Dynamic behavior of flexible polymers at a solid/liquid interface

Pefferkorn, E.; Carroy, A.; Varoqui, R.

doi:10.1002/pol.1985.180231002

Cited by 90 publications

(88 citation statements)

References 12 publications

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“…One study [122,124,125] involved labeled polyacrylamide (PAM) in water adsorbed through hydrogen bonding onto aluminol-grafted glass beads. The beads were exposed to a dilute solution of labeled PAM for approximately 30min until time-independent coverage was achieved.…”

Section: Experiment: Departure From Equilibrium Picturementioning

confidence: 99%

Non-equilibrium in adsorbed polymer layers

O’Shaughnessy

Vavylonis

2005

J. Phys.: Condens. Matter

121

152

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Abstract.High molecular weight polymer solutions have a powerful tendency to deposit adsorbed layers when exposed to even mildly attractive surfaces. The equilibrium properties of these dense interfacial layers have been extensively studied theoretically. A large body of experimental evidence, however, indicates that non-equilibrium effects are dominant whenever monomer-surface sticking energies are somewhat larger than kT , a common case. Polymer relaxation kinetics within the layer are then severely retarded, leading to non-equilibrium layers whose structure and dynamics depend on adsorption kinetics and layer ageing. Here we review experimental and theoretical work exploring these non-equilibrium effects, with emphasis on recent developments. The discussion addresses the structure and dynamics in non-equilibrium polymer layers adsorbed from dilute polymer solutions and from polymer melts and more concentrated solutions. Two distinct classes of behaviour arise, depending on whether physisorption or chemisorption is involved. A given adsorbed chain belonging to the layer has a certain fraction of its monomers bound to the surface, f , and the remainder belonging to loops making bulk excursions. A natural classification scheme for layers adsorbed from solution is the distribution of single chain f values, P (f ), which may hold the key to quantifying the degree of irreversibility in adsorbed polymer layers. Here we calculate P (f ) for equilibrium layers; we find its form is very different to the theoretical P (f ) for non-equilibrium layers which are predicted to have infinitely many statistical classes of chain. Experimental measurements of P (f ) are compared to these theoretical predictions.

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Section: Experiment: Departure From Equilibrium Picturementioning

confidence: 99%

Non-equilibrium in adsorbed polymer layers

O’Shaughnessy

Vavylonis

2005

J. Phys.: Condens. Matter

121

152

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“…For example, the fraction of chains with long loops and tails of order N will be reduced by a factor N −1/5 , thus strengthening the outer region of the layer which is exposed to the bulk. Similarly in experiments probing the kinetics of exchange between chains in the bulk and those in the layer [24,25,26,27,28,29,30,33,36,37,38,39], we expect strong aging effects since the number of easily exchangeable, loosely attached chains is decreasing with increasing aging time. This would lead to a decrease of the initial exchange rate with aging time as observed [28,29,37,38].…”

Section: Differences Between Irreversible and Equilibrium Layersmentioning

confidence: 99%

“…Available experimental evidence suggests that desorption processes and relaxation kinetics within the layer are then sharply slowed down [24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40]. For ǫ values of several k B T time scales become so long that the layer build-up becomes essentially an irreversible process leading to non-equilibrium structure [31,32].…”

Section: Introductionmentioning

confidence: 99%

Irreversible adsorption from dilute polymer solutions

2003

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Abstract. We study irreversible polymer adsorption from dilute solutions theoretically. Universal features of the resultant non-equilibrium layers are predicted. Two broad cases are considered, distinguished by the magnitude of the local monomer-surface sticking rate Q: chemisorption (very small Q) and physisorption (large Q). Early stages of layer formation entail single chain adsorption. While single chain physisorption times τ ads are typically micro to milli-seconds, for chemisorbing chains of N units we find experimentally accessible times τ ads = Q −1 N 3/5 , ranging from seconds to hours. We establish 3 chemisorption universality classes, determined by a critical contact exponent: zipping, accelerated zipping and homogeneous collapse. For dilute solutions, the mechanism is accelerated zipping: zipping propagates outwards from the first attachment, accelerated by occasional formation of large loops which nucleate further zipping. This leads to a transient distribution ω(s) ∼ s −7/5 of loop lengths s up to a maximum size s max ≈ (Qt) 5/3 after time t. By times of order τ ads the entire chain is adsorbed. The outcome of the single chain adsorption episode is a monolayer of fully collapsed chains. Having only a few vacant sites to adsorb onto, late arriving chains form a diffuse outer layer. In a simple picture we find for both chemisorption and physisorption a final loop distribution Ω(s) ∼ s −11/5 and density profile c(z) ∼ z −4/3 whose forms are the same as for equilibrium layers. In contrast to equilibrium layers, however, the statistical properties of a given chain depend on its adsorption time; the outer layer contains many classes of chain, each characterized by a different fraction of adsorbed monomers f . Consistent with strong physisorption experiments, we find the f values follow a distribution P (f ) ∼ f −4/5 .

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“…reaction rate constant has also been evaluated and is of the order of (2.3 ± 0.4) x i0o cm hr-1. These experiments do not allow us to determine the order of the reaction with respect to the adsorbed protein molecules, as has been done for polymers (2). Such a determination would require labeling only part of the adsorbed proteins and performing similar experiments as in set II.…”

Section: Resultsmentioning

confidence: 99%

“…(iv) For synthetic homopolymers of the same chemical nature, the affinity for a surface increases with the molecular weight (12). (v) It has been shown experimentally that for homopolymers of the same nature and the same molecular weight, the exchange process can be modeled by a first-order chemical reaction with respect to both the bulk molecules and the adsorbed polymers (2). This result has been explained theoretically by De Gennes (13).…”

mentioning

confidence: 86%

Kinetics of exchange processes in the adsorption of proteins on solid surfaces.

Ball

Huetz

Elaı̈ssari

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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The homogeneous exchange process whereby IgG molecules adsorbed onto latex particles are replaced by IgG molecules from the bulk solution was studied by means of ts radiolabeling. The exchange mechanism was Investigated on surfaces saturated with either labeled or unlabeled proteins in the presence of a solution of the opposite species in two sets of independent experiments. After rinsing of the surface by pure buffer followed by supplementary IgG adsorption, the exchange process.followed a kinetic law of first order with respect to the IgG molecules from the bulk solution, and the apparent exchange rate constant was (2.3 ± 0.4) x 10-5 cm hr'1.One of the main differences between adsorption processes of "small" molecules and of macromolecules on solid surfaces is that macromolecules can reach the surface by two different mechanisms (1): by direct adsorption or by a progressive exchange reaction. In the first case the molecules reach the adsorption surface directly on free available space. In contrast, for the exchange mechanism the molecules reach the surface by progressive removal of already-adsorbed macromolecules. This occurs in particular when the surface is saturated with preadsorbed molecules. This second process has never been observed in the adsorption of small molecules on surfaces.The physical origin of this second adsorption process lies in the fact that macromolecules interact with a surface through several links. These links along the macromolecule change with time, even if the molecule is in an equilibrium configuration. Interactions between macromolecule and surface must thus be considered as a dynamic and not a static process. Moreover, macromolecules are not rigid bodies. Thus, if such a molecule enters into the vicinity of a surface already covered by adsorbed macromolecules, it can change its conformation and diffuse into the adsorbed layer. Once part of the backbone of the diffusing molecule reaches the adsorption surface, it interacts with it. This interaction can then be followed by sequential, segmental, reptation-like adsorption of the molecule, in competition with the dynamic process of the formation and annihilation of links of previously adsorbed macromolecules. Finally, the diffusing molecules progressively replace those already adsorbed on the surface, completing the exchange process.Such processes have been observed for synthetic polymers (2) as well as for proteins (3,4) by means of radioactive labeling techniques. NevertHeless, and in spite of a great number of investigations, little is known about adsorption processes of macromolecules (5). Let us rapidly summarize the main results that have been established. (i) The affinity of proteins for a given surface usually increases with their molecular weight. High molecular weight proteins usually exchange preferentially with lower molecular weight adsorbed proteins (6, 7). (ii) The higher the hydrophobicity of the surface is, the larger is the adsorbed quantity (8, 9). (iii) These amounts are maximal for pH values close to the ...

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Dynamic behavior of flexible polymers at a solid/liquid interface

Cited by 90 publications

References 12 publications

Non-equilibrium in adsorbed polymer layers

Non-equilibrium in adsorbed polymer layers

Irreversible adsorption from dilute polymer solutions

Kinetics of exchange processes in the adsorption of proteins on solid surfaces.

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