Polymerisation Polymethyl methacrylate

Another useful, and quite sensitive, test is the initiation of polymerisation (c/ p. 320). Polymerisation can be initiated, in suitable substrates, by cations and anions as well as by radicals, but the effect of these several species can be differentiated by using a 50/50 mixture of phenylethene (styrene), PhCH=CH2, and methyl 2-methyl-propenoate (methyl methacrylate), CH2=C(Me)C02Me, as substrate cationic initiators are found to produce polystyrene only, anions polymethyl methacrylate only, while radicals produce a copolymer containing equal amounts of the two monomers. 

For example, Melville [26] studied the ultrasonically induced polymerisation of monomers such as styrene, methyl methacrylate and vinyl acetate in the presence and absence of polymethyl methacrylate and found that the polymerisation rates ( 1 % conversion/h) were not substantially increased by the presence of polymer. He concluded, in contrast to Driscoll, that the degradation of polymer was not the major source of radical production. Using hydroquinone as an inhibitor, he was able to deduce, from retardation times, that the rate of radical production was 2 X 10 mol dm s. A typical value for radical production using as an example the thermal initiation of AZBN (10 mol dm ) at 60 °C is 2 x 10" mol dm s" ... 

Polyacrylic acid stabilised latices have been prepared by aqueous dispersion polymerisation. The method used is analogous to the non-aqueous dispersion (NAD) polymerisation methods originally used to prepare polymethyl methacrylate particles in aliphatic hydrocarbons (1. In effect the components of a NAD polymerisation have been replaced as follows aliphatic hydrocarbon by aqueous alcohol, and degraded rubber, the stabiliser, by polyacrylic acid (PAA). The effect of various parameters on the particle size and surface charge density of the latices is described together with details of their colloidal stability in the presence of added electrolyte. 

Copolymerisation reactions do not always succeed in the presence of phenols. Cardanol, converted to the acrylate (R = H) by reaction with acryloyl chloride, has been co-polymerised in the presence of benzoyl peroxide with methyl methacrylate leading to a product vrith improved thermal stability compared with polymethyl methacrylate alone (ref. 265). In a similar way an acrylate and a methacrylate (R = Me) have been synthesised from 3-pentadecylphenol. Polymerisation yielded moderately high molecular weight compounds of potential interest as pressure-sensitive adhesives (ref. 266). 

Many modem composite materials are prepared by microemulsion methods. Polyaniline was prepared by one-step micellar chemical polymerisation of aniline with dodecyl benzene sulfonic acid via complex formation [297]. A transparent polyaniline suspension was made by dispersing polyaniline in m-cresol. Polyaniline composites blended with polymethyl methacrylate (PMMA) exhibits relatively high conductivity at low polyaniline volume fractions and keeps good mechanical properties equivalent to those of PMMA. It should be noted that most methods proposed for the preparation of new materials are at a laboratory level, however, a widespread commercial use can be predicted for the next decade. 

The preparation of polymer materials based on heterochain polymer polycarbonates (PC), polyethers, polyethercarbonates (PFC) or joint mixtures of polycondensational and polymerisational polymers [PC with polymethyl methacrylate (PMMA)]. 

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