title: Exploiting photoinduced reactions in polymer blends to create hierarchically ordered, defect-free materials.
abstract: Computer simulations reveal how photoinduced chemical reactions can be exploited to create long-range order in binary and ternary polymeric materials. The process is initiated by shining a spatially uniform light over a photosensitive AB binary blend, which thereby undergoes both a reversible chemical reaction and phase separation. We then introduce a well-collimated, higher intensity light source. Rastering this secondary light over the sample locally increases the reaction rate and causes formation of defect-free, spatially periodic structures. These binary structures resemble either the lamellar or hexagonal phases of microphase-separated diblock copolymers. We measure the regularity of the ordered structures as a function of the relative reaction rates for different values of the rastering speed and determine the optimal conditions for creating defect-free structures in the binary systems. We then add a nonreactive homopolymer C, which is immiscible with both A and B. We show that this component migrates to regions that are illuminated by the secondary, higher intensity light, allowing us to effectively write a pattern of C onto the AB film. Rastering over the ternary blend with this collimated light now leads to hierarchically ordered patterns of A, B, and C. The findings point to a facile, nonintrusive process for manufacturing high quality polymeric devices in a low-cost, efficient manner.
authors.affiliation: Chemical Engineering Department, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Rui D M
authors.initials: RD
authors.lastname: Travasso
authors.forename: Olga
authors.initials: O
authors.lastname: Kuksenok
authors.forename: Anna C
authors.initials: AC
authors.lastname: Balazs