Molecular Dynamics Simulations of the Effect of Elastocapillarity on Reinforcement of Soft Polymeric Materials by Liquid Inclusions

HY Liang and Z Cao and AV Dobrynin, MACROMOLECULES, 49, 7108-7115 (2016).

DOI: 10.1021/acs.macromol.6b01499

We use molecular dynamics simulations to study mechanical properties of polymeric nanocomposites of liquid inclusions in polymeric network matrix. The shear modulus of nanocomposite is shown to be a universal function of the elastocapillary number gamma(NL)/(G(N)R(0)), where gamma(NL) is the surface tension of the liquid/network interface, G(N) is the shear modulus of the network and R-0 is the initial size of liquid inclusions. First, in the range of elastocapillary numbers, gamma(NL)/(G(N)R(0)) < 1, the composite shear modulus increases with increasing elastocapillary number. In this interval of elastocapillary numbers, liquid inclusions soften the network such that the composite modulus G(C) is smaller than G(N). However, for elastocapillary numbers gamma(NL)/(G(N)R(0)) approximate to 2, the liquid inclusions begin to reinforce the network resulting in G(C) > G(N). In such composites, the surface energy of the deformed liquid inclusions stiffens the composite. When the elastocapillary number increases further, gamma(NL)/(G(N)R(0)) >> 1, the interfacial energy of network/liquid interface dominates the mechanical response of the composite. Elongation ratio of the liquid inclusions monotonically decreases with increasing elastocapillary number gamma(NL)/(G(N)R(0)).

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