4-chlorostyrene copolymerization

It was found that a mixture of 4-vinylpyridine with p-chlorostyrene copolymerizes without any initiator in the presence of poly(maleic anhydride) at 50°C in DMF. The fact that poly(maleic anhydride) cannot initiate the polymerization of styrene or phenyl vinyl ether shows that poly(maleic anhydride) does not act as a normal anionic or cationic initiator. The compositions of copolymers obtained with various initial compositions of... 

The n and n, values in hexane for isobutylene and chlorostyrene copolymerization are both equal... 

The effect of solvents on the reactivity ratios in cationic copolymerizations can be seen from copolymerizations of isobutylene with p-chlorostyrene, using aluminum bromide as the initiator [376]. The ri and r2 values in hexane for isobutylene and chlorostyrene copolymerization are both equal to 1.0. In nitrobenzene, however, ri is equal to 14.7 and r2 is equal to 0.15. 

Among the most extensive studies of monomer reactivity have been those involving the copolymerization of various meta- and para-substituted styrenes with other styrene monomers (styrene, a-methylstyrene, and p-chlorostyrene) as the reference monomer [Kennedy and Marechal, 1983], The relative reactivities of the various substituted styrenes have been correlated by the Hammett sigma-rho relationship ... 

TABLE 6-9 Steric Effects in Cationic Copolymerization of a- and (i-Methylstyrenes (Mx) with p-Chlorostyrene (M2)a b... 

It has previously been shown that large changes can occur in the rate of a cationic polymerization by using a different solvent and/or different counterion (Sec. 5-2f). The monomer reactivity ratios are also affected by changes in the solvent or counterion. The effects are often complex and difficult to predict since changes in solvent or counterion often result in alterations in the relative amounts of the different types of propagating centers (free ion, ion pair, covalent), each of which may be differently affected by solvent. As many systems do not show an effect as do show an effect of solvent or counterion on r values [Kennedy and Marechal, 1983]. The dramatic effect that solvents can have on monomer reactivity ratios is illustrated by the data in Table 6-10 for isobutylene-p-chlorostyrene. The aluminum bromide-initiated copolymerization shows r — 1.01, r2 = 1.02 in n-hexane but... 

Radical Copolymerization of Styrene with 4-Chlorostyrene (Determination of the Reactivity Ratios)... 

Donor-acceptor interaction between monomer and polymer template offers an elegant methods of replication degree of polymerization. Similar system was described for copolymerization of vinylpyridine with p-chlorostyrene in the presence of poly(maleic anhydride) used as template. " ... 

Copolymerization of 3-chlorostyrene with glycidyl methacrylate to form GMC, resulted in G(x) increasing from 0.61 to 1.02 and G(s) from 0.16 to 0.42. Polyalkylmethacrylates are well-known to undergo main chain scission upon irradiation (10,23-6) e.g., polymethylmethacrylate has a G(x) =0 and G(.y) = 1.4(27). The increase in G(s) can therefore be attributed entirely to the presence of the methacrylate moiety. The enhanced G(x) value of GMC arises from the epoxide ring opening upon exposure and initiating cross-linking. 

Polymerization of Styrene Solutions of Volatile Hydrocarbons. Addition of Hydrocarbon before Polymerization. Bulk Polymerization. Expandable polystyrene was prepared inadvertently in 1945 in an attempt to bulk copolymerize 10% isobutylene with styrene. The product formed a low density foam when heated (96). An early method (1950) for rendering polystyrene expandable by petroleum ether was to dissolve 6 parts of petroleum ether in a 40% solution of polystyrene in benzoyl peroxide-catalyzed styrene and to hold the mass for 28 days at 32 °C. (124). In a recent version of this process, the monomer (chlorostyrene) and blowing agent (trichlorofluoromethane) in a poly (vinyl fluoride) bag were irradiated with y-rays (105). 

Considerable efforts have been directed, primarily in Kennedy s group [3], to synthesize a series of block copolymers of isobutene with isoprene [90,91], styrene derivatives [92-104], and vinyl ethers [105-107]. Figure 7 lists the monomers that have been used for the block copolymerizations with isobutene. The reported examples include not only AB- but also ABA- and triarmed block copolymers, depending on the functionality of the initiators (see Chapter 4, Section V.B, Table 3). Obviously, the copolymers with styrene derivatives, particularly ABA versions, are mostly intended to combine the rubbery polyisobutene-centered segments with glassy styrenic side segments in attempts to prepare novel thermoplastic elastomers. These styrene monomers are styrene, p-methylstyrene, p-chlorostyrene, a-methylstyrene, and indene. 

Dienes were copolymerized with vinyl monomers such as p-chlorostyrene 17), acrylic esters18,19), vinyl carborane, isoprenylborane 20,2)), and ferrocenyl derivatives 21). The reaction conditions were similar (65 °C, dioxane, 72 h, 3 mole % of initiator). Liquid low-molecular-weight (Mn < 7000) copolymers were obtained. High concentration of p-chlorostyrene 17), acrylates, or methacrylates18,19) in the initial solution leads to higher copolymerization yields compared with systems rich in diene. Molecular weight and polydispersity vary in the same manner 15). The reactivity of dienes decreases in the series chloroprene (85-98%) > butadiene (64-83%) > isoprene (43-73%). 

The effect of solvent on monomer reactivity ratios cannot be considered independent of the counterion employed. Again, the situation is difficult to predict with some comonomer systems showing altered r values for different initiators and others showing no effects. Thus the isobutylene-p-chlorostyrene system (Table 6-10) shows different ri and r-i for AlBrs and SnCU. The interdependence of the effects of solvent and counterion are shown in Table 6-11 for the copolymerization of styrene and p-methylstyrene. The initiators are listed in order of their strength as measured by their effectiveness in homopolymeiization studies. Antimony pentachloride is the strongest initiator and iodine the weakest. The order is that based on the relative concentrations of different types of propagating centers. 

Ionic copolymerizations are more complicated than free-radical ones. Various complicating factors arise from effects of the counterions and from influences of the solvents. These affect the reactivity ratios. In addition, monomer reactivity is affected by the substituents. They influence the electron densities of the double bonds and, in cationic polymerizations, the resonance stabilization of the resultant carbon cations. Yet, the effects of the counterions, the solvents, and even the reaction temperatures can be even greater than that of the substituents in cationic polymerizations. There are only a few studies reported in the literature, where the reactivity ratios were determined for different monomers, using the same temperature, solvent, and counterion. One such study was carried out on cationic copolymerizations of styrene with two substituted styrenes. These were a-methylstyrene, and with chlorostyrene. " The relative reactivity ratios of these substituted styrenes were correlated with Hammett pa values. The effect of the substituents on reactivity of styrene fall in the following order ... 

The effect of solvents on the reactivity ratios in cationic copolymerizations can be seen from copolymerizations of isobutylene withp-chlorostyrene, using aluminum bromide as the initiator. ... 

In copolymerization with styrene, isobutene is the monomer with the highest reactivity [594-596], In analogy with this it is possible to produce copolymers with a-methylstyrene or 4-chlorostyrene. 

This insensitivity to solvent polarity and temperature may relate to early cationic copolymerization studies carried out by Overberger, Arnold and Taylor and by Marvel and Dunphy. These groups found reactivity ratios for the cationic copolymerization of styrene and a-methylstyrene with chlorostyrene to also be insensitive to solvent and temperature changes. 

Subsequently, Overberger and coworkers proposed that insensitivity of reactivity ratios of these experimental parameters resulted from preferential solvation of the propagating carbenium ion by the most polar component present in the system (either nitrobenzene from the mixed solvent system they employed or chlorostyrene monomer). The active center in m-DIPB/m-DMB copolymerizations could be preferentially solvated by free m-DMB thus screening any effect of changing bulk solvent. However, Overberger, Ekrig, and Tanner 1 noted no dependence of reactivity ratios on initiation system whereas m-DMB/ m-DIPB copolymerizations are very dependent on the nature of the initiation system. Obviously, a more detailed study is required. 

Reactivity Ratio,s and r2 for the Copolymerization of Isobutylene (M ) and -Chlorostyrene (M2) in Various Solvents... 

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