A PFS/PLA block copolymer was studied to probe the effect of strong surface interactions on pattern formation in PFS block copolymer thin films. Successful synthesis of PFS-b-PLA was demonstrated. Thin films of these polymers show phase separation to form PFS microdomains in a PLA matrix, and ultrathin films (<5 nm) formed SINPATs on silicon and mica. The SINPATs consisted of strongly surface-adsorbed PLA blocks on top of which the PFS blocks dewetted into sphere-like features. The lateral spacing between these features was regular, and was typically much larger than the length scale associated with regular block copolymer phase separation.