Conformational transition of poly(<scp>L</scp>‐glutamic acid) in aqueous solution

Barone, G.; Crescenzi, V.; Quadrifoglio, Franco

doi:10.1002/bip.1966.360040505

Cited by 33 publications

(20 citation statements)

References 12 publications

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“…It only apparently differs for the two classes of polyelectrolytes. In the case of PAA and PMA the intrinsic viscosity continuously increases with increasing a, [20] while the experimental data of the reduced viscosity and the calculated intrinsic viscosity show a maximum at half neutralisation for the MA copolymers. [4,5c] In fact, the correct comparison must consider the whole a range for the acrylates with the first dissociation only of the MA copolymers, i.e.…”

Section: Resultsmentioning

confidence: 99%

Potentiometric Titrations of Maleic Acid Copolymers in Dilute Aqueous Solution: Experimental Results and Theoretical Interpretation

Delben¹,

Paoletti²,

Porasso³

et al. 2006

Macro Chemistry & Physics

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Summary: The paper reports a study on the flexibility of a family of 1:1 hydrolysed maleic anhydride (maleic acid, MA)–olefin copolymers in dilute aqueous solution. The copolymers were MA–ethene, MA–propene and MA–isobutene. The study was carried out in the absence and in the presence of monomonovalent salts and at different polymer concentrations. Experimental data showing the negative logarithm of the ‘apparent’ dissociation constant, pKa versus the degree of dissociation, α, experimental data were obtained from potentiometric titrations using NaOH, KOH or tetramethylammonium hydroxide as the base. The pKa data were fully described with calculated curves obtained using an extension of the counterion condensation theory of linear polyelectrolytes, in which a semiflexible model for the polymers was introduced. Under the present experimental condition, no relevant specificity of the monovalent counterions was apparently observed for the different copolymers. The calculated pKa versus α curves allowed the derivation of both the intrinsic dissociation constants of the first and the second dissociation steps for the different copolymers and the corresponding stiffness parameters built into the model. The agreement between the experimental and calculated data shows an appreciable success of the model. The results pointed to an increase of stiffness parallel to the increase of size of the olefin comonomer, in qualitative agreement with already published findings. Furthermore, for all copolymers the chain rigidity was larger in the α range of the first dissociation than in that of the second one. The former rigidity was attributed to the formation of intramolecular hydrogen bonds upon the first ionisation of the MA repeating units, followed by an increase of rotational freedom upon breaking of the H‐bond in the second dissociation step. Comparison of the rigidity parameters of the MA copolymers with the data obtained for other polyelectrolytes, both natural—poly(L‐glutamic acid) and pectic acid—and synthetic—poly(acrylic acid) and poly(methacrylic acid)—was also performed. magnified image

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Section: Resultsmentioning

confidence: 99%

Potentiometric Titrations of Maleic Acid Copolymers in Dilute Aqueous Solution: Experimental Results and Theoretical Interpretation

Delben¹,

Paoletti²,

Porasso³

et al. 2006

Macro Chemistry & Physics

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“…At pH 4, a "tightening" of the collapsed state occurs [26,88,112,113] as a consequence of hydrogen bonding interactions between carboxylic acid units and carboxylate anions [24]. viscometric measurements [3,117] indicate that PAA undergoes a relatively smooth change from a statistical coil at low pH to an extended state at high degrees of ionization as repulsive interactions between carboxylate anions dominate. At a critical pH, the concentration of anions is such that a macroscopic switch in conformation occurs between pH 4 and 6 to the expanded water-swollen state.…”

Section: Discussionmentioning

confidence: 99%

“…The fact that PAA adopts a random conformation at low pH [3,4,47,49,117] results in the inability of the polyelectrolyte to solubilize low molar mass organic material [17]. This is in stark contrast to the behavior observed for PMAA [6,17,18,60] as highlighted in Section 2.2.1.1: PMAA is known [6,17,18,60] to solubilize low-molecular weight hydrocarbons in its compact form in aqueous media.…”

Section: Steady-state Spectroscopymentioning

confidence: 99%

Optical Properties of Polyelectrolytes

Swanson

2010

Photochemistry and Photophysics of Polymer Materials

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A polyelectrolyte can be defined as a macromolecule with ionizable repeat units, which can consequently display pH-dependent behavior when dissolved in aqueous solution.As the term polyelectrolyte can also be extended to encompass natural biopolymers, which contain ionizable groups such as peptides, proteins, and DNA, it is perhaps not surprising that synthetic polyelectrolytes are often used as simple models for more complex biological systems. Indeed, many of the photophyscial techniques discussed in this chapter were developed by biologists and biophysicists interested in the conformational behavior and interactions of biopolymers [1].

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“…Isotactic poly(methacry1ic acid) (n?, = 250.000), conventional poly(methacry1ic acid) (n?, = 260.000), and styrene-methacrylic acid copolymer (1:4) were synthetized and purified in our laboratory. Preparation and characterization techniques have been described elsewhere (10). Poly(styrene sulfonic acid) was obtained by sulfonation of polyfstyrene) (Bios product, = 160.000), as already reported (11).…”

Section: Methodsmentioning

confidence: 99%