Polymerization, condensation

To interpret the kinetics of the condensation poljmierization of diethylene glycol and adipic acid. 

The simplest possible assumption is that the reaction is of the second order with respect to the functional groups and that each reaction has the same rate constant  

We plot (1 — f)- against t in fig. 1. We see that up to about 70% reaction the points lie on a satisfactory straight line through the 

Flory (loc. dt.) analysed only the last 20% of reaction and showed that over this range the results can be fitted to a third-order kinetic equation. 

In the mechanism of condensation polymerization, the polymer is formed and grows with condensation reaction between monomer units by splitting off a small molecule such as water or carbon dioxide. The process of condensation is the mechanism for formation of only a few synthetic polymers as nylon but most of the natural polymers are formed by condensation polymerization. 

Step of initiation and prolongation during synthesis of the natural polymer glycogen by condensation polymerization. 

It is to be remembered here that as in any chemical reaction involving either formation or breaking of a covalent bond, the energy of activation is to be achieved by any means, for formation of a free radical state in one of the reaction participant to initiate the reaction and once initiated, the reaction will continue until the 

Though less prevalent than addition polymerization, condensation polymerization produces important polymers such as polyesters, polyamides (nylons), polycarbonates, polyurethanes, and phenol-formaldehyde resins (Chapter 12). 

A reaction between two different monomers. Each monomer possesses at least two similar functional groups that can react with the functional groups of the other monomer. For example, a reaction of a diacid and a dialcohol (diol) can produce polyesters  

A similar reaction between a diamine and a diacid can also produce polyamides. 

Reactions between one monomer species with two different functional groups. One functional group of one molecule reacts with the other functional group of the second molecule. For example, polymerization of an amino acid starts with condensation of two monomer molecules  

In these two examples, a small molecule (water) results from the condensation reaction. 

Most natural polymers are condensation polymers. Condensation polymerization is a commonly used polymerization technique for preparing various biomedical polymers. The majority of these are step-growth polymerizations, which involve the stepwise condensation of bifimctional monomers with the elimination of small molecules such as water and HCl. A generalized equation for the linear polycondensation reaction involving two bifunctional monomers A and B can be given as  

For example, polyesters, an important class of biomedical polymers, are commonly prepared by condensation pol3mieiization between a diol and a diacid with the elimination of water molecules (Fig. 2.1). 

The polymerization proceeds in a step-wise manner with the initial formation of dimers, trimers, tetramers, etc. In equimolar concentrations of the diol and diacids and in the absence of any exogenous catalysts, the polymerization is found to catalyzed by the diacid itself. Under these conditions, the rate of polymerization can be given as [3, 4]  

Integration of Eq. (2.4) within limits [COOH]=[COOH]o to [COOH]=[COOH], and t =0 to t = t, the integrated rate equation can be given as  

The extent of polymerization (p) at a given time t can be correlated to the monomer concentration as 

The hydrolysis of RR SiCl2 leads to the formation of a diorganosilanediol which undergoes self-condensation to afford a variety of cyclic and linear products (see Eq. 6.19) [1, 3, 5], This is the original route to silicones and still continues to be a proeess that is important. 

This process is very sensitive to the nature of the reaction conditions. We have already alluded to the preferential synthesis of [Me2SiO]4 by choosing the correct reaction conditions. Using less dilution leads to linear polymeric products. Use of basic catalysts tends to favor high-molecular-weight linear products. On the other hand, it has been noted that use of aeidic catalysts tends to tilt the balance in favor of low-molecular-weight polymers or cyelic products. 

Apart from the hydrolysis route to polysiloxanes there have been efforts to prepare appropriate difunctional silicon derivatives that can be used for step-growth polymerization. For example, diaminosilanes are good syn-thons for condensation with diorganosilanediols. This method is quite effective because of the labiUty of the Si-N bond. Thus, the reaction of Me2Si(NMe2)2 with diphenylsilanediol affords a random copolymer [26] (see Eq. 6.20). The randomization occurs because of the catalytic action of the liberated amine to cleave Si-O bonds. 

The reaction of Ph2Si(OH)2 with NMe2-[Si(Me2)0]3-NMc2 also affords a copolymer however, this process also leads to random copolymers [26] (see Eq. 6.21). 

Polyurethanes find many uses, but the most common is as the soft foams found, for example, in car seats, cushions, and bedding. Along with the structural properties of the polymer, polyurethane foams take advantage of another important reaction of isocyanates. 

Condensation polymers. A. Polyester/polyamide/polyimide formation by combining A2 and 82 monomers or from a single AB monomer. Several common polymers of this class are shown. B. The diisocyanate route to polyurethanes and polyureas. C. Bakelite synthesis. Note that the final product is heavily cross-linked because of the presence of bis and tris adducts in the initial reaction with formaldehyde. 

When an isocyanate reacts with water, CO2 is given off. When just the right amount of water is added to the polymerization, the CO2 gas that is generated in situ acts as a blowing agent and creates the cavities in the final material that make it a foam. 

The development of nylon. Dacron, and a host of other synthetic fibers revolutionized many industries, including clothing, carpeting, and the like. One of the most remarkable members of this family is Lycra, the trademark ascribed by DuPont to a family of fibers known generically as spandex. In the 1960s, Lycra was introduced as a great improvement over natural rubber in ladies foundation garments . 

The modem market for spandex includes active wear and a wide range of light-weight, highly flexible materials. DuPont s market alone is 1.5 billion per year. Spandex is always blended with other fibers such as cotton or wool. It is lighter in weight than threads made 

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Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

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 ... 

The kinetics of this type of polymerization are the same as for simple condensation for this reason, the use of the term polycondensation is perhaps more appropriate. Unless kinetic evidence suggests otherwise, polymerizations involving the formation of chain polymers from cyclic compounds, following ring scission, are classed as condensation polymerizations. Some important con-... 

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... 

Ia. Rawe and J. T. Khamis, Addition and Condensation Polymerization Processes, Advances in Chemistry Series, Vol. 91, American Chemical Society Publications, Washington, D.C., 1969. 

These last expressions provide two very useful views of the progress of a condensation polymerization reaction with time. Equation (5.14) describes how the concentration of A groups asymptotically approaches zero at long times Eq. (5.17) describes how the degree of polymerization increases linearly with time. 

Unsaturated polyester resins prepared by condensation polymerization constitute the largest industrial use for maleic anhydride. Typically, maleic anhydride is esterified with ethylene glycol [107-21-1] and a vinyl monomer or styrene is added along with an initiator such as a peroxide to produce a three-dimensional macromolecule with rigidity, insolubiUty, and mechanical strength. 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

Polyethylene terephthalate [25038-59-9] (8) is a polyester produced by the condensation polymerization of dimethyl terephthalate and ethylene glycol. Polyethylene terephthalate sutures are available white (undyed), or dyed green with D C Green No. 6, or blue with D C Blue No. 6. These may be coated with polybutylene adipate (polybutilate), polyydimethylsiloxane, or polytetrafiuoroethylene [9002-84-0]. The sutures are distributed under the trade names Ethibond Exel, Mersdene, Polydek, Silky II Polydek, Surgidac, Tevdek II, Polyester, and Tl.Cron. 

Polybutester (10) is a polyether—ester produced by the condensation polymerization of dimethyl terephthalate, polytetramethylene ether glycol [25190-06-17, and 1,4-butanediol [110-63-4]. Polybutester sutures are available in clear, ie, undyed, or blue, ie, melt-pigmented with (phthalocyaninato(2-)) copper. Monofilament polybutester is sold under the trade name Novafil. 

The diacids are characterized by two carboxyHc acid groups attached to a linear or branched hydrocarbon chain. AUphatic, linear dicarboxyhc acids of the general formula HOOC(CH2) COOH, and branched dicarboxyhc acids are the subject of this article. The more common aUphatic diacids (oxaUc, malonic, succinic, and adipic) as weU as the common unsaturated diacids (maleic acid, fumaric acid), the dimer acids (qv), and the aromatic diacids (phthaUc acids) are not discussed here (see Adipic acid Maleic anhydride, maleic acid, and fumaric acid Malonic acid and derivatives Oxalic acid Phthalic acid and OTHERBENZENE-POLYCARBOXYLIC ACIDS SucciNic ACID AND SUCCINIC ANHYDRIDE). The bihinctionahty of the diacids makes them versatile materials, ideally suited for a variety of condensation polymerization reactions. Several diacids are commercially important chemicals that are produced in multimillion kg quantities and find appHcation in a myriad of uses. 

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. 

The general definition of a condensation reaction is a one that involves product formation by expulsion of water (or other small molecule) as a by-product. By this definition, activation and methylolation are also condensations. In more precise terms the chain-building process should be described as a condensation polymerization, however, in the jargon of the phenolics industry, the term condensation is usually reserved for the chain-building process. This terminology is not necessarily observed in the literature [88]. Many literature reports correctly refer to methylolation as a condensation reaction. The molecular weight development of the phenol alcohol adducts may also be classified as a step-polymerization. 

Process in wliich the addition of heat, catalyst or both, with or without pressure, causes the physical properties of the plastic to change through a chemical reaction. Reaction may be condensation, polymerization or addition reactions. 

Most of the compounds in this class have been prepared from preexisting crown ether units. By far, the most common approach is to use a benzo-substituted crown and an electrophilic condensation polymerization. A patent issued to Takekoshi, Scotia and Webb (General Electric) in 1974 which covered the formation of glyoxal and chloral type copolymers with dibenzo-18-crown-6. The latter were prepared by stirring the crown with an equivalent of chloral in chloroform solution. Boron trifluoride was catalyst in this reaction. The polymer which resulted was obtained in about 95% yield. The reaction is illustrated in Eq. (6.22). 

Polymerization (Section 6.21) Process by which a polymer is prepared. The principal processes include free-radical, cationic, coordination, and condensation polymerization. 

Even within the small numbers of studies conducted to date, we are already seeing potentially dramatic effects. Free radical polymerization proceeds at a much faster rate and there is already evidence that both the rate of propagation and the rate of termination are effected. Whole polymerization types - such as ring-opening polymerization to esters and amides, and condensation polymerization of any type (polyamides, polyesters, for example) - have yet to be attempted in ionic liquids. This field is in its infancy and we look forward to the coming years with great anticipation. 

The role of silyl groups in condensation polymerization is different from that in GTP. The use of silylated monomers in condensation polymerization was studied first by Klebe [90-92] in 1964. N-trimethylsilyl-substi-... 

Uses of Formaldehyde. Formaldehyde is the simplest and most reactive aldehyde. Condensation polymerization of formaldehyde with phenol, urea, or melamine produces phenol-formaldehyde, urea formaldehyde, and melamine formaldehyde resins, respectively. These are important glues used in producing particle hoard and plywood. 

Condensation polymerization can occur hy reacting either two similar or two different monomers to form a long polymer. This reaction usually releases a small molecule like water, as in the case of the esterifrcation of a diol and a diacid. In condensation polymerization where ring opening occurs, no small molecule is released (see Condensation Polymerization later in this chapter). 

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. 

Although no small molecule gets eliminated, the reaction can be considered a condensation polymerization. Monomers suitable for polymerization by ring opening condensation normally possess two different functional groups within the ring. Examples of suitable monomers are lactams (such as caprolactam), which produce polyamides, and lactons, which produce polyesters. 

Thermoplastic polyesters are among the large-volume engineering thermoplastics produced by condensation polymerization of terephthalic... 

This group includes many plastics produced by condensation polymerization. Among the important thermosets are the polyurethanes, epoxy resins, phenolic resins, and urea and melamine formaldehyde resins. 

When a diamine (molecule containing two NH2 groups) reacts with a dicarboxyiic acid (two COOH groups), a polyamide is formed. This condensation polymerization is entirely analogous to that used to make polyesters. In this case, the NH2 group of the diamine reacts with the COOH group of the dicarboxyiic acid ... 

As noted in Section 23.2, molecules containing NH2 and COOH groups can undergo condensation polymerization. Amino acids contain both groups in the same molecule. Hence, two amino add molecules can combine by the reaction of the COOH group in one molecule with die NH2 group of the other molecule. If the adds involved are different, two different structural isomers are possible ... 

How would you explain to a young science student how to decide whether a given compound might be useful as a monomer for addition polymerization Condensation polymerization ... 

The sulfonium precursor route may also be applied to alkoxy-substituted PPVs, but a dehydrohalogenation-condensation polymerization route, pioneered by Gilch, is favored 37]. The polymerization again proceeds via a quinomethide intermediate, but die syndicsis of the conjugated polymer requires only two steps and proceeds often in improved yields. The synthesis of the much-studied poly 2-methoxy-5-(2-ethylhexyloxy)-l,4-phenylene vinylene], MEH-PPV 15 is outlined in Scheme 1-5 33, 35]. The solubility of MEH-PPV is believed to be enhanced by the branched nature of its side-chain. 

Polymerization involves the chemical combination of a number of identical or similar molecules to form a complex molecule of high molecular weight. The small units may be combined by addition polymerization or condensation polymerization. 

Condensation polymerization, 346 Conservation of atoms, 40 of charge, 80, 218 of mass, 40... 

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