CONFORMATIONAL TRANSITIONS OF END-ADSORBED COPOLYMER CHAINS AT THE LIQUID SOLID INTERFACE/

Using the surface force apparatus, the conformational rearrangements o f end-adsorbed diblock and triblock copolymer chains at the liquid/sol id interface have been investigated. While the end-adsorbed poly(ethyl ene oxide)-polystyrene, PEO-PS, diblock copolymer ''blushes'' at a tol uene/mica interface were seen to collapse upon the replacement of tolu ene by cyclohexane, rapid conformational transitions between ''loops'' and ''tails'' were observed for the end-adsorbed (2-vinylpridine)-pol ystyrene-poly(2-vinylpridine), PVP-PS-PVP, triblock copolymer chains a t the toluene/mica interface during compression- decompression cycles. It was demonstrated for the first time that the newly formed tail-lik e triblock copolymer chains could be mechanically stretched beyond the ir equilibrium dimensions, a process which to some extent can be descr ibed by Rabin and Alexander's scaling model. The dynamics of the confo rmational rearrangements was followed by surface force measurements at the molecular level.