Condensation polymerisation polymers

The third approaeh to synthetic polymers is of somewhat less commereial importance. There is in fact no universally accepted deseription for the route but the terms rearrangement polymerisation and polyaddition are commonly used. In many respects this process is intermediate between addition and condensation polymerisations. As with the former teehnique there is no moleeule split out but the kinetics are akin to the latter. A typical example is the preparation of polyurethanes by interaction of diols (di-alcohols, glycols) with di-isocyanates Figure 2.7). 

A mass of polymer will contain a large number of individual molecules which will vary in their molecular size. This will occur in the case, for example, of free-radically polymerised polymers because of the somewhat random occurrence of ehain termination reactions and in the case of condensation polymers because of the random nature of the chain growth. There will thus be a distribution of molecular weights the system is said to be poly disperse. 

The early development of the nylons is largely due to the work of W. H. Carothers and his colleagues, who first synthesised nylon 66 in 1935 after extensive and classical researches into condensation polymerisation. Commercial production of this polymer for subsequent conversion into fibres was commenced by the Du Pont Company in December 1939. The first nylon mouldings were produced in 1941 but the polymer did not become well known in this form until about 1950. 

Condensation polymerisation In this case reaction between two groups occurs which leads to the production of a polymer and also a simple molecule, e.g. reaction between adipic acid and hexamethylene diamine yields nylon 66 and water ... 

The properties of a polymer network depend not only on the molar masses, functionalities, chain structures, and proportions of reactants used to prepare the network but also on the conditions (concentration and temperature) of preparation. In the Gaussian sense, the perfect network can never be obtained in practice, but, through random or condensation polymerisations(T) of polyfunctional monomers and prepolymers, networks with imperfections which are to some extent quantifiable can be prepared, and the importance of such imperfections on network properties can be ascertained. In this context, the use of well-characterised random polymerisations for network preparation may be contrasted with the more traditional method of cross-linking polymer chains. With the latter, uncertainties can exist with regard to the... 

In the condensation polymerisation or step growth polymerisation, the polymer molecules are built up through many separate reaction of functional groups. 

These polymers possessing amide linkages are Important examples of synthetle fibres and are termed as nylons. The general method of preparation eonslsts of the condensation polymerisation of diamines with dlearboxylle aelds and also of amino acids and their laetarns. 

Melamine formaldehyde polymer is formed by the condensation polymerisation of melamine and formaldehyde. 

In addition polymerisation, the molecules of the same or different monomers add together to form a large polymer molecule. Condensation polymerisation is a process in which two or more bi-functional molecules undergo a series of condensation reactions with the elimination of some simple molecules and leading to the formation of polymers. 

The polymers can be categorised as formaldehyde containing and formaldehyde free and as thermoset or thermoplastic resins. Typical formaldehyde containing resins are melamine formaldehyde sulfonamide resins, where the sulfonamide is ortho and para toluenesulfonamide. The sulfonamide, which is a solvent for the dye, undergoes a condensation polymerisation with formaldehyde and melamine, the latter acting as a cross-linking agent. Non-formaldehyde, thermoplastic resins are usually polyamides and polyesters. 

The range of monomers which can be employed is largely dictated by the physical chemistry of the emulsion system. For instance, monomers must be sufficiently hydrophobic to allow the formation of stable w/o HIPEs. In addition, most systems which have been studied have used polymerisation methods which require either an initiation step, or addition of a catalyst. This is due to the fact that the first step in the preparation of the polymer is the preparation of HIPE this can only proceed satisfactorily in the absence of any significant degree of polymerisation. Thus, it can be seen that radical addition polymerisation is suitable for the synthesis of PolyHIPE polymers, whereas condensation polymerisation can be more problematical. Also, the latter reactions often generate water as the by-product, hence the aqueous component of the HIPE is inhibiting to the polycondensation. 

We can obtain different polymers with different properties if we carry out condensation polymerisation reactions between other monomer molecules. For example, if we react ethane- 1,2-diol with benzene-1,4-dicarboxylic acid, then we produce a polymer called Terylene. 

If the monomers are bifunctional, as in the above example, then a linear polymer is formed. Terminating monofunctional groups will reduce the average degree of polymerisation. Polyfunctional monomers, such as glycerol and phthalic acid, are able to form branching points, which readily leads to irreversible network formation (see Chapter 9). Bakelite, a condensation product of phenol and formaldehyde, is an example of such a space-network polymer. Linear polymers are usually soluble in suitable solvents and are thermoplastic - i.e. they can be softened by heat without decomposition. In contrast, highly condensed network polymers are usually hard, are almost completely insoluble and thermoset - i.e. they cannot be softened by heat without decomposition. 

Indicate a, tu-diene monomers that will undergo metathesis condensation-polymerisation to the following polymers ... 

Walsh et al. (1995) considered an industrial batch reactive distillation problem originally presented by Leversund et al. (1993) as a case study. A condensation polymerisation reaction between a dibasic aromatic acid (R1) and two glycols (R2, R3) was considered. The reaction products were a polymer product (P) and water... 

First study of co-polymerisation by Wagner-Jauregg Early theories of rubber-elasticity (Mark, Meyer, Guth, Kuhn and others) Carothers famous work proves by means of organic synthesis that polymers are giant, stable molecules. He first proves it by the discovery of neoprene (polychloro-butadiene), then by the condensation polymerisation of amino acids and esters. As a consequence the first fully synthetic textile fibre, nylon, is developed. In Carothers group Flory elucidates the mechanisms of radical and condensation polymerisation... 

Polymer A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the mer e.g., polyethylene, rubber, cellulose. Synthetic polymers are formed by addition or condensation polymerisation of monomers. If two or more monomers are involved, a copolymer is obtained. Some polymers are elastomers, some plastics. 

Condensation polymerisation occurs when multifunctional monomers, which possess more than one chemically reactive group per molecule, react together with the elimination of small molecules, typically either water or HC1. With a bifunctional monomer the product is a linear polymer, e.g. the polyamide Nylon-6 is derived from e-amino caproic acid as follows ... 

Conjugated polymers can also be prepared by condensation polymerisation, usually from a dihalide with the elimination of the related acid. The dehalogenation reaction for the preparation of polyfp-phenylenevinylene) is a typical example ... 

Vapour Deposition Polymerisation. This is a little studied approach but one that offers significant potential for the fabrication of very thin films and for elaborate multilayer structures. A commercial process has been developed by the Ulvac Corporation in Japan to coat magnetic relay switches with an insulating polyimide layer. A polyamic acid is sythesised by co-deposition of two reactive monomers and is then thermally imidised. The same approach can be used for the condensation polymerisation of poly(azomethine)s, ° poly(ox-adiazoles) and poly(quinoxalines) all of which have been used in LED structures. This approach to polymer synthesis is ripe for further development. 

The synthesis of cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain by condensation polymerisation of epichlorohydrin with benzylamine in various proportions, and their characterisation by proton NMR and GPC, is described. The antimicrobial activity of the polymers against bacteria, yeast and fungi was investigated and the results are discussed. 12 refs. 

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