Molecular weight of polystyrene

Mean dimension of particles in packing (pm) Molecular weight of polystyrene ... 

FIGURE 11.2 Selectivity of several individual pore size columns. This graph shows the resolution capability of Styragel HT 3, HT 4, HT S, and HT 6 columns. The selectivity [Eq. (I)] of these columns vs the molecular weight of polystyrene is plotted. (Courtesy of Waters Corp.)... 

Fig. 16. Changes in the number average molecular weight of polystyrenes prepared in toluene at 30°C using Zr(benzyl) as initiator at different initial monomer concentrations...

The characterisation of polymers is very difficult because of various inherent weaknesses observed in case of various polymers. The difficulty in characterisation can be well grasped from the fact that unlike low Molecular weight compounds, like benzene (M=78), methacrylate (M =100.12), vinyl chloride (M=62.5), etc. which have a fixed value o/Molecular weight, the polymers which are macromolecules, do not have a certain definite and permanent Molecular weight. For example, the Molecular weights of polystyrene varies between 50,000 to 10 million. 

Figure 5. Variation of relative spreading factor with the molecular weight of polystyrene standards. Key o SG, SEC unit 1 and 2 SDG, SEC unit 3 and U.

FIGURE 6.3 Molecular weight of polystyrene (PS) as a function of solvent and solvent concentration A = -butylmercaptan, B = carbon tetrabromide, C = carbon tetrachloride, D = o-cresol, E = p-cresol, F = m-cresol, G = phenol, H = s-ec-butylbenzene, 1 = cumene, J = ethylbenzene, K = chloroform, L = -heptant, M = toluene, N = benzene, where [S] = concentration of chain-transfer agent and [M] = concentration of styrene monomer. 

Figure 8 Distribution of the molecular weight of polystyrene after y-irradiation at 295 K of MTHF solution containing 10 wt.% of coupled polystyrene.

Molecular weight of polystyrene (av.) = 235,000 grams/gram mole... 

Figure 5. Graph of the diffusion coefficient extrapolated to infinite dilution (D°) vs. molecular weight of polystyrene (31).

Figure 2. Experimentaldata of average molecular weight of polystyrene formed in...

Fig. 8. Exclusion molecular weight of polystyrene gels, 30% styrene, 10% DVB, and 60% inert compound diethylbenzene, i-amyl alcohol a toluene do decane ...

Fig. 5. The dependence of the limiting volume fraction of the free polymer,

Fig. 10. The fraction of polystyrene intercalated C18FH for various annealing temperatures (PS 30, Mw=30,000) (left) and for various polymer molecular weights at 180 °C (right). The lines are the best fits to the data using equation 1.1. The molecular weights of polystyrene used were Mw=30,000 (PS30), Mw=68,000 (PS68) Mw=90,000 (PS90) and Mw =152,000 (PS152) adopted from reference [12].

The coefficients of transfer to styrene are larger than those to isobutene. For example, the molecular weights of polystyrene obtained by bulk... 

V/hile analysing the composition of phases of the full separation of the emulsion it was fo xnd that the experimentally found concentrations of polymers in these solutions differ from those calculated for the case when each polymer is present in one phase only. It can be supposed that due to the partial compatibility in both emulsion phases there are both polymers present, but the "rubber" phase is a polybutadiene solution with the admixture of small quantity of PS, and the "polystyrene" phase represents a polystyrene solution with the admixture of PB, On the basis that in model emulsions of equal compositions the voliirae of rubber phase increases as the molecular weight of polystyrene decreases, and My of homopolystyrene in the polystyrene phase increases (table IIlJ we can draw a conclusion that low-molecular fractions of polystyrene migrate into the rubber phase. 

The critical block sizes needed for domain formation are greater than those needed for phase separation in physical mixtures of the corresponding homopolymers. This is because the conformational entropy of parts of molecules in the block domains is not as high as in mixtures, since placement of segments is restricted by the unlike components to which they are linked. Thus the minimum molecular weights of polystyrene and c/i-polybutadiene for domain formation in AB block copolymers of these species are about 5,000 and 40,000, respectively [29]. 

The comparison of copolymers SEO and SCL has shown that the nature of the crystallizable blocks governs both the number of mesophases in the copolymers and the number of folds of the crystallizable chains In a solvent for the crystallizable block as well as in a solvent for the amorphous block, SEO and BEO copolymers dependent on temperature exhibit two mesophases separated by the melting of the PEO chains. SCL copolymers contain mesophases only in a solvent for the amorphous blocks and these mesophases disappears at the melting temperature of the PCL chains, where the two types of blocks become compatible For SEO copolymers containing less than 50% PEO, the number of folds of the PEO chains is determined by the molecular weight of polystyrene which remains the dominating factor at higher PEO contents. For SCL copolymers on the contrary, the number of folds of the PCL chains increases with the PCL content of the copolymer ... 

Kamath et ai (I97S) showed that the nonionic octylphenoxypolyethylene oxide emulsifier Triton X-ICK) contains a labile proton so that the molecular weight of polystyrene prepared using this emulsifier is abnormally low because of extensive transfer to the emulsifier. 

The molecular weight of polystyrene less than 500,000 MW can be measured accurately in THF with a two-angle light-scattering instrument... 

Figure 4.13 Light-scattering determination of the molecular weight of polystyrene in benzene (Problem 4.12).

Hi = height of curve at various counts XHi = total of all heights measured Mi = molecular weight of polystyrene at various counts. 

Molecular weight of polystyrene blocks, 23,500 overall molecular weight 107,000. 

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