National Technical University of Athens
School of Chemical Engineering
Department of Materials Science and Engineering
Computational Materials Science and Engineering Group (Co.M.S.E.)

On the 17th of September 2017, Prof. Doros N. Theodorou was awarded with the European Materials Medal, in recognition of development of new statistical mechanics-based molecular and multiscale simulation methods for the calculation of thermodynamic, structural, interfacial, and permeability properties of polymeric materials, and zeolites.

Sincerest congratulations to our Master thesis student Dora Argyropoulou on winning a postgraduate studies scholarship of the Bodossaki Foundation.

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Directed Self-Assembly (DSA) of Copolymers

When two or more different monomers unite together to polymerize, their result is called as copolymer. Block Copolymers is a special kind of copolymers which are composed of two more chemically distinct, and frequently immiscible, polymer blocks covalently bound together.

Figure 1: (top) 3D representation of a PS-b-PMMA copolymer chain (bottom) depicted as a simple two-color chain for simplicity [REF].

Block copolymers are able to self-assemble into highly ordered lamellar, cylindrical, spherical and network morphologies. The ultimate morphology of the microphase system is determined from the Flory-Huggins interaction parameter, χAB , the degree of polymerization, N, and the relative composition fractions fA and fB.

Figure 2: Schematics of thermodynamically stable diblock copolymer phases [REF].

Self-assembling materials and especially block copolymers are very attractive for patterning and fabricating structures at the nanoscale.

Nanostructures and functional devices fabricated using block copolymers, including quantum dots, magnetic storage media, flash memory devices, semiconductor capacitors, photonic crystals, and nanopores have either required or benefited from the highly ordered and periodic nature of the self-assembled material.

Directed self-assembly (DSA) of block copolymers is one of the most promising techniques to enable the continued miniaturization of integrated circuits. It combines top-down photolithography of guiding patterns with engineered new materials and processes to facilitate cost effective bottom-up techniques for pattern density multiplication and defect rectification.

Figure 3: DSA technique combines top-down photolithography with the self-assembly of BCPs [REF].

Co.M.S.E. group develops atomistic and coarse-grained models which will be invoked to guide the selection of high χ BCPs, as well as the selection of substrates for their self-organization. Atomistic models of liquid oligomeric analogs of the blocks under consideration will be employed within molecular dynamics simulations to assess χ parameters. The same models will be simulated adjacent to the substrates under consideration to assess interfacial tensions and enthalpies of adsorption, hence the affinities of the blocks for the substrates.

Relevant projects

[1] EU CoLiSA.MMP, Computational Lithography for Directed Self-Assembly: Materials, Models and Processes.