Neutron Reflectometry Study of the Segment-Density Profiles in End-Grafted and Irreversibly Adsorbed Layers of Polymer in Good Solvents

Marzolin, Christian; Auroy, P.; Deruelle, Martial; Folkers, John P.; Léger, Liliane; Menelle, A.

doi:10.1021/ma010156z

Cited by 48 publications

(47 citation statements)

References 46 publications

(82 reference statements)

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“…Tails are connected and unadsorbed segments where one end is free and the other is adsorbed, while a free segment is a segment that belongs to an unadsorbed chain. The definitions for loops, trains, and tails are consistent with the definitions in the reflectometry study by Leǵer et al 5 and theoretical work by Guiselin 17 for which our simulation results were compared.…”

Section: ■ Simulation Methodssupporting

confidence: 78%

Untangling the Effects of Chain Rigidity on the Structure and Dynamics of Strongly Adsorbed Polymer Melts

Carrillo¹,

Cheng²,

Kumar³

et al. 2015

Macromolecules

114

115

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We present a detailed analysis of coarse-grained molecular dynamics simulations of semiflexible polymer melts in contact with a strongly adsorbing substrate. We have characterized the segments in the interfacial layer by counting the number of trains, loops, tails, and unadsorbed segments. For more rigid chains, a tail and an adsorbed segment (a train) dominate while loops are more prevalent in more flexible chains. The tails exhibit a nonuniformly stretched conformation akin to the "polydisperse pseudobrush" originally envisioned by Guiselin. To probe the dynamics of the segments, we computed the layer z-resolved collective intermediate dynamic structure factor, S(q,t,z), mean-square displacement of segments, and the second Legendre polynomial of the time autocorrelation of unit bond vectors, ⟨P 2 [n⃗ i (t,z)·n⃗ i (0,z)]⟩. Our results show that segmental dynamics is slower for stiffer chains, and there is a strong correlation between the structure and dynamics in the interfacial layer. There is no "glassy layer", and the slowing down in dynamics of stiffer chains in the adsorbed region can be attributed to the densification and a more persistent layering of segments. ■ INTRODUCTIONThe adsorption of polymers on surfaces is a fundamental problem in polymer physics 1,2 which has been extensively examined experimentally, 3−12 theoretically, 13−22 and through computer simulations. 23−35 Particularly of technological interest are systems involving polymer nanocomposites and polymer− electrolyte systems for organic electronic applications. The importance of a thorough understanding of polymer chain behavior in contact with a substrate cannot be overstated. It is known that in the presence of interfaces the structure and dynamics of polymers are influenced by the interface where dynamics differ from bulk and polymer conformations are perturbed within an interfacial layer. 7,8,36−47 There is now growing experimental evidence of the formation of the "reduced mobility interface" (RMI) layer in between unadsorbed chains in a matrix and the adsorbed layer where the dynamics is intermediate and distinguishable from those of the bulk and the adsorbed layer. 6,37,39,47,48 This leads in particular to the observed shift in the glass transition temperature, T g . 49−51 However, there are still considerable gaps in the understanding of the underlying physics and dependencies on polymer properties and its interaction with the substrate.In general, a fully flexible chain model is inadequate in describing experimental results 52 since the backbone of a real polymer chain is not completely flexible. A more accurate description of experimental results can be achieved when another length scale, representing the stiffness of the chain along the molecular backbone, is introduced. 24,52−54 This highlights the importance of chain stiffness in polymer− substrate contacts and interactions. In this article we attempt to describe the structure and dynamics of semiflexible polymer melts at the segment level. We believe that in this framework, co...

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Section: ■ Simulation Methodssupporting

confidence: 78%

Untangling the Effects of Chain Rigidity on the Structure and Dynamics of Strongly Adsorbed Polymer Melts

Carrillo¹,

Cheng²,

Kumar³

et al. 2015

Macromolecules

114

115

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“…Their measurements of the density profile of the swollen layer were consistent with a power law decay, with an exponent whose value was about twice the predicted value of equation (8), while measured layer heights were smaller, h ∼ N 0.72±0.03 . Marzolin et al [219] also used neutron reflectivity to study hydrogen-bonding of PDMS and deuterated PDMS (dPDMS) onto silicon wafers. Wafers were incubated in a PDMS melt for 12-24 h at 110 o C and unattached chains were rinsed by solvent (deuterated toluene for PDMS and octane for dPDMS).…”

Section: Physisorption: the Guiselin Brushmentioning

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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“…Plusieurs autres problèmes pourront être étudiés. Par exemple, des études sur l'adsorption de polymères [23,24] ou le greffage [24] à une surface à partir d'une solution. (Evidemment, il y en a beaucoup plus que ces deux références.)…”

Section: Discussionunclassified

Avantages de la réflectométrie des neutrons pour l'étude des polymères en couches minces

Reiter

Geoghegan

2007

Journées de la Neutronique

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Résumé. Nous présentons quelques exemples qui démontrent l'utilité et la puissance de la réflectométrie de neutrons pour l'étude des surfaces et des interfaces de polymères. Ces exemples concernent l'interdiffusion entre deux polymères miscibles, la pénétration d'une chaîne greffée dans un réseau du même polymère, la cinétique de la formation d'une « brosse » de polymère et l'enrichissement d'un polymère à la surface d'un mélange homogène de deux polymères.

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Neutron Reflectometry Study of the Segment-Density Profiles in End-Grafted and Irreversibly Adsorbed Layers of Polymer in Good Solvents

Cited by 48 publications

References 46 publications

Untangling the Effects of Chain Rigidity on the Structure and Dynamics of Strongly Adsorbed Polymer Melts

Untangling the Effects of Chain Rigidity on the Structure and Dynamics of Strongly Adsorbed Polymer Melts

Non-equilibrium in adsorbed polymer layers

Avantages de la réflectométrie des neutrons pour l'étude des polymères en couches minces

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