REU Supplement: Characterization of Polymer Interphases Using Surface-Enhanced Raman Scattering

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An innovative analytical technique known as surface-enhanced Raman scattering (SERS) is being used in combination with other surface analysis techniques for the non-destructive characterization of "interphases" formed when polymer systems are adsorbed onto or cured against metal substrates. SERS is being used to investigate the adsorption of block copolymers and mixtures of homopolymers onto substrates such as silver and copper. SERS is also being used to determine the effect that metal substrates have on the molecular structure of polymers cured against them. The goal is to obtain fundamental information regarding catalysis or inhibition of curing reactions by metals, configurations of polymers adsorbed onto metal substrates, preferential adsorption of components of polymer systems onto metals, mechanisms by which polymers and small molecules interact with metals, extent of cure as a function distance away from a metal surface and into a polymer cured against the metal, and migration of metal ions into polymers cured against metal substrates. Processes such as preferential adsorption of components of a polymer systems onto a substrate and catalysis or inhibition of reactions within the polymer by the substrate lead to the formation of an interphase in the polymer adjacent to the substrate that has chemical and physical properties distinct from those of the bulk polymer. Since the macroscopic properties of adhesive bonds and composites are controlled by the interphase, it is essential to determine and control the molecular structure of interphases. SERS is ideal for this purpose since it is inherently surface selective and does not require a polymer to be separated from a substrate for the interphase to be examined as do virtually all other surface analysis techniques. The results obtained are being used to tailor the molecular structure of interphases so as to obtain enhanced environmental stability in structural adhesive joints and composites.