(226aj) Continuous Growth of Vertically Aligned SBS Via in-Situ Crosslinking in Electrospray

Electrospray has been recently developed as a novel technique for continuous deposition of ordered block copolymer thin films as an analog to physical vapor deposition. The development of well phase-separated microstructures is achieved by balancing thermal equilibration, deposition rate and residual solvent content, which are all readily tuned by spray parameters. We have demonstrated previously that well-ordered common diblock copolymers such as PS-b-PEO, PS-b-PMMA and PS-b-P4VP can be deposited by electrospray with film morphology strongly dependent on spray parameters. Here we explore the preservation of non-equilibrated vertical orientation through in-situ crosslinking in a cylinder-forming SBS (Styrene-Butadiene-Styrene) triblock copolymer deposited by electrospray. We performed parametric studies of solvent composition, flow rate, collection distance, deposition temperature on determining the surface morphology. Perpendicular morphology can be accomplished on preferential substrates through the evaporation of solvent from deposited material in the ‘wet’ spray regime, which then equilibrate with substrate over time and reorganize into parallel orientation under thermal annealing. The addition of thermal initiator, however, allows in-situ crosslinking of the polymer matrix thereafter locking in the as-sprayed morphology during deposition. By balancing the rate of crosslinking and ordering with the right amount of initiator, we achieve quasi-epitaxial growth of vertically oriented domain of SBS over micron-thick films.