Morphology of poly(styrene—block—dimethylsiloxane)(PS—b-PDMS)copelymer thin films was analyzed by atomic force microscopy(AFM)observation and transition electron microscopy(TEM)measurements．The asymmetric copelymer thin films spin—cast from toluene on mica presented a mesh-like structure

which was different from the spheriealop structure in the bulk．The annealing temperature affected the surface morphology of PS-b-PDMS eopelymer thin films

PDMS microdomains at the surface were increased when the annealing temperature was higher than the PDMS glass transition temperature．The morphology of PS—b-PDMS copelymer thin films was different from solvent to solvent

for thin films spin-cast from toluene

the PS phase was pits in PDMS matrix．While the thin film spin-cast from cyclohexane solution exhibited an island—like structure．small separated PS phase appeared as protrusions over the macroscopically flat surface．The microphase structures of the PS—b-PDMS copolymer thin films were also strongly influenced by the different substrates

for an asymmetric block copolymer thin film

the PDMS and PS phases on silicon substrate presented lamellae structure parallel to the film surface．