Directed assembly of polymer blends using nanopatterned templates

Nano-patterned polymer structures by directed assembly of polymer blends using chemically heterogeneous patterns in thin films have many applications in biosensors, integrate circuits, and thin-film optoelectronic devices.;Polystyrene (PS)/poly(acrylic acid) (PAA) blends were patterned into both uniform and non-uniform geometries by directed assembly of polymer blends using chemically heterogeneous patterns. Spin-coating speed and solution concentration were used to control the characteristic length of polymer blends. Critical spin speeds or solution concentrations that produced the required characteristic length commensurate with the given pattern periodicity were predicted. A new method of image analysis was introduced to quantitatively evaluate the quality of replication of the underlying pattern. When the range of commensurability was within 20%, well-ordered morphologies were produced.;The characteristic length of polymer blends on homogeneous substrate was increased with increasing Mw of PAA. Further increasing M w of PAA did not change the characteristic length obviously. The influence of Mw of PAA on directed assembly of polymer blends was not obvious when characteristic length was commensurate with pattern periodicity. The pattern morphologies became disordered with increasing Mw of PAA when polymer blends replicated the patterns with periodicities smaller than the characteristic length. 1-hydroxy-1-undecanethiol (HUT) improved the pattern replication of polymer blends with PAA of 1079 kDa by increasing the work adhesion between polymers and substrates. With reducing the Mw of PS, directed assembly of the polymer blend with width of 100 nm was observed.;The addition of block copolymer in improving the directed assembly of polymer blends into uniform and non-uniform geometries was demonstrated. Addition of block copolymer allowed the fabrication of well-ordered morphologies of patterns of lines with angles of 30 to 150° on a single template, much smaller angles than previously reported; T-junctions and circle arrays; and for the first time, letter-shaped polymer structures. This approach has the potential to improve the assembly of polymer blends for many kinds of non-uniform patterns in a high rate manner.