Microcapsule Buckling Triggered by Compression-Induced Interfacial Phase Change.

Andrew R Salmon,Richard M Parker,Roger J Coulston,Chris Abell,Armando Maestro,Oren A Scherman,Jonas Hegemann,Jan Kierfeld,Alexander S Groombridge

doi:10.1021/acs.langmuir.6b03011

Andrew R Salmon, Richard M Parker + Show 7 more

Open Access

https://doi.org/10.1021/acs.langmuir.6b03011

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Abstract

There is an emerging trend toward the fabrication of microcapsules at liquid interfaces. In order to control the parameters of such capsules, the interfacial processes governing their formation must be understood. Here, poly(vinyl alcohol) films are assembled at the interface of water-in-oil microfluidic droplets. The polymer is cross-linked using cucurbit[8]uril ternary supramolecular complexes. It is shown that compression-induced phase change causes the onset of buckling in the interfacial film. On evaporative compression, the interfacial film both increases in density and thickens, until it reaches a critical density and a phase change occurs. We show that this increase in density can be simply related to the film Poisson ratio and area compression. This description captures fundamentals of many compressive interfacial phase changes and can also explain the observation of a fixed thickness-to-radius ratio at buckling, [Formula: see text].

Highlights

It is shown that compression-induced phase change causes the onset of buckling in the interfacial film
The interfacial film both increases in density and thickens, until it reaches a critical density and a phase change occurs
The poly(vinyl alcohol) (PVA) backbone is modified by the covalent attachment of stilbene side groups as “handles” for supramolecular polymer cross-linking through a

Summary

Introduction

It is shown that compression-induced phase change causes the onset of buckling in the interfacial film. On deflation an elastic shell will initially undergo an isotropic (“spherical”) deformation until:14 the presence of CB[8] the interface was observed to buckle for surface area compressions ΔA > 0.5 (Figure 3b). With the Poisson ratio and film thickness measured here (Table 1) a shell volume reduction, ( )ΔV , of order 10−3 would be sufficient to trigger buckling if V buck

Results

Conclusion