Azeotropic copolymers

The molecular weight of SAN can be easily determined by either intrinsic viscosity or size-exclusion chromatography (sec). Relationships for both multipoint and single point viscosity methods are available (18,19). Two intrinsic viscosity and molecular weight relationships for azeotropic copolymers have been given (20,21) ... 

In the Type II case, the copolymerization tends toward an alternating arrangement of monomer units. Curve II of Figure 1 shows an example of an alternating copolymer that has an azeotropic copolymer composition, ie, a copolymer composition equal to the monomer feed at a single monomer feed composition. This case is analogous to a constant Foiling mixture ia vapor—Hquid equihbria.T) III... 

Because of a difference in the reactivity of monomers, expressed as reactivity ratios (r), the composition of the copolymer (k) may be different from that of the reactant mixture or feed (x). When x equals n, the product is said to be an azeotropic copolymer. 

ABS Three-component copolymer of acrylonitrile, butadiene, and styrene, alloy Rubber-toughened materials in which the matrix can be a mixture of polymer tyrpes. alternation copolymer Ordered copolymer in which every other building is a different mer. azeotropic copolymer Copolymer in which the feet and composition of the copolymer are the same, blends Mixtures of different polymers on a molecular level may exist in one or two phases, block copolymer Copolymer that contains long sequences or runs of one mer or both mers. 

As in the case of binary copolymerization (29), also in the case of the copolymerization of three or more monomers an azeotropic copolymer is that in which the relative concentrations of the monomers are the same in the feed and in the copolymer being formed. The conditions for the formation of an azeotropic copolymer of n monomers are (2) ... 

The parameters rA and rs are known as monomer reactivity ratios representing the ratio of rate constants for a radical to add to its own type polymer vs. rate constants for a radical to add to the other type polymer. When kAA = 0 and ksB = 0, it can be seen that rA = 0, re = 0, and each radical reacts exclusively with the other monomer. Rel. (2.3.20) is then reduced to d[P ]/d[P ] = 1, and the monomers alternate regularly along the chain of the copolymer, regardless of the composition of the monomer feed (an excess of one monomer may remain unreacted). This is an ideal case, but copolymers such as that made from (a) styrene and (b) diethyl fumarate (rA = 0.3, re = 0.07) can be close to the ideal case. The styrene/diethyl fumarate polymerization has the tendency to lead to an azeotropic copolymer with 57 mole percent styrene, regardless the feed composition. When the initial composition of the monomers is different from 57 mole percent, the alt-copolymer is formed until one of the materials is finished and the remaining monomer forms a homopolymer. 

Quantitative spectra can give an estimate of the probability parameters according to the copolymerization theory. Poly-(2-methylpentadiene-co-4-methylpentadiene) possesses a Bernoullian distribution of monomer units, moreover polymer composition is the same as that of the monomer mixture used for the formation of the inclusion compound. It can therefore be considered as an ideal azeotropic copolymer. In other instances, we observed that p + p is often lower than 1, (or that the product r. r is greater... 

Figure 7.2 shows curves for several nonideal cases, that is, where r T2 1. It is seen that when both r and T2 are less than 1 there exists some point on the i i-versus-/i curve where the copolymer composition equals the feed composition and at this point the curve crosses the line F = f (that is, the diagonal line). At this point of intersection, polymerization proceeds without change in either feed or copolymer composition. Distillation terminology is again borrowed for this instance. Azeotropic copolymerization is said to occur at such points and the resulting copolymers are called azeotropic copolymers. 

A very simple method to obtain polymeric dispersions in liquid polyethers is to make a mixture between a polyether polyol and a polymeric latex, such as the azeotropic copolymer styrene - ACN (StACN copolymer), obtained by emulsion copolymerisation, having around 20-40% solid content. The water is eliminated step-by-step by vacuum... 

Since all azeotropic copolymers must have a point of constant composition, the critical composition (Ji)c for the azeotrope can be evaluated by solving Eq. 

GL1 Gldckner, G., Francuskiewicz, F., and Reichardt, H.-U., On the behaviour of styrene-acrylonitrile copolymers in solution IV. Light scattering investigation of azeotropic copolymers intetrahydrofuran,AciaPo/v/w., 30, 551, 1979. 

Table 23-1. Fraction f of Unreacted Groups in the Bifunctional Bonding of Substituents R in Homopolymers or Azeotropic Copolymers Where p Is the Fraction of Groups Capable of Reacting...

The foregoing r values lead to the following situation. In accordance with Eq. (39), an azeotropic copolymer is formed when the acrylonitrile charge is... 

The quantities k , k,p, kpp, and kp, are the rate constants of the four basic propagation reactions of copolymerization. The Stockmayer distribution function takes into account only a chemical polydispersity resulting fi om the statistical nature of copolymerization reactions. This means that all units of all chains are formed under identical conditions. If a monomer is removed from the reacting mixture at a rate which changes the monomer concentration ratio, the monomer concentration will drift, forming a copolymer which varies in the average composition and is broader in the chemical distribution. No such chemical polydispersity can be described by the Stockmayer distribution. Therefore, Eq. (84) has to be restricted in its application to random copolymers synthesized at very low conversions or under azeotropic conditions. For azeotropic copolymers, the feed monomer concentrations [a ] and are chosen in such a way that the second factor on the right-hand side of the basic relation of copolymerization kinetics... 

Azeotropic copolymer n. A copolymer in which the relative numbers of the different mer units are the same as in the mixture of monomers from which the copolymer was obtained. During a copolymerization reaction, the copolymer has the same composition as the monomer feed mixture, and a polymeric product of constant composition is formed throughout the copolymerization reaction. Kricheldorf HR, Swift G, Nuyken O, Huang SJ (2004) Handbook of polymer synthesis. CRC Press, Boca Raton, FL. Odian GC (2004) Principles of polymerization. John Wiley and Sons Inc., New York. 

Statistical copolymer (random copolymer ) The monomeric units A and B are distributed statistically (randomly) in the polymer chain -AABBBABAABABBB- (azeotropic copolymer the composition in the copolymer is the same as that of the reaction feed) NBR, EVAC, SAN, SB... 

In terpolymerizations with MA, where two azeotropic copolymer pairs can be formed, Slocombe described an azeotropic copolymer index. In the method, the monomer-terpolymer composition plots take the form of a triangular coordinate graph. A line connecting the points that represented the composition along the azeotropic line have unique properties, i.e., give clear terpolymers, whereas compositions removed from the line gave increasingly turbid polymers as their distance from the azeotropic line increased. 

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