Polymer thin films instability

Pattern Formation by Rim Instability in Dewetting Polymer Thin Films... 

Another described method of polymer surface modificahon consists in application of thin film instability enhanced by external electric field. Linear structures were created by the effect of locally limited electric field in thin polymer films heated to fluid temperature. 

Xu L, Sharma A, Joo SW. Substrate heterogeneity induced instability and slip in polymer thin films Dewetting on silanized surfaces with variable grafting density. Macromolecules 2010 43 7759-7762. 

In contrast to swollen homopolymer films, only a limited number of studies on thin films of block copolymers have been reported in which the degree of the film swelling has been directly accessed. In situ SE has been used to evaluate the polymer-solvent interaction parameters [144], to construct phase diagrams of surface structures [49, 51], and to control the mechanism of lamella reorientation in thick swollen films [118, 163, 164], Spectroscopic reflectometry combined with real-time GISAXS has been used to follow structural instabilities in swollen lamella films [165], Recently, it was demonstrated that swelling of diblock copolymer films in organic selective and non-selective solvents follows the same physical behavior as in thin films of homopolymers [119]. 

Keywords wrinkling Thin-film Elastomeric polymer Polydimethylsiloxane Patterns Deformation Surfaces Self-assembly Polyelectrolyte multilayer films Thin-films Polymer brushes Colloidal crystallization Mechanical-properties Assembled monolayers Buckling instability Elastomeric polymer Tobacco-mosaic-virus Soft lithography Arrays... 

In addition, patterns created by surface instabilities can be used to pattern polymer films with a lateral resolution down to 100 nm [7]. Here, I summarize various possible approaches that show how instabilities that may take place during the manufacture of thin films can be harnessed to replicate surface patterns in a controlled fashion. Two different approaches are reviewed, together with possible applications (a) patterns that are formed by the demixing of a multi-component blend and (b) pattern formation by capillary instabilities. 

The formation and replication of patterns into polymer films using instabilities is a new contribution in the field of soft lithography, which typically requires the mechanical contact between a patterned master and the resist. Two classes of instabilities were discussed. The demixing of two incompatible polymers leads to a well known spinodal pattern. In thin films, this structure formation process can be guided by a pattern in surface energy. 

Stereo-transmission electron microscopy of craze tips has shown that the meniscus instability is the operative craze tip advance mechanism in a wide variety of glassy polymers Figure 4 shows a craze tip in a thin film of a styrene-acrylonitrile copolymer (PSAN). The void fingers are clearly visible. No isolated voids can be... 

J. S. Sharp, K. R. Thomas, and M. P. Weir, mechanically driven wrinkling instability in thin film polymer bilayers. Phys. Rev. E 75, 011601 (2007). 

If the concentration is low, rather than thin films dissipative structures (e.g., convection patterns, fingering instabilities) are produced [87]. Such work was subsequently used to topographically control neurite extension on stripe-patterned polymer films [150], fabrication of periodic micro-structured honeycomb films having multiple periodicities, and polymer nanoparticles [151]. Large-scale ordering was observed. This was defined by the periodic thickness modulation of a block-copolymer film due to the self-organization of the receding contact line [152]. 

S. Y. Heriot, R. A. L. Jones, An Interfacial Instability in a Transient Wetting Layer Leads to Lateral Phase Separation in Thin Spin-Cast Polymer-Blend Films. Nat. Mater 2005,4,782-786. 

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