Polymerisation method vinyl monomers

This is the third report on attempts to measure the propagation rate constant, kp+, for the cationic polymerisation of various monomers in nitrobenzene by reaction calorimetry. The first two were concerned with acenaphthylene (ACN) [1, 2] and styrene [2]. The present work is concerned with attempts to extend the method to more rapidly polymerising monomers. With these we were working at the limits of the calorimetric technique [3] and therefore consistent kinetic results could be obtained only for indene and for phenyl vinyl ether (PhViE), the slowest of the vinyl ethers 2-chloroethyl vinyl ether (CEViE) proved to be so reactive that only a rough estimate of kp+ could be obtained. Most of our results were obtained with 4-chlorobenzoyl hexafluoroantimonate (1), and some with tris-(4-chlorophenyl)methyl hexafluorophosphate (2). A general discussion of the significance of all the kp values obtained in this work is presented. 

This review has clearly matured on the basis of long and arduous experience. Years ago, Cheradame and Sigwalt demonstrated the occurrence of initiation by direct acid-base reaction between a Lewis acid and a vinyl monomer, wiiile Gandini and Flesch first put pseudocationic polymerisation involving propagation by undissociated ester intermediates on the map. Each of the two authors of this review was, accordingly, trained by one of the pioneers of cationic polymerisation. From them they learned the rigorous vacuum techniques which no other methods have yet been able to displace. 

It is possible to obtain a bimodal distribution of final particles median diameter (distribution with two maxima), by seeded radical polymerisation. For example, if a polymer polyol having particle diameter of 0.3-0.6 pm is added to the poly ether before the radical polymerisation, after the normal polymerisation of the vinylic monomers, polymer polyols with a bimodal distribution of particles are obtained. As a general rule, a bimodal distribution leads to lower viscosities than an unimodal distribution of particle diameters, at the same solid content [32]. This is a method to obtain high, solid polymer... 

The basic process was first patented by Inmont, USA, in 1982 [9]. They simply claimed polymerisation of vinyl polymers in DPUR. In 1986, a patent for another method of preparation of hybrid acrylic-urethane dispersions (diluting of prepolymer-ionomer with monomers, emulsifying the resulting solution in water and polymerisation) was granted to Witco, USA [26]. 

Typically, a solid epoxy of 3000 to 4000 EEW (Epikote 1007 or 1009 types or an analogue material manufactured by the chain extension of a lower M liquid epoxy resin) is modified to provide an acid functional epoxy. In general, the acid functionality ctm be conferred by two methods, acid capping (see resin 1 and resin 2) of the oxirane groups or by the graft polymerisation of an epoxy with a carbonyl functional co-polymer (see resin 3). The co-polymer can consist of Ae reaction product of a free radical polymerisation of any approved ethylenic unsaturated monomers containing carbon-carbon unsaturadon, e.g. carboxyl functional acrylic monomers, (acrylic add, methacrylic acid, etc.), the lower alkyl esters, vinyl monomers (acrylamides), vinyl esters (vinyl acetate, vinyl butyrate), vinyl aromatic monomers (styrene, a methylstyrene) etc. The acrylic caj ing resin is add fimctional, being based upon either methacrylic or acrylic acid. The former is normally preferred. An acid value of 50-100 mg KOH/g would be typical. 

Emulsions resulting from the emulsion polymerisation of acrylic or vinyl monomers are unique compared to other resins used for surface coating applications. As such they have properties which are totally different to a conventional solution acrylic, polyester or alkyd resins. Their mechanism of film formation is totally different to other types of resins. Because particles are present it is necessary for them to coalesce to film form and pigmentation is also different to conventional solution polymers. Consider first the unique properties and test methods of emulsion polymers. 

Before the development of CRP methods, ionic (cationic and anionic) or metal-catalysed polymerisations were efficient techniques for the synthesis of glycopolymers with controlled architectures. However, the use of ionic polymerisations quickly became limited because of the harsh polymerisation conditions and the requirement for protected monomers. Anionic polymerisation was limited to vinyl monomers possessing electron-withdrawing groups (nitrile, carbonyl) and required aprotic solvents and low reaction temperatures [ 110-112]. With the development of metal-based catalysis, which was tolerant to a number of functional groups, ring-opening metathesis... 

The most important commercial polymers prepared by this method are obtained from monomers containing a carbon-carbon double bond. In such cases the reaction is called vinyl polymerisation. The addition polymerisation is also important for carbonyl compounds and 1, 2-epoxides. 

Some polar monomers such as vinyl chloride, vinyl-acetate and acrylonitrile may be polymerised by this method using an active solvent such as tetrahydrofuran. 

The binders vary quite widely—the most common being starch, soy protein and latexes in conjunction with other soluble polymers. Styrene-butadiene latexes have been the most popular but ethylene-vinyl acetate binders are also used. The method of polymer synthesis provides a way of modifying the properties of the latex. For example, adjustment of the ratio of styrene butadiene in the co-polymer gives rise to different degrees of softness or hardness. This property has a profound influence on the quality of the coating. It is also possible to co-polymerise monomers so as to introduce, for example, carboxy groups on to the surface of the latex particle which in turn assist in... 

Some exploratory experiments with ethyl vinyl ether showed that it polymerised too rapidly for our method to be useful. The polymerisation of 2-methyl butene-2 had a manageable rate but the results showed inconsistencies which we did not have time to resolve, as this was the last monomer to be studied. 

The calorimetric method was applied by Bowyer et al. (1971) to the polymerisation of N-vinyl carbazole (NVC) by tropylium hexafluoroantimonate and perchlorate in CH2C12 at 0 °C and -25 °C. The reactions were very fast and the reaction curves had a monotonically decreasing rate from the start. The initial reaction rate, R0, was correlated with the initiator and monomer concentrations by the equation... 

The relationship between the surface characteristics of colloidal copper particles and the kinetic parameters of heterogeneous catalytic initiation in aqueous polymerisation was investigated. The dependence of the rate of emulsion polymerisation initiated by the colloidal copper on the nature of the monomer used (styrene, methyl methacrylate, vinyl acetate and N-vinyl pyrrolidone) and method of manufacture of the copper powder was examined. The characteristics of styrene emulsion polymerisation initiated by modified and unmodified colloidal copper particles are reported and the ability of... 

Light-induced polymerisation is one of the most efficient methods to rapidly cure monomers that are inactive towards radical species, like vinyl ethers [49,50] or epoxides [51-54], The subject has been recently covered extensively by Crivello and Dietlieker in an excellent textbook [55]. This technology has not yet achieved the commercial significance of corresponding free-radical processes, mainly because of the more limited choice of monomers available and their lower reactivity. 

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