Reactivity ratios values

Data points fall in Figure 11 fall between predictions using the two reactivity ratio values quoted by Gruber and Knell (10) in classical kinetics. 

Another reason for errors of the reactivity ratio values are an exactitude in the course of the treatment of the experimental data using the differential or integrated form of the copolymer composition equation. In the first pase, the dependence of X(x°) on the monomer feed composition x° experimentally determined at low conversions is used. In the second case, one should use the data on the dependence of the copolymer composition on conversion p or the current values of x under the measurements of p. 

Figure 7-2 includes some representative copolymer-feed composition curves for r, varying with rj constant at 0.8. Azeotropic feed compositions containing appreciable quantities of both polymers can be achieved only when the reactivity ratio values are close to each other. 

The fitting of corresponding feed and copolymer compositions to the copolymer equation to obtain reactivity ratio values is not without pitfalls. Many of the available rj and values in the literature are defective because of unsuspected problems which were involved in estimation procedures, use of inappropriate mathematical models to link polymer and feed compositions, and experimental or analytical difficulties. 

The last four methods cited [8-11] are statistically inexact, in that they cannot give good estimates of the reactivity ratio values, but they can provide good estimates of r and r2 if the copolymerization experiments are suitably designed. 

Deviations from the behavior of the simple copolymer model have been noted for various systems and have prompted the development of alternative models, all of which use more parameters than the two reactivity ratios in Eq. (7-1. ). Such models will often fit particular sets of copolymerization data better than the simple copolymer model. It appears in retrospect, however, that many of the apparent deviations from this model may be accounted for by large uncertainties in reactivity ratio values. The inadequacy of the simple copolymer theory can be established only if deviations between calculated and observed copolymer compositions arc shown to be systematic as the feed composition or monomer dilution is varied. Random errors do not necessarily show that the basic model is inapplicable. 

These monomers differ greatly in reactivity (Fig. 24), propene being the more reactive. Reactivity ratio values with three catalyst systems have been reported (Table 23) [199]. 

The effect of reversibility in Scheme (15-1) is shown by the influence of [THF], and temperature on reactivity ratio values for the copolymerization of THF with PO. A quantitative description of a system with one monomer copolymerizing reversibly is given below. 

The viscosity data of the copolymers are shown in Table 4. The intrinsic viscosity data were found to be in the range of 0,23 to 0.91 dl/gm in toulene at 26 C. This reveals that as the TCA content in the copolymer increases the viscosity decreases. This is due to the greater reactivity of TCA radical at the growing chain end facilitating the propagation rates as compared to termination. This is proved by the reactivity ratio values shown in Table 3. 

Table 3.5 summarizes typical reactivity ratio values for binary systems including styrene, alkyl methacrylate, alkyl acrylate and vinyl acetate. Values for the (meth)acrylates have negligible differences within the series of alkyl esters (e.g., methyl, butyl, dodecyl) [27]. Figure 3.1... 

Ueda et al. conducted a systematic study involving the copolymerization of MPC with other vinyl compounds by conventional radical polymerization. Typically, when the MPC was copolymerized in solution with styrene (St) and various alltyl methacrylates such as n-butyl methacrylate (BMA, forming PMB), f-butyl methacrylate (t-BMA), n-hetyl methacrylate (HMA, forming PMH), n-dodecyl methacrylate (DMA, forming PMD), or n-stearyl methacrylate (SMA, forming PMS), the polymerization progressed very well, and a statistically random sequence was obtained. The radical copolymerization of MPC (Ml) and St (M2) in ethanol resulted in the following copolymerization parameters monomer reactivity ratio for Mi and M2 are ri = 0.39, V2 = 0.46, respectively. Also, the Qi and values of the MPC are calculated as Qi = 0.76 and e-i = + 0.51, respectively. In addition, for an MPC (Mi) and MMA (M2) system, the monomer reactive ratio values are ri = 1.61, r2 = 0.66. 

Siloxy substitution at the 3-position of the indenyl ligand (17) was found to remarkably improve the 1-olefin copolymerization ability, whereas substitution at the 2-position (15) slightly reduced the copolymerization ability as compared to the unsubstituted 5. The reason for this was suggested to be mainly the increased coordination gap aperture of the 3-siloxy-substituted complexes. Table 1 summarizes the ethylene reactivity ratio data obtained for the siloxy-substituted complexes 15, 16, and 17 The large difference in the ethylene and comonomer reactivity ratio values, the product of which is much below unity, emphasizes the prevailing tendency of the catalysts to produce copolymers with isolated comonomer units. The reason for the 15 0% lower incorporation of 1-hexadecene than 1-hexene was explained by the higher steric bulk and lower rate of diffusion of the longer a-olefin. 

Using Eq. (32) and feed and terpolymer composition data, a copolymerization composition diagram can be drawn, compared with the theoretical curves, and the coefficients of the Mayo-Lewis equation, riK and / 2jK estimated (Table 10.23). Fineman-Ross plots may also be used to estimate the Mayo-Lewis coefficients. These dimensioned apparent or modified reactivity ratios deviate from the true reactivity ratio values the more greatly the equilibrium constants differ from unity. 

Table 1. Literature terminal reactivity ratio values for SAN copr mer-ization...

VDF-HFP copolymerizations with in-line monitoring of the NIR and the MIR region provide access to conversion of both monomers as a function of time, as is illustrated in Figure 26(a). Since reacted monomer is converted into copolymer units, information on copolymer composition as a function of monomer feed composition is available. With one reactivity ratio value being below unity and the other one above unity, copolymer composition always differs from comonomer feed. 

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