Yawen Zhong

Highly ordered microporous films containing a polyolefin segment fabricated by the breath-figure method using well-defined polymethylene-b-polystyrene copolymers

Highly ordered microporous films containing polyolefin segment were successfully fabricated via the breath-figure (BF) method using well-defined polymethylene-b-polystyrene (PM-b-PS) diblock copolymers in CS2 under a static humid condition. The effects of molecular weight of diblock copolymers, relative humid, fabrication method and temperature on the morphology of film are investigated. The honeycomb porous films with different pore size (1.2–2.5 μm) were obtained by using PM-b-PS with different PM : PS ratio. The thick (7 μm) and thin (2 μm) films were fabricated via a different process. The film with a pothole-like structure was fabricated when using PM-b-PS with the shortest PS segment. Smaller satellite pores were found to surround the regular micropores of honeycomb films when the BF process was carried out at 28 °C.

Constructing robust 3-dimensionally conformal micropatterns: vulcanization of honeycomb structured polymeric films

Here, we present the static breath figure process for constructing 3-dimensionally conformal microporous films on nonplanar substrates, with a commercially available triblock polymer, polystyrene-b-polyisoprene-b-polystyrene. The polymer can cover the surface of nonplanar substrates with ordered porous morphology despite the sharp corners and irregular shapes, which was ascribed to the fluid-like character of the matrix. In the subsequent vulcanization, the micro-patterned polymer films were effectively crosslinked and became self-supported even after removing the sacrificial templates. The 3D structures became resistant to a wide range of organic solvents and thermally stable up to 350 °C, an increase of more than 300 K as compared to the un-crosslinked films. The surface features on the 3D structures along the direction of the descending solvent level were investigated in detail by scanning electron microscopy. Furthermore, the versatility of this patterning method was also demonstrated by forming hierarchical micro-structures on bas-relief Si substrates with different patterns. Particularly, hydroxy groups were introduced into another commercially available triblock polymer, polystyrene-b-polybutadiene-b-polystyrene by hydroboration. The functionalized 3D micro-patterns feasible for site-directed grafting were created by the hydroxyl-containing polymers.

Breath figure lithography: A facile and versatile method for micropatterning

We describe a facile method to micropattern solid substrates: breath figure lithography (BFL). A honeycomb structured gold mask was prepared by sputter-coating a micro-porous polymer film with BF arrays, and then inductively coupled plasma reactive ion etching (ICP-RIE) transferred the patterns onto silicon wafer. The large etching rate selectivity between golden mask and substrate plays an important role in the effective transfer of the patterns. The versatility of the method was demonstrated by forming micropatterns on various solid substrates with adjustable sizes. Furthermore, the micropatterns on solid substrate could be replicated by PDMS stamp.

Fabrication of robust micro-patterned polymeric films via static breath-figure process and vulcanization

Here, we present the preparation of thermally stable and solvent resistant micro-patterned polymeric films via static breath-figure process and sequent vulcanization, with a commercially available triblock polymer, polystyrene-b-polyisoprene-b-polystyrene (SIS). The vulcanized honeycomb structured SIS films became self-supported and resistant to a wide range of organic solvents and thermally stable up to 350°C for 2h, an increase of more than 300K as compared to the uncross-linked films. This superior robustness could be attributed to the high degree of polyisoprene cross-linking. The versatility of the methodology was demonstrated by applying to another commercially available triblock polymer, polystyrene-b-polybutadiene-b-polystyrene (SBS). Particularly, hydroxy groups were introduced into SBS by hydroboration. The functionalized two-dimensional micro-patterns feasible for site-directed grafting were created by the hydroxyl-containing polymers. In addition, the fixed microporous structures could be replicated to fabricate textured positive PDMS stamps. This simple technique offers new prospects in the field of micro-patterns, soft lithography and templates.

Constructing honeycomb micropatterns on nonplanar substrates with high glass transition temperature polymers

In Qiaos previous report, only star polymers with T(g) (glass transition temperature) below 48°C were found forming homogeneous honeycomb coatings on the nonplanar substrates. The polymers with high T(g) are believed not able to duplicate nonplanar substrate due to their brittleness. This article presents a comprehensive study on the construction of macroporous polymeric films on various nonplanar substrates with static breath figure (BF) technique, using linear polymers with high T(g). Two kinds of linear polymers with high T(g), polystyrene-b-poly(acrylic acid) and polystyrene without polar end groups, are employed to prepare 3-dimensional macroporous films on different nonplanar substrates. Scanning electronic microscopy views on the side wall in addition to views in-plane prove that polymer films with BF array perfectly replicated the surface features of these substrates. The formation processes of macropores on these substrates are analyzed in detail, and it demonstrates that neither molecular topography nor T(g) of polymers is the critical factor contouring nonplanar substrate. A new hypothesis involving polymer plasticization and conformation during the solvent evaporation is formulated.