Nanostructuring from Self-Assembly of Block Copolymers

10 NANOSTRUCTURING FROM SELF-ASSEMBLY OF BLOCK COPOLYMERS 

Materials with nanoscopic features have several interesting applications in the areas of low dielectric materials, catalysis, membrane separation, molecular engineering, photonics, biosubstrates, and various other fields. Synthesis methods include use of polymers as templates, phase separation processes, and multistep templating chemical reactions. Deficiencies in these methods include complexity in execution economically prohibitive for scale-up mechanically weak, nonuniform in structure materials with little use in application. 

IBM patented a process for making materials with predefined morphology. Table 7.1 provides a list of experiments and theoretical predictions for forming materials with predetermined morphology. Self-assembly of block copolymer principles are used in this approach. Let the block copolymers be characterized by volume fractions, q i and q 2 respectively. A cross-linkable polymer is also added to the mixture that is miscible with the second block copolymer. The volume fraction of the cross-linkable polymer is (P3. The first and second block species have volume fractions of (piA and q 2A respectively, in the two components of the mixture. The mixture is applied to a substrate. The assembly consists of a substrate, a mixture coating/struc-tural layer having nanostructures, and a interfacial layer without nanostructures. The thickness of the layer is 0.5-50 nm. 

A cross-sectional transmission electron microscopy (TEM) image of a material with predetermined morphology of spherical pores was examined. The structure consists of an interfacial layer, structural layer, and a substrate. The substrate is in direct mechanical contact with the interfacial layer. The structural layer is composed of spherical nanopores nanostructure, and essentially consists of the cross-linkable polymer. The interfacial layer lacks the spherical nanopores. The thickness of the interfacial layer is 2-30 nm. The structural layer thickness is of the range 50-300 nm. 

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