Styrene viscosity measurements

Dawkins and Taylor109 dispersed poly(methyl methacrylate) (PMMA) or polystyrene (PS) particles in n-alkanes stabilized by AB block copolymers of styrene and dimethyl-siloxane. In these cases, styrene blocks act as anchors and dimethylsiloxane blocks give a surface layer. The thickness 6 of the dimethylsiloxane layer was determined by viscosity measurements as a function of the molecular weight of dimethylsiloxane blocks. 

Research grade poly(styrene-b-butadiene-b-styrene), designated as TR-41-1647, TR-41-1648, and TR-41-1649, were received from Shell Development Co. These block copolymers contain 26.8, 29.3, and 48.2 wt% polystyrene (PS), respectively. The average molecular weights, determined by intrinsic viscosity measurements in toluene at 30°C, were found to be 7-36-6, 16-78-16, and 14-30-14 in units of thousands. The microstructure of polybutadiene (PB) blocks was found to contain about 40 mol% in cis-1,4, 50% in trans-1,4, and 10% in 1,2 units. 

Problem 6.22 Weighed amounts of styrene (M) and -butyl mercaptan (S) in sealed glass ampoules were heated at 60° C for different periods of time. The polymers were then precipitated in methanol, dried in oven, and degrees of polymerization evaluated by intrinsic viscosity measurements. From.the data given below calculate the chain transfer constant (Cs) for the st5Tene/dodecyl mercaptan system at 60°C. 

T02 Torrens, F., Soria, V., Monzo, I.S., Abad, C., and Campos, A., Treatment of poly(styrene-co-methacrylic acid)/poly(4-vinylpyridine) blends in solution under liquid-liquid phase-separation conditions. A new method for phase-separation data attainment from viscosity measurements, J. Appl. Polym. Sci., 102, 5039, 2006. 

One often makes do with a viscosity measurement at a single concentration (usually 0.5%) to give what is called the inherent viscosity 17)0 = (lni7rei/c)c for this concentration. Fikentscher constants K are also used, particularly in the German literature, to characterize the classic polymers such as poly (styrene) and poly (vinyl chloride). [The K here is not to be confused with the K, defined by Equation (9-151), of the modified Staudinger equation.] K is evaluated from the relative viscosity at relatively high concentrations from tabular data and the equation... 

Torikai et aU have y-irradiated poly(styrene-co-methacrylate) copolymers and blends of polystyrene and polymethacrylate. They investigated the influence of irradiation on PMMA by ultraviolet and Fourier transform infrared spectroscopies and by viscosity measurements. In the case of the blends, the degradahon of the PMMA is similar to that awaited. No shielding effect... 

Oxidative degradation by splitting off the double bonds in the butadiene blocks allows the styrene blocks to be isolated. The degradation of the chains can be followed by molecular weight determinations or viscosity measurements (see Examples 3.47, 5.12, 5.14, and 5.15). 

Recently, Veith and Cohen (3) analyzed nylon 6 in TFE using the universal calibration method and peak retention data from narrow PMMA fractions. Silanized silica columns obviate the solvent incompatibility problem of TFE with styrene-based packings and give reproducible results. The accuracy of the calculated nylon 6 molecular weights was cross-checked with an independent end-group analysis (for M ) and intrinsic viscosity measurement (forMJ. 

One way to overcome such problems is to consider solvent(l)/polymer(2)/ polymer(3) ternary systems any method that determines either AG or its derivatives should make it possible to calculate Xi3- Thus, for example, osmotic pressure measurements were used to characterize PS/PVME blends dissolved in either toluene or ethylbenzene (Shiomi et al. 1985). The Xi3 was found to depend on the blends composition. Elimination of the solvent effects gave X23/E1 = —10 (7.41 — 11.0103). Thus, the system was expected to remain miscible up to a PVME volume fraction of 03 = 0.67. Osmotic pressure has also been used to determine X23 = 0.070 for PS with poly(p-chloro styrene) in toluene, 2-butanone, and cumene (Ogawa et al. 1986). For the same system, X23 = 0.087 was calculated from intrinsic viscosity measurements. Thus, the system is thermodynamically immiscible. More recently, osmotic pressure measurements in cyclohexanone of a ternary system resulted in X23ipoly(vinylchloride-co-vinylacetate) blends with a series of acrylic copolymers (Sato et al. 1997). 

Intrinsic viscosity measurements have been used to determine the molecular weight of PP [192-195], PET [196, 197], PE [198-204], PVC [203], polyacrylamide [205, 206], polyvinyl pyrrolidone [207], and styrene-methyl methacrylate copolymers [208]. 

The chemical resistance of polyester amide glass fibre composite is excellent [126]. A solvent mixture of CF3COOH/CHCI3 was used as a solvent for thermotropic LC polyester, based on 4-chlorocarbonyl phenyl esters of aromatic dicarboxylic acids and phenols or aliphatic diols for viscosity measurement. This indicates thermal stability in various organic solvents. [127]. Unsaturated aromatic LC polyesters, synthesized with the aim to fix the LC state, can be crosslinked by using styrene. The crosslinked matrix can be degraded by refluxing in 3 M aqueous sodium hydroxide solution and methanol in a vol. ratio of 3 2 [128]. 

The thermal polymerization of -MeOSt has already been mentioned by Staudinger and Dreher [239]. Heating a bulk sample to 90 °C for several days yielded a polymer with a DP = 390 (by viscosity measurements). Later, Russian authors [269] polymerized thermally all three isomers at 100 to 125 °C and found the p and m isomers to polymerize less rapidly than styrene, but the o isomer more rapidly. The stereoregularity of poly(/ -MeOSt) prepared by thermal polymerization in bulk at 60 °C was examined by Yuki et al. [270]. 100-MHz H-NMR spectra showed a rather split signal for the methoxy group and was interpreted in terms of pentad sequences. The analysis of the thermally polymerized sample showed a rather low content of syndiotactic triads. Kawamura et al. [244] studied the C-NMR spectra of o- and -MeOSt polymers prepared with BPO in toluene at 80 °C. They found both polymers to be rich in syndiotactic sequences [o derivative,, = 0.80 p derivative, P = 0.1 (P, = probability of racemic addition of monomer to the growing chain)]. 

In addition to these high charge density ampholytes, low charge density ampholytes were prepared by copolymerization of acrylamide with styrene sulfonate and MPTMA [96,97]. These polymers were studied by viscosity measurements in various concentrations of salts and HCI. In general these species showed chain expansion with increases in the salt concentration (using NaCI and CeCl2 salts) as well as with hydrochloric acid concentration. Some polyelectrolyte behavior was seen due to the non-stoichiometric ratios of the ionic species present. 

Depending on the concentration, the solvent, and the shear rate of measurement, concentrated polymer solutions may give wide ranges of viscosity and appear to be Newtonian or non-Newtonian. This is illustrated in Eigure 10, where solutions of a styrene—butadiene—styrene block copolymer are Newtonian and viscous at low shear rates, but become shear thinning at high shear rates, dropping to relatively low viscosities beyond 10 (42). The... 

Fig. 22.—Inhibition of the thermal polymerization of styrene at 90°C by benzoquinone. The log of the viscosity relative to that of pure monomer is here used as a measure of polymerization. The small induction period in the absence of quinone presumably was caused by spurious inhibitors present in the monomer. (Results of Foord. )...

The data in Table I are not directly comparable, since the viscosity of the 3-isomer was determined in benzene while the others were measured in DMSO. In addition, the first two polymers were prepared in bulk polymerizations, while the polymerization of methyl 3-vinylsalicylate was carried out with the monomer diluted 1 1 with benzene. Thus no certain conclusion can be drawn the data are, however, an indication of possible difficulty in radical polymerization of substituted styrenes bearing a phenol ortho to the vinyl group. 

V, is the molar volume of polymer or solvent, as appropriate, and the concentration is in mass per unit volume. It can be seen from Equation (2.42) that the interaction term changes with the square of the polymer concentration but more importantly for our discussion is the implications of the value of x- When x = 0.5 we are left with the van t Hoff expression which describes the osmotic pressure of an ideal polymer solution. A sol vent/temperature condition that yields this result is known as the 0-condition. For example, the 0-temperature for poly(styrene) in cyclohexane is 311.5 K. At this temperature, the poly(styrene) molecule is at its closest to a random coil configuration because its conformation is unperturbed by specific solvent effects. If x is greater than 0.5 we have a poor solvent for our polymer and the coil will collapse. At x values less than 0.5 we have the polymer in a good solvent and the conformation will be expanded in order to pack as many solvent molecules around each chain segment as possible. A 0-condition is often used when determining the molecular weight of a polymer by measurement of the concentration dependence of viscosity, for example, but solution polymers are invariably used in better than 0-conditions. 

Mechanistic Ideas. The ordinary-extraordinary transition has also been observed in solutions of dinucleosomal DNA fragments (350 bp) by Schmitz and Lu (12.). Fast and slow relaxation times have been observed as functions of polymer concentration in solutions of single-stranded poly(adenylic acid) (13 14), but these experiments were conducted at relatively high salt and are interpreted as a transition between dilute and semidilute regimes. The ordinary-extraordinary transition has also been observed in low-salt solutions of poly(L-lysine) (15). and poly(styrene sulfonate) (16,17). In poly(L-lysine), which is the best-studied case, the transition is detected only by QLS, which measures the mutual diffusion coefficient. The tracer diffusion coefficient (12), electrical conductivity (12.) / electrophoretic mobility (18.20.21) and intrinsic viscosity (22) do not show the same profound change. It appears that the transition is a manifestation of collective particle dynamics mediated by long-range forces but the mechanistic details of the phenomenon are quite obscure. 

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