Controlling Volume Shrinkage in Soft Lithography through Heat-Induced Cross-Linking of Patterned Nanofibers

Miyamura, Y.; Park, C.; Kinbara, K.; Leibfarth, F.A.; Hawker, C.J.; Aida, T.;
J. Am. Chem. Soc.,
133, 2840- 2843.

When poly(isopropylidene diallylmalonate) rich in threo-disyndiotactic sequences (strich-2) was utilized as a cross-linkable ink for microcontact printing, the resultant submicrometer-scale patterns featuring 700 and 300 nm wide stripes were successfully insolubilized while maintaining their high dimensional integrity by heat-induced cross-linking with elimination of CO2 and acetone. In sharp contrast, although the thermal properties and reactivities of a polymer rich in threo-diisotactic sequences (itrich-2) and a polymer having low stereoregularity (2low) are little different from those of strich-2, the patterns printed with these reference polymers collapsed considerably upon heating as a result of a volume shrinkage effect. The striking difference between strich-2 and the other two polymers most likely arises from the nanofiber-forming character of strich-2, where the printed stripes are porous and much less affected by the volume shrinkage of individual nanofibers.