Addition polymerisation reactions

Acetaldehyde is a highly reactive compound exhibiting the general reactivity of aldehydes (qv). Acetaldehyde undergoes numerous condensation, addition, and polymerisation reactions under suitable conditions, the oxygen or any of the hydrogens can be replaced. 

This second reaction leads to the small amount of branching (usually less than 5%) observed in the alcohol product. The alpha olefins produced by the first reaction represent a loss unless recovered (8). Additionally, ethylene polymerisation during chain growth creates significant fouling problems which must be addressed in the design and operation of commercial production faciUties (9). 

By contrast, addition polymers are those formed by the addition reaction of an unsaturated monomer, such as takes place in the polymerisation of vinyl chloride (Reaction 1.2). 

As outlined in Chapter 1, polymerisation reactions can be classified as either condensation or addihon processes, the basis of the classification suggested by W. H. Carothers in 1929. More useful, however, is the classification based on reaction kinetics, in which polymerisation reactions are divided into step and chain processes. These latter categories approximate to Carothers condensation and addition reactions but are not completely synonymous with them. 

Additions to C=C are almost certainly the most important group of reactions involving radicals. This is due largely to the importance of addition (vinyl) polymerisation (p. 320), and the consequent extent to which its mechanism has been investigated but addition of halogens and of halogen hydracids is also of significance. 

Polymers can be formed from compounds containing a c=c double bond. Alkenes, such as ethene, can undergo addition polymerisation to form a polymer. A polymer is a compound consisting of very long chain molecules built up from smaller molecular units, called monomers. The polymerisation of ethene, to form poly(ethene), is a free radical addition reaction. 

Most polymerisation reactions can be assigned to two catagories usually described as addition and condensation polymerisation (sometimes called chain reaction polymerisation and step reaction polymerisation , respectively). In both types of reaction, some form of initiator or catalyst is usually required. The tranformation which occurs in the addition polymerisation of a single monomer species can be represented as... 

In fact, the first description of a polymeric vinyl ester dates back to 1912 when Klatte [1] managed to polymerise vinyl chloroacetate to obtain a solid resin. However, the potential of these materials was not seen at that time [2]. Additionally the polymerisation reaction faced severe practical problems leading to products... 

In Chapter 14 (p. 226) you studied the different addition polymers produced from alkenes. Not all polymers are formed by addition reactions, though. Some are produced as a result of a different type of reaction. In 1935 Wallace Carothers discovered a different sort of plastic when he developed the thermoplastic, nylon. Nylon is made by reacting two different chemicals together, unlike poly(ethene) which is made only from monomer units of ethene. Poly(ethene), formed by addition polymerisation, can be represented by ... 

The metathesis polymerisation of dicyclopentadiene, an inexpensive monomer (commercially available cyclopentadiene dimer produced by a Diels-Alder addition reaction containing ca 95 % endo and ca 5 % exo form), leads to a polymer that may be transformed into a technically useful elastomer [144-146, 179] and thermosetting resin [180,181]. The polymerisation has characteristics that make it readily adaptable to the reaction injection moulding ( rim ) process [182], The main feature of this process comes from the fact that the polymerisation is carried out directly in the mould of the desired final product. The active metathesis catalyst is formed when two separate reactants, a precatalyst (tungsten-based) component and an activator (aluminium-based) component, are combined. Monomer streams containing one respective component are mixed directly just before entering the mould, and the polymerisation into a partly crosslinked material takes place directly in this mould (Figure 6.5) [147,168,183-186],... 

The thermal reactions of l-oxa-l,3-butadienes such as acroleine 2-78 with alkenes such as 2-79 usually need relatively harsh conditions (150°C-250°C) [120]. As a side reaction polymerisation of the a,/l-unsaturated carbonyl compound can take place addition of radical inhibitors such as hydroquinone or 2,6-di-ferf-butyl-4-methylphenol can be helpful in avoiding this unwanted transformation. In the described hetero Diels-Alder reaction the cycloadduct 2-80 was obtained which was then transformed into racemic-/3-santalene 2-81 (Fig. 2-22). 

Homochain polymers, containing only carbon atoms in the main chain. These polymers are normally prepared by addition or chain-reaction polymerisation. 

The first detailed study of a cationic polymerisation of vinyl ethers induced by stable carbenium salts was reported in 1971 by Bawn et Isobutyl vinyl ether was polymerised with trityl and trc ylium hexadiloroantimonates and trityl fluoroborate. From calorimetric measurements of the rate of polymerisation, it was concluded that all the initiator used was consumed roon after mixii and the assumption was made that an equal number of active species was formed in this fast initiation reaction. Propagation rate constants were thus obtained and attributed to the action of free ions. It was als) claimed that no significant termination took place during the polymerisation ce successive monomer additions produced polymerisations having the same propagation rate constant. Later work performed in the same laboratory on other vinyl ethers... 

Recently, Mengoli and Vidotto restudied these systems and obtained evidence for a direct addition reaction in the initiation of the polymerisation of isobutylvinyl ether by the radical cation perchlorate of 9,10-dijiienylanthracene. The kinetics of styrene polymerisations by the above initiator in nitrdienzene at 10°C were also studied. Important termination reactions giving indanyl-type cations were detected and attrSmt-ed to the perchlorate anion. This system was in fact found to display many similarities with that involving the same monomer and perchloric acid ... 

After workup with ammonium chloride (liberation of NH3 and NaCl) and extraction with hot dimethylsulfoxide products 4 and 5 can be isolated as white solids in yields of ca. 30 %. The low yield of the desired product observed for the epoxide addition reaction is attributed to an anionic epoxide polymerisation process [5],... 

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