Methyl styrene, determination

This method was first applied by McCormick27 and by Bywater and Worsfold11 to the system a-methylstyrene/poly-a-methyl-styrene, and the free energy, entropy and heat of polymerization as well as the ceiling temperature were determined. Similar studies concerned with the system styrene/polystyrene are being carried out in our laboratories. 

Various techniques have been used for the determination of oligomers, including GC [135], HPLC [136-138], TLC for polystyrene and poly a-methyl-styrene [139] and SEC for polyesters [140,141]. GC and PyGC-MS can also profitably be used for the analysis of the compositions of volatile products formed using different flame retardants (FRs). Takeda [142] reported that volumes and compositions of the volatile products and morphology of the char were affected by FRs, polymers (PC, PPE, PBT) and their reactions from 300... 

The Curie Point flash evaporation-pyrolysis gas chromatography-mass spectrometric method [32] described in section 2.2.1.2 for the analysis of aliphatic hydrocarbons in soil has also been applied to the determination of polystyrenes in soil via identification and determination of their unzipping pyrolysis products, such as styrene monomer, a-methyl styrene, 3-methyl styrene, 4-methyl styrene, a-3 dimethyl styrene, 3-ethylstyrene, a-4 dimethyl styrene, 3.5 dimethyl-styrene, a-2 or 2,5 or 2.4 dimethyl styrene also various phenyl ethers. 

Siviani, R. F., D. J. Worsfold and S. Bywaxer Anionic polymerization of a-methyl styrene. Part 3. Molecular weight determinations of sharp distribution polymers. Trans. Faraday Soc. 55, 2124 (1959). 

Tg taken as midpoint in baseline transition at a heating rate of 10°C/min. b Inherent viscosity, (lnijr i)/c, where c = 0.25 g/dL, in benzene. c Rohm and poly (methyl methacrylate). Plexiglas type V-811. d Prepared by radical suspension bead polymerization by J. L. Tucker. Dissolved in benzene, precipitated, and freeze dried from benzene. Numbers in parentheses are the percentages of styrene determined by NMR. 

The dimeric dianions are stable. The rate of dissociation of K", a,a ,K" was determined by the following procedure (2)- a-methyl styrene perdeuterated in phenyl groups, a5D, was prepared and converted into dimeric dianions, K , a5j) a5j) Their THF solution... 

The a-methyl resonance in poly(o -methyl styrene) is found to be split into three peaks which are assigned to isotactic, heterotactic and syndiotactic triads. Fractions of the polymers in the three configurations determined by the area of these peaks are given below for poly(o -methyl styrene) prepared with two different catalysts [S. Brownstein, S. Bywater, and D. J. Worsfold, Makromol. Chem., 48, 127 (1961)] ... 

An attempt to determine the sequential equilibrium constants, Ki, K2, etc., was reported by Vrancken et al.183). They initiated polymerization of a-methyl styrene by a stepwise addition of the monomer to a dilute solution of its dimeric dianions in tetrahyd-rofuran. After each addition the concentration of the residual, equilibrated monomer was determined, and its value was plotted vs. the total concentration of the supplied monomer. The resulting curve is shown in Fig. 4, and its shape allows, in principle, the determination of Ki, K2 and Kp = K3 = K4, etc. Although the approach is sound, this method gives only a reasonable estimate of Kt because the deviation of K2 from the Kp s value is too small to be determined. The maximum seen in Fig. 4 arises from an increase in the activity coefficient of the monomer caused by increasing volume fraction of the polymer - an effect discussed earlier. 

It is appropriate to describe at this junction a technique leading to the determination of the dimerization rate of radical-anions derived from the monomers96. Flash-photolysis of 1(T6 M THF solution of the potassium salt of the dimeric-dianions of a-methyl styrene, K+, aa, K+, results in their photodissociation into a-methyl styrene radical-... 

Noda, Kato, Kitano, and Nagasawa23 have made systematic measurements of the osmotic pressure in order to verify (15.4.21). They used seven samples of poly(a-methyl) styrene of different molecular masses (see Table 15.13). Each sample was obtained by anionic polymerization, followed by a fractionation aimed at a reduction of polydispersity. The latter is characterized by the ratio Mw/Afn < 1.01. The solvent used was toluene. The interaction b for poly(a-methyl)styrene in toluene, experimentally determined, is about 1.5 nm1. 

The other structural feature that plays a dominant role in determining radical cation lifetimes is the presence or absence of methyl groups at the p-position. For example, the p-methyl-styrene radical cation has a lifetime that is 100-fold longer than that of the parent styrene radical cation and the addition of the methyl group to the P-position of the 4-methoxystyrene radical cation results in a further threefold increase. Conversely, the presence of an a-methyl group has little effect, with the lifetimes of the a-methylstyrene and a-methyl-4-methoxystyrene radical cations being similar to those of the styrene and 4-methoxystyrene radical cations, respectively. 

From these data determine the second virial coefficient and the theta temperature of poly(a-methyl styrene) in cyclohexane, knowing that K = K hl AhlAcf, where K = 18.17 mol cm , the refractive index increment (d /dc) is 0.199 ml gr, and the temperature dependence of the refractive index is expressed by = -0.0005327 x T (°C) + 1.446. Static light-scattering measurements were carried out by Zimm (1948b) on polystyrene in butanone at 340 K at two concentrations. 

The equilibrium concentrations [M] of the monomer at the poly-merization equilibrium fluctuate widely according to the constitution. At 25°C, it is found, for example, in bulk polymerization that [M] is 10" mol/dm for vinyl acetate, 10 mol/dm for styrene, 10" mol/dm for methyl methacrylate, and 2.8 mol/dm for a-methyl styrene. Since the equilibrium concentrations are related to the free energy of polymerization, and this depends on the enthalpy and entropy of polymerization, then it is necessary to determine the influence of the constitution on HZp and S p. 

Fig. 25. Solubility values for styrene and methyl methacrylate in aqueous emulsions. A water in styrene, determined with either Karl-Fischer titration or cloud point (261) A strene in water, determined with formaldehyde-sulfuric acid reagent (261) V styrene in...

The critical value above which the two polymers phase separate can be determined from equation 22 for various mixtures with ri = r2, and xi2 can be compared to the corresponding difference in solubility parameters, as shown in Table 1. The tolerated difference between the solubility parameters for miscibility to be achieved decreases with r and, for high molecular weight polymers to mix, the solubility parameter must be very close. For example, polystyrene ([5 = 18.4 (J/cm )° l and polyla-methyl styrene) [5 = 18.1 (J/cm )° ] are predicted to be miscible up to Mn fi0000 while for miscibility to be achieved between poly(methyl methacrylate) [3 = 19.0 (J/cm )° ] and poly(methyl acrylate) [5 = 19.fi (J/cm )° l Mn needs to be lower than 13000. Miscibility is expected to be strongly molecular/weight-dependent, as illustrated for polystyrene/polyla-methyl styrene) blends in References 11 and 12. 

The monomer ratio of styrene-methacrylate/acrylate copolymers is determined from the intensity ratio of the carbonyl band at 1730 cm for the methacrylate and aromatic ring band at 699 cm for the styrene component. In the measurement, a baseline is drawn between 1990 and 630 cm , and the intensity ratio of the 1730 and 699 cm bands is determined. Styrene content is determined from the empirical equation, percent styrene = 71.4 x ( 599/ 1730) [66,67]. If the methacrylate and acrylate are both present in the same copolymer, the methacrylate content may be determined from the intensity ratio of the ester-ether bands at 1032 cm" (acrylate) and 1021 cm (methacrylate). Figure 38 illustrates the procedure [68] for the measurement of styrene and styrene methacrylate in methyl styrene-acrylate copolymers and methyl methacrylate-modified styrene-acrylate copolymers, respectively. 

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