Copolymerization parameter

Equation (70) itself is, of course, no more illustrative than eqn. (66) but its graphical representation provides a clearer picture of the dependence of copolymer composition on the momentary relative contents of the two monomers in the mixture. The copolymerization diagram, as the F, = fft) dependence is called, also clearly illustrates the role of the copolymerization parameters in copropagation (see Fig. 17). 

It has become customary to divide the common copolymerizations into several groups. The grouping depends on the parameter values 

In this case, copolymerization is ideal the relative contents of the two monomers in the monomer mixture and in the product are identical. The copolymerization curve forms a diagonal in the square copolymerization diagram. 

Neither of the monomers is able to homopolymerize. If a polymeric product is formed, it can only be a strictly alternating copolymer. The copolymerization curve is a horizontal straight line dividing the diagram into two equal rectangles (Fl = 1/2, independent of/,). 

Copolymer composition can be expressed by a single parameter. The copolymerization equation (66) is simplified to a form derived by Wall [168] in the first attempt to characterize copolymerization quantitatively 

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Acrylamide copolymerizes with many vinyl comonomers readily. The copolymerization parameters ia the Alfrey-Price scheme are Q = 0.23 and e = 0.54 (74). The effect of temperature on reactivity ratios is small (75). Solvents can produce apparent reactivity ratio differences ia copolymerizations of acrylamide with polar monomers (76). Copolymers obtained from acrylamide and weak acids such as acryUc acid have compositions that are sensitive to polymerization pH. Reactivity ratios for acrylamide and many comonomers can be found ia reference 77. Reactivity ratios of acrylamide with commercially important cationic monomers are given ia Table 3. 

Table 4. Copolymerization Parameters of Vinyl Acetate (M ) and Comonomers (M2)...

Several wide-porous affinity and size-exclusion chromatographic supports were prepared by Ivanov, Zubov et al. by means of acylation of aminopropyl-glass supports by copolymers of N-vinyl pyrrolidone (N-VP,1) and acryloyl chloride (AC,2), M = 7700 and 35000 respectively [50, 51]. The copolymers prepared by free radical copolymerization contain their units almost in equimolar proportion, with high tendency to alternation expected from the copolymerization parameters (rj = 0.035, r2 = 0.15 [52]). Residual carbonyl chloride groups of the chemisorbed copolymer could be transformed to 2-hydroxyethylamides which were solely... 

Table 3 shows that the small activation enthalpies of the reactions (3) and (4) are clearly affected by the zero point energy corrections. But the relative order of the activation enthalpies remains the same with or without the corrections. The activation entropies have great negative values, which is of mechanistic interest (see part 4.3.1). However, because of their similarity, when comparing the three reactions to one another they have only small importance, e.g. for estimation of copolymerization parameters (see part 4.3.2). 

It was possible to formulate a rule describing how the copolymerization parameters depend on the polarity of the solvent used. This rule is a result of contemplation about the connection between the copolymerization parameters and propagation rate constants during the cationic polymerization as well as about the changes of solvation of educts and activated complexes of the crossed propagation steps in solvents with varied polarity 14 U7). The rule is as follows ... 

The copolymerization parameters for copolymerization of dilactide and e-caprolactone catalyzed by stannous octoate, stannous chloride, and tetrabutyl titinate have been determined (5). 

Please note due to differences in the copolymerization parameters of n-butyl acrylate and methacrylic acid a continuous addition of the monomer mixture is necessary in order to achieve a homogeneous composition of the copolymer product. 

N, N, iV-trimethyl-lV-methacrylamido-2-ethylammonium chloride (salt V), can be compared with networks copolymerized with salt I. For the system AAm/ salt V, one can expect more favourable copolymerization parameters than for salt I of the methacrylate type, which will lead to a more random structure of the copolymer formed. 

Internal plasticizing demands a chemical relationship between the components which constitute the product. Therefore, good effects can be expected from copolymers of styrene and isobutylene, ethylene, or diolefins like butadiene or isoprene. Internal plasticizing of PVC can be effected by copolymerizing vinyl chloride with acrylates of higher alcohols or maleates and fumarates. The important ABS products are internal copolymers of butadiene, styrene, and acrylonitrile. The hardness of the unipolymers of styrene and acrylonitrile can be modified by butadiene which, as a unipolymer, gives soft, rubberlike products. As the copolymerization parameters of most monomers are known, it is relatively easy to choose the most suitable partner for the copolymerization. When the product of the r—values is l, there is an ideal copolymerization, because the relative reactivity of both monomers toward the radicals is the same. Styrene/butadiene, styrene/vinyl thiophene, and... 

Copolymerization experiments38) have shown that 11 can be copolymerized with MMA, styrene and ethyl acrylate. The copolymerization parameters are listed in Table 3.10. 

Table 3.10. Copolymerization parameters of II with MMA, Styrene and Ethyl acrylate381...

On the basis of the copolymerization parameters (cf. Sect. 3.2.3) it could be assumed that the incorporation of the azo monomers into the terpolymer was invariably complete and this was also proved experimentally 50, 51 ... 

Recently the copolymerization parameters Zj and r2 have been determined for the copolymerization of poly-1,3-butylene glycol fumarate (Mj) with styrene (M2) and found equal respectively to 3.0 and 0.03 (211,219). 

Hart and de Pauw 98) used this emulsion technique on the system vinyl acetate-acrylic acid. It is well known that the copolymerization parameters rx and r2 are unfavorable in this system therefore the relative solubility of the two monomers exerces only a small influence on the composition of both sequences. The degree of homogeneity of the sequences has been evaluated, after alkaline hydrolysis, by measuring the tendency to lactonization in acid medium. While 72% of the acetate groups could be lactonized in the case of a random copolymer containing 37% vinyl acetate, only 14% are transformed in a block copolymer with the same initial composition. 

Table IV. Copolymerization Parameters from Calculations Using Equation 33...

Using Equation 37 copolymerization curves can be calculated again. A suitable choice of the copolymerization parameters allows a good fit of the curve to the experimental results. 

The copolymerization parameters for the higher temperatures were calculated from the values at lower temperatures using the Arrhenius equation. The copolymerization curves calculated by Equations 33 and 34 do not agree with the experimental results. 

Figure 15 shows that the copolymerization parameter r used in Equation 33 does not follow the Arrhenius equation. In a previous publication (29) measurements were carried out only in the temperature... 

Table VII. Copolymerization Parameters Used To Describe tbe Copolymerization of a-Methylstyrene (Mi) and Acrylonitrile (M2)...

Table VII gives all copolymerization parameters ri and r2 calculated by the different equations.

These investigations have demonstrated the successful application of cyclodex-trins in polymer synthesis in aqueous solutions via free radical polymerization or via a oxidative recombination mechanism. Some special aspects of cyclodextrins were found concerning the kinetics, chain transfer reaction, and copolymerization parameters [63],... 

The similarity in chemical structure of BD and IP allows the copolymerization by many Ziegler/Natta catalysts. To our knowledge, the first study on Nd-catalyzed copolymerization of BD and IP was reported by Monakov et al. [ 152, 153]. Theses authors copolymerized the two dienes with the catalyst system Nd stearate/TIBA/DEAC in toluene at 25 °C. The respective copolymerization parameters reported in this study are ted = 194 and np = 0.62. 

Shen et al. determined the BD/IP copolymerization parameters for the polymerization with the ternary catalyst system NdN/TIBA/EASC at 50 °C ted = 1.4 and np = 0.6 [92]. Over a wide range of BD/IP copolymer compositions the experimentally determined Tg values significantly deviate from the theoretical curve which was calculated by the Fox equation for random copolymers. Only for IP-contents < lOwt. % does the experimentally determined data coincide with the theoretical curve. Shen et al. also succeeded to synthesize block copolymers comprising poly(butadiene) and poly(isoprene) building blocks [92]. 

Hsieh et al. used NdCU-based catalysts for the copolymerization of BD and IP [134]. They determined the following copolymerization parameters ted = 1 and rip = 1. For a copolymer with a 50/50 composition (wt. % based) a single Tg = - 85 °C was found and for the dependence of 1/Tg on copolymer composition a linear relationship was obtained. 

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