Using the surface force apparatus, the conformational rearrangements of end-adsorbed diblock and triblock copolymer chains at the liquid/solid interface have been investigated. While the end-adsorbed poly(ethylene oxide)-polystyrene, PEO-PS, diblock copolymer "blushes" at a toluene/mica interface were seen to collapse upon the replacement of toluene by cyclohexane, rapid conformational transitions between "loops" and "tails" were observed for the end-adsorbed poly(2-vinylpridine)-polystyrene-poly(2-vinylpridine), PVP-PS-PVP, triblock copolymer chains at the toluene/mica interface during compression- decompression cycles. It was demonstrated for the first time that the newly formed tail-like triblock copolymer chains could be mechanically stretched beyond their equilibrium dimensions, a process which to some extent can be described by Rabin and Alexander’s scaling model. The dynamics of the conformational rearrangements was followed by surface force measurements at the molecular level.