Surface Analysis Overview

The Polymer Technology Group, Inc. develops new surface technologies with the use of Sum-Frequency Generation (SFG) analysis. SFG is a sophisticated, non-destructive laser technique to study polymer surfaces. This highly-sensitive method possesses several unique advantages to conventional surface analysis techniques, including:

Biocompatible surfaces are essential to the success of a continuously-increasing number of polymer applications in the biomedical field. Surface chemistry controls numerous chemical and physiological properties of a polymer, including thromboresistance, biostability, lubricity, permeability, and abrasion resistance. Surface-modified polymers need to be well characterized in order to correlate the surface chemistry to the biofunctionality of the application.

Historically, it has been a challenge to obtain such detailed information about surface structure due to the lack of probe techniques that are sensitive to molecular features, such as conformational sequences and hydrogen bonding. Various spectroscopic techniques-reflection infrared spectroscopy, attenuated total reflection infrared spectroscopy, and Raman spectroscopy-have been used to characterize polymer surfaces; however, these methods lack surface specificity, and the resulting spectra are often obscured by the bulk concentration. Surface-sensitive techniques, such as contact angle measurement, neutron reflection, and X-ray photoelectron spectroscopy (XPS) often do not provide structural information, and/or do not allow in situ measurement. (Table 1)

Comparison of SFG to other conventional surface analysis techniques

Table 1. Comparison of SFG to other conventional surface analysis techniques

To address this problem, physicists at the University of California at Berkeley recently developed a surface-specific analytical technique with monolayer sensitivity, and have successfully applied it to various kinds of surfaces and interfaces. Through IR and visible sum-frequency generation spectroscopy, they created a powerful and versatile in situ surface probe that not only permits identification of surface molecular species, but also provides information about orientation of functional groups at the surface. SFG has all the common advantages of laser techniques; specifically, it is nondestructive, highly sensitive, and has good spatial, temporal, and spectral resolution. Because the technique works in real time under water and protein solutions (and, theoretically, under blood) it is very well suited for studying biomaterials.

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