Effect of shear flow on the phase‐separation behavior in a blend of polystyrene and polyvinyl methyl ether

Abstract

The phase behavior and phase‐separation dynamics of polystyrene/polyvinyl methyl ether (PS/PVME) blend with a critical composition of 70 vol % PVME were examined with a light scattering technique under a shear‐rate range of 0.1–40 s−1. If the shear rates were less than 8 s−1 and the starting temperatures of the measurement were 343 and 383 K, respectively, two cloud points were observed, whereas after the shear rate was higher than 8 s−1, only one cloud point existed, 20 K higher than that of the static state of the blend. Investigation of the phase‐separation dynamics at 443 K suggested that in the vorticity direction the phase‐separation behavior at the early stage and the later stage can be explained by Cahn–Hilliard linearized theory and the exponent growth law, respectively. Phase separation occurs after a shearing time, which was called a delay time τd. The delayed time τd, the apparent diffusion coefficient, and the exponent term of the blend show strong dependence on shear rates. A theoretical prediction of the phase behavior of PS/PVME under a shear flow field by introducing an elastic energy term into Flory's equation‐of‐state theory was made, and the prediction was consistent with the experimental results. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 661–669, 2003

Tunable Antireflection Coating to Remove Index‐Matching Requirement for Interference Lithography

“…Figure a shows the wavelength‐dependent refractive index of blends at ≈10% composition intervals. Due to interactions between PS and PVME in blends the variation in refractive index due to composition cannot be modeled using methods that treat the components as distinct phases . To enable selection of the appropriate blend for a given interference experiment, we fit the refractive index and composition through a linear interpolation of refractive index of the pure components and a 2nd order Redlich–Kister deviation, which can be written as…”

“…The fact that the interference pattern can be controlled through the wavelength, propagation direction, intensity, and polarization of the interfering beams, enables a diversity of structures to be formed . In principle, all Bravais lattices can be made using 4 beams . Photoacid generators and sensitizers can be added to the resist, making it sensitive to different wavelengths of light, allowing the pattern to be uniformly scaled .…”

“…PS and PVME are one of the few pairs of homopolymers that are completely miscible, ensuring no phase separation, which would lead to significant light scatter, over the full composition range . Films of these blends can be made with precisely controlled compositions and thicknesses by spincoating from a solution of toluene . These polymers also have very different refractive indices, n ≈ 1.47 for PVME and n ≈ 1.6 for PS, which enables BARCs which provide near zero reflection for SU‐8 on substrates with refractive indices between 1.3 and 1.6, which includes even low refractive index materials such as CaF 2 and NaF 2 , commonly used substrates for UV and IR optics due to their broad transmission range.…”

Thermal Behavior of Polyamide‐12 and Poly (Styrene‐Co‐Acrylonitrile) Blend

“…The phase behavior of the PA-12/SAN blend was studied using a homemade, small angle light scattering (SALS) apparatus as described by Lei, et al [18] The sample of PA-12/SAN was held at 1208C for 10 min and then heated at a heating rate of 28C/min to 2258C. In isothermal experiments, the sample was rapidly heated from room temperature to a selected high temperature.…”

Effect of nanoCaCO3on crystallisation behaviour of LLDPE studied by SALS

“…The schematic of a laboratory constructed small angle light scattering (SALS) apparatus 22,23 was shown in Fig. 1, where h and m are the polar and azimuthal scattering angles.…”