INFLUENCE OF CONFINEMENTS ON THE ORDER OF DIBLOCK COPOLYMER FILMS

The order in very thin films (12 nm to 92 nm) of the symmetric diblock copolymer poly(styrene-b-paramethylstyrene) near the order-to-disorde r transition has been investigated by N-15 nuclear-reaction analysis. Lamellar ordering parallel to the surface is observed, qualitatively v ery similar to that of thick films. The order parameter L is found to depend linearly on film thickness d, when d is smaller than the natura l order parameter L0 observed in the absence of constraints. The thick ness dependence of L arises from the competition between the two chara cteristic dimensions of the system, L0 and d. The results are compared with recent theoretical predictions.