Surface interaction controlled microphase separation leading to the formati
on of chemically heterogeneous surface nanopatterns in dry ultrathin films
of A-B diblock copolymers is studied experimentally and theoretically in th
e strong segregation limit. On a planar surface one of the blocks (A block)
is strongly adsorbed, forming a tightly bound monomolecular layer (two-dim
ensional melt). The nonadsorbed B blocks can aggregate due to incompatibili
ty with the A-block layer on the substrate and with the air. As a result, a
chemically heterogeneous surface pattern can emerge. Depending on the bloc
k length ratio and the interaction parameters, the dewetting B blocks can a
ssemble to either globular surface micelles or wormlike surface aggregates,
that is, a point or a striped surface pattern. The region of stability of
these morphologies and the main parameters, such as aggregation number, siz
e, and periodicity, of the surface micelles and wormlike surface aggregates
have been determined as functions of the lengths of the blocks and the int
eraction energies of the blocks with each other and with the air. The phase
diagram is compared with experimental data for poly(styrene)-block-poly(4-
vinylpyridine) on mica.