| Abstract
| - Hybrid brushes composed of two liquid polymers, poly(dimethylsiloxane) (PDMS) and a highly branched ethoxylatedpolyethylenimine (EPEI), were synthesized on Si wafers by the “grafting to” method and by applying a combinatorialapproach (fabrication of gradient brushes). The combinatorial approach revealed a strong effect of “layer assistedtethering”, which allowed us to synthesize hybrid brushes twice as thick as the reference homopolymer brushes. Thehybrid brushes are stable thin films that can rapidly and reversibly switch between hydrophilic and hydrophobic statesin water and air, respectively. The switching in water affects a rapid release of amino functional groups which canbe used to regulate adhesion and reactivity of the material. The switching in air rapidly returns the brush to a hydrophobicstate. The hybrid brush is hydrophilic because of two mechanisms: (1) exposure of EPEI chains to the brush−waterinterface under water, and (2) retention of some fraction of water via swollen EPEI chains (the EPEI chains swellby 2−3 times), which are conserved by a PDMS cap in air. The hybrid brush is wettable under water, and at the sametime, the brush is nonwettable in air because water droplets are trapped in a metastable state when the water contactangle is above 90°.
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