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Schematic representation of the process used to fabricate 2DPRG of tethered PMMA layer. (a) Si wafer treated with HMDS in a thermal evaporator, photoresist spin-coated onto the Si surface presenting Si(CH3)3 groups, and lithography process used to pattern the photoresist as a hole array. (b) OPT used to chemically modify the exposed regions presenting Si(OCH3)3 groups and to convert the topographic photoresist pattern into a chemical surface pattern. (c) Initiator selectively assembled onto bare regions of the Si surface. Sample grafting via surface-initiated ATRP of MMA from the functionalized areas of the patterned SAM as pillar arrays of PMMA brushes. (d) Finally, photoresist removed from the substrate. The 2DPRG of tethered PMMA layer on the surface exhibited VOC-dependent morphology and optical properties according to solvent species.
3D (left), 2D (right), and line cross-section (bottom) analysis AFM topographic images of 200 nm-resolution 2DPRG of tethered PMMA surface (a) in dry state, under VOC exposing of (b) toluene and (c) chloroform at 20 Torr of partial pressure for 5 h. (d) Variation in the scale of the pillar array of 2DPRG after five cycles of VOC exposing and exhausting of chloroform.
Swelling ratios of tethered PS layer under VOC exposing with their polarity indices of solvent species.
neff response and calculated filling factor of 2DPRG of tethered PMMA layer as a function of solvent species for VOC exposing in the order of chloroform (A), DCE (B), dioxane (C), toluene (D), THF (E), cyclohexane (F), acetone (G), and in dry state (H). Photographic images demonstrate the grating effect of the 2DPRG under VOC exposing of chloroform, dioxane, THF, and acetone, from left to right.
Dry layer parameters (molecular weight Mn and Mw, surface conversion Sc, grafting distance dg, grafting density σ, and the roughness), the refractive indices, and static water contact angle (SWCA) of typical PMMA brush layer a on silicon surface.
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