Copolymerabilities of monomers

Copolymerization of monomer mixtures often leads lo materials with properties quite different from those of either corresponding homopolymer, giving the polymer chemist a vast amount of flexibility for devising new materials. Table 31.1 lists some common copolymers and their commercial applications. 

Uses. There are about forty to fifty organic peroxides commercially available in more than seventy formulations designed for specific applications which include (1) initiators for vinyl monomer polymerizations, and copolymerizations of monomers such as vinyl chloride, ethylene, styrene, vinyl acetate, acrylics, fluoroolefms and buta-dienestyrene (2) curing agents for thermoset polyesters, styrenated alkyds and oils, silicone rubbers and poly allyl diglycol carbonates ... 

Anionic copolymerization of monomers which do not polymerize by themselves sometimes yields alternating copolymers. 

Ra, Ra symbol of a-type radical or ion and its concentration kap constant of propagation reaction between Ra and M klap constant of termination reaction between Ra and R rap> rfia reactivity ratios for binary free-radical copolymerization of monomers Ma and M ... 

With respect to the polymeric backbone, two approaches exist for the preparation of functional polymers, the polymerization or copolymerization of monomers which carry the desired functionality, and secondly the chemical modification of preformed polymers. The former concept, the polymerization of prefunctionalized monomers, was often tested in the early days of polymer-assisted syntheses, e. g. in the preparation of polymers containing pyridine [12] or quinone [13] residues, and benzaldehyde [14] or phosphine [15] functionalities. Although the latter approach demands that the synthetic organic chemist acquires profound knowledge of polymers and polymerization, this strategy can have advantages because... 

It is highly unlikely that the reactivities of the various monomers would be such as to yield either block or alternating copolymes. The quantitative dependence of copolymer composition on monomer reactivities has been described [Korshak et al., 1976 Mackey et al., 1978 Russell et al., 1981]. The treatment is the same as that described in Chap. 6 for chain copolymerization (Secs. 6-2 and 6-5). The overall composition of the copolymer obtained in a step polymerization will almost always be the same as the composition of the monomer mixture since these reactions are carried out to essentially 100% conversion (a necessity for obtaining high-molecular-weight polymer). Further, for step copolymerizations of monomer mixtures such as in Eq. 2-192 one often observes the formation of random copolymers. This occurs either because there are no differences in the reactivities of the various monomers or the polymerization proceeds under reaction conditions where there is extensive interchange (Sec. 2-7c). The use of only one diacid or one diamine would produce a variation on the copolymer structure with either R = R" or R = R " [Jackson and Morris, 1988]. 

The reactivity ris is the monomer reactivity ratio for copolymerization of monomer 1 with styrene. Since styrene has very little polar character, ris measures the intrinsic reactivity of Mi- radical. The polarity of Mi- radical % is obtained from... 

The first case is the copolymerization of monomer A with diene BB where all the double bonds (i.e., the A double bond and both B double bonds) have the same reactivity. Methyl methacrylate-ethylene glycol dimethacrylate (EGDM), vinyl acetate-divinyl adipate (DVA), and styrene-p- or m-divinylbenzene (DVB) are examples of this type of copolymerization system [Landin and Macosko, 1988 Li et al., 1989 Storey, 1965 Ulbrich et al., 1977]. Since r = Yi, Fi = f and the extent of reaction p of A double bonds equals that of B double bonds. There are p[A] reacted A double bonds, p[B] reacted B double bonds, and p2[BB] reacted BB monomer units. [A] and [B] are the concentrations of A and B double bonds,... 

Radiation processing of monomers and polymers by electron beam, such as polymerization and copolymerization of monomers, cross-linking, grafting, and degradation of polymers, is induced by these different chemically reactive species. ... 

Copolymerization of monomers with an antioxidant active moiety with the elastomeric monomers, and... 

Because of the problems associated with copolymerizations of monomers of very different reactivity, many authors have looked at an alternative approach which is to synthesise appropriate sections of the desired polymer chain, then couple them electrochemically to get the final polymer. Naitoh et al.199) synthesised the dimer, 2,2 -thienylpyrrole and used this as a monomer to prepare the alternating pyrrole-thiophene copolymer. They claimed that the copolymer film obtained with HSO as the counter-ion is more conductive than either of the corresponding homopolymers by a factor of 10 to 20. McLeod et al. 200) synthesised 2,5-dithienylpyrrole and polymerized it electrochemically with silver p-toluenesulphonate as the electrolyte. They obtained films of polymer whose conductivity could be varied in the range 10 8 to 0.1 Scm-1. Surprisingly, some low conductivity films were soluble in acetone or acetonitrile and evaporation of the solvent gave a powder of similar conductivity. Based on the shift in the absorption maximum in the visible spectrum on polymerization, it was concluded that the soluble films were polymers with molecular weights of 4000. 

Time-temperature superposition in materials with multiple transitions can be studied advantageously in block copolymers. Although exceptions have been noted (25), random copolymerization of monomers... 

This model is based on the particle formation during polymerization where the polymer particles are sterically stabilized by graft-copolymerized PEO chains on the particle surface. In the later stage the polymer particles were supposed to grow in size mainly by copolymerization of monomers occluded in the particles which may favor the substrate monomer (styrene) over the macromonomer as compared to the composition in the continuous phase. 

In polymer chemistry, there are two known CDSD techniques (i) the chemical modification (polymer-analogous transformation) of homopolymers and (ii) the step-growth copolymerization of monomers with different properties under special conditions. We will address both these techniques. 

The essence of this technique consists of the copolymerization of monomers differing in their affinity to the template and therefore differently distributed in the reaction system. In contrast to conventional types of template polymerization [73,74], in the CDSD copolymerization, all the monomers are bifunctional and form linear polymers, not cross-linked ones. The sequence of the segments in the resulting molecularly imprinted copolymer is determined by the template-controlled conformation of the propagating macroradical [24,25]. 

Thermoplasticization of Wood by Graft Copolymerization in De-crystallized State. We have reported that wood can effectively be decrystallized without a weight-loss by treating with a non-aqueous cellulose solvent, the SO2-DEA-DMSO solution (11). Thus, use of the non-aqueous cellulose solvent as a reaction medium for the graft-copolymerization of monomers to wood was expected to result in products with branch polymers more uniformly distributed. The results obtained by the homogeneous grafting of cellulose (10) were expected to support this idea. 

From an industrial point of view the other aspects dealt with in this section are less exciting. Therefore, the homopolymerization of substituted dienes other than IP, the copolymerization of BD and styrene and the copolymerization of BD with ethylene and higher 1-alkenes are only briefly summarized. The Nd-catalyzed homo- and copolymerization of monomers with polar entities are not dealt with in this review. 

The diradical nature of the intermediate in the copolymerization of monomers through a charge transfer intermediate has been suggested by Zutty et al. (88) as a result of studies on the copolymerization and terpolymerization of monomer systems containing bicycloheptene and sulfur dioxide. The third monomer apparently enters the copolymer chain as a block segment, while the donor-acceptor monomer pair enter the chain in a 1 1 molar ratio, irrespective of the ratio present in the monomer mixture. 

The copolymerization of monomers where one of the monomers acts as the hydrophobe was reported by Reimers and Schork [26]. MMA was copolymerized with p-methylstyrene, vinyl hexanoate, or vinyl 2-ethylhexanoate. The resulting copolymer composition tended to follow the predictions of the reactivity ratios, i.e., the reaction progresses as a bulk reaction. In contrast, copolymer compositions obtained from the (macro)emulsion copolymerizations tended to be more influenced by the relative water solubility of the comonomer and mass transfer. Wu and Schork used monomer combinations with large differences in reactivity ratios and water solubility vinyl acetate/butyl acrylate,... 

The copolymerization of monomer pairs such as butadiene and styrene follows a different course in hydrocarbon solvents than in more polar solvents such as ethers. The copolymerization in tetrahydrofuran is fairly straightforward, but the behavior in hydrocarbon solvents is often considered... 

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