyesters derived by condensation of diols with dicarboxylic acids (or their derivatives) or by the ROP of cyclic monoesters. Polyesters derived from cyclic diesters or microbial polyesters are beyond the scope of this review. 

A commercially available hyper-branched polyester derived from bis-MPA was used as the multifunctional initiating core for the ROP of e-CL and this led to the synthesis of hybrid dendritic linear star polymers. The reactivities of the chain-end hydroxymethyl groups in the dendrimer were significantly greater than in the isomeric hyper-branched case. 

Synthetic Strategies to Develop Aliphatic Polyesters Deriving from Renewable Resources... 

Poly(amino acids) are insoluble in common solvents, are difficult to fabricate due to high melting point, and absorb a significant amount of water when their acid content reaches over 50 mol%. To solve these problems, polyesters derived from amino acids and lactic acids [e.g., poly (lactic acid-co-lysine) PLAL] are developed. The PLAL system is further modified by reaction with lysine A-carboxyanhydride derivatives. Another modification of poly(amino acids) includes poly(iminocarbon-ates), which are derived from the polymerization of desaminotyrosyl tyrosine alkyl esters. These polymers are easily processable and can be used as support materials for cell growth due to a high tissue compatibility. Mechanical properties of tyrosine-derived poly(carbonates) are in between those of poly(orthoesters) and poly(lactic acid) or poly(gly-colic acid). The rate of degradation of poly(iminocarbonates) is similar to that of poly (lactic acid). 

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