Static and dynamic light scattering of maleic acid copolymers (original) (raw)
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Structural and Dynamical Properties of Semirigid Polyelectrolyte Solutions: A Light-Scattering Study
Macromolecules, 2000
Dynamic and static light-scattering experiments were performed on aqueous solutions of the highly charged semiflexible polyelectrolyte chitosan in the dilute and the semidilute regime. In the dilute regime, typical good solvent behavior is found. However, in the overlapped regime the time autocorrelation function of the scattered electric field is found to be bimodal. The short time relaxation has a typical q 2 dependence, characteristic of diffusion, and the long time relaxation an approximately q 2 dependence, where q is the scattering wave vector. Static and dynamic light-scattering experiments were carried out to analyze the two modes. The fast mode is attributed to the relaxation of concentration fluctuations characterized by a cooperative diffusion mechanism of the polymer network meshes. The slow relaxation time appears to be related to the diffusion of polymer associations. The effect of the excess of salt concentration and polymer concentration was investigated.
Macromolecules, 1997
We combine static and dynamic light scattering techniques to study the structure and dynamics of hydrophobically modified polyacrylamide in aqueous solution. Two different length scales can be distinguished in the solutions. The first one corresponds to the usual structure of an ideal semidilute polymer solution, with a correlation length given by the size of the blobs. On that length scale, fluctuations of concentration relax by a cooperative diffusion mechanism. On a much larger length scale (>2000 Å), there is experimental evidence for a texture. The corresponding relaxation times appear to be related to the macroscopic viscosity of the surrounding polymer solution and might correspond to a viscoelastic relaxation of the texture embedded in this solution. This texture appears to be responsible for the interesting thickening properties of these associating random block copolymers.
Polymer, 2001
The coil-globule transitions of random (statistical) and alternating copolymers of styrene and methyl methacrylate in their theta solvents, cyclohexanol and 2-ethoxy ethanol were studied by using dynamic light scattering technique. The dimensions of the copolymeric chains show smooth and continous contractions below u temperatures. The hydrodynamic size, R h , of a random copolymer P(St-co-MMA) M w 4:59 £ 10 6 g=mol in cyclohexanol u 68:68C decreases to 48% of that in the unperturbed state at 56.58C. This copolymer shows a similar contraction behavior in a second theta solvent 2-ethoxy ethanol u 58:48C: The R h of this copolymer decreases again to 48% of that in the unperturbed state at 45.38C. An alternating copolymer of the same monomers P(St-alt-MMA) M w 2:62 £ 10 6 g=mol displayed a comparable chain contraction. The hydrodynamic size of this sample in cyclohexanol was reduced to 59% of that in the unperturbed state by decreasing temperature from 60.8 to 53.38C. For the random and alternating copolymers studied in this work, the temperature interval from the u-state to the collapsed state is narrower compared to that of the PMMA homopolymer. q
Macromolecules, 2004
The structure of aqueous solutions of sodium maleate copolymers with comonomers of variable hydrophobicity are examined using a combination of small-angle neutron scattering, small-angle X-ray scattering, and rheometry. Semidilute solutions of the copolymers made with mildly hydrophobic comonomers exhibit scattering and rheology that are typical of flexible polyelectrolytes, with a correlation length scaling with polymer concentration as c -R with R ) 1 /2 and specific viscosity scaling as c 1/2 /c 3/2 when unentangled/entangled. In contrast, copolymers with more than eight carbons in their hydrocarbon comonomer form micelles (globules) at low concentrations and molecular weights. For these more hydrophobic copolymers, the correlation length scales as c -R with R < 1 /3 and the viscosity remains small until a relatively high concentration at which the globules start to overlap. Once these more hydrophobic copolymers overlap, the micelles open up and allow intermolecular associations that cause the viscosity to increase rapidly with concentration, typical of associating polymer solutions.
Polymer, 1992
Static and dynamic light scattering studies are presented on the temperature induced sol gel transition of an aqueous system of the non-ionic cellulose derivative ethyl hydroxyethyl cellulose in the presence of a cationic surfactant. In dilute solution coil expansion is observed with increasing temperature. In the semidilute range structural changes of the network are found when approaching the sol-gel transition. These effects are explained by an enhanced binding of surfactant to the polymer. The relaxation of the correlation function, in the semidilute regime~ is shifted towards longer times as the gelation threshold is approached. These results are interpreted in the framework of a model that has been constructed with the aid of the theoretical approach of Semenov. In this model the correlation function initially decays by a fast cooperative mode (single exponential), followed by a non-exponential decay (reptation-like mode) at longer times. The cooperative relaxation time is only slightly influenced by temperature, whereas the reptation-like relaxation time exhibits a drastic increase during the gelation process. This effect is attributed to a slowing down of the motion of the individual chains in the gelation zone. Within the framework of the model the determination of the gel point seems possible.
Macromolecules, 1999
A polycation poly(methacryloylethyl trimethylammonium methylsulfate), PMETMMS, with molar mass M w ) 26 × 10 6 has been studied by viscosity and light scattering in a mixture of water and acetone. Various amounts of a base (sodium hydroxide) or acids (hydrochloric, sulfuric, or phosphoric acid) have been added to the samples. PMETMMS shows typical polyelectrolyte behavior of the reduced viscosity in water-acetone mixtures with acetone mass fraction, γ, below 0.80. When γ g 0.80, PMETMMS undergoes a reversible coil-to-globule transition. The collapse can also be induced by dilution of the polymer solution, keeping the solvent composition constant, γ ) 0.70. Correlation functions measured using dynamic light scattering show a decrease of the relaxation time as well as the narrowing of the size distribution of the polymer with dilution. It has been shown that a compact structure instead of an extended coil is formed in a very dilute solution. Base or acid added into the solvent increases the value of the critical polymer concentration at which the collapse occurs. In a medium with low dielectric constant, base or acid molecules strongly interact with the charged groups of the polycation. Addition of NaOH into the solvent (less than 6 × 10 -4 mol/L) decreases the degree of ionization of the polycation. However, the addition of acid (0.3 × 10 -4 mol/L) introduces counterions that not only screen the positive charges of the polymer chain but also form inter-and intramolecular links. The latter effect becomes more profound with increasing the counterion valency. Upon dilution of the polymer solution, the number of the contacts between the polymer and added base/acid increases, but the number of inter-and intramolecular ion pairs of the polycation decreases. The balance of inter-and intramolecular interactions changes, and at high dilution, the intramolecular interactions dominate, owing to the poor quality of the solvent.
Light scattering study of stereocomplex behaviour in solutions of poly(methyl methacrylate)
Polymer, 1986
The behaviour of mixtures of iso-and syndiotactic poly(methyl methacrylate) (PMMA) as a function of time and polymer whole concentration in several solvents has been studied by light scattering and laser light scattering. The different solvents investigated in this study are acetonitrile, ethyl acetate, dimethylformamide (DMF), tetrahydrofuran (THF) and 1,4-dioxane. We have found that the last one behaves as a weakly complexing solvent, while the others show a complexing power decreasing from acetonitrile to THF.
The Journal of Physical Chemistry B, 1997
Dynamic and static light scattering experiments on solutions of the flexible highly charged polyelectrolyte sodium poly(styrenesulfonate) have been performed in the semidilute concentration regime. Over a very wide polyelectrolyte concentration range double-exponential correlation functions were found. At the lowest polyelectrolyte concentrations the correlation functions became single exponential. Apparent fast and slow diffusion coefficients were determined for three molar masses at a fixed added salt concentration of 0.01 M. The fast diffusion coefficient is both molar mass and polyelectrolyte concentration dependent at the lowest concentrations and becomes molar mass independent at semidilute concentrations. At even higher polyelectrolyte concentration the apparent fast diffusion coefficient is independent of both the molar mass and polyelectrolyte concentration. In the semidilute regime the fast diffusion coefficient follows the power law D f ∝ c 0.72 , close to the theoretical prediction of Odijk's scaling theory for a transient polyelectrolyte network. The apparent slow diffusion coefficient decreases with increasing molar mass and increasing polyelectrolyte concentration. The reciprocal normalized scattering intensity shows a strong angular dependence. The slow mode is interpreted as aggregates or domains that form in semidilute and concentrated solutions. The dimensions of these aggregates decrease with decreasing polyelectrolyte concentration and decreasing molar mass. The existence of aggregates and the change in their dimensions are directly seen with conventional light microscopy. The general trend of the apparent diffusion coefficients of NaPSS in 0.01 M NaCl resembles earlier data on NaPSS without added salt.
Conformation of neutral polyampholyte chains in salt solutions: a light scattering study
Macromolecules, 1994
The salt aqueous solution properties of a low charge density polyampholyte terpolymer with a balanced stoichiometry of charges were investigated by static and dynamic light scattering. At high ionic strength, the sample is entirely soluble and the chains exhibit an excluded volume conformation. When the salt content is lowered, part of the sample precipitates, leaving in the supernatant highly swollen chaing. The rmulta are interpreted by assuming that, due to different reactivity ratios of the monomers, there is adistribution of the net charges among the polymer chains. By varying the salt content, one performs a fractionation of the polyampholyte chains according to their net charge.