Copolymers azeotrope

Equation (13.42) gives the condition that a copolymer azeotrope exists. The azeotropic composition is... 

Because of this parallel with liquid-vapor equilibrium, copolymers for which ri = l/r2 are said to be ideal. For those nonideal cases in which the copolymer and feedstock happen to have the same composition, the reaction is called an azeotropic polymerization. Just as in the case of azeotropic distillation, the composition of the reaction mixture does not change as copolymer is formed if the composition corresponds to the azeotrope. The proportion of the two monomers at this point is given by Eq. (7.19). 

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) ... 

Styrene Copolymers. Acrylonitrile, butadiene, a-methylstyrene, acryUc acid, and maleic anhydride have been copolymerized with styrene to yield commercially significant copolymers. Acrylonitrile copolymer with styrene (SAN), the largest-volume styrenic copolymer, is used in appHcations requiring increased strength and chemical resistance over PS. Most of these polymers have been prepared at the cross-over or azeotropic composition, which is ca 24 wt % acrylonitrile (see Acrylonithile polya rs Copolyp rs). 

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... 

In cases where rAB>l and rBA>l or rAB<.l and rBAazeotropic composition1 or critical point where the copolymer composition will exactly reflect the monomer feed composition (Figure 7.1). 

The existence of an azeotropic composition has some practical significance. By conducting a polymerization with the monomer feed ratio equal to the azeotropic composition, a high conversion batch copolymer can be prepared that has no compositional heterogeneity caused by drift in copolymer composition with conversion. Thus, the complex incremental addition protocols that arc otherwise required to achieve this end, are unnecessary. Composition equations and conditions for azeotropic compositions in ternary and quaternary eopolymerizations have also been defined.211,21... 

The heterogeneous copolymerization of styrene and acrylonitrile in various diluents as reported by Riess and Desvalois (22). Although the copolymer composition in these studies was not strongly influenced by the diluent choice, the preferential adsorption of acrylonitrile monomer onto the polymer particles shifted the azeotropic copolymerization point from the 38 mole % acrylonitrile observed in solution to 55 mole % acrylonitrile. 

Determine the copolymer composition for a styrene-acrylonitrile copolymer made at the azeotrope (62 mol% styrene). Assume = 1000. One approach is to use the Gaussian approximation to the binomial distribution. Another is to synthesize 100,000 or so molecules using a random number generator and to sort them by composition. 

The Asahi process for wet-spinning the copolymer involves water dilution at below 0°C of a solution of the copolymer in aqueous 68 wt% nitric acid (the azeotropic composition). The potential for slow self heating and decomposition have been investigated experimentally with variations in several parameters in a Sikarex safety calorimeter. At 20% polymer content, the slow self heating starts even at ambient temperature, and later involves evolution of 30 mol of uncondensable gas per kg of copolymer with comcommittant boiling of the nitric acid. A 2 step mechanism has been proposed. 

Bajoras and Makuska investigated the effect of hydrogen bonding complexes on the reactivities of (meth)acrylic and isotonic acids in a binary mixture of dimethyl sulfoxide and water using IR spectroscopy (Bajoras and Makuska, 1986). They demonstrated that by altering the solvent composition it was possible to carry out copolymerization in the azeotropic which resulted in the production of homogeneous copolymers of definite compositions at high conversions. Furthermore, it was shown that water solvent fraction determines the rate of copolymerization and the reactivity ratios of the comonomers. This in turn determines the copolymer composition. 

By virtue of the conditions xi+X2 = 1>Xi+X2 = 1, only one of two equations (Eq. 98) (e.g. the first one) is independent. Analytical integration of this equation results in explicit expression connecting monomer composition jc with conversion p. This expression in conjunction with formula (Eq. 99) describes the dependence of the instantaneous copolymer composition X on conversion. The analysis of the results achieved revealed [74] that the mode of the drift with conversion of compositions x and X differs from that occurring in the processes of homophase copolymerization. It was found that at any values of parameters p, p2 and initial monomer composition x° both vectors, x and X, will tend with the growth of p to common limit x = X. In traditional copolymerization, systems also exist in which the instantaneous composition of a copolymer coincides with that of the monomer mixture. Such a composition, x =X, is known as the azeotrop . Its values, controlled by parameters of the model, are defined for homophase (a) [1,86] and interphase (b) copolymerization as follows... 

Under homophase synthesis in real systems the azeotrop (a) exists only provided n < 1 and r2 < 1. In this case, however, it is a repeller, unlike in the case of interphase copolymerization where the azeotrop (b) is an attractor. This means that at the final stage of homophase copolymerization homopolymer molecules are primarily formed in all real systems whereas under the interphase synthesis the majority of copolymer chains formed at p —> 1 have the azeotropic composition x. ... 

Methyl methacrylate (MMA), 16 227 Alfrey-Price parameters, 7 617t azeotropic mixtures with, 16 236t block copolymer synthesis, 7 647t C-2 routes to, 16 252-254 C-3 routes to, 16 246—252 C-4 routes to, 16 254—257 carbon monoxide in production of, 5 6 chain-transfer constants for, 16 284t comonomer with acrylonitrile, 1 451t cumene as feedstock, 8 156 in flame-retardant resin formulation,... 

The azeotropic terpolymer, being atypical in general, one is faced with the prospect of solving at least five simultaneous sets of Eq. (108) in order to obtain M. This manipulation is exact, but the inherent inaccuracies in five different measurements of M are coupled with those involved in measuring the refractive index increments. It is as true for a terpolymer as it is for a copolymer that the difference between specific increments (for example, vA - pB or — vc) must be measured for high... 

The reactions were carried out in dilute homogeneous solution in dipolar aprotic solvents ([ester]g=0.2-0.4 mole.l- ) using stereoregular (pure I or S) or predominantly syndiotactic radical (R) PMMA, polymethylacrylate (PMA) and radical azeotropic styrene-MMA copolymer (PSMMA, MMA mole.fraction = 0.47) as well as model monomeric (methylpivalate) and dimeric (dimethylglutarate) compounds. The overall reaction is outlined in the simplified scheme ... 

Compositional heterogeneity of the substituted PMMA For all systems investigated (36), the substituted PMMA are characterized by a fairly high chemical homogeneity over the whole range of DSm(DSm<0.76), quite comparable to that of a radical azeotropic S-MMA copolymer (40) (a = 1.6x10 ). The mean square standard deviation o related to two copolymers of DPn =... 

In a very similar way, hydroxy functionalized ATRP initiators such as 2,2,2-tribromoethanol can be used for the simultaneous polymerization of eCL and MMA (Scheme 25) [83]. Purposely, the ROP of eCL is promoted by Al(OfPr)3 added in catalytic amount so that the rapid alcohol-alkoxide exchange reaction (see Sect. 2.4) activates all the hydroxyl functions. In order to avoid initiation by the isopropoxy groups of Al(0/Pr)3. The in-situ formed zPrOH is removed by distillation of the zPrOH/toluene azeotrope. On the other hand, the ATRP of MMA is catalyzed by NiBr2(PPh3)3. The two aforementioned one-step methods provide block copolymers with controlled composition and molecular weights, but with a slightly broad MWD (PDI=1.5-2). 

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. 

If equimolar quantities of Mi and M2 are used in an azeotropic copolymerization, what is the composition of the feed after 50% of the copolymer has formed ... 

The plots in Fig. 6-2 illustrate an interesting characteristic of copolymerizations with a tendency toward alternation. For values of r and r2 both less than unity, the F /f plots cross the line representing F — j. At these interesections or crossover points the copolymer and feed compositions are the same and copolymerization occurs without a change in the feed composition. Such copolymerizations are termed azeotropic copolymerizations. The condition under which azeotropic copolymerization occurs, obtained by combination of Eq. 6-12 with d[Mi]/ii[M2] = [Mi]/[M2], is... 

Corresponding data for the alternating radical copolymerization of styrene (Mi)-diethyl fumarate (M2)(n = 0.30 and r2 = 0.07) are shown in Figs. 6-6 and 6-7. This system undergoes azeotropic copolymerization at 57 mol% styrene. Feed compositions near the azeotrope yield narrow distributions of copolymer composition except at high conversion where there is a drift to pure styrene or pure fumarate depending on whether the initial feed contains more or less than 57 mol% styrene. The distribution of copolymer compositions becomes progressively wider as the initial feed composition differs more from the azeotropic composition. 

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