Polymer fractionation poly

Fig. XV-1. Plots of t/CRT vs. C for a fractionated poly(methyl acrylate) polymer at the indicated temperatures in degrees Celsius. [From A. Takahashi, A. Yoshida, and M. Kawaguchi, Macromolecules, 15, 1196 (1982) (Ref. 1). Copyright 1982, American Chemical Society.]...

The phenomena we discuss, phase separation and osmotic pressure, are developed with particular attention to their applications in polymer characterization. Phase separation can be used to fractionate poly disperse polymer specimens into samples in which the molecular weight distribution is more narrow. Osmostic pressure experiments can be used to provide absolute values for the number average molecular weight of a polymer. Alternative methods for both fractionation and molecular weight determination exist, but the methods discussed in this chapter occupy a place of prominence among the alternatives, both historically and in contemporary practice. 

If the poorer solvent is added incrementally to a system which is poly-disperse with respect to molecular weight, the phase separation affects molecules of larger n, while shorter chains are more uniformly distributed. These ideas constitute the basis for one method of polymer fractionation. We shall develop this topic in more detail in the next section. 

For additional evaluation of the effect of hydrophobization and the molecular weight of the polymers on the biological immuno-stimulating activity, we investigated the ex vivo cytokine (interIeukin-6 [IL-6], and tumor necrosis factor [TNFj-inducing activity from human peripheral whole blood cells of hydrophobized polymers by use of fractionated poly(M A-CDA) with narrow poly-dispersity. Since this assay uses the intact human cells, it shows more accurate results than in vitro assay using cultured cell line [25]. 

As has been described in Chapter 4, random copolymers of styrene (St) and 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) form a micelle-like microphase structure in aqueous solution [29]. The intramolecular hydrophobic aggregation of the St residues occurs when the St content in the copolymer is higher than ca. 50 mol%. When a small mole fraction of the phenanthrene (Phen) residues is covalently incorporated into such an amphiphilic polyelectrolyte, the Phen residues are hydrophobically encapsulated in the aggregate of the St residues. This kind of polymer system (poly(A/St/Phen), 29) can be prepared by free radical ter-polymerization of AMPS, St, and a small mole fraction of 9-vinylphenanthrene [119]. 

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... 

Polymer gels and ionomers. Another class of polymer electrolytes are those in which the ion transport is conditioned by the presence of a low-molecular-weight solvent in the polymer. The most simple case is the so-called gel polymer electrolyte, in which the intrinsically insulating polymer (agar, poly(vinylchloride), poly(vinylidene fluoride), etc.) is swollen with an aqueous or aprotic liquid electrolyte solution. The polymer host acts here only as a passive support of the liquid electrolyte solution, i.e. ions are transported essentially in a liquid medium. Swelling of the polymer by the solvent is described by the volume fraction of the pure polymer in the gel (Fp). The diffusion coefficient of ions in the gel (Dp) is related to that in the pure solvent (D0) according to the equation ... 

Another complex obtained by template polymerization of dimethylaminoethyl methacrylate in the presence of polyCacrylic acid) was synthesized and analyzed by Abd-Ellatif. The procedure of separation was as follows to the complex dissolved in 10% NaCl solution, 10% NaOH solution was added dropwise and white gel was precipitated. Addition of sodium hydroxide was continued until no more precipitate was separated. The soluble polymer after dialysis was dried and identified as poly(acrylic acid). The insoluble polymer fraction was found to be insoluble in toluene, benzene, tetrahydrofurane, but soluble in acetone/water (2 1 v/v). Elemental analysis and IR spectra lead to the conclusion that this fraction consists of pure poly(dimethyl aminoethyl methacrylate) which was expected as a daughter polymer. 

Lopes JA, Gourgouillon D, Pereira PJ et al (2000) On the effect of polymer fractionation on phase equilibrium in C02 + poly(ethylene glycol)s systems. J Supercrit Fluids 16(3) 261-267... 

Cao, A., Arai, Y., Yoshie, N., Kasuya, K.I., Doi, Y. and Inoue, Y. 1999. Solid Structure and Biodegradation of the Compositionally Fractionated Poly(3-Hydroxybutyric Acid-Co-3-Hydroxypropionic Acid)s. Polymer, 40, 6821-6830. 

In solution, the UV absorption characteristics of polygermanes may be different from those in the solid state. Poly(dihexyl)germane in solution has a kmax value of 327 nm, whereas the same polymer fraction deposited as a thin film on a quartz plate exhibits two... 

In later studies on the homopolymerization of E-l,3-pentadiene with NdO/ TIBA/DEAC crystalline polymers with cis- 1,4-contents in the range 84-99% and a high isotacticity were obtained. It was found that the cis- 1,4-content increases when the polymerization temperature is decreased from room temperature to -30°C. The polymerization of E-2-methyl-l,3-pentadiene resulted in polymers which almost exclusively comprised cis- 1,4-units and no dependence of the cis- 1,4-content on polymerization temperature was observed. The obtained poly(2-methyl-l,3-pentadiene) was composed of various polymer fractions with different stereo regularities [165,166]. 

Milled rigid sheets of poly (vinyl chloride) on heating at 185°C. lose weight at a rate which increases with time. By polymer fractionation procedures, it was shown the rate of hydrogen chloride loss increases as the content of tetrahydro-furan-insoluble resin increases. The insoluble resin content accumulates at a rate which depends, in part, on the additive present. This insolubilization reaction is catalyzed by cadmium compounds. The increased dehydrochlorination rate of the insoluble crosslinked resins may result from the susceptibility of the crosslinked structures to oxidation and from the subsequent thermal degradation of the oxidation products. The effects of various common additives on the rates of insolubilization and weight loss are described. 

The chlorine content of Polymer Fractions I, II, and III was determined by gravimetric analysis and found in all cases to be within 1% of the value for undegraded poly (vinyl chloride). (Since it was difficult to remove the last traces of solvent, the actual chlorine content of the polymers was probably even closer to the theoretical value.) The chlorine content of the insoluble residue was much lower. Thus, the insoluble residue of samples obtained from the experiments illustrated by Table III contained typically only 46-49% Cl. 

Milled rigid sheets of poly (vinyl chloride) on oven aging at 185 °C. undergo a slow initial dehydrochlorination which, if continued long enough, results in the formation of a tetrahydrofuran-insoluble fraction. This insoluble polymer dehydrochlorinates much more rapidly than the soluble polymer fractions. 

The limiting volume fraction of free polymer <) ahove which phase separation occurs for two different solvents. M is the molecular weight of the free polymer. System poly isobutene-stabilized silica particles with polystyrene as the free polymer, a - 48 nm, fi = 5 nm. Initial concentration of particles, p/p0 = 0.05 temperature 308 K... 

Poly-s-caprolactone (—O—(CH2)4—CO—) , PCL, is a crystalline polymer of density 1.1 g/coT. When a sample of molecular weight M — 50,000 g/mol is blended with amorphous poly(vinyl phenol), PVPH, of molecular weight 1500 g/mol and density 1.2 g/cm, homogeneous mixtures are formed. The table below gives the values determined for the melting point of PCL as a function of the volume fraction poly(vinyl phenol), v. ... 

For low molecular weight fractions, the variation in the values of the compliance function increases as either the chain length or the temperature increases. The changes observed in the compliance with temperature for very low molecular weight fractions are illustrated in Figure 8.17 (16). This lack of thermorheological simplicity was also observed for other amorphous polymers, specifically poly(ethyl methacrylate) (21), poly( -butyl methacrylate) (22), poly( -hexyl methacrylate) (23), and low molecular weight poly(methylphenyl siloxane) (24). 

The styrene oxide polymerization by the ZnEt2/H20 (1/0.8) catalyst was found to result in the formation of two polymer fractions, a partly crystalline fraction, I, and an amorphous fraction, II. The syntheses of poly(styrene oxide) starting from the R monomer showed both polymers were formed by almost exclusively... 

From the Ah-NMR analysis of poly(3,8-d2-styrene oxide) obtained using ZnEt2/H20 as initiator Figure 2), the formation of the partly crystalline fraction can be described by first order Markov statistics, while that for the amorphous fraction follows Bemoulllan statistics. Different chain propagation mechanisms are, therefore, responsible for the formation of the two different polymer fractions obtained from this particular catalyst. Consequently, the existence of two different active centers, responsible for the two polymerization mechanisms and for formation of fractions I and II, are clearly indicated. 

This atom-abstraction route was also used for the preparation of polymeric networks from alkylated [3,3 ]bis-(trithia)ferrocenophanes. A bimodal molecular weight distribution, with maxima at 4/n 5,000 and 5 x 10, was obtained by GPC for the material from which a polymer fraction was isolated (4/ = 8.5 x 10 ). Low molecular weight poly(ferrocenylene perselenides) have also been prepared from the selenium analog of 114. These materials also undergo photodegradation upon exposure to UV light in air. ... 

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