Hydrophobic polyacids

Dubin P, Strauss UP. Conformational transitions of hydrophobic polyacids in denaturant solutions. The effect of urea. J Phys Chem 1973 77 1427-1431. 

The hydrophobic microdomains in the macromolecules discusssed here occur also in soaps and proteins. Indeed, one may consider our hydrophobic polyacids as a link between these two substances. Because these synthetic macromolecules allow the investigator great latitude in the design of their chemical structure, they promise to continue to enhance our insight into hydrophobic phenomena, as well as to permit their exploitation for a variety of attractive applications. 

ULRICH P. STRAUSS, Professor of Chemistry, Rutgers University, the State University of New Jersey, graduated from Columbia University (A.B. 1941), then attended Cornell University to obtain a Ph.D. (1944). He was a Sterling Postdoctoral Fellow at Yale University from 1946-48. He has been on the Rutgers University faculty since 1948. His main areas of research are polyelectrolytes, polysoaps, DNA, specific counterion binding and hydrophobic polyacids and polyampholytes. 

Fig. 8. Schematic illustration of intramolecular micellization of a hydrophobic polyacid at varying...

In the present study a relation was sought for between the ionisation of an anionic monolayer and calcium binding. A hydrophobic polyacid the alternate copolymer of maleic acid and hexadecylvinylether has been utilised. 

In the present work, we use the model of the penetrated interface to interpret our results. We study the interfacial potential of ionized films of a hydrophobic polyacid H.P.A. the copolymer of maleic acid and of hexadecylvinylether. 

For block copolymers with a polyacid or polybase block, the structure and properties of micellar solutions depend on the pH. For example, Morishima et al. (1982b) found that for a poly(9-vinylphenanthrene)-poly(methacrylic acid) (PVPT-PMA) diblock in water, the rate constant for the fluorescence quenching of phenanthrene groups by oxidative non-ionic quencher is pH dependent. These authors suggested that at low pH the polyacid units are not fully ionized and may participate in the formation of hydrophobic domains, cooperatively with PVPT. An alternative explanation is that the PM A chains are less solvated when... 

The IMM of the polymer decreases peatly, when intramolecular hydrogen bonds are formed in macromolecules. This effect becomes apparent, for example, if the data on PMMA and PMA and the corresponding acids are compared. The data on organic solvents should be compared (Table 10). In water the IMM of polyacids decreases markedly not only because intramolecular hydrogen bonds are formed but also for other reasons (formation of intramolecular structures in PMAA and hydrophobic interactions of non-polar groups). For aqueous solutions of PAA, the action of intramolecular hydrogen bonds on IMM can be seen, if the values of timm for non-ionized (a = 0) and ionized PAA are compared (Table 10). 

In this respect, and to focus attention simply on PMA, the body of data presented by Liquori and coll, seems fairly conclusive. It should also be recalled that it had previously bear concluded from light scattering studies that the heat and entropy of dilution of PMA are negative 16). And this evidence leads Silberberg, Eliassaf and Katchalsky to assiune that there is a "particularly marked build-up of structure (of the solvent) in the solutions of PMA in other words hydrophobic bonding would greatly impose on the physico-chemical properties of this polyacid in dilute aqueous solution. In the system considered, "specific solvent effects thus appear to be extremely relevant. 

In Figure 4 we first present some typical adsorption data as a function of time. These data, taken from Paris and Cohen Stuart [25] are for the adsorption of a hydrophobically modified, weak polyacid (carboxypullulan modified with 12% hydrophobic dodecyl groups) onto the neutral, hydro-phobic substrate polystyrene. Measurements were made at low pH (where the polymer carries hardly any charge) and in the absence of salt. In Figure 4 we plot T(f) as a function of cbt as explained above, this will make curves measured at varying cb coincide, provided the adsorption resistances do not explicitly depend on time. As can be seen, this is an adequate assumption over a range of polymer concentrations from 5 mg L 1 to 100 mg L 1 and and within experimental error the curves coincide nicely. 

In studies on hydrophobic interactions and conformational transitions of selected hydrolyzed maleic anhydride-alkyl vinyl ether copolymers (I, 2), we found that under certain conditions neutralization by base caused phase separation in aqueous solutions of the hexyl and octyl copolymers. Both the hexyl and octyl copolymers are insoluble at low pH and require partial neutralization by a base for complete dissolution. Under certain conditions, these copolymers will again precipitate as their degree of neutralization is raised with more base. Insolubility at low pH has been reported for other polyacids (3, 4). However, the phase separation at high pH contradicts the wealth of data indicating that neutralization increases the water affinity of polyacids. 

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