Tao Chen and Stefan Zauscher. Duke University, Durham, NC
The ability to fabricate three-dimensional (3D) gradient microstructure is of increasing importance for the miniaturization of mechanical and fluidic devices, and in the area of tissue-engineering scaffolds.[1] Recently, topographic 3D features of polymer brushes have been fabricated by combining surface-initiated atom-transfer radical polymerization with electron-beam chemical lithography (EBCL), a new patterning technique.[2] However, the process is usually cumbersome and inaccessible to the majority of researchers. Here, we present a simple strategy to fabricate novel, micropatterned, stimulus-responsive, and surface confined poly(N-isopropylacrylamide) (pNIPAM) brushes in a “grafting-from” approach that combines microcontact printing (µCP) based on phase separation to obtain surface confined gradient initiator with amplification using SI-ATRP. Furthermore, we show how bowl-shaped pNIPAM brushes (brush anemones) with inducible conformation transition behavior can be used as a particle-container to dock nano- and micro- particles. Our fabrication approach is generic and can likely be extended to a wide range of vinyl monomers or mixture of different vinyl monomers and other special shape via the transfer and amplification of the phase separation on the surface of PDMS stamp. We are currently using this property to synthesize dual stimulus-responsive random copolymers PNIPAM-PAA that have two different trigger mechanisms. Further, the “living” nature of ATRP initiators allows the reinitiation of pNIPAM nanopatterns to synthesize various stimulus-responsive block copolymers that have interesting properties.