Monomers copolymerization

Butadiene—Acrylonitrile Latices. Nitrile latices are copolymers of butadiene and acrylonitrile ia which those copolymerized monomers are the main constituents (see Elastomers, synthetic-nitrile rubber). The latices differ mainly ia ratio of comonomer and stabilizer type. They can be classified as low and medium acrylonitrile (ACN) types. The latter contain 35—40 wt % nitrile mbber, and low types ca 27—29 wt %. 

Reactive polymers can be synthesized by either polymerizing or copolymerizing monomers containing the desired functional groups, or performing one or more modifications on a suitable polymer to introduce the essential functionality. Polymers produced directly by polymerization of functionalized monomers have well defined structures, but the physical and mechanical properties of the... 

As in the case of the oxidation of saturated esters, the rate of chain copolymerization monomer and dioxygen obeys the equation similar to that for aliphatic ester oxidation. 

Another characteristic feature of ionic copolymerizations is the sensitivity of the monomer reactivity ratios to changes in the initiator, reaction medium, or temperature. This is quite different from the general behavior observed in radical copolymerization. Monomer reactivity ratios in radical copolymerization are far less dependent on reaction conditions. 

Rimmer [118] and Caffetera [119] focused their studies on the reactivity of polymers bearing double bonds in order to synthesize macroinitiators able to give block copolymers. These authors copolymerized monomers such as methyl methacrylate (MMA) or styrene (St) with 2-3 dimethyl butadiene giving copolymers presenting the structure shown in Scheme 36 with... 

Copolymerization Monomer, acrylonitrile, 9.09 g impregnation 15 min, 25°C surfactant (Tween-80), 0.9 g distilled water, 210 ml 02 (cone. 30%) 5 ml SO, to pH 5 reaction time, up to 19 hrs atmosphere, nitrogen reaction temperature, 25 C quenching of polymerization washing of product with distilled water and 1% of K2S2O2, 5 min washing with 1000 ml of distilled water. 

Figure 4-22. Mechanism of ethylene-methyl acrylate copolymerization monomer insertion...

The Q and e scheme has been the subject of considerable attention. It promised new possibilities of monomer classification, calculation of copolymerization parameters from known values of Q and and predictions about the behaviour of copolymerizing systems. However, to such ends the Q and e values should be known, and they are not directly measurable. In order to calculate them from copolymerization parameters, the easily copolymerized styrene has been selected as the reference monomer, with the assigned values Q = 1 and e = -0.8. Data on the Q and e factors of practically all copolymerizing monomers are now available (see Tables 3 and 3A) some kinetic significance is ascribed to monomer position in the Q — e plane (see Fig. 21). Monomers with a high Q value are expected to form poorly reactive radicals with a low tendency to add further monomer units monomers with widely differing e values usually copolymerize easily, etc. 

When the copolymerizing monomers have different parameters and when the concentrations of the two monomers are not kept constant (as is customary in continous reactors), the copolymer composition changes with conversion. This problem was treated mathematically by Skeist [167]. 

The value of the exponent in eqn. (106) lies in the range 1 m 2. Monomers of widely differing polarity represent the extreme case with m = 2. This behaviour is observed, for example, with the pairs styrene—methyl methacrylate and acrylonitrile—methyl methacrylate. The other extreme, represented by the condition (105), was observed in copolymerizing monomers of very similar polarity with m = 1 (e. g. styrene—isoprene). The rate of co-addition generally increases with increasing temperature, and m decreases to 1, even for very dissimilar monomers (acrylonitrile—methyl methacrylate [194]). 

When one of the copolymerizing monomers is unable to homopolymerize, eqn. (110) is simplified to... 

These equilibria also strongly affect copolymerization. Monomer reactivity ratios in controlled/living systems should be identical to those in conventional cationic copolymerizations, if the comonomers react exclusively with carbocationic species. The equilibrium between active and... 

In an emulsion copolymerization, monomer partitioning between the monomer droplet, polymer particle and aqueous phases plays a key role in determining the rate of copolymerization and the copolymer composition. Two approaches (empirical and thermodynamic) have been proposed to predict the monomer concentrations in the polymer particles in an emulsion copolymerization system. In the emulsion copolymerization of St and MMA, Nomura et al. [45,122,140] first proposed an empirical approach for predicting the saturated concentration of each monomer in the polymer particles as a function of the monomer composition in the monomer droplets, as shown by... 

This results from research at Goodyear ( 2, T3) and a commercial grade of nitrile rubber (Chemigum HR 665) is now produced containing a small proportion (< 2%) of a copolymerized monomer, IV. 

Attempts to copolymerize monomer I with sulfur resulted in formation of just the poly(arylene polysulfide) since all the sulfur separated out on cooling to room temperature. This is apparently because when eight or more sulfur atoms appear in sequence in a polymeric chain, the chain is unstable, and some of the sulfur eliminates to form the more stable eight-membered rings instead. 

Copolymerization. Monomer reactivity ratio parameters (rj and ra) have been defined as the ratio of the rate constant for a reactive species adding to its own type of monomer to the rate constant for its addition to the other monomer. The parameters have been very useful in predicting sequence distributions among different monomers in multicomponent polymerizations and in delineating compositional variations with conversion. 

Chemical crosslinks may be obtained by randomly joining segments in already formed chains, by random copolymerization, or by end-linking functionally-terminated chains. Sulfur cures, peroxide cures, and high-energy irradiations are familiar methods of random crosslinking. Copolymerization monomers where at least one type has three or more reactive sites also lead to randomly crosslinked networks. Formation of networks by end-linking... 

Pre-activate polymer substrate (e.g., by peroxidation in air or ozone) using plasma discharge, ioniring radiation or chemical treatment, llien contact with monometfs) solvents and initiate using heat and/or catalyst to graft copolymerize monomer onto polymer substrate. Remove solvent and any unreacted monomer. ( Indirect Method )... 

Much attention has been paid to the propagating terminal radicals in alternating copolymerization via charge-transfer complexes of the two copolymerizing monomers (see e.g. Ref. ). We believe that our method is very useful for identifying these radicals... 

Leclerc and coworkers copolymerize monomer 44 with brominated monomers to prepare polymers 15 and 16 (Chart 19.4). The reactions are carried out in a sealed microwave vial, which is charged with 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2/f,5//)-dione 45, 2-octyl-thieno[3,4-t( -thiazole 44, Herrmann-Beller catalyst (2mol%), pivalic acid (0.3 equiv.), tri(o-anisole)phosphine (4mol%) and cesium carbonate (3 equiv.) (Scheme 19.10). THF [0.1 M] is added, and the reaction mixture heated to 120 °C under pressure for 24 h. The mixture is cooled to room temperature and... 

The sequence distribution of two copolymerizing monomers depends on the catalyst or initiator used, the method of pol5merization, and the concentration and reactivities of the monomers. Reactivity ratios for many monomer pairs have been measured for free-radical, anionic, and coordination polymerization of butadiene (128). 

At the first-order level, the preference of the metallocene for one monomer over the other is quantified by the two reactivity ratios, r (= knlkn) and r2 (= 22/ 21)- Since ethylene is invariably more reactive than any other monomer, ri > 1 and T2 < 1. Study of the First-Order Markov constants (Table 2) reveals important correlations with metallocene and comonomer structure. As is to be expected, the larger the comonomer, the higher the r value, indicating a steric hindrance to its insertion. Bridged metallocenes, such as structure 2, give catalysts with much lower ri values than do unbridged metallocenes. In general, metallocenes copolymerize monomers with a tendency toward alternation of monomers, as indicated by a value for r r2 less than 1. 

Type of Catalyst Systems and Reactivity Ratios in Ethylene/ Propylene Copolymerization (Monomer 1 = Ethylene Monomer 2 = Propylene)... 

Random, graft, and alternating copolymerization Monomer polymer composition—copolymers Monomer polymer composition—terpolymers Monomer polymer composition—multi-component terpolymers Free radical concentration Reactivity ratios... 

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