Buckling in polymer monolayers: Molecular-weight dependence

Srivastava, S and Basu, JK (2009) Buckling in polymer monolayers: Molecular-weight dependence. In: Physical Review E - Statistical, Nonlinear and Soft Matter Physics, 79 (4, Par). 041603-1.

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Abstract

We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of ~2–3 nm of well-defined periodicity, lambdab. Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner et al. for fluidlike films on water. However anomalously low values of bending rigidity and Young's modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young's modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films.

Item Type:	Journal Article
Publication:	Physical Review E - Statistical, Nonlinear and Soft Matter Physics
Publisher:	The American Physical Society
Additional Information:	Copyright of this article belongs to The American Physical Society.
Keywords:	bending;buckling;membranes;molecular weight;monolayers;polymer films;shear modulus;surface morphology;viscoelasticity;Young's modulus.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	01 Jun 2009 09:09
Last Modified:	19 Sep 2010 05:33
URI:	http://eprints.iisc.ac.in/id/eprint/20540

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