Composition curve, copolymer

When Fj = 1/f2, the copolymer composition curve will be either convex or concave when viewed from the Fj axis, depending on whether Fj is greater or less than unity. The further removed from unity rj is, the farther the composition curve will be displaced from the 45° line. This situation is called ideal copolymerization. The example below explores the origin of this terminology. 

Aromatic polyesters that do not contain any flexible structural units are often nonmeltable or extremely high melting polymers that cannot be processed. Copolymerization is a way to obtain processable wholly aromatic polyesters The Tm versus copolyester composition curve is a U-shaped curve exhibiting a minimum that is generally well below the Tm of corresponding homopolymers. Liquid crystalline aromatic polyesters, for instance, are usually copolymers.72 An example is Ticona s Vectra, a random copolyester containing 4-oxybenzoyl and 6-oxy-2-naphthoyl units in ca. 70 30 mol ratio. This copolymer melts at ca. 

Variation of Styrene Content with Extent of Conversion. Figure 8 gives the relationship between copolymer composition and the extent of conversion for copolymers of butadiene and styrene (25 wt.7. styrene) prepared in toluene, at 30°C, with n-BuLi and barium salts of t-butanol and water. For comparison purposes, the copolymer composition curve is shown for the reaction initiated using n-BuLi alone. Copolymerization using n-BuLi results in very little incorporation of styrene into the copolymer chain until about 757. conversion, after which the styrene content increases very rapidly. In contrast, copolymerization using the barium salts and n-BuLi results in an increased incorporation of styrene at the same extents of conversion. 

Copolyesters of poly(3HB-co-3HV) have approximately the same degree of crystallinity as the homopolymer PHB and all copolymers show similar conformation characteristics as those observed for PHB [24,26,65]. They show a minimum in their melting point versus composition curve at a 3HV content of approximately 40 mol%. The apparent ability of the two different monomeric units to cocrystallize might result from the fact that the copolymers are prone to show isodimorphic behavior [21, 26, 66-70]. However, the considerable reduction of the heat of fusion upon 3HV inclusion, as reported by Bluhm et al. 

Figure 8 Effect of plasticization or copolymerization on (A) the modulus-time and (B) modulus -temperature curves. The curves correspond to different plasticizer concentrations or to different copolymer compositions. Curve B is unplasticized homopolymer A is eithei a second homopolymer or plasticized B.

The composition curve of the copolymers of MMA with St by the copolymerization initiated with PSS-Na was shown in Fig. 11. 

Second example was obtained from the copolymerization initiated with starch. The results were shown in Fig. 12. The copolymer isolated from the monomer phase was produced by the thermal polymerization and the composition curve was completely similar to the ordinary curve of the radical copolymerization product. The copolymer isolated from the water phase differed from the usual copolymer. The upper curve indicated that the HA formed by starch were soft, and soft MMA was much more easily incorporated than hard St. 

Figure 12. Composition curves of the copolymers of MMA and styrene by the copolymerization initiated with starch on standing (starch 0.1 g, CuCh 2HtO 0.5 mg, HsO 10 cm3, (MMA styrene) 3 cm 85°C,3hr)...

Copolymer composition curves in the copolymerization of MMA (Mi) and TrMA ( 2) with BuLi at -78°C are shown in Figure 1. From these curves the monomer reactivity ratios were determined to be ri=6.28 and 2 = 0.13 in toluene and ri = 0.62 and 2 0.62 in THF. In THF both the monomers showed similar reactivity. The compositional and configurational analyses of the copolymers indicated that the copolymerization approximately follows the terminal model in this solvent. 

T. C. Tranter (36) has studied the binary copolymers based on hexamethylene diamine and -phenylene dipropionic, 3-(/>-carboxy-methyl)phenyl-butyric, 2-(/>-carbomethoxy)phenylpropionic, hydro-quinone diacetic, terephthalic, adipic, or sebacic acids. In spite of the fact that only the copolymers of hexamethylene diamine with/>-phenylene dipropionic and with 2-(/>-carbomethoxy)phenylpropionic acids show a linear softening point composition curve, Tranter claims for isomorphism in the copolymers of all the systems. In fact, their X-ray examination shows that they behave in the same basic manner, the second component dissolving in the lattice of the first until a certain critical concentration is reached, where the lattice structure changes quite abruptly to that of the second component. 

Figure II. Composition of copolymers as a function of the polymerization temperature. Calculated by Equations 17 and 33. Dotted curves calculated by Equation 33.

Fig. 1. Copolymer composition curves for the copolymerization of methyl a-methoxyacrylate and styrene by AIBN in the presence (o) and absence ( ) of ZnCl2 at 60 °C and the polymerization rate in the presence of ZnCl2 (a).

Figure 4. Copolymer composition curves Top MMA-isoprene. Bottom MMA-acrylic acid.

The copolymer and feed compositions in random copolymerizations are identical only in the rare case when both reactivity ratios equal unity. The copolymer composition curves in Fig. 7-1 are typical of copolymerizations which are effectively random r r2 1). The curves show no inflection points they do not cross the 45° line corresponding to equal feed and copolymer compositions. There is no appreciable range of monomer feeds over which both monomers enter random copolymers in significant quantities if both reactivity ratios are not near unity, and the difficulty of making such copolymers becomes more severe as the difference in absolute values of and V2 increases. 

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. 

Thus by the use of Wood s approximation we were able to construct a complete 7 /composition curve for the polyfisobutylene-co- -pinene) system. In view of the experimental difficulties in obtaining the Tg for poiy( -pinene), the accuracy of the dot is questionable beyond V2 = 63 volume% ie., above 63 volume% pinene in the copolymer. Howewr, in the range from 0 to 63 volume% /3-pinene, the curve is considered to be accurate and, importantly, reveals that useful rubbery poly(isobutylene-co-j3 pinene) could be made with up to about 28 vohime% pinene, re, to a Tg of —40 °C. In agreement with cnir spectroscopic and reactivity ratio studies, the (admittedly somewhat limited) applicability of Eq. (1) developed for random copolymers also suggests a statistically random copdymer structure for our poly(isobutylene-co- pinene) products. 

Some data recently obtained on high pressure ethylene copolymerizations illustrate the quantitative aspects of an ethylene-based Q-e scheme (6). In Figures 3 and 4 copolymer composition curves for the ethylene-vinyl chloride and the ethylene-vinyl acetate copolymerizations are given. The monomer reactivity ratios for these two systems are tabulated in Table III along with Q values and e values for vinyl chloride and vinyl acetate calculated using ethylene as the standard (Q = 1.0 and g = 0). These Q and e values may be compared with those obtained using styrene as the standard. 

Equally important, the two comonomers were polymerized in parallel, with MMA consumption slightly faster, and the copolymer composition curve shows a shallow S-shaped profile, similar but not identical to those for the textbook examples of free radical MMA/styrene copolymerization. Thus, once again, the observation is consistent with some radical growth in the metal catalysis, and their difference from a conventional radical copolymerization is not deniable but not conclusive. 

The styrene-based random copolymers R-12 and R-13 were prepared by ruthenium and copper catalysts, respectively. For the former copolymer (R-12), the copolymerizations were investigated with various compositions of the two monomers, which revealed that the composition curve is similar to that of conventional radical copolymerizations.205 The latter copolymers (R-13) obtained with R—Br/CuBr have... 

As found previously for the PPO/PS system ( 2 ). the agreement between this prediction and experiment is fairly good when the trimethyl comonomer level in the copolymer is low. As the trimethyl comonomer level increases, however, the observed Tg variation with PEC in the blend falls increasingly below the line predicted by the Fox equation. The reason for this behavior is unclear. The concave upward Tg behavior shown for these blends is relatively normal for miscible systems, and there is no evidence of strong interactions, such as hydrogen bonding, between the components which can lead to convex upward Tg vs. composition curves (26). 

Figure 1, Monomer-copolymer composition curve for l-ethenyl-4-(2,3-epoxy-l-propoxy) benzene (Mi) with 4-vinylpyridine (Mg) f---------) Ti = 0.467 and T2 =...

Equation (7.18) may be used to calculate the instantaneous composition of copolymer as a function of feed composition for various monomer reactivity ratios. A series of such curves are shown in Fig. 7.1 for ideal copolymerization, i.e., r r2 = 1. The term ideal copolymerization is used to show the analogy between the curves in Fig. 7.1 and Aose for vapor-liquid equilibria in ideal liquid mixtures. The vapor-liquid composition curves of ideal binary mixtures have no inflection points and neither do the polymer-composition curves for random copolymerization in which riV2 = 1. Such monomer systems are therefore called ideal. It does not in any sense imply an ideal type of copolymerization. 

Thermodynamic equations are formulated for the isomorphic behavior of A-B type random copolymer systems, in which both A and B comonomer units are allowed to cocrystallize in the common lattices analogous to, or just the same as, those of the corresponding homopolymers poly(A) or poly(B). It is assumed that, in the lattice of poly (A), the B units require free energy relative to the A units and vice versa. On the basis of the derived thermodyn-amie equations, phase diagrams are proposed for the A-B random copolymers with cocrystallization. The melting point versus comonomer composition curve predicted by this diagram is very consistent with that experimentally observed for the P(3HB-co-3HV) copolymers, as shown in Fig. 21.1. It is suggested that the minor comonomer unit with a less bulky structure cocrystallize thermodynamically simpler than that with a more bulky structure. 

Copolymerization of tetrafluoroethylene and carboxylated perfluorovinyl ether is carried out either in solution, bulk or emulsion system with a radical initiator. A typical copolymer composition curve is given in Figure 1, where Ml or M2 was copolymerized with tetrafluoroethylene in bulk system at 70°C. The monomer reactivity ratios of tetrafluoroethylene and each vinyl ether are calculated as 7.0 and 0.14, respectively. 

Ml or M2 Content in feed (mole%) Figure 1. Copolymer composition curve. 

A composition curve of the copolymerization is shown in Figure 7. The composition of one component in copolymers is exactly 50 mole % over a wide range of monomer concentration of the component in monomer mixtures. These results strongly indicate that an alternating copolymerization takes place in the ethylene-hexafluoroacetone system. 

Figure 3. Copolymer composition curve for styrene-acrylonitrile...

---