Composition, thickness and properties of grafted copolymer brush coatings determined by ellipsometry: calculation and prediction.

The composition, thickness and properties of poly(4-vinylpyridine-co-oligo(ethylene glycol)ethyl ether methacrylate246) [P(4VP-co-OEGMA246)] copolymer grafted brush coatings attached to glass were studied in the dry and swollen states using ellipsometry. These measured data are in good agreement with predicted (estimated) changes in the amount of water, refractive index and thickness of the grafted copolymer brush coatings on swelling. For POEGMA brushes the thickness of the coatings on swelling at 20 °C can be more than double, in contrast to P4VP where those changes are insignificant. The presence of 4VP units in the structure of the P(4VP-co-OEGMA246) copolymer grafted brushes significantly decreases the hydration degree even for coatings with very low concentrations of 4VP units.

Cholesterol-Based Grafted Polymer Brushes as Alignment Coating with Temperature-Tuned Anchoring for Nematic Liquid Crystals.

Novel alignment coating with temperature-tuned anchoring for nematic liquid crystals (NLCs) was successfully fabricated in three step process, involving polymerization of poly(cholesteryl methacrylate) (PChMa) from oligoproxide grafted to the glass surface premodified with 3-aminopropyltriethoxysilane. Molecular composition, thickness, wettability of the PChMa coating and its alignment action for a NLC were examined with time of flight-secondary ion mass spectrometry, ellipsometry, contact angle measurements, polarization optical microscopy and commercially produced PolScope technique allowing for mapping of the optic axis and optical retardance within the microscope field view. We find that the PChMa coating provides a specific monotonous increase (decrease) in the tilt angle of the NLC director with respect to the substrates normal upon heating (cooling) referred to as anchoring tuning.

Method for determination of the parameters of transparent ultrathin films deposited on transparent substrates under conditions of low optical contrast.

In the present work we suggest an original ellipsometric technique for independently determining strongly correlated refractive index and thickness of transparent ultrathin films. We demonstrate significant accuracy improvement for the single-wavelength null-ellipsometry measurements when using multiple incidence angles for the system "transparent film on a transparent substrate" studied in the thickness range of 1.0-20.0 nm and the low-contrast region for the film-substrate surface. A straightforward relationship is obtained between the refractive index n(1) of the transparent film and the incidence angle φ. It follows from invariability ensured for the amplitude ellipsometric parameter Ψ with respect to the film thickness changes.