The optical properties of the stable icosahedral quasicrystal Al63.5Cu24.5Fe12 have been measured from 40 to 25 000 cm -1 at 300 K and at 80 K. Unlike metallic glasses with a Drude spectrum with strong elastic scattering by disorder, or semiconductors with a conductivity gap, the optical conductivity of this quasicrystal is distinctive: Starting from the very low dc value it increases linearly with frequency well into the near infrared. A prominent peak in the conductivity is observed at 245 cm -1 ; its position and strength suggest that it arises from a direct excitation of phonons.

Angular-resolved photoelectron spectra from the fivefold surface of single-grain icosahedral Al70Pd21.5Mn8.5 exhibit a quasiperiodic dispersion of 300 meV at 2.3 eV binding energy. Low energy electron diffraction studies confirm quasicrystalline order at the surface. A distinct pseudogap feature is observed with a density of states near the Fermi level decreasing as a square-root power law.

Conductometric titration of poly(N‐isopropylacrylamide) (polyNIPAM) with sodium dodecyl sulfate (SDS) gave two apparent transitions labeled C1 and C2. The C1 transition was independent of polyNIPAM concentration in the 0.05–0.3 wt % range, whereas C2 was proportional to the polymer concentration. C1 corresponded to the onset of binding of surfactant with polymer. Arguments based on a simple mass action model for micellization are presented to show that C2, the second transition, is not due to any simple explanation such as being the point above which only free micelles are formed with surfactant addition. The cloud point of polyNIPAM increased with the amount of bound surfactant. This was attributed to electrostatic contribution of bound sulfate groups to the increased solubility of polyNIPAM. © 1993 John Wiley & Sons, Inc.

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