X-ray scattering study of a poly(methacrylic acid) sample as a function of its neutralization degree

Heitz, Caroline; Rawiso, M.; François, Jeanne

doi:10.1016/s0032-3861(98)00252-3

Cited by 65 publications

(78 citation statements)

References 56 publications

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“…8,11,13 Recently, Heitz et al have shown that at low pH the conformation of PMA is larger than a compact sphere without water molecules inside it. 12 Also, they found that there is not aggregates in the whole range of pH.…”

Section: Introductionmentioning

confidence: 98%

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Effect of the Molecular Weight on the Dynamics of the Conformational Transition of Poly(methacrylic acid)

1999

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Stop flow pH jump experiments were carried out on poly(methacrylic acid), PMA, solution of various molecular weights. The fluorescence changes of the probe pyrene, which can locate in the hydrophobic PMA coil or in the aqueous phase, were used to monitor pH-induced events in the PMAwater system. At least two well-separated time regions for the pH-induced conformational change of PMA were observed: one with τ ) 1-2 s and another with τ ) 50-100 s. A theoretical model to quantitatively explain the observed kinetic changes is given. This is based on a model developed by Schwarz for the helix-coil transition of polypeptides and can be briefly described as follows. Any configuration of the polymer is characterized by a statistical distribution of segments in polar and hydrophobic regions. Then a conformational transition involves the change of a number of segments from one state to the another, and its kinetics corresponds to a relaxation process with the pH jump as the initial perturbation. Several details pertinent to unambiguous interpretation are also described briefly. This includes the rate of neutralization of the acid groups on PMA and the rate of solution of small pyrene crystals in a colloidal system. The above confusing effects were established and thus could be avoided in the actual pH-induced conformational changes of PMA.

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Section: Introductionmentioning

confidence: 98%

“…[1][2][3][4][5][6][7][8][9][10][11][12] The measurement of equilibrium properties, as a function of pH, has established that, at low pH, the macromolecule expands slowly as the charge density increases. At higher pH, after a certain expansion of the coil is achieved, a remarkable expansion of the PMA chain takes place.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Molecular Weight on the Dynamics of the Conformational Transition of Poly(methacrylic acid)

1999

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“…contraction of the polyelectrolyte was induced by chemical variation of the charge fraction on the polyelectrolyte chains [18][19][20], by lowering the pH [21], by addition of an organic solvent to aqueous solutions [24] or by addition of an inert salt [27]. Only some of those authors attempted to explicitly discriminate between compact spheres and pearl necklace chains [18,23,24,27], or at least considered their results to be a consequence of pearl necklace chains [17,20,21].…”

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confidence: 99%

“…Only some of those authors attempted to explicitly discriminate between compact spheres and pearl necklace chains [18,23,24,27], or at least considered their results to be a consequence of pearl necklace chains [17,20,21]. Although, the AFM technique revealed the first direct evidence of pearl necklace chains [27], results measured with dried films cannot be unambiguously transferred to the original solution.…”

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confidence: 99%

Shrinking of anionic polyacrylate coils induced by Ca2+, Sr2+ and Ba2+: A combined light scattering and ASAXS study

2006

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Abstract. Anionic polyacrylate chains (NaPA) form precipitates if alkaline earth cations are added in stoichiometric amounts. Accordingly, precipitation thresholds were established for three different alkaline earth cations Ca 2+, Sr 2+ and Ba 2+. Close to the precipitation threshold, the NaPA chains significantly decrease in size. This shrinking process was followed by means of combined static and dynamic light scattering. Intermediates were generated by varying the ratio MCl 2 /[NaPA] with M denoting the respective alkaline earth cation. All experiments were performed at an inert salt level of 0.01 M NaCl. Similar coil -to -sphere transitions could be observed with all three alkaline earth cations Ca 2+ , Sr 2+ and Ba 2+. Based on these findings, supplementary conventional and anomalous small angle x-ray scattering experiments using selected intermediates close to the precipitation threshold of SrPA were performed. The distribution of Sr-counterions around the polyacrylate chains in aqueous solution provided the desired scattering contrast. Energy dependent scattering experiments enabled successful separation of the pure-resonant terms, which solely stem from the counterions. The Sr 2+ scattering roughly reflects the monomer distribution of the polyacrylate chains. Different ratios of the concentrations of [SrCl 2 ]/[NaPA] revealed dramatic changes in the scattering curves. The scattering curve at the lowest ratio indicated an almost coil-like behaviour, while at the higher ratios the scattering curves supported the model of highly contracted polymer chains. Most of X-ray scattering experiments on intermediate states revealed compact structural elements which were significantly smaller than the respective overall size of the NaPA particles.

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“…[6,7] The solubilityand pH-induced conformational transitions of PMA depend on the stereochemical structure of the chain. [7] X-ray scattering, potentiometric titrations and viscosity experiments conducted on high-molecular-weight PMA in aqueous solution in the dilute and semi-dilute regime, in order to investigate the conformational structure and physical behaviour as a function of the degree-ofionisation, [8] have revealed that conformation of the PMA chain in the acid form ( f ¼ 0) is not exactly equivalent to that of a compact water-free sphere and that it exhibits coiled conformation for 0% ionisation (i.e. f ¼ 0) and a conformational transition induced by a change in the degree-of-ionisation.…”

Section: Introductionmentioning

confidence: 99%

Self-association behaviour ofatacticpolymethacrylic acid in aqueous solution investigated by atomistic molecular dynamics simulations

Chockalingam

Natarajan

2014

Molecular Simulation

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The self-association behaviour of atactic poly(methacrylic acid) (a-PMA) in water was investigated by atomistic molecular dynamics (MD) simulations. Simulations show that interchain association of a-PMA occurs only in its un-neutralised form, by hydrogen bonding between ZCOOH groups, which is in agreement with the experimental observation. Chain conformations, dihedral angle distributions, hydration behaviour, scattering structure factor and enthalpy-of-hydration (i.e. aqueous solvation) were analysed as a function of concentration for un-neutralised PMA, across dilute to concentrated regimes. The average kR g l of the chain remains unaffected in solution and also for amorphous undissolved a-PMA phase, confirming the occurrence of the approximate theta-solution condition for the first time, as revealed by simulations, in a polar hydrogen-bonding polymer aqueous solution. Chain hydration behaviour and scattering structure factor show significant changes in concentrated regime. Scattering intensity collapse occurs in concentrated PMA solution, due to the existence of the swollen regime captured for the first time by explicit-MD-simulations. The hydration of PMA is driven by H-bonding, specifically between H atoms of the COOH groups and O atoms of water molecules in the closest coordination shell. The enthalpy of hydration of PMA is dominated by PMA -water interactions (charges and H-bonding). The thermodynamic contributions of PMA -PMA and PMA-water interactions towards the electrostatics as well as the dispersion components of the total solvation-enthalpy become more favourable than water -water interactions.

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X-ray scattering study of a poly(methacrylic acid) sample as a function of its neutralization degree

Cited by 65 publications

References 56 publications

Effect of the Molecular Weight on the Dynamics of the Conformational Transition of Poly(methacrylic acid)

Effect of the Molecular Weight on the Dynamics of the Conformational Transition of Poly(methacrylic acid)

Shrinking of anionic polyacrylate coils induced by Ca2+, Sr2+ and Ba2+: A combined light scattering and ASAXS study

Self-association behaviour ofatacticpolymethacrylic acid in aqueous solution investigated by atomistic molecular dynamics simulations

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