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Abstract
The adhesion of micrometer-size particles to an alternating block copolymer composed of polydimethyisiloxane and polyester was found to be accompanied by substantial viscoelastic flow of the substrate polymer. This flow gave rise to contact radii, which were substantially larger than those predicted by the JKR theory. Moreover, tensile-induced creep of the substrate resulted in anomalously large menisci that actually flowed up several particle heights. The flow of the material occurred over a period of days and, in some instances, the observed contact radii were greater than a critical radius for substantial engulfment of the particles by the substrate. Craters were left behind after particle removal, suggesting plastic-rather than elastic response of the substrate polymer to the surface-force-induced stresses. Size-exclusion chromatography has identified the presence of lower molecular weight polydimethylsiloxane-rich copolymer species in the n-hexane soluble mobile phase responsible for the unexpected behavior exhibited by this polymer substrate.