Wettability of maleimide copolymer films: Effect of the chain length of n-alkyl side groups on the solid surface tension

We report bulk and surface properties of maleimide copolymers with two diff erent backbones, poly(propene-alt-N-(n-alkyl)maleimides) (PAIkMI) and poly( styrene-alt-N-(n-alkyl) maleimides) (SAlkMI), with different lengths of n-a lkyl side chains (methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, and d odecyl), The contact angle and solid surface tension results suggest that, for the longer side chains, the surface properties are dominated by the sid e chains. Indeed, the surface tension of the two types of copolymers with l ength of the side chain above C=6 are essentially equal, indicating complet e shielding of the polar backbone chain. For the two copolymers containing dodecyl side chains, the solid surface tension is similar to that of solid surfaces consisting exclusively of CH3 groups. Apparently, these side group s are long enough to allow arrangement in the configuration of the lowest s urface free energy possible for alkyl chains. For the short side chain copo lymers the styrene compounds are more hydrophobic than the propene compound s. The bulkier phenyl rings shields the polar backbone chain more effective ly than the small alkyl groups.