RADICAL COPOLYMERISATION

It is noteworthy that photoluminescent poly(vinylene-arsine)s have also been prepared by radical copolymerisation of phenylacetylene and an arsenic atomic biradical equivalent [71]. 

Polar monomers in which a heteroatom is conjugated with the olefinic double bond [CH2=CH-C(Z)=X, CH2=CH-C=X] undergo radical copolymerisation with olefins when initiated with Ziegler-Natta catalysts [544,545], One of the possible reaction schemes of the formation of initiating radicals in the system acrylonitrile/VOCL AlEtCl2 is as follows [546] ... 

Free radical copolymerisation of divinylbenzene gives crosslinked resins that have been shown to often still bear many unreacted pendant vinyl groups7. These remaining pendant vinyl bonds as well as the crosslinking level can be quantified by FTIR. The value obtained for the produced support is about 3.0 mmol/g of pendant vinyl bonds. 

By setting the temperature of the reaction medium at 60 C from the beginning of the IPN formation, the PUR synthesis is accelerated, and that of the methacrylic system begins after the usual inhibition period. The competition between the two processes can still favour the complete formation of PUR before appreciable radical copolymerisation may have taken place, though the kinetic curves may change or even cross. For this reason, a second factor, the content of PUR catalyst, is varied too with less stannous octoate, the formation of the first network is more or less delayed, even at 60 C, and counterbalances to some extent the effect of temperature. In such a case, the conversion of the methacrylic phase may proceed further before higher or even post-gel conversions are reached for polyurethane. Thus, IPNs in which both networks have been formed more or less simultaneously, are obtained by this... 

Copolymers are obtained by free-radical copolymerisation of hexafluoroacetone with, for example, alkenes, tetrafluoroethene and epoxides. 

Tidweli, P. W., and G. A. Mortimer Reactivity in free-radical copolymerisation. Polymer Letters 4, 527 (1966). 

The present volume is particularly concerned with the use of the different modes of controlled radical polymerisation for the preparation of copolymers such as random copolymers, linear block copolymers, as well as graft copolymers and star-shaped copolymers. It also presents the combination of controlled radical polymerisation with non-controlled radical copolymerisation, cationic and anionic polymerisation,both of vinyl monomers and cyclic monomers, and ringopening metathesis polymerisation. 

A novel monomer 2-acryloylthioxanthone has been prepared and found to undergo radical copolymerisation with a number of other monomers . Of particular interest is a conventional and laser flash photolysis study on the copolymers with methyl methacrylate where triplet formation was found to be significantly quenched compared with that of the monomer itself. Here intramolecular self quenching was shown to be important in the former case. 

The macromers used in the stabilisation of polymer dispersions are in fact polyether polyols with terminal double bonds, able to copolymerise with vinylic monomers (ACN, styrene) and to form graft species during the radical copolymerisation. The resulting graft polyether polyol, formed in situ by the copolymerisation process, is in fact a NAD ... 

Figure 6.4 The structure of ternary copolymer ACN-styrene-maleic anhydride macromer, a NAD generated in situ by radical copolymerisation...

The presence of macromers in the synthesis of polymer polyols has another important technological advantage it avoids the formation of crusts of vinylic polymer on the walls of the reactor used for radical copolymerisation. 

Acrylic polyols represent a special group of amorphous polyols, of molecular weight (MW) of 8000-13000 daltons, obtained by radical copolymerisation of acrylic monomers (ternary or quaternary copolymers), such as acrylic or methacrylic acids and esters. The source of hydroxyl groups in these acrylic polyols is the utilisation in the radical copolymerisation reaction of hydroxyalkyl acrylates or hydroxyalkyl methacrylates [1,2] as comonomers. The acrylic polyols are used in high performance polyurethane (PU) coatings. 

The general radical copolymerisation reaction for synthesis of acrylic polyols is shown in reaction 10.1. It is obligatory that one of the comonomers is a hydroxyalkyl acrylate or hydroxyalkyl methacrylate (mainly hydroxyethylacrylate and hydroxyethylmethacrylate) in order to introduce hydroxyl groups (as lateral groups, not as terminal groups) available for the reaction with -NCO groups of diisocyanates (reaction 10.1). 

Generally, the radical copolymerisation reactions of acrylic comonomers are performed in an adequate solvent, by drop wise addition of monomer - initiator (peroxides) mixture. 

The insoluble polymeric resin is synthesised by the suspension-radical copolymerisation of styrene with divinylbenzene (DVB) (see Figure 4.3). The polymerisation results in a three-dimensional column framework which is porous in character and can thus allow diffusion of ions to take place through it. By conducting the polymerisation in an aqueous medium beads of definite size can be produced. The extent of cross-linkage and hence pore size can be varied by altering the proportion of DVB. 

Influence of the structure on the reactivity of fluorine-containing methacrylates in the bulk radical copolymerisation with vinyl monomers, as well as the dependence of structure of macromolecular chain of copolymers obtained on these factors is not well-studied [3]. 

As mentioned previously, special attention has been paid to optical polymeric materials obtained by radical copolymerisation of fluorine-containing methacrylates in mixture with various vinyl monomers [3]. Study of kinetics and mechanism of this reaction over a wide range of degrees of reaction remains one of the main problems of chemistry of polymerisational polymers as a whole, and synthesis of copolymers for optical purposes based on alkyl methacrylates, in particular. On the one hand, there is an increased interest in the studies of the mechanism during the initial stages of the radical copolymerisation [65, 66], and on the other hand, the processes occurring in specific comonomeric pairs, for the point of view of those which display the gel-effect and lead to systems with excellent optical characteristics [1,3]. 

Raman fibre optics has been used to study the emulsion homopolymerisations of styrene and n-butyl acrylate (35). An IR spectroscopic technique for the examination of radical copolymerisations of acryl and vinyl monomers was developed. A comparative study of the copolymerisation of model monomer pairs was made using monofunctional and polyfunctional compounds. The data established the role of structural-physical transformations, involved in the formation of crosslinked polymers, on the copolymerisation kinetics and on the nonuniformity of distribution of crosslinks in the copolymers formed (151). Raman fibre optics of polymerisation of acrylic terpolymers was also used to monitor as well as an on-line measurement of morphology/composition (66). The high temperature (330 °C) cure reaction of 4-phenoxy-4 -phenyl-ethynylbenzophenone was monitored using a modulated fibre optic FT-Raman spectrometer (80). 

FTIR spectroscopy was used to study the polymerisation of random copolymers of 4-vinylphenol with n-alkyl methacrylates which were prepared by free radical copolymerisation of 4-t-butyldimethyl-silyloxystyrene and the corresponding alkyl methacrylates in benzene at 60 °C using azobisiso-butyronitrile (AIBN) as an initiator (321). The thermal reaction of polyphenylene-1,2-dibromoethylene under argon flow was investigated using in situ kinetic IR spectroscopy (345). 

Near-IR spectroscopy (10000-4000/cm) was successfully used to monitor conversion dining conventional, anionic solution polymerisation of styrene and isoprene to homopolymers and block copolymers. The conversion of the vinyl protons in the monomer to methylene protons in the polymer was easily monitored under conventional (10-20% solids) solution polymerisation conditions. In addition to the need for an inert probe, high sampling frequencies were required since polymerisation times ranged from 5s in tetrahydrofuran to 20 minutes in cyclohexane. Preliminary data indicate that near IR is capable of detecting sequence distribution for tapered block copolymers, geometric isomer content, and reactivity ratios for free-radical copolymerisation. 20 refs. USA... 

Random copolymers of 4-vinylphenol with n-alkyl methacrylates were prepared by free radical copolymerisation of4-t-butyldimethylsilyloxystyrene and the corresponding alkyl methacrylates in benzene at 60C using AIBN as initiator. Reactivity ratios were determined by the Kelen-Tudos method. Selective removal of the t-butyldimethylsilyl protective group was effected by tetrabutylammonium fluoride in THE at ambient temperature. The copolymers were characterised by IR spectroscopy. 20 refs. 

Synthetic butadiene methylstyrene rubber of various grades. Butadiene-ct-methylstyrene rubbers ( hot and cold free radical copolymerisation of butadiene with a-methylstyrene), at the stages of emulsion formation, emulsion mixing with an initiator, and introducing a terminator to the reaction mixture. 

Figure 1.18 Expected network structures for (a) anionically copolymerised and (b) radically copolymerised St-DVB copolymers. Reproduced with permission from H. Nakagawa, Y. Matsushita and S. Tsuge, Polymer, 1987, 28, 1512. 1987,...

Chambard, G. Control ot Monomer Sequence Distribution - Strategic Approaches Based on Novel Insights in Atom Transfer Radical Copolymerisation, Eindhoven University ot Technology Eindhoven, The Netherlands, 2000. 

For the free radical copolymerisation of unsaturated polyester resins containing an inhibitor, the following simplified mechanism could be used. 

A new method has recently been devised for determining comonomer reactivity ratios [45], following a suggestion by Maitland that proton NMR spectroscopy can be used as a convenient monitor of free-radical copolymerisation reactions performed in situ in an NMR tube [46]. From the... 

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