Combinatorial methods involving data collection in multiparameter space allow a rapid identification of measured property trends as a function of system parameters. The technique has been applied with success to pharmaceutical, inorganic and organic materials synthesis, but not significantly to measurements of polymeric films and coatings. We demonstrate the use of 2-D combinatorial libraries to investigate thin-film dewetting. We have prepared libraries of thin films of polystyrene on silicon substrates containing orthogonal, continuous variations of thickness (h), and temperature (T) that represent about 1200 practical state points per library. The libraries were screened for dewetting behavior using automated optical microscopy. Dewetting trends were visibly apparent on the libraries, and a comprehensive map of the T, h, and time (t) dependence was generated in a few hours. The combinatorial libraries, spanning a large T, h, and t range, not only reproduced known dewetting structures and phenomena but also enabled a novel T, h superposition of the heterogeneous nucleated hole dewetting kinetics. We observed three hole nucleation regimes as a function of thickness: heterogeneously nucleated holes (h > 55 nm), a crossover regime where both heterogeneous and capillary instability nucleation compete (33 nm < h < 55 nm), and a regime of holes nucleated by capillary instability (16 nm < h < 33 nm).
Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M. Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L0, and we attribute this effect to an increase in the surface chain density with h in the outer brushlike copolymer layer. We also observe apparently stable labyrinthine surface patterns for other h ranges, and the average size of these patterns is found to scale as lambda approximately L0(-2.5). Hole and island patterns occur for h ranges between those of the labyrinthine patterns and the smooth regions, and their size similarly decreases with L0 and M.
The C 1s and O 1s X-ray absorption spectra of poly(ethylene terephthalate) (PET) have been recorded using transmission, fluorescence, and electron yield detection. The corresponding electron energy loss spectra (EELS) have been recorded in a scanning transmission electron microscope. These results are compared to the C 1s and O 1s spectra of gas phase 1,4-dimethyl terephthalate (the monomer of PET) recorded using EELS. The comparison of monomer and polymer materials in different phases and with different techniques has aided the understanding of the relative strengths and limitations of each technique as well as assisting the spectral interpretation. Good agreement is found in the overall shape and the energies of the spectral features. Relatively minor differences in intensities can be understood in terms of the properties of the individual spectroscopic techniques. The critical dose for radiation damage by 100 keV electrons incident on PET at 100 K is found to be (1.45 ( 0.15) × 10 3 eV nm -3 . In contrast, the critical dose for radiation damage by 302 eV X-rays incident on PET at 300 K is (1.2 ( 0.6) × 10 4 eV nm -3 . A figure of merit involving the product of critical energy dose and spectral efficiency (as expressed by the appropriate G value) is developed. This indicates that, for near-edge studies involving a 20 eV spectral width, there is ∼500-fold advantage of X-ray absorption studies on room temperature PET relative to electron energy loss studies of cooled PET.
Surface‐pattern formation in thin block copolymer films was investigated by utilizing a high‐throughput methodology to validate the combinatorial measurement approach and to demonstrate the value of the combinatorial method for scientific investigation. We constructed measurement libraries from images of subregions of block copolymer films having gradients in film thickness and a range of molecular mass, M. A single gradient film covers a wide range of film morphologies and contains information equivalent to a large number of measurements of films having a fixed thickness, h. Notably, the scale of the surface patterns is generally much larger than the molecular dimensions so that the interpretation of the patterns is more subtle than ordering in bulk block copolymer materials, and there is no predictive theory of this type of surface‐pattern formation. We observed a succession of surface patterns that repeat across the film with increasing h [extended smooth regions, regions containing circular islands, labyrinthine (“spinodal”) patterns, holes, and smooth regions again]. The extended smooth regions and the labyrinthine patterns appear to be novel features revealed by our combinatorial study, and these patterns occurred as bands of h that were quantized by integral multiples of the bulk lamellar period, Lo. The magnitude of the height gradient influenced the width of the bands, and the smooth regions occupied an increasing fraction of the film‐surface area with an increasing film gradient. The average size of the spinodal patterns, λ, was found to scale as λ ∼ L −2.5italico or λ ∼ M−1.65 and reached a limiting size at long annealing times. The hole and island features had a size comparable to λ, and their size likewise decreased with increasing M. The smooth regions were attributed to an increase in the surface‐chain density in the outer brushlike block copolymer layer with increasing h, and the scaling of λ with M was interpreted in terms of the increasing surface elasticity with M. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2141–2158, 2001
Combinatorial gradient techniques are used to map the morphology dependence of thin symmetric diblock copolymer films on film thickness and substrate surface energy. An inversion from symmetric to anti‐symmetric lamellar morphology occurs with a progressive change in surface energy. An intermediate neutral region is found between these limiting types of ordering. The width ω of this transitional energy range scales as a power of copolymer mass M, ω ∝ M1.9.Optical photograph of a combinatorial map of the thin‐film block‐copolymer morphology on a film thickness and surface energy gradient. Island and holes on the surface scatter light causing the film to appear cloudy (lighter in color) in the areas where they exist. The darker areas do not have surface features and do not scatter light.magnified imageOptical photograph of a combinatorial map of the thin‐film block‐copolymer morphology on a film thickness and surface energy gradient. Island and holes on the surface scatter light causing the film to appear cloudy (lighter in color) in the areas where they exist. The darker areas do not have surface features and do not scatter light.
The C 1s X-ray absorption spectra (XAS) of poly(diallyl phthalate), poly(diallyl isophthalate), and poly(ethylene terephthalate) (PET) have been recorded using transmission detection. The phthalate segments of these polymers are isomers with different patterns of substitution (ortho, meta, para) of the methyl carboxylate groups on the phenyl ring. The C 1s and O 1s electron energy loss spectra (EELS) of the corresponding isomeric monomers, dimethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate, have also been recorded in the gas phase using inelastic electron scattering under conditions dominated by electric dipole transitions. Good agreement is found in overall shape and in the energies of the spectral features of the same isomer in monomeric (EELS) versus polymeric (XAS) form. Ab initio calculations are used to provide a detailed interpretation of the spectra, in particular the origin of the isomeric variations. The analytical potential for using inner shell excitation spectroscopy to identify isomeric character and to map spatial distributions of polymer isomeric substitution is assessed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.