Topcoat compositions comprise: a matrix polymer; a surface active polymer comprising a polymerized unit formed from a monomer of the following general formula (I): wherein: R1 represents H, F, methyl or fluorinated methyl; R2 represents optionally substituted C1 to C8 alkylene or optionally substituted C1 to C8 fluoroalkylene, optionally comprising one or more heteroatom; R3 represents H, F, optionally substituted C1 to C10 alkyl or optionally substituted C5 to C15 aryl, optionally comprising one or more heteroatom; R4 represents optionally substituted C1 to C8 alkyl, optionally substituted C1 to C8 fluoroalkyl or optionally substituted C5 to C15 aryl, optionally comprising one or more heteroatom; X represents O, S or NR5, wherein R5 is chosen from hydrogen and optionally substituted C1 to C5 alkyl; and a is 0 or 1; and a solvent. Also provided are coated substrates and pattern-forming methods which make use of the topcoat compositions. The invention has particular applicability in photolithographic processes as a photoresist topcoat layer in the manufacture of semiconductor devices.