Fractionation, of poly

Thus the quantity on the left evaluated for a series of polymer fractions differing only in chain length should be independent of M. Results shown in Table XLII for fractions of poly-(methyl methacry-late) and of polyisobutylene covering unusually wide ranges confirm this prediction within experimental error. It is borne out also by less extensive results of sedimentation measurements on several other systems. Introduction of the values of v, p, and rjo enables... 

The polymers of 1,4-hexadienes have unusually wide molecular weight distributions. This is illustrated by the gel permeation chromatogram of the methanol-insoluble fraction of poly(5-methyl-1,4-hexadiene) in tetrahydrofuran (Figure 9). The polymer was obtained in 82% conversion and had an inherent viscosity of 2.1 dl./g. in toluene at 25°C. 

Figure 9. Gel permeation chromatogram of methanol-isoluble fraction of poly(5-methyl-1,4-hexadiene). THF solvent.

Fig. 3 Thermonephelometry curves of aqueous solutions of the o-, p- and s-fractions of poly(NVCl-co-NVIAz) synthesized at 65 °C from the feeds with initial molar ratios of comonomers equal to a 85 15 and b 90 10 (the data from [27])... 

All the described properties of such a s-fraction of poly(NVCl-co-NVIAz) synthesized at the temperature above the PST of the reacting system allowed us to draw the conclusion that the chains of this type had the comonomer sequence, which at the temperatures above the conformation transition facilitated the formation of polymer particles, where H-blocks are in the interior shielded by the P-blocks against additional intermolecular association. Such a behaviour of this copolymer in aqueous media is close to that of oligomeric proteins similar to casein [46] possessing a rather hydrophobic core surrounded by the polar segments. 

Unfortunately, data on the temperature-dependent solution behaviour of these fractions are not available to date, although it will be of considerable interest to compare, e.g., HS-DSC and NMR results for the bound and unbound fractions of poly(NiPAAm-co-NVIAz) over the temperature range characteristic of the conformational and phase transitions of NiPAAm homopolymers and copolymers. 

OC of Other Polymers. Figure 10 shows the fractionation of poly(ethyl methacrylate), polystyrene and poly(lauryl methacrylate). The THF/n-heptane mobile phase worked well for these polymers and UV absorptivity was sufficient for detection. The detection requirement was especially important because of the low concentrations resulting in OC. 

Fig. 29. Chromatograms of the fractions of poly(diethylene glycol adipate) and cyclic molecules obtained at critical conditions. (Column Si-100, eluent hexane-methylethyl ketone 8/92 vol.-%, u = 1 ml/min, volume of sample 10 pi, refractometer, t = 24 °C)...

Fig. 5.3. Extinction angle % vs. shear rate q for solutions of a fraction of poly(para-tert-butyl-phenyl methacrylate) (M = 7.4 x 10e) in carbon tetrachloride according to Tsvetkov and Shtennikova (140). Concentrations are indicated near the...

A remarkable enhancement of optical activity has been observed for the most stereoregular fractions of poly-a-olefins, with respect to the optical activity of the low-molecular-weight model compounds (Table 9). 

From the O. R. D. curves of the most stereoregular fractions of poly-[ S)-l-methyl-propyI]-vinyl-ether and poly-[(S)-2-methyl-butyl]-vinyl-ether and their model compounds, [(S)-2-methyl-butyl]-ethyl-ether and [(S)-l-methyl-propyl]-ethyl-ether(773a), it actually appears that, as in the... 

Osmometric measurements were also carried out for different fractions of poly [4-(l,l,3,3-tetramethylbutyl)phenyl methacrylate] in toluene at 25°C [50], The measurements were made at five or six different concentrations and extrapolated to infinite dilution. Figure 1.6 shows the plot tt/c versus c, which agrees with classical relations [51,52]... 

Table 1.3 Reduced osmotic pressures (tt/c)c=0, number average molecular weights M and osmotic second virial coefficient A2 for fractions of poly(l,l,3,3-tetramethylbutylphenyl methacry-late)(la) in toluene at 25°C. (From ref. [50])...

Table 17 Dependence of the weight fraction of poly(e-caprolactone) (PCL) grafted on silyldextran on the catalysator and the initial weight fraction of e-caprolactone by ROP in toluene...

Daneshvar M, Gulari E (1992) Supercritical-fluid fractionation of poly(ethylene glycols). J Supercrit Fluids 5(2) 143-150... 

Fig. 1 Fractionation of poly(vinylchlorides) using HPLC/GPC — Polyscience PVC VHMW Aldrich PVC solid line experimental Occidental Chemical Co. Suspension-polymerized PVC PD = polydispersity index = 2 (random distribution).

Dendrons attached as side chains on linear polymer chains behave different from free dendrimers and dendrons. Block copolymers, poly(3,5-bis(3,5-bis (benzyloxy)benzyloxy)-benzyl methacrylate-random-methacrylic acid)-block-poly(2-perfluorooctylethyl acrylate), possess poly(benzylether) dendrons and perfluorinated alkyl chains in their side chains (Fig. 4) [85], While an LB film of a copolymer with a medium substitution fraction of poly(benzylether) dendron side chain in poly(methacrylic acid) displays flat surface, a copolymer with high fraction of poly(benzylether) dendron side chains produces the zone texture. Dendron rich blocks are hydrophobic and oleophilic but perfluorinated blocks are solvophobic. Therefore, in this case, the solvophobicity-to-solvophilicity balance must be considered. As a result, copolymers with medium fraction of dendron are laid on solid substrate, but dendron blocks of copolymers with high fraction prefer to arrange at air side of air/ water interface and the fluorocarbon blocks are enforced to exist close to water subphase, resulting in the zone texture [86]. These situations of molecular arrangements at air/water interface are kept even after transfer on solid substrate. By contrast, when perfluorooctadecanoic acids are mixed with block copolymers with high dendron fraction, the flat monolayers are visualized as terrace [87], The monolayers are hierarchized into carboxyl, per-fluoroalkyl, and dendron layers, that is, hydrophilic, solvophobic, and oleophilic layers. In this case, perfluorooctadecanoic acids play a role for ordering of block copolymers. 

T 5 Tsvetkov, V. N., and O. V. Kaixktov Light dispersion and viscosity of solutions of the fractions of poly-p-tert-butylphenylmethacrylate in acetone. Zhur. Fiz. Khim. 33, 710 (1959). 

Fractionalization of Poly(2-Hydroxethyl Methacrylate-co-Methacrylic Acid)... 

The experimental dispersion curves which are similar to those in Fig. 66 yields the values of cellulose carbanilate versus molecular weight M (Fig. 71). The general character of experimental curves corresponds to the theoretical dependence depicted in Eq. (86 ). This permits the determination of the dipole moment of the monomer unit, mq. fto the initial slopes (mq/Mq) and the calculation of the parameter of chain rigidity S from their limit (mq/M) S. 

Figure 6.36 Shear rate at which the shear viscosity suddenly jumps dis-continuously upward as a function of the volume fraction of poly(vinyI chloride) (PVC) spheres of various diameters in dioctyl phthalate. Point A denotes the volume fraction at which two-dimensional hexagonal close-packed layers of spheres first touch. Point B is the volume fraction for three-dimensional simple cubic packing. (From Hoffman, reprinted from Trans. Soc. Rheol. 16 155, Copyright 1972 American Institute of Physics.)...

A fraction of poly (methyl acrylate) presents maximum damping at 0.50 Hz at 25°C. Make a rough estimation of the diluent that must be added to shift the maximum damping to 100 Hz at the same temperature. The glass transition temperatures of the diluent and the polymer are —70°C and 10°C, respectively, and their expansion coefficients are 8.5xlO K and 4,2 X respectively. 

SCF technology has spread quickly from molecules such as naphthalene to more complex substances such as polymers, biomolecules, and surfactants. Supercritical fluids can be used to reduce the lower critical solution temperature of polymer solutions in order to remove polymers from liquid solvents(6.26 The technology has been extended to induce crystallization of other substances besides polymers from liquids, and has been named gas recrystallization(4). In other important applications, SCF carbon dioxide has been used to accomplish challenging fractionations of poly(ethylene glycols) selectively based on molecular weight as discussed in this symposium, and of other polymers(. ... 

Table 2 Molecular parameters of the thermally precipitating and non-precipitating fractions of poly(NVCl-co-NVlAz) in aqueous solutions at 20 and 50 °C (the data from [42])... 

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