Photofixation of Diels–Alder Networks

Photoresists generally utilize a photochemical reaction that results in a solubility change in the resist.  In the case of a negative resist where a material is polymerized by irradiation the fabrication of complex three dimensional shapes is hindered by the liquid nature of the resist that allows unsupported features to float out of position.  This problem can be avoided by the use of a reversible polymer scaffold to support the desired shape.  Reversibly crosslinked networks can be formed by the Diels–Alder reaction of furan and maleimide.  Spatio-selective fixation of the crosslinks by radical reactions renders them irreversible within a well-defined region generated using 2-photon photolithography.  Subsequent reversion of the crossli­­­nks in the unexposed regions to monomer yields the patterned image.  This allows complex shapes, such as sets of interlocked rings to be readily fabricated.  This approach provides several key advantages over current techniques including solventless preparation, the ability to pattern arbitrary three dimensional shapes, and reduced complexity.