Structure and dynamics of a polymer melt at an attractive surface

Virgiliis, Andrés De; Milchev, A.; Rostiashvili, V. G.; Vilgis, Thomas A.

doi:10.1140/epje/i2012-12097-6

Cited by 48 publications

(110 citation statements)

References 30 publications

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“…We have ensured that the z dimension is large enough such that the chains situated at the middle of the slab are bulk-like. Despite employing a smooth analytical substrate, the results obtained in our MD simulations, such as the layering of the segments in the vicinity of the substrate, qualitatively agree with the results of the MD simulations by Vilges et al 23,29 where the substrate was setup as discrete Lennard-Jones beads. Furthermore, we believe that real systems have discrete adsorption points (i.e., hydrogen-bonding points); hence, other parameters are critical in determining the adsorbed polymer structure.…”

Section: ■ Simulation Methodssupporting

confidence: 89%

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

Carrillo¹,

Cheng²,

Kumar³

et al. 2015

Macromolecules

116

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: 89%

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

Carrillo¹,

Cheng²,

Kumar³

et al. 2015

Macromolecules

116

115

View full text Add to dashboard Cite

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“…An increasing relaxation time approaching the rough substrate has also been observed in a computational study of a binary LennardJones liquid, as well as in a bead-spring model of polymer melts with a relatively strong interaction. 16,17,38,39 Evidently, substrate roughness is highly relevant for the polymer film dynamics, and this factor must be controlled for consistent results.…”

Section: B Local Structure and Dynamicsmentioning

confidence: 99%

A unifying framework to quantify the effects of substrate interactions, stiffness, and roughness on the dynamics of thin supported polymer films

Hanakata

Betancourt

Douglas

et al. 2015

The Journal of Chemical Physics

131

180

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Changes in the dynamics of supported polymer films in comparison to bulk materials involve a complex convolution of effects, such as substrate interactions, roughness, and compliance, in addition to film thickness. We consider molecular dynamics simulations of substrate-supported, coarse-grained polymer films where these parameters are tuned separately to determine how each of these variables influence the molecular dynamics of thin polymer films. We find that all these variables significantly influence the film dynamics, leading to a seemingly intractable degree of complexity in describing these changes. However, by considering how these constraining variables influence string-like collective motion within the film, we show that all our observations can be understood in a unified and quantitative way. More specifically, the string model for glass-forming liquids implies that the changes in the structural relaxation of these films are governed by the changes in the average length of string-like cooperative motions and this model is confirmed under all conditions considered in our simulations. Ultimately, these changes are parameterized in terms of just the activation enthalpy and entropy for molecular organization, which have predictable dependences on substrate properties and film thickness, offering a promising approach for the rational design of film properties. C 2015 AIP Publishing LLC. [http://dx

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“…Formation of loops and also trains and tails by the polymer chains on the attractive surface was observed by computer simulations [26] and theory [27,28]. In particular, it was found that the loop distribution follows a power law relationship.…”

Section: Interphase Formationmentioning

confidence: 90%

Polymer dynamics in nanoconfinement: Interfaces and interphases

Krutyeva

Wischnewski

Richter

2015

EPJ Web of Conferences

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Abstract. The dynamics of polymers in nanoconfinement was studied by using neutron spectroscopy. A number of pronounced effects on different time and length scales for the polymers confined in nanopores of anodic aluminium oxide were observed. Local segmental dynamics was found to be dependent on the type of the interaction between the solid pore wall and polymer: attractive interactions lead to the formation of a surface layer with the dynamics slowed down as compared to the dynamics of pure polymer; neutral/repulsive interaction do not change the local dynamics. Attractive interactions cause anchoring of polymer segments on the surface creating an interphase between the polymer in close vicinity to the solid surface and pure polymer. In addition, at strong confinement conditions the dilution of the entanglement network is observed.

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Structure and dynamics of a polymer melt at an attractive surface

Cited by 48 publications

References 30 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

A unifying framework to quantify the effects of substrate interactions, stiffness, and roughness on the dynamics of thin supported polymer films

Polymer dynamics in nanoconfinement: Interfaces and interphases

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