Polycondensation glycols

Condensation polymerization differs from addition polymerization in that the polymer is formed by reaction of monomers, each step in the process resulting in the elimination of some easily removed molecule (often water). E.g. the polyester polyethylene terephthalate (Terylene) is formed by the condensation polymerization (polycondensation) of ethylene glycol with terephthalic acid ... 

Reactions of the Methyl Groups. These reactions include oxidation, polycondensation, and ammoxidation. PX can be oxidized to both terephthahc acid and dimethyl terephthalate, which ate then condensed with ethylene glycol to form polyesters. Oxidation of OX yields phthaUc anhydride, which is used in the production of esters. These ate used as plasticizers for synthetic polymers. MX is oxidized to isophthaUc acid, which is also converted to esters and eventually used in plasticizers and resins (see Phthalic acids and otherbenzenepolycarboxylic acids). 

Starting with DMT, methanol is removed from the reaction starting with TA, water is removed. Catalysts ate used to transesterrfy DMT but not for direct esterification of TA. The second step is the polycondensation reaction which is driven by removing glycol. A polycondensation catalyst is used. 

The second largest use at 21% is for unsaturated polyester resins, which are the products of polycondensation reactions between molar equivalents of certain dicarboxyhc acids or thek anhydrides and glycols. One component, usually the diacid or anhydride, must be unsaturated. A vinyl monomer, usually styrene, is a diluent which later serves to fully cross-link the unsaturated portion of the polycondensate when a catalyst, usually a peroxide, is added. The diacids or anhydrides are usually phthahc anhydride, isophthahc acid, and maleic anhydride. Maleic anhydride provides the unsaturated bonds. The exact composition is adjusted to obtain the requked performance. Resins based on phthahc anhydride are used in boat hulls, tubs and spas, constmction, and synthetic marble surfaces. In most cases, the resins contain mineral or glass fibers that provide the requked stmctural strength. The market for the resins tends to be cychcal because products made from them sell far better in good economic times (see Polyesters,unsaturated). 

The synthesis of high-molar-mass PLA and PGA by two-step polycondensations of lactic and glycolic acids, respectively, has recently been reported.374,375 It involves the formation of a low-molar-mass oligomer followed by a polycondensation step either in the solid state374 or in the melt under vacuum.375 The procedures are detailed in Section 2.4.1.5.2. 

The preparation of PGA given below (Scheme 2.51) is a polycondensation of glycolic acid followed by a solid-state postpolycondensation.374 (Reproduced from ref. 374. Copyright 2000 Elsevier Science Ltd, by permission of the copyright owner.) This method is different from the commonly used ring-opening polymerization of lactide (see Section 2.3.6). 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

Polycondensation of dicarboxylic acids or their derivatives with glycols... 

Polycondensation of dicarboxylic acid derivatives and glycols to polyesters... 

Alkyl esters often show low reactivity for lipase-catalyzed transesterifications with alcohols. Therefore, it is difficult to obtain high molecular weight polyesters by lipase-catalyzed polycondensation of dialkyl esters with glycols. The molecular weight greatly improved by polymerization under vacuum to remove the formed alcohols, leading to a shift of equilibrium toward the product polymer the polyester with molecular weight of 2 x 10" was obtained by the lipase MM-catalyzed polymerization of sebacic acid and 1,4-butanediol in diphenyl ether or veratrole under reduced pressure. ... 

The blend is partially crosslinked with a vinyl monomer when dissolved in an organic aprotic solvent and has a pH of 5.0 or lower. The first block copolymer is prepared by polycondensing a bis-hydroxyalkyl ether, such as dipropylene glycol, diethylene glycol, and the like, with propylene oxide. Next, the resulting propoxylated diol is reacted with ethylene oxide to produce the block copolymer. The second copolymer is prepared by polycondensing 2-amino-2-hydroxymethyl-1,3-propanediol, commonly known as TRIS, with... 

Figure 25.3 b) shows a generic polyester-based polyurethane. The most common polyester repeat units are derived from the polycondensation of adipic acid and a diol, such as ethylene glycol, which results in the structure shown in Fig, 25.4. The average molecular weight of the polyester sequences between urethane links commonly ranges between 400 and 6,000 g/mol. 

PET is a polycondensation polymer based on the reaction of terephthalic acid (TA) and mono-ethylene glycol (MEG) or alternatively with di-methyl terephtha-late (DMT) plus MEG (Figure 10). 

Unactivated esters, typically alkyl esters, often show low reactivity toward lipase catalyst for transesterifications. In the case of the lipase-catalyzed polycondensation of dialkyl esters with glycols, the polymer of high molecular weight was not obtained. The molecular weight improved when vacuum conditions were used Mw reached more than 2 x 104 in the combination of diethyl sebacate and 1,4-butanediol catalyzed by lipase MM [30]. 

PPL catalyzed polycondensation of bis(2,2,2-trichloroethyl) alkanediaoates with glycols in anhydrous solvents of low polarity to produce the polyesters [34, 35]. In the polymerization of bis(2-chloroethyl) succinate and 1,4-butanediol using Pseudomonas fluorescens lipase (lipase PF) as catalyst, the polyester with low molecular weight was formed [36]. This may be due to the low enzymatic reactivity of the succinate substrate. 

Lipase CA catalyzed the polymerization of cyclic dicarbonates, cyclobis (hexamethylene carbonate) and cyclobis(diethylene glycol carbonate) to give the corresponding polycarbonates [105]. The enzymatic copolymerization of cyclobis(diethylene glycol carbonate) with DDL produced a random ester-carbonate copolymer. As to enzymatic synthesis of polycarbonates, reported were polycondensations of 1,3-propanediol divinyl dicarbonate with 1,3-propanediol [110], and of diphenyl carbonate with bisphenol-A [111]. 

Hoftyzer, P. J., Kinetics of the polycondensation of ethylene glycol terephthalate, Appl. Polym. Symp., 26, 349-363 (1975). 

Yokoyama, H Sano, T Chijiiwa, T. and Kajiya, R., Degradation reactions in ethylene glycol terephthalate polycondensation process,. /. Jpn. Petrol. Inst., 21, 194-198 (1978). 

According to reports Po et al. [31] and Amoco [32], the reaction rate of PEN is lower than other polyesters. Considerations about this fact lead to the assumption that the structure-dependent reactivities of the acid and glycol components and their mobilities are responsible for the individual reaction rates of these polymers. Based on unpublished data, rigid or voluminous co-monomers result in reduced reactivities during melt polycondensation and SSP. The mobility of the component, as a result of its structure and stiffness, seems to explain this observation. 

PTT is made by the melt polycondensation of PDO with either terephthalic acid or dimethyl terephthalate. The chemical structure is shown in Figure 11.1. It is also called 3GT in the polyester industry, with G and T standing for glycol and terephthalate, respectively. The number preceding G stands for the number of methylene units in the glycol moiety. In the literature, polypropylene terephthalate) (PPT) is also frequently encountered however, this nomenclature does not distinguish whether the glycol moiety is made from a branched 1,2-propanediol or a linear 1,3-propanediol. Another abbreviation sometimes used in the literature is PTMT, which could be confused with poly(tetramethylene terephthalate),... 

PTT, with three methylene units in its glycol moiety, is called an odd-numbered polyester. It is often compared to the even-numbered polyesters such as PET and PBT for the odd-even effect on their properties. Although this effect is well established for many polycondensation polymers such as polyamides, where the number of methylene units in the chemical structures determines the extent of hydrogen bonding between neighboring chains and thus their polymer properties, neighboring chain interactions in polyesters are weak dispersive, dipole interactions. We have found that many PET, PTT and PBT properties do not follow the odd-even effect. While the PTT heat of fusion and glass transition temperature have values between those of PET and PBT, properties such as modulus... 

Step-growth condensation polymers, such as polyesters and polyamides, are formed by reversible reactions. In the case of PET, the commercial synthesis is essentially carried out by two reactions. The first is the formation of bishydroxyethyl terephthalate by esterification of a diacid with a glycol or by transesterification of a diester with a glycol. The second is the formation of the polymer by a polycondensation reaction. 

For the polymerization, either in the melt or solid phase, the reaction is driven to the polymer by removing ethylene glycol. The polymerization reaction is typically catalyzed by solutions consisting of antimony trioxide or germanium oxide. Both polycondensation catalysts also catalyze the reverse reaction, which is driven by an excess of ethylene glycol at melt conditions, generally above 255 °C. The polymerization reaction follows second-order kinetics with an activation energy of 22 000 cal/mol [6],... 

Polyesters are one of the most important classes of polymers in use today. In their simplest form, polyesters are produced by the polycondensation reaction of a glycol (or dialcohol) with a difunctional carboxylic acid (or diacid). Hundreds of polyesters exist due to the myriad of combinations of dialcohols and diacids, although only about a dozen are of commercial significance. 

---