writer：Tao Chen, Jianmin Zhang, Debby P. Chang, Andres Garcia, and Stefan Zauscher
keywords：microcontact printing, bromothiol initiator, initiator gradient, polymer brushes, micro-containers
source：期刊
specific source：Advanced Materials, 2009, 21(18), 1825-1829
Issue time：2009年

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We present a simple strategy to fabricate stimulus-responsive patterned pNIPAAM brush microstructures (‘anemones’). Our approach relies on the combination of three phenomena: (1) the unusual phase separation of two differently functionalized alkanethiols on the stamp surface or during ink transfer in mCP on the substrate surface, (2) the preferred deposition of the polar, bromine-terminated thiol ink component (initiator) over that of the methyl-terminated thiol component during the first mCP step, and (3) the apparently enhanced ink transfer of the re-inked stamp at its periphery in the second mCP step. This second print step results in steep, radial initiator concentration gradients within the SAM micro-patterns. These patterns can be amplified into annular polymer brush microstructures via SI-ATRP. The size of the microstructures can be adjusted by setting the composition of thiol chemical and contact pressure. We demonstrate that the patterned pNIPAAM brush microstructures have a triggerable and reversible conformation transition and can potentially be used as micro-containers to reversibly dock and release micro particles. Our patterning approach and the subsequent SI-ATRP are generic and can likely be extended to include a wide range of vinyl monomers or mixtures of different vinyl monomers.