Condensation polymerization, catalyzed

Aromatic Substitution in Condensation Polymerization Catalyzed by Solid-Liquid Phase Transfer... 

Polymerization of olefins such as styrene is promoted by acid or base or sodium catalysts, and polyethylene is made with homogeneous peroxides. Condensation polymerization is catalyzed by acid-type catalysts such as metal oxides and sulfonic acids. Addition polymerization is used mainly for olefins, diolefins, and some carbonyl compounds. For these processes, initiators are coordination compounds such as Ziegler-type catalysts, of which halides of transition metals Ti, V, Mo, and W are important examples. 

Acid catalysts, such as metal oxides and sulfonic acids, generally catalyze condensation polymerizations. However, some condensation polymers form under alkaline conditions. For example, the reaction of formaldehyde with phenol under alkaline conditions produces methy-lolphenols, which further condense to a thermosetting polymer. 

Polyester polyols (Scheme 4.4) are prepared by condensation polymerization of dicarboxylic acids and diols. An excess of diol ensures OH functional product, minimizing die possibility of residual acid groups which react with isocyanates to generate C02 and act as inhibitors in catalyzed urethane reactions. The reactants are heated at 200-230°C under vacuum to remove the water by-product and drive the reaction to completion. The most common coreactants include adipic... 

Knani D, Gutman AL, Kohn DH (1993) Enzymatic polyesterification in organic media. Enzyme-catalyzed synthesis of linear polyesters. I. Condensation polymerization of linear hydroxyester. II. Ring-opening polymerization of e-caprolactone. J Polym Sci A Polym Chem 31 1221-1232... 

Wohl4 was the first to refer to the formation of higher saccharides by the action of acids on monosaccharides as reversion. This process, the acid-catalyzed formation of glycosidic bonds between sugar residues, constitutes the most rudimentary form of condensation polymerization. Reversion of oligosaccharides has also been observed. 0 The relationships between the hydrolysis of polysaccharides and the reversion of mono- and oligo-saccha-rides is illustrated for amylose in Fig. 1. 

In summary, the acid-catalyzed condensation polymerization of sugars in methyl sulfoxide results in the formation of copolymers of the sugars with formaldehyde. The glycosyl residues probably occur in blocks, instead of being evenly separated by methylene bridges. The polymers are highly branched, and the glycosyl residues appear to be substituted in a random fashion. 

Acid-catalyzed condensation polymerization of /3-D-glucopyranosyl mes-itoate (37) has also been explored. This method takes advantage of the acid-catalyzed, stereospecific displacement of the mesitoyl group of /3-D-glucopyranosyl mesitoate111 by alcohols to give, with methanol,1 2 methyl... 

As outlined earlier, three methods of polymerization have been established for the preparation of thiophenes, viz. electrochemical polymerization [189, 190], oxidative chemical polymerization using Lewis acid catalysts such as FeCl3 [191,192], and step-growth condensation polymerization using transition metal-catalyzed coupling reactions [lj]. 

A quite different approach to chain-growth condensation polymerization is phase-transfer-catalyzed polycondensation of solid monomer dispersed in an... 

However, the most important furan resins are those produced with 2-furfuryl alcohol, for example, the 2-furfuryl alcohol-formaldehyde-based resins, which are normally synthesized by a condensation reaction catalyzed by acidic sites and promoted by heat [224] or the poly(furfuryl alcohol) thermosetting resin that is usually synthesized by the cationic condensation of its monomer 2-furfuryl alcohol, which polymerizes exothermically in the presence of a catalyst such as acid and iodine in methylene chloride, producing black, amorphous, and branched and/or cross-linked structures [225],... 

The rate equation (equation 24) for strong-base-catalyzed silanol condensation was based on model studies with trimethylsilanol that were intended to mimic silanol condensation polymerizations (73). 

The rate equation with strongly acidic catalysts is also second order in silanol and first order in catalyst (75). The mechanism is proposed to proceed via protonation of silanol, followed by an electrophilic attack of the conjugate acid on nonprotonated silanol. The condensation processes outlined in reactions 16a and 16b for sulfonic acids is also an applicable mechanism for the acid catalysis. The condensation polymerization in emulsion catalyzed by dodecylbenzenesulfonic acid is second order in silanol, but the rate has a complex dependence on sulfonic acid concentration (69). This process was most likely a surface catalysis of the oil-water interface and was complicated by self-associations of the catalyst-surfactant. 

Poly(ethylene oxide) can be made using a catalyzed chainwise polymerization of ethylene oxide, or through stepwise condensation polymerization of ethylene glycol. 

Condensation Polymerization. Condensation polymerization generally affords telechelic polymers with functional terminals, which thus can be transformed into reactive carbon—halogen bonds for the metal-catalyzed radical polymerizations (Figure 24). 

The self-condensing copper-catalyzed polymerization of macromonomer of poly(tBA) with a reactive C—Br bond (H-6) affords hyperbranched or highly branched poly(tBA).447 Copolymerization of H-1 and TV-cyclohexylmaleimide induced alternating and self-condensing vinyl polymerization.448 The residual C—Cl bond was further employed for the copper-catalyzed radical homopolymerization of styrene to give star polymers with hyperbranched structures. Hyperbranched polymers of H-1 further serve as a complex multifunctionalized macroinitiator for the copper-catalyzed polymerization of a functional monomer with polar chromophores to yield possible second-order nonlinear optical materials.325... 

Acid Catalyzed Condensation Polymerizations. The strong protonic acids produced by the photolysis of onium salts I-III can also be employed to catalyze the condensation of phenolic, melamine, and urea formaldehyde resins. Very durable photoresists based on these inexpensive and readily available resins can be made. Such resists generally require a postbake prior to development to complete the condensation and to enhance image formation. 

Simultaneous Radical and Acid Catalyzed Condensation Polymerization. As shown in Equations 1-7, the photolysis of diaryliodonium and triarylsulfonium salts produces in addition to strong protonic acids, a variety of radical fragments. These photoinitiators are, therefore, capable of initiating free radical polymerizations. A number of hybrid imaging systems which take advantage of both radical and acidic species formed from the photolysis of these salts have been designed. For example, Equation 26 illustrates one such system based on simultaneous radical and acid catalyzed condensation polymerizations which has been explored in our laboratory. 

A time course study of 11-hydroxydecanoic acid polymerization catalyzed by Candida cylindracea lipase was reported by O Hagan and Zaidi [28]. The authors revealed that oligomers are formed relatively rapidly and then later condense to generate higher molecular weight polyesters. After 7 days, they reported formation of a polyester with molecular weights up to Mw = 35000. 

Table 4.1 Enzyme-catalyzed polyester condensation polymerizations.

A compilation of enzyme-catalyzed self-condensation polymerizations that have thus far appeared in the literature is given in Table 4.1. 

Scheme 4.5 Lipase-catalyzed condensation polymerization of sebacic acid ester with butanediol.

Much of the earlier work carried out on lipase-catalyzed condensation polymerizations focused on the use of activated diacids such as enol esters (see also Table 4.1). This was due to the belief that such activation was necessary to achieve... 

Russell et al. [38] also studied Novozym 435-catalyzed A-A/B-B type condensation polymerizations to prepare aromatic polyesters and polycarbonates. Polymerizations between divinylesters or dicarbonates with aromatic diols, conducted for 24h in bulk catalyzed by Novozym 435 (lOwt %) at preferably 70°C, gave low molecular weight polycarbonates and polyesters. The aromatic diols included 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 2,6-pyridinedimethanolor4,4-isopropylidenebis(2-(2,6-dibromophenoxy)ethanol) and bisphenol-A. The Mw of polycarbonates and polyesters did not exceed 5200 and 3500 (yields <35%), respectively. When various isomers of benzenedimethanol... 

Scheme 4.9 Lipase-catalyzed condensation polymerization of various divinyl esters with diols of varying length.

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