Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coincident Molecular Auxeticity and Negative Order Parameter in a Liquid
  Crystal Elastomer   "Auxetic" materials have the counter-intuitive property of expanding rather
than contracting perpendicular to an applied stretch, formally they have
negative Poisson's Ratios (PRs).[1,2] This results in properties such as
enhanced energy absorption and indentation resistance, which means that
auxetics have potential for applications in areas from aerospace to biomedical
industries.[3,4] Existing synthetic auxetics are all created by carefully
structuring porous geometries from positive PR materials. Crucially, their
geometry causes the auxeticity.[3,4] The necessary porosity weakens the
material compared to the bulk and the structure must be engineered, for
example, by using resource-intensive additive manufacturing processes.[1,5] A
longstanding goal for researchers has been the development of a synthetic
material that has intrinsic auxetic behaviour. Such "molecular auxetics" would
avoid porosity-weakening and their very existence implies chemical
tuneability.[1,4-9] However molecular auxeticity has never previously been
proven for a synthetic material.[6,7] Here we present a synthetic molecular
auxetic based on a monodomain liquid crystal elastomer (LCE). When stressed
perpendicular to the alignment direction, the LCE becomes auxetic at strains
greater than approximately 0.8 with a minimum PR of -0.8. The critical strain
for auxeticity coincides with the occurrence of a negative liquid crystal order
parameter (LCOP). We show the auxeticity agrees with theoretical predictions
derived from the Warner and Terentjev theory of LCEs.[10] This demonstration of
a synthetic molecular auxetic represents the origin of a new approach to
producing molecular auxetics with a range of physical properties and functional
behaviours. Further, it demonstrates a novel feature of LCEs and a route for
realisation of the molecular auxetic technologies that have been proposed over
the years.

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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th