Infrared Imaging: A Complementary Tool to AFM for Adhesive Surface Analysis

Atomic force microscopy (AFM) is a useful tool for probing pressure sensitive surfaces (PSA) at the micron and sub-micron level. Investigators hope that the spatial resolution of microstructure will provide clues to function. Nevertheless, AFM cannot distinguish functional group chemistry associated with topology. In contrast, FT-IR imaging microscopy is an emerging technology that has the power to spatially resolve chemical composition at the functional group level. No single technique exists that can determine the chemical nature and degree of orientation within a surface system while simultaneously being able to determine the morphology. Our interest in this study was to complement AFM with FT-IR imaging to examine structural features, chemistry, and topology. We report that FT-IR imaging can be a useful adjunct to AFM in adhesive surface analysis. Introduction. Atomic force microscopy (AFM) is a useful tool for probing pressure sensitive surfaces (PSA) at the micron and sub-micron level. Investigators hope that the detail of microstructure will provide'clues to function [3, 12, 13]. However, the details of AFM are limited to spatially resolved structures that are described in physical terms like force, friction, and texture. Functional group chemistry cannot be spatially resolved at the microstructural level by AFM. In contrast, FT-IR imaging microscopy is an emerging technologythat has the power to spatially resolve functional group chemical composition at the micron level [ 1, 2,12,15]. The aim of this study is to combine AFM and FT-IR imaging to see if information from these two powerful analytical tools can compliment surface analysis of adhesive systems, and provide insight into the relationship of structure and property. Relating form and function is important in microstructural analysis. Chemical identification in morphology removes the "black-box" undertone [5] of strictly physical analysis. Here we look to associate functional group chemistry with topology. Background. We were interested in following the work of Hock [6 ] and Wetzel [ 16]. In Hock's classic work he described the relationship of rosin ester loading to tack (see Figure 1.). Hock showed that beyond a blend of 70:30 w/w rosin ester-to-rubber, tack was lost. Our question in this case was "how is tack lost?" In our work we study a rosin ester-rubber model PSA using FT-IR imaging and AFM in contrast to Hock and Wetzel who studied their surfaces with scanning electron microscopy (SEM). In this study we describe surface changes as a function of increasing the rosin ester-rubber ratio with the