Scaling up polymer blobs

Scaling up polymer blobs

Scientists use simulations to test the limits of their object of study—in this case thin films of polymers—to extremes of scale. In a study about to be published in the European Physical Journal E, Nava Schulmann, a researcher at Strasbourg University, France, and colleagues use a well-known model capable of providing information on heat and mechanical energy exchange between these polymer chains. They found that polymer blends confined to ultrathin two-dimensional films displayed enhanced compatibility. This was made possible by simulations using a fairly standard model, which is simple enough to allow the efficient computation of dense large-chain systems.

The authors focused on making simulations of self-avoiding and highly flexible without chain intersections. To do so, they varied the level of polymer density, as well as their chain length, while using numerical methods to arrive at a universal view of polymer behaviour.

Thanks to molecular dynamics and so-called , they confirmed that such polymers adopt a scaling behaviour following a power law as a function of density and chain length. This scaling behaviour applies, for example, to polymer pressure and, hence, polymer compressibility. French Pierre-Giles de Gennes predicted this property in his so-called blob picture approach. Accordingly, a polymer chain is akin to a succession of blobs, like beads in a necklace.

Schulmann and colleagues focused on a regime relevant for applications, referred to as a semi-dilute regime. There, scaling occurs more universally as long as the initial blob size is well defined. Understanding the limit of a system of long chains can currently only be realised in simulations of simplified models. However, the authors hope their findings will facilitate the work of polymer experimentalists.²


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More information: N. Schulmann, H. Meyer, P. Polińska, J. Baschnagel, and J.P. Wittmer, Strictly two-dimensional self-avoiding walks: Thermodynamic properties revisited, (2012) European Physical Journal E 35:93 DOI 10.1140/epje/i2012-12093-x
Journal information: European Physical Journal E

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Citation: Scaling up polymer blobs (2012, September 27) retrieved 19 June 2019 from https://phys.org/news/2012-09-scaling-polymer-blobs.html
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