Surface-Induced Microphase Separation in Spin-Cast Ultrathin Diblock Copolymer Films on Silicon Substrate before and after Annealing

Abstract

The microphase structures of ultrathin symmetric polystyrene/poly(methyl methacrylate) diblock copolymer films on silicon substrate under variation of film thicknesses in the nanometer range were investigated by using AFM. The microphases were identified by simultaneously measuring the topography and the phase-shift image in TappingMode and by comparing the results with the topography after selectively etching the poly(methyl methacrylate) phase. The thinnest spin-cast film showing complete wetting was only 1.8 nm thick. However, even for this film a microphase separation in the range of the correlation length (L) of the diblock bulk material was observed. For this minimum film thickness, the calculated PMMA microdomain volume approaches the volume of a single PMMA coil, which may be discussed as the limiting microdomain volume necessary as a critical wetting condition. Geometrical considerations lead to an average PMMA/silicon substrate contact angle of 46° in the spin-cast and vacuum-dried ultrathin diblock copolymer films. Annealing of these films at 130 °C reveals a second minimum thickness, at which the microphases show coplanar lamellar ordering with the PMMA at the substrate and the PS at the surface. This minimum thickness of coplanar ordering is about 40% higher than the calculated width of the interface between PS and PMMA in the bulk.

Modulation of Protein−Surface Interactions on Nanopatterned Polymer Films

“…PS surfaces were revealed as dark regions with a phase shift smaller than for the light PMMA regions. 36,37 Alternating stripes of PS and PMMA ( Figure 1A-D) and hexagonally ordered PS domains arrayed in a PMMA matrix ( Figure 1E,F) resulted, respectively, from PSb-PMMA self-assembly into lamella and cylindrical morphologies oriented normal to the surface. [22][23][24] The periodic domain center-to-center distance (λ C-C ) was varied over an order of magnitude from 29 to ∼300 nm, corresponding to characteristic PS domain widths (d PS ) of 13 to ∼200 nm.…”

Supramolecular Organization of Polymeric Materials in Nanoporous Hard Templates

“…First, low molecular mass species such as the triphenylene compound enrich at interfaces in the presence of a polymer for entropic reasons [150,151]. Secondly, taking into account the high compatibility of the liquid crystal used and PS, PMMA should have a higher affinity to the AAO pore walls [152][153][154]. Reducing the D p -value of the AAO hard template to 60 nm resulted in the occurrence of a striking morphological crossover.…”

Morphology of poly(styrene‐block‐dimethylsiloxane) copolymer films

“…29,30 Solvent effects with different solubility and selectivity values on the surface morphology of copolymer films have seldom been studied. To investigate the effect of the casting solvent on the domain structure, cyclohexane was used to prepare the spin-coating solution.…”

“…The substratesegment interactions have been studied extensively for thin films of copolymers, including interplays and competitions and hence the parameters to control the morphologies. [30][31][32][33][34][35][36][37] There are long-and shortrange interactions either between the air surface and the copolymer or between the substrate surface and the copolymers, giving rise to even richer unconfined thin films. Block-selective segregation at the substrate will occur when the wetting component provides the lowest interfacial tension or exhibits a specific affinity for the substrate.…”