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Abstract A block copolymer (BCP) with specific monomer structures of fluoroacrylate polymers was designed by exploiting the inorganic superhydrophobicity and low glass transition temperature of polydimethylsiloxane (PDMS). With the use of a fluorine-containing block providing a surface tension as low as that of PDMS (19.9 < $$\gamma$$ γ

To enable the large-area manufacture of solution-processed organic electronics, direct photocrosslinking processes has emerged as a promising technology solution. Here, the authors report an efficient universal crosslinking agent for micropatterning of stacked multi-layered organic electronics.

Self-assembled block copolymer (BCP) thin films necessarily require a distinct chemical contrast between the blocks (or microdomain homogeneity) for the purpose of high-resolution pattern transfer applications. Despite its importance, however, there has been difficulty in measuring the chemical distribution associated with the self-assembling processes, i.e. solvent vapor annealing (SVA) or thermal annealing (TA). Herein, we present a simple yet effective method to probe the chemical distribution over polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films that underwent the SVA or SVA + TA processes. An IR nanospectroscopy using scattering-type scanning near-field optical microscopy (s-SNOM), in concert with X-ray scattering analyses, provides the relative chemical concentration of the perpendicular lamellar patterns. The chemical mapping for the components based on the s-SNOM reveals that the SVA process leaves a considerable portion of the intermixed zones of PS and PMMA blocks, whereas the subsequent TA process facilitates the chain segregation towards high-contrast chemical distribution. Interestingly, such a microdomain homogeneity critically affects the quality of the unidirectional Al2O3 lines that were substituted from topographically guided lamellae. Our results substantiate an important insight into understanding the chain redistribution behavior in the self-assembled BCP films using non-destructive s-SNOM technique.

A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC71BM (phenyl-C71-butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC71BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC71BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC71BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 °C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency. [ABSTRACT FROM AUTHOR]

We modulated the grafting density (σ) of a random copolymer brush of poly(styrene-r-methyl methacrylate) on substrates to probe its effect on the formation of perpendicularly aligned lamellae of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). Supported by coarse-grained simulation results, we hypothesized that an increase in σ will allow us to systematically tune the block copolymer interfacial interactions with the substrates from being preferential to one of the blocks to being neutral toward both blocks and will thereby facilitate enhanced regimes of perpendicularly aligned lamellae. We verified such a hypothesis by using a simple grafting-to approach to modify the substrates and characterized the thickness window for perpendicular lamellae as a function of brush thickness (or σ) on the grafted substrates using scanning force microscopy (SFM) images and grazing incidence small-angle X-ray scattering (GISAXS) measurements. The experimental results validated our hypothesis and suggested that the σ of random copolymer brushes can be used as an additional versatile parameter to modulate the interfacial interactions and the resulting alignment of block copolymer films. [ABSTRACT FROM AUTHOR]