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Directed self-assembly (DSA) is a type of directed assembly which utilizes block co-polymer morphology to create lines, space and hole patterns, facilitating for a more accurate control of the feature shapes. Then it uses surface interactions as well as polymer thermodynamics to finalize the formation of the final pattern shapes. [1]
These kinetic effects, such as trapping in metastable states, slow coarsening kinetics, and pathway-dependent assembly, are often viewed as complications to be overcome in, for example, the formation of block copolymers. [12] [18] Amphiphile self-assembly is an essential bottom-up approach of fabricating advanced functional materials.
This method uses the well-studied methods of producing block copolymers with well-defined geometries and compositions across a large variety of substrates. [3] [34] Synthesis of Janus particles by self-assembly via block copolymers was first described in 2001 by Erhardt et al.
Self-assembly is a process which is easily influenced by external parameters. This feature can make synthesis rather complex because of the need to control many free parameters. Yet self-assembly has the advantage that a large variety of shapes and functions on many length scales can be obtained. [31]
Much progress had been reported on the use of PMMA-PS block copolymers to define sub-20 nm patterns by means of self-assembly, guided by surface topography (graphoepitaxy) and/or surface chemical patterning (chemoepitaxy). [71] The key benefit is the relatively simple processing, compared to multiple exposures or multiple depositions and etching.
block copolymer: A copolymer that is a block polymer. In the constituent macromolecules of a block copolymer , adjacent blocks are constitutionally different, i.e. adjacent blocks comprise constitutional unit derived from different species of monomer or from the same species of monomer but with a different composition or sequence distribution ...
Block copolymers are interesting because they can "microphase separate" to form periodic nanostructures,[13][14][15] Microphase separation is a situation similar to that of oil and water. Oil and water are immiscible - they phase separate. Due to incompatibility between the blocks, block copolymers undergo a similar phase separation.
For example, an alternating copolymer synthesized by radical polymerization is a sequence-controlled polymer, even if it is also a non-uniform polymer, in which chains have different chain-lengths and slightly different compositions. [2] A biopolymer (for example a protein) with a perfectly-defined primary structure is also a sequence ...