Styrene solutions

This paper will describe the ways in which the present needs in tire rubbers can be met by preparing butadiene-styrene solution polymers of controlled structure. This appears especially realizable today, as a result of two new classes of organo-alkaline earth polymerization initiators,... 

Since we could not prepare a stable solution of the ester, we attempted its preparation in the styrene solution to be polymerised. Silver perchlorate was dissolved in this and the reaction was started by the crushing of a phial containing 1-phenylethyl bromide (under our conditions styrene was not polymerised by the silver perchlorate alone). The solutions became cloudy because of the formation of colloidal silver bromide, but no colour formation could be observed until the end of the polymerisation then the solutions became yellow, very like the reaction mixtures in which perchloric acid had been used as catalyst. The ester was found to be as effective a catalyst as anhydrous perchloric acid. Equal concentrations of the ester and the acid produced very similar polymerisations as shown in the Figure. The accelerating parts of the curves obtained with the ester as catalyst are readily explained by the fact that the reaction between silver perchlorate and 1-phenylethyl bromide is not instantaneous and therefore a steady increase in catalyst concentration characterises the first part of the polymerisation. 

Detailed studies led Gandini and Plesch to formulate the concept of pseudocationic polymerisations. These are reactions which show many of the characteristics of cationic polymerisations, but do not involve ions. Since they could see no other alternative compatible with general chemical knowledge, they formulated the reactive species as an ester, and they were able to support this view by direct experiments (formation of the ester in the styrene solution by metathesis). The evidence indicates that in the system styrene, perchloric acid, methylene dichloride, the poly(styryl perchlorate) ester requires four molecules of styrene for its stabilisation. When these are no longer available, the ester ionises, and the residual styrene is consumed by a very fast, truly cationic polymerisation ionisation of the ester is a complicated reaction which has been only partly elucidated. The initiation and propagation of the pseudocationic polymerisation can be represented thus ... 

The specific conductivity of the styrene solutions in ethylene dichloride was (1 to 2) x 10"9 mho/cm that of a 4.0 x 10 2 M solution of perchloric acid was 9 x 10 8 mho/cm. The conductivity of the acid solutions increased very slowly, and linearly, with time, but this change was so small that it did not cause any ambiguity in our results. It is due to a slow attack of the acid on the tungsten leads carrying the Pt electrodes. 

The main reason for introducing the oligostyryl ion VII into the scheme is that we believe it to be responsible for the very fast polymerisation of the last styrene molecules (Figure 5) and also the fast, abnormal polymerisation, especially obvious at low temperatures, which occurs when a high local concentration of acid is introduced into a styrene solution. 

The most widely used graft copolymer is the styrene-unsaturated polyester copolymer (Equation 7.35). This copolymer, which is usually reinforced by fibrous glass, is prepared by the free radical chain polymerization of a styrene solution of unsaturated polyester. 

Fig. 9. Hydrovinylation in a CFMR using 6a (a) and 6b (b) Conditions T = 23°C, p = 30 bar, flow rates ethene solution 2.5mLh (lOM), styrene solution 2.5mLh (1.8M), r = 4h, MPF-60 NF membrane (Koch Int., Diisseldorf, Ger.). Y, space time yield (mgL for 6a 0.05mmol Pd,...

Consider propagation by polystyryl sodium ion pairs in a 1 M styrene solution in tetrahydrofuran. For an ion pair concentration of 2.0 x 10-3 M, calculate the relative contributions of contact and solvent-separated ion pairs to the propagation process. Use appropriate data from Table 5-12. 

We wanted to be able to correct measurements of dielectric loss (conductance) and dielectric constant of polymerizing styrene solutions for whatever contribution arose from the dead polystyrene present in the solutions. What better way to make polystyrene that was free of all catalyst fragments and polar groups than to irradiate pure, dry styrene Using the same exhaustive drying technique that we were developing for our a-methylstyrene studies, we prepared a batch of pure, dry styrene. This was then to be irradiated under such conditions that approximately 15% conversion to polymer would occur. 

Fig. 8.16. Superimposed plots of y(y)M0 and J(y)/J° as functions of shear rate for poly( -methyl styrene) solutions (199). Curve A is for data at low concentrations and molecular weights curve B is for data at high concentrations and molecular weights. Data have been shifted along the shear rate axis to produre superposition. [Reproduced from Macromolecules 5,791 (1972).]...

Styrene in the irradiated glass matrix of an equimolar mixture of 2-methyltetrahydrofuran and n-butylchloride gives no spectrum. The absence of any spectrum due to the added styrene is a result of the fact that both the electrons and positive charges are captured and stabilized by the n-butylchloride and 2-methyltetrahydrofuran molecules, respectively, and they are unable to react with the styrene solute. This observation implies that the spectrum in the 2-methyltetrahydrofuran glass and that in the n-butylchloride cannot be attributed to the same intermediates, though their shapes are similar except for the difference in the width. 

Articles in which glass fibers are imbedded to improve impact strength often are made by mixing the fibers with an ethenylbenzene (styrene) solution of a linear glycol (usually l,2-propanediol)-butenedioic anhydride polyester and then producing a cross-linked polymer between the styrene and the double bonds in the polyester chains by a peroxide-induced radical polymerization (Section 29-6E). 

In connection with this discussion it is interesting to notice that the addition of sodium to a styrene solution in liquid ammonia does not produce any red color, while a transient red color is produced in a solution of stilbene (77). This unexpected phenomenon might be due to a steric hindrance operating in the molecule of stilbene. Apparently the transfer of an electron to the resulting radical is not obstructed while the transfer of a hydrogen atom is hindered. 

As explained above the rubber particle size in the final product is a measure for the rate of agitation—under otherwise equal reaction conditions—within the rubber-polystyrene-styrene solution during prepolymerization. Figure 1 shows that agitation is least effective if the organic... 

Secondly, if the first oxidation wave cannot be attributed to metallic copper oxidation, only one oxidisable compound is left, namely Cu(I). Indications for this can be found in the fact that in Cu(I)-containing styrene solutions, the limiting-current of this first oxidation wave is much higher than for Cu(II)-containing solutions. As a matter of fact, the first oxidation wave is expected to be absent in Cu(II) solutions. Apparently, the presence of this wave has to be attributed to the fact that some Cu(I) is present in the vicinity of the electrode surface. When the position of the current-potential curves in Fig. 12.2 reflects the standard potentials of the... 

Calibration curve of Cu(0) dissolution charge as a function of (x) Cu(l) or (o) Cu(ll) concentration in styrene solution containing 0.11 moll-1 THAP at 298.0K and v=50mVs 1. (Reprinted from Microchemical Journal, Vol 77, De Wael et al, Electrochemical detection. .., pp 85-92 (2004), with permission from Elsevier.)... 

An HDPE sample together with aliquots of TBPB/styrene solution (0.3 mol % TBPB) were sealed in stainless-steel-high pressure vessels that were purged with C02 gas, tared, and heated to the soak temperature of 80 °C. A heated high-pressure C02 manifold was used to pressurize the vessel to 243 bar. The vessel was then weighed to determine the mass of C02 transferred and then heated for 5 h at 80 °C. The styrene in C02 concentration was 28 wt %. After this initial soaking period, the vessel was heated to 100 °C and maintained at this temperature for the desired reaction time. The vessel was then vented, refilled with nitrogen, and maintained at 100 °C for 6 h. 

M. J. Menosveta and D. A. Hoagland, Light scattering from dilute poly(styrene) solutions in uniaxial extensional flow, Macromolecules, 24,3427 (1991). 

This explanation for the acid effect on the radiation polymerisation of styrene solutions has a direct application in a grafting context in that higher G(H) yields or lowered effective concentrations of radical scavenging impurities will enhance existing hydrogen abstraction reactions from the substrate to create potential grafting sites as well as increasing the... 

Fig. 20. Desorganization of the lamellar structure by dilution. Case of the copolymer SB.ll in styrene solution. The Figs, a, b, c, d, and e correspond, respectively, to styrene concentration 32,49, 70, 85, and 99%...

In toluene or styrene solution, SI and SIS copolymers exhibit a behaviour characteristic of copolymers swollen by a non-selective solvent11,35. In fact, the partition coefficient of the solvent is slightly in favour of polystyrene ([Pg.126]

The propagation stages of the cationic polymerization are not well understood. Egusa et al. have claimed that the long-lived absorption at 340 nm observed from the styrene solution in n-butyl chloride might be due to the bonded-trimer radical cation St St St4 which was formed by the reaction of a bonded dimer cation with a styrene monomer [24]. 

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