Micromechanical Properties of Elastic Polymeric Materials As Probed by Scanning Force Microscopy

Abstract

Scanning force microscopy (SFM) was used for probing micromechanical properties of compliant polymeric materials. Classic models of elastic contacts, Sneddon's, Hertzian, and JKR, were tested for various indentation depths and for a variety of polymeric materials. We selected extremely compliant polyisoprene rubbers (Young's modulus, E ) 1-3 MPa), elastic polyurethanes (E ) 5-50 MPa), and hard surfaces of polystyrene (PS) and polyvinylchloride (PVC) (E ) 1-5 GPa). Both Sneddon's and Hertzian elastic models gave consistent and reliable results in the range of indentation depths up to 200 nm which are close to JKR solution. Close correlation is observed between absolute values of elastic moduli determined by SFM and known values for bulk materials.

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…A comparison of the reliability of Hertz and JKR theories on polymers can be found in Refs. [276,277]. Also the effect on the sample deformation of maximum load [278], contact time [279], and loading rate [280] have been characterized.…”

AFM of Poly(vinyl alcohol) Crystals Next to an Inorganic Surface

“…28,29 As the sample is probed by the tip at a constant force, soft regions will deform more than stiff regions. Thus, soft regions will appear to be lower in height.…”

Design of nanocomposite polymer coatings for MEMS applications

“…We collected the data in a 32 x 32 array and extracted adhesive force values (pull-off forces as defined by the force-distance curve 169 ) and elastic compression moduli. 170 (a) (b) (c) Collected for 32 x 32 pixels, lateral size is 3 x 3 jim.…”

“…Elastic moduli and adhesive forces are much lower along the debris area, but they are very homogeneous on the PS layer surface far from the damaged area. From the analysis of elastic modulus depth profiles according to Chizhik et al, 170 we concluded that the AFM tip indents and compresses very thin polymer layers and probes the underlying solid substrate. However, after tip retraction, the initial surface morphology (thickness, roughness, homogeneity) is completely restored without any trace of high local compression.…”

“…These values are within a range of values measured for glassy polymers of different molecular weights with AFM probing. 180,181 In contrast, the PB A layer possesses the elastic modulus of 40 MPa, typical for rubbery polymer phases (Table 5). Under identical normal load, the elastic, reversible indentation of the AFM tip is much higher (3-5 times) for the rubbery PBA layer ( Figure 68).…”