Terpolymerization reactivity ratios

The terpolymerization and multicomponent composition equations are generally valid only when all the monomer reactivity ratios have finite values. When one or more of the... 

In copolymerizations of three monomers there are nine growing steps to be taken into account. From these, six reactivity ratios can be derived. They are difficult to obtain from terpolymerizations and are therefore taken from binary copolymerizations. 

The parameters a = l/rij5 the number of which equals m(m — IX are reciprocal reactivity ratios (2.8) of binary copolymers. Markov chain theory allows one, without any trouble, to calculate at any m, all the necessary statistical characteristics of the copolymers, which are formed at given composition x of the monomer feed mixture. For instance, the instantaneous composition of the multicomponent copolymer is still determined by means of formulae (3.7) and (3.8), the sums which now contain m items. In the general case the problems of the calculation of the instantaneous values of sequence distribution and composition distribution of the Markov multicomponent copolymers were also solved [53, 6]. The availability of the simple algebraic expressions puts in question the expediency of the application of the Monte-Carlo method, which was used in the case of terpolymerization [85,99-103], for the calculations of the above statistical characteristics. Actually, the probability of any sequence MjMjWk. .. Mrl 4s of consecutive monomer units, selected randomly from a polymer chain is calculated by means of the elementary formula ... 

When the reactivity ratios ry can be expressed in terms of the parameters of the well-known Q-e scheme of Alfrey-Price [20,157], the condition (4.20) always holds [147, 150] and in the case of terpolymerization the general Eqs. (3.8) and (4.10) transform into the simplified equation [158]. It is rather curious that similar equations have been derived at the end of the 1940s [159] within the framework of the Alfrey-Price scheme, being investigated even for the general case of copolymerization of arbitrary number m of monomer types. 

For the symmetrical copolymers the formula x4 = A, /A of the azeotropic composition has a surprisingly simple form since in this case A- = cOj/Bj = G)ia.iJa.Vv where the values of tOj = D4/D were determined above. Their expressions in a particular case of terpolymerization obtained by means of relations (4.16) and (4.17) lead to the well-known formulae [119, 166], where the azeotropic composition is expressed explicitly through the reactivity ratios ry. Note, that the terms partial and limited azeotropes were introduced initially for the processes of the production of symmetrical copolymers [126, 127],... 

First let us demonstrate the possibilities of predicting transparency and heat resistance of (styrene + methylacrylate + heptyl acrylate) terpolymerization of the products prepared at complete conversion of monomers. The elements ry of the matrix of reactivity ratios ... 

To predict the glass transition temperature of (styrene + methylacrylate + hep-tyl acrylate) terpolymerization products from Eq. (7.2) one should calculate the fractions of all dyads using reactivity ratios (7.4). Combining such calculations with experimental data on glass transition temperatures of homopolymers and alternating binary copolymers... 

The composition of llie copolymer formed from n monomers in addition polymerization can be expressed in terms of the monomer feed composition and n n — 1) binary reactivity ratios. Thus, for terpolymerization [16],... 

The coefficients 8.10 and 0.010 in the second equation are usually ascribed to the reactivity ratios rj and rj (Table 19). This catalyst produces poly-propene consisting mainly of syndiotactic stereoblocks, together with short disordered blocks resulting from head-to-head (hh) and tail-to-tail (tt) pro-pene enchainment and occasional isolated isotactic units, and if these features apply to copolymers prepared with vanadium catalysts, the reaction is in effect a terpolymerization. Locatelli et al. [322] derive the equation for monomer/polymer composition ratios... 

Whereas in the case of terpolymerization there is only one relationship of type (17), in the case of n monomers there are them. In fact, if a monomer, e.g. M, is fixed, the othas can follow it in n— 1) ways, to which (w — 1) products of the reactivity ratios correspond. 

The effect of the penultimate unit in binary copolymerization has been studi i extensivety 33,34,33). The analogous probkm in the ca of teipolymerization is rather complex 26) owing to the existence of twenty seven possible propagation reactions, compared with eight in the case of binary copolymerization. If for a certain terminal monomer imit in the growing chain a penultimate effect exists, the reactivity ratios in the Alfrey-Goldfinger terpolymerization eqs. (7) may be replaced as follows ... 

The conventional [Eq. (7.77)] and simplified [eq. (7.81)] terpolymeriza-tion equations can be used to predict the composition of a terpolymer from the reactivity ratios in the two-component systems M1/M2, M1/M3, and Ms/Ms- The compositions calculated by either of the terpolymerization equations show good agreement with the experimentally observed compositions. Neither equation is found superior to the other in predicting terpolymer compositions. Both equations have been successfully extended to multicomponent copolymerizations of four or more monomers [30,31]. 

The terpolymer composition can be predicted on the basis of binary copolymerization experiments. If, however, one (or more) monomer is slow to propagate one of the reactivity ratios will approach zero and eq. 36 will become indeterminate. This situation arises in terpolymerizations involving, for example, MAI I or AMS. Alfrcy and Goldfingcr" derived eq. 37 for the ease w hcrc one monomer (C) is slow to propagate i.e. and hence rc, and ren — 0). 

Effects of Composition. Reactivity ratio studies of the NaAMPS-AMPDAC pair showed high alternation as expected for ion-paired systems (i, 33). The acrylamide functionality of both monomers would also be expected to terpolymerize well with acrylamide. Therefore, the series of ter-polymers shown in Table II was prepared. Molecular weights, second virial coefficients, and intrinsic viscosities at 25 °C in 1.0 M NaCl solutions are given in Table III. The numbers following the AD AS AM acronym represent... 

Terpolymerizadon of la, Ic, and SO2 were carried out to prepare resist polymers by varying the la/lc ratio in the feed. The results are summarized in Table II. The terpolymerization proceeded smoothly, providing the polymer in >90 % yields in 3-4 hrs. Since the terpolymedzations were carried to near completion, the la/lc ratios in the terpolymers are similar to the feed ratios. We suspect that the reactivity ratios of la and Ic are not much different. What is noteworthy is that M and M, become exponentially smaller as the concentration of the fluoroalcohol unit increases in the polymer, pointing to the chain transfer involving the OH group. 

It can be seen that the monomer-polymer composition for terpolymerization in a CSTR will depend on the valnes of reactivity ratios. Consider the expression derived for monomer-polymer composition during copolymerization in a CSTR. Equation (10.12) rewritten in terms of monomer 1 composition only is... 

In the terpolymerization composition equation derived for terpolymers and given by Equations (10.23-10.25), what is the significance of equal reactivity ratios such as r 2 = 13 ... 

Consider the preparation of styrene-acrylonitrile and methyl methacrylate terpolymer in a CSTR. There can be 3x3 = 9 possible dyads formed. These are AA, AS, SA, SS, SM, MS, AM, MA, and MM. The reactivity ratios can be read from Chapter lO, Table 10.1 The terpolymer composition can be calculated using the terpolymerization composition equations for a CSTR given in Equations (10.23-10.25). The dyad probabilities were calculated using an MS Excel spreadsheet and listed in Table 11.3. Let AN be denoted as monomer 1, styrene as monomer 2, and methyl methacrylate as monomer 3. Assuming that the bond formation order does not influence the rate, that is. 

Co— and Terpolymerization of Ethene and Higher a—Olefins with MgHa Supported Ziegler Catalysts New Mechanistic Insight via the True Reactivity Ratios... 

Jenner and Kellou recently studied the pressure effect on azeotropy in free-radical terpolymerization of MA with acrylonitrile, dielthyl fumarate, methyl acrylate, methyl methacrylate, methyl vinyl ketone, vinylidene chloride, norbornene, a-methylstyrene, indene, and vinyl acetate, with styrene as the second comonomer common in all cases. It was found that ternary azeotropes were only possible for those systems where the first comonomers had positive e values, i.e., diethyl fumarate, acrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone, and vinylidene chloride. Surprisingly, the coordinates of the ternary azeotropes were very little affected by variations of the pressure from 1-3,000 bars. Since reactivity ratios in multi-component polymerizations are sensitive to pressure, causing terpolymer composition to also be pressure dependent, a shift of the ternary azeotropic point would be expected. Why this occurs awaits further clarification. 

Table 10.23. MA Terpolymerizations with Donor and Neutral Monomers Apparent and True Reactivity Ratios... 

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