Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Velocity dependence of friction of confined polymers   We present molecular dynamics friction calculations for confined hydrocarbon
solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are
considered: (a) polymer sliding against a hard substrate, and (b) polymer
sliding on polymer. We discuss the velocity dependence of the frictional shear
stress for both cases. In our simulations, the polymer films are very thin
(approx. 3 nm), and the solid walls are connected to a thermostat at a short
distance from the polymer slab. Under these circumstances we find that
frictional heating effects are not important, and the effective temperature in
the polymer film is always close to the thermostat temperature. In the first
setup (a), for hydrocarbons with molecular lengths from 60 to 1400 carbon
atoms, the shear stresses are nearly independent of molecular length, but for
the shortest hydrocarbon C20H42 the frictional shear stress is lower. In all
cases the frictional shear stress increases monotonically with the sliding
velocity. For polymer sliding on polymer [case (b)] the friction is much
larger, and the velocity dependence is more complex. For hydrocarbons with
molecular lengths from 60 to 140 C-atoms, the number of monolayers of lubricant
increases (abruptly) with increasing sliding velocity (from 6 to 7 layers),
leading to a decrease of the friction. Before and after the layering
transition, the frictional shear stresses are nearly proportional to the
logarithm of sliding velocity. For the longest hydrocarbon (1400 C-atoms) the
friction shows no dependence on the sliding velocity, and for the shortest
hydrocarbon (20 C-atoms) the frictional shear stress increases nearly linearly
with the sliding velocity.

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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
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The categories of this paper are: q-alg