Polymer condensation reaction

Oikawa H et al. (2002) Synthesis and basic characteristics of novel T7-Phenylsilsesquioxane derivatives using hydrolytic condensation reaction. Polym Prep Jpn (Soc Polym Sci Jpn)... 

According to these earlier studies, a reaction mechanism involving diradical intermediates of the type (SiF2) (where n = 1, 2, 3, etc.) was established (70, 73, 80). This idea is particularly attractive if one considers the facts that in co-condensation reactions polymers are the major products obtained, and that volatile products of co-condensation reactions often contain (SiF2) units with n > 1. The earlier ESR study also supported this idea (52). 

Previous attempts to synthesize ferrocene-backbone macromolecules of type 4 (y > 0) in which the ferrocene units are separated via a spacer group have also focused on the use of condensation reactions. Polymers 4 (y > 3) in which the spacer is very long have been successfully prepared (36), but well-characterized materials of substantial molecular weight where the ferrocene units are held in close proximity to one another are extremely rare. Previous work on such polymers and other ferrocene-... 

Proteins are condensation reaction polymers of the 20 naturally occurring amino acids. With the exception of proline, the amino acids have the generic chemical form of ... 

In Section 21.12 you learned that carboxylic acids react with alcohols to form esters and with ammonia and amines to form amides. In each reaction, a molecule of water is split out in a condensation reaction. Polymer chemists use these same reactions to form polyesters and polyamides. However, to form the polymer chain by repeated condensation reactions, you must use a t/tcarboxylic acid (two carboxyl groups), such as terephthalic acid, and a t/talcohol (two hydroxyl groups), such as ethylene glycol, as shown here. 

The leader of DuPont s effort was Wallace H Carothers who reasoned that he could reproduce the properties of silk by constructing a polymer chain held together as is silk by amide bonds The neces sary amide bonds were formed by heating a dicar boxylic acid with a diamine Hexanedioic acid adipic acid) and 1 6 hexanediamme hexamethylenedi-amine) react to give a salt that when heated gives a polyamide called nylon 66 The amide bonds form by a condensation reaction and nylon 66 is an example of a condensation polymer... 

The polymer repeat unit arises from reacting together two different functional groups which usually originate on different monomers. In this case the repeat unit is different from either of the monomers. In addition, small molecules are often eliminated during the condensation reaction. Note the words usual and often in the previous statements exceptions to both statements are easily found. 

The product molecules have the functional groups formed by the condensation reactions interspersed regularly along the backbone of the polymer molecule ... 

Discussion of ladder polymers also enables us to introduce a step-growth polymerization that deviates from the simple condensation reactions which we have described almost exclusively in this chapter. The Diels-Alder reaction is widely used in the synthesis of both ladder and semiladder polymers. In general, the Diels-Alder reaction occurs between a diene [XVI] and a dienophile [XVll] and yields an adduct with a ring structure [XVlll] ... 

Haward et al.t have reported some research in which a copolymer of styrene and hydroxyethylmethacrylate was cross-linked by hexamethylene diisocyanate. Draw the structural formula for a portion of this cross-linked polymer and indicate what part of the molecule is the result of a condensation reaction and what part results from addition polymerization. These authors indicate that the crosslinking reaction is carried out in sufficiently dilute solutions of copolymer that the crosslinking is primarily intramolecular rather than intermolecular. Explain the distinction between these two terms and why concentration affects the relative amounts of each. 

The cyanoacryhc esters are prepared via the Knoevenagel condensation reaction (5), in which the corresponding alkyl cyanoacetate reacts with formaldehyde in the presence of a basic catalyst to form a low molecular weight polymer. The polymer slurry is acidified and the water is removed. Subsequendy, the polymer is cracked and redistilled at a high temperature onto a suitable stabilizer combination to prevent premature repolymerization. Strong protonic or Lewis acids are normally used in combination with small amounts of a free-radical stabilizer. 

Synthesis. The first hiUy alkyl/aryl-substituted polymers were reported in 1980 via a condensation—polymeri2ation route. The method involves, first, the synthesis of organophosphine-containing alkyl or aryl substituents, followed by the ready oxidation of the phosphine to a phosphorane with leaving groups suitable for a 1,2-elimination reaction. This phosphorane is then thermally condensed to polymers in which all phosphoms atoms bear alkyl or aryl substituents. This condensation synthesis is depicted in Eigure 2 (5—7,64). 

Phenolic Resins. At elevated temperatures, phenoHc resins are cured with polysulfide resins through a condensation reaction. The product may be considered a block copolymer of the rigid phenoHc resin and the flexible polysulfide. Thus, the polysulfide acts to flexibiHze the resulting polymer. 

The second step is a condensation reaction that involves the linking together of monomer units with the Hberation of water to form a dimer, a polymer chain, or a vast network. This is usually referred to as methylene bridge formation, polymerization, resinification, or simply cure, and is illustrated in the following equation ... 

Nylon, also a linear polymer, is made by a condensation reaction. Two different kinds of molecule react to give a larger molecule, and a by-product (usually HjO) the ends of large molecules are active, and react further, building a polymer chain. Note how molecules of one type condense with those of the other in this reaction of two symmetrical molecules... 

Most network polymers (the epoxies and the polyesters, for instance) are made by condensation reactions. The only difference is that one of the two reacting molecules is multifunctional (polyester is three-functional) so the reaction gives a three-dimensional lacework, not linear threads, and the resulting polymer is a thermoset. 

Although polyethylene is virtually defined by its very name as a polymer of ethylene produced by addition polymerisation, linear polymers with the formula (CH2), have also been prepared by condensation reactions. For example in 1898 von Pechmann produced a white substance from an ethereal solution of... 

The condensation reaction is promoted by certain polar solvents and of the many which have been tested dimethyl sulphoxide appears to be the most effective. As usual with linear condensation polymers molecular equivalence and near-absence of monofunctional material is necessary to ensure a high molecular weight. Moisture and alcohols can also have a devastating effect on the molecular weight. In the case of water it is believed that 4-chlorophenyl 4-hydroxyphenyl sulphone is formed which functions as an effective chain terminator. Gross contamination with air is also believed to reduce the maximum attainable molecular weight as well as causing intense discolouration. 

This particular polymer is a fibre-forming material (Perlon U). Although in many respects this reaction resembles the formation of polyesters and polyamides it is not a condensation reaction but involves a transfer of hydrogen atoms and thus may be considered as an example of rearrangement polymerisation. 

There are two great families of synthetic polymers, those made by addition methods (notably, polyethylene and other polyolefines), in which successive monomers simply become attached to a long chain, and those made by condensation reactions (polyesters, polyamides, etc.) in which a monomer becomes attached to the end of a chain with the generation of a small by-product molecule, such as water. The first sustained programme of research directed specifically to finding new synthetic macromolecules involved mostly condensation reactions and was master-... 

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