Jian Li

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.

Breath figure in non-aqueous vapor

In this paper we reported the preparation of porous honeycomb polymer film using a static breath figure (BF) method under non-aqueous atmospheres. Methanol and ethanol vapors were chosen as the atmosphere in which the BF process was conducted. It is found that honeycomb films with ordered pores can be obtained with methanol and ethanol droplets arrays as the templates. The influence of the atmosphere on the film morphology, including the pore shape, size and the degree of pore packing order, was investigated. Furthermore, the formation process of the BF arrays under these alcohol vapors was investigated using a non-planar substrate method. Finally it is shown that the honeycomb films with different pores can be used to prepare highly ordered ceramic micropatterns with adjustable sizes, as well as the siloxane-based soft stamps. Our results prove that the BF method is not only suitable for water vapor, but is also compatible with other organic vapors. Also this paper develops a facile way to control the morphology features of the BF honeycomb films by changing the vapor atmospheres, which is valuable when designing and fabricating ordered microstructures.