Strain Induced Elastomer Buckling Instability for Mechanical Measurements (SIEBIMM)

We introduce a new technique (SIEBIMM) for high-throughput measurements of the mechanical properties of thin polymeric films.  This technique relies upon a highly periodic strain-induced buckling instability that arises from a mismatch of the moduli of a relatively stiff polymer coating on a soft silicone sheet.  The modulus-dependent buckling wavelength, typically (1 to 10) microns for 100 nm thick glassy films, is measured rapidly by conventional light scattering.  The SIEBIMM-measured modulus is shown to agree with that measured by conventional Instron-like techniques.  We show directly that the buckling instability is highly sinusoidal for low strains thereby insuring the suitability of simple mechanical analysis.   Utilizing our expertise in preparing thickness gradients by flow coating, we demonstrate that the flexural rigidities of thin films having a wide range of thicknesses can be measured in minutes.  By measuring the temporal decay of strain-induced diffraction peaks for plasticized coatings, we show that this technique can evaluate viscoelastic properties, such as creep. We also show that a large amount of strain induces cracking in films, resulting in an optical signature where the scattering intensity decays smoothly with wavenumber.  We demonstrate SIEBIMMÕs capability with several academic and industrially-relevant polymeric systems, including polystyrene loaded with a wide range of plasticizer, a blend of block copolymers with polystyrene and polyisoprene blocks, and a thiolene-based ultraviolet curing adhesive.