Low-surface-energy fluoromethacrylate block copolymers with patternable elements

A series of block polymers were synthesized from tetrahydropyranyl methacrylate (THPMA) and several fluorinated methacrylates. By changing both the length of the fluorinated side chain and the nature of its end group, the surface properties of these polymers were greatly influenced. The polymers with perfluoroheptyl groups showed the lowest surface tension, similar to 7 mN/m, whereas those with perfluoropropyl groups showed surface tension around 12 mN/m. The surface tension changed dramatically when the perfluorinated side chain with a CF2H end group was capped, increasing to 18 mN/m for three -CF2- units. The relative volume ratios of different block copolymers did not affect the resulting surface energy. After thermal decomposition of labile THP- groups in these polymers, acid and acid anhydride groups were produced. Thermal cross-linking of these groups increased mechanical robustness and led to better surface stability and adhesion of the polymer to the substrate. Because these polymers were designed for their lithographic abilities, some aspects of their photoimaging properties are discussed.