Aggregation in solutions of poly(γ-benzyl-l-glutamate) monitored by static and dynamic light scattering

Wissenburg, Petra; Odijk, Theo; Kuil, Maxim E.; Mandel, M.

doi:10.1016/0032-3861(92)90820-m

Cited by 8 publications

(11 citation statements)

References 8 publications

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“…1,4 There is clear evidence that aggregation can be observed in fresh solutions (within 24 h from preparation), but the kinetics of this process is characterized by much longer times. 27 Phenomenology suggests that a simple mass-action model 28 can describe the main features of aggregation in terms of cluster formation (dimers and higher-order associations), as shown recently in the case of poly(p-phenylene terephthalamide) solutions. 29 However, it cannot explain the origin of aggregation.…”

Section: Main Features Of Aggregation Processes and The Challengementioning

confidence: 79%

“…It has been known for several years that rodlike polymers in solution aggregate in various solvents. , The physical grounds of this process are not clearly understood yet, but it seems that the balance of interparticle forces results in a dominance of van der Waals attractions, leading to aggregation. It is recognized, however, that the nature of interparticle forces cannot be easily determined for solutions of anisotropic particles, since electrostatic and hard-core forces act on the particles positions and orientations in a different way; typically, with increasing concentration hard-core repulsion induces a nematic order of the particles, whereas uniformly charged rods tend toward a perpendicular orientation. , There is clear evidence that aggregation can be observed in fresh solutions (within 24 h from preparation), but the kinetics of this process is characterized by much longer times . Phenomenology suggests that a simple mass-action model can describe the main features of aggregation in terms of cluster formation (dimers and higher-order associations), as shown recently in the case of poly( p -phenylene terephthalamide) solutions .…”

Section: Main Features Of Aggregation Processes and The Challenge For...mentioning

confidence: 99%

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Association Dynamics in Solutions of Hairy-Rod Polymers

et al. 1997

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Photon correlation spectroscopy in the polarized (VV) and depolarized (VH) geometries has been utilized in order to investigate the aggregation dynamics in toluene solutions of a hairy-rod polymer, poly(p-phenylene) with flexible dodecyl side chains. Static and dynamic results from the dilute regime suggest that polymer molecules form small aggregates, typically trimers, even at very low concentrations. In the semidilute regime, results at different scattering wavevectors (q) in both the VV and VH geometry reveal two new relaxation processes (slow and ultra slow), in addition to the faster cooperative diffusion and reorientation of the trimers, respectively. They are attributed to the formation of large anisotropic clusters (of typical size 570 nm), with inherent crystallization, as revealed by X-ray scattering. After about 2 weeks the clusters settle under the action of gravity and form an opaque sediment. Assessment of the aggregation modes has been carried out by sediment redispersion. The first stages of this process, which exhibit multiple scattering, reveal a steeper than exponential relaxation, associated with a sedimentation-induced velocity gradient in a transient pseudonetwork formed by the dispersed clusters. In the single scattering limit, reached at later stages, the two relaxation processes are related to reorientation (slow) and number density fluctuation (ultraslow) of the anisotropic clusters. On the basis of simple thermodynamic arguments, we argue that rodlike macromolecules exhibit a larger activation energy barrier compared to their flexible counterparts, in agreement with the experimental evidence.

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Section: Main Features Of Aggregation Processes and The Challengementioning

confidence: 79%

Section: Main Features Of Aggregation Processes and The Challenge For...mentioning

confidence: 99%

Association Dynamics in Solutions of Hairy-Rod Polymers

et al. 1997

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“…There is limited research in the literature on the dimensional properties of polypeptides indicating a head-to-tail dimerization for PBLG in 1,2-dichloroethane by light scattering. 39,40 Therefore, the chain extension phenomenon by dilution for these 2 polypeptides reported in this work is a novel observation.…”

Section: Dynamic Light Scattering Results Related To Chain Extension mentioning

confidence: 51%

Quasielastic light scattering studies of polypeptides : Evidence for chain extension in a solution

BAYSAL¹

2013

Turk J Chem

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Dynamic light scattering and viscosimetric methods were used to study polypeptides including polyleucine, poly ( γ -benzyl-L-glutamate), poly ( α -L-glutamic acid), and polyproline II. Chain extension showing rod-like and flexible conformations occurred in poly( γ -benzyl-L-glutamate) and polyproline II solutions as these solutions were diluted in glacial acetic acid or in a mixed solvent of acetic acid and dichloromethane. The elongation of chains in poly( γ -benzyl-L-glutamate) and polyproline II solutions was studied by dynamic light scattering and viscosimetric methods. This nonenzymatic growth of peptide chains provides data on primordial synthesis of protein molecules in the absence of cell machinery and for this reason these reactions may yield valuable data for further studies.

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“…Since τ is very sensitive to any change in L due to the L 9 factor, it is tempting to explain our results by a temperature-driven variation of L . Dynamic aggregation, as observed in the case of PBLG, may be a mechanism that could account for the data. However, such an aggregation process has not been documented so far in our system.…”

Section: Reorientation Dynamics Of the Nematic Directormentioning

confidence: 62%

Deuterium Nuclear Magnetic Resonance Study of the Nematic Phase of Vanadium Pentoxide Aqueous Suspensions

1999

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This article describes deuterium NMR experiments on nematic single domains of vanadium pentoxide suspensions in D 2 O. Despite V 2 O 5 volume fractions as low as 0.7%, the spectra are well-resolved quadrupolar doublets, characteristic of a uniaxial symmetry. We show that a simple model for the behavior of water in these suspensions accounts for the value of the splitting and for its concentration dependence. In this way, we obtain information on the interaction between water molecules and V 2 O 5 colloidal ribbons. Then, the solvent (D 2 O) is used as a probe to study the reorientation time of the nematic phase. We show that this technique is sensitive enough to distinguish between reorientation through a transient instability or through a homogeneous rotation. In this latter case, we measure the characteristic time of reorientation τ in a magnetic field, as a function of volume fraction and temperature. We show a very strong temperature dependence of τ, which contrasts with the athermal phase diagram of this system.

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Aggregation in solutions of poly(γ-benzyl-l-glutamate) monitored by static and dynamic light scattering

Cited by 8 publications

References 8 publications

Association Dynamics in Solutions of Hairy-Rod Polymers

Association Dynamics in Solutions of Hairy-Rod Polymers

Quasielastic light scattering studies of polypeptides : Evidence for chain extension in a solution

Deuterium Nuclear Magnetic Resonance Study of the Nematic Phase of Vanadium Pentoxide Aqueous Suspensions

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