Poly fractionation systems

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... 

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. 

Ceresa (78,79) studied in detail the system poly(methyl methacrylate)-acrylonitrile. Figure 25 shows the change in composition with mastication time. A study of gel formation by the block copolymers was made by subjecting the isolated fractions of block copolymers to further mastication. A wide range of block copolymers with varying composition and structure was obtained (Fig. 26). 

Fig. 23. Density (in Mg/m3) of the system poly(2-hydroxyethyl methacrylate)-urea as a function of the weight fraction w of urea...

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... 

When these results are compared with those from the polymerization of the other monosubstituted oxiranes (9), it should be emphasized that the partly crystalline fraction of poly(styrene oxide), I, obtained in the presence of the ZnEt2/H20 catalyst is so far the only polyoxirane reported which does not follow Bernoullian statistics. Only one other case, namely that of the polymerization of phenylthiirane by a coordination catalyst system, is known until now which follows first-order Markov statistics (10). 

Figure 35.6 Dependence of p /p° on volume fraction of polymer. Curves a, b, and c are Raoult s law, Eq. (35.11), for p = 1, 100, and 1000, respectively. Curve d is Flory s equation, Eq. (35.9). Curvee is Eq. (35.14) with w/kT = 0.38. The experimental points are for the system poly-styrene/toluene O, 25°C A, 60°C , 80°C. (Adapted from E. A. Guggenheim, Mixtures. London Oxford University Press, 1952. Data from Bawn, Freeman, and Kamaliddin, Trans. Faraday Soc. 46 677, 1950.)...

An alternative solvent system for the fractionation of poly(vinyl acetate) consists of the precipitation of an acetone solution of the polymer with petroleum ether [60]. 

We have very little idea about the stoichiometry of the two major polysomal mRNP proteins, or their location on the mRNA, apart from the fact that the 8,000 dalton protein seems to be associated with the poly A tract at the 5 end (59) The function of the proteins is even more obscure. In cell-free translation assays the activity of polysomal mRNP is no greater than that of deproteinised mRNA (20). This result is open to the qualification that in crude cell-free systems the added deproteinised mRNA mi t pick up proteins from the cell-free extract and thereby be effectively converted into polysomal mRNP particles, but since the same result is obtained in highly fractionated systems (11) this reservation can probably be discounted. The major polysomal mRNP proteins are distinct from all seven recognised initiation factors (ll), and initiation complex formation is found to require the same set of seven factors regardless of whether polysomal mRNP or deproteinised mRNA is used (11). In short, there is no evidence that these proteins play a role in mRNA translation. 

Figure 3. Upper critical miscibility gaps in the system poly(isoprene)/poly(styrene) for indicated M values in kg/mol. Heavy curves cloud-points light curve splnodal by light scattering (10) W2 = weight fraction poly (styrene).

ZAV Zavarzina, A.G., Demin, V.V., Nifant eva, T.L, Shkinev, V.M., Danilova, T.V., and Spivakov, B.Ya., Extraction of humic acids and their fractions in poly(ethylene glycol)-based aqueous biphasic systems, Chim. Acta, 452, 95, 2002. 

Fig. 12 Cloud-point pressures in the system poly(ethylene-co-l-butene)/propane for different copolymer compositions (B is mole percent butene in the backbone 0% B = LDPE). Polymer weight fraction is about 0.05 wt%. Symbols represent experimental data [54], Lines show PC-SAFT calculations [53]...

Tables of Fractionation Systems for Different Poly(siloxanes) VII41 8...

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. 

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