This report describes the design and synthesis of a series of lamella‐forming, silicon‐containing block copolymers (Si‐BCPs) and evaluation of these materials as potential candidates for lithographic applications. The interaction parameter χ of each Si‐BCP is measured by both the mean‐field theory predicted order‐disorder transition and by analysis of X‐ray scattering profiles. The introduction of more‐polar methoxy and less‐polar methylsilyl moieties increases χ to about 2–3 times that of the reference material, poly(styrene‐block−4‐trimethylsilylstyrene). The incremental increases appear to be essentially additive in this family of block copolymers, suggesting that improvements in χ can be predicted from appropriate monomer choice. Perpendicularly oriented thin‐films of the ordered Si‐BCPs generated by thermally annealing between two “neutral” polymeric surfaces and developed by etching on commercial RIE equipment show excellent image fidelity. These images demonstrate the excellent etch contrast of the Si‐BCPs and document improvements in pattern fidelity that are realized with more strongly segregated BCPs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 344–352

The thickness and refractive index of poly(dimethylsiloxane) (PDMS) thin films on silicon, exposed to high-pressure carbon dioxide, have been measured in-situ by spectroscopic ellipsometry. The swelling of the film is determined from the thickness and the sorption of CO2 from the refractive index. The sorption and swelling values for the thin films exceed those of the bulk films. These increases may be attributed to excess CO2 at the polymer thin film−CO2 and polymer−silica interfaces and the influence of the silica surface and CO2 on the orientation of the polymer. Pressure-induced birefringence of the fused-silica windows was addressed in the model calculations and corrections were found to be successful for a thermal oxide reference wafer and the PDMS films. Large surface excesses of CO2 on the reference wafer were observed in regions where CO2 is highly compressible due to critical adsorption.

The application of membranes in gas separation and pervaporation requires materials that are resistant to plasticizing feed streams. We demonstrate the relationship between CO2 sorption, permeability, and film swelling of a polyimide gas separation membrane and how these properties are affected by systematic changes to the polymer structure induced by thermal annealing and covalent cross-linking. Dilation of polyimide thin films (∼120 nm) exposed to high-pressure CO2 (up to 100 atm at 35 °C) was measured by in situ spectroscopic ellipsometry to decouple the effects of thermal and chemical treatments on the film swelling. The refractive index of the CO2-swollen polymer is also used to estimate the CO2 sorption for comparison against that measured on thick films (∼50 μm) by the pressure-decay method. Differences in sorption levels in thin and thick films appear to be related to accelerated physical aging of the thin films. Both thermal annealing and covalent cross-linking of the polyimide films reduce polymer swelling to prevent large increases in the CO2 diffusion coefficient at high feed pressures. The CO2 permeability and polymer free volume strongly depend on the annealing temperature, and different effects are observed for the cross-linked and un-cross-linked membranes. The so-called “plasticization pressure” in permeation experiments (i.e., upturn in the permeation isotherm) appears to correlate with a sorbed CO2 partial molar volume of 29 ± 2 cm3/mol in the polymer. Furthermore, cross-linking of high glass transition polyimides produces a much greater reduction of the CO2-induced dilation than does cross-linking of rubbery polymers such as PDMS for swelling up to 25%.

Top coat design, coating, and optimization methodologies are introduced that facilitate the synthesis, application, and identification of neutral top coats for block copolymer (BP) thin films. Polymeric top coat composition, controlled via synthesis, determines interfacial wetting characteristics. Trimethylammonium salts of top coats improve solubility and coating uniformity. A "confined" island and hole test conveniently establishes (non)preferential wetting at the top coat/BP interface, which depends upon top coat composition. The utility of these three concepts was demonstrated with two high-χ, lamella-forming BPs, poly(styrene-block-4-trimethylsilylstyrene) (PS-b-PTMSS) having two periodicities L 0 = 18 and 22 nm and poly(styrene-block-methyltrimethylsilylmethacrylate) (PS-b-PTMSM) with L 0 = 15 nm. The combination of neutral top and bottom interfaces resulted in a perpendicular orientation of lamellae independent of BP film thickness (1−3 L 0 ) when thermally annealed for 60 s or less.