a b s t r a c tA series of polyethyleneimine (PEI)-fatty acid complexes using oleic acid (OA), isostearic acid (ISA), and stearic acid (SA) were prepared through a simple process. While PEI was not soluble in toluene, the complex with OA and ISA became soluble when its additive content was greater than 5 mol% based on the ethyleneimine (EI) unit of PEI. PEI-SA had similar solubility in toluene when more than 5 mol% of SA was added; however, the complex precipitated when the additive ratio of SA was increased to 40 mol%. The effect of fatty acid of PEI complexes on their TiO 2 nanoparticle adsorption properties and the flow curves of TiO 2 nanoparticle/toluene suspension was then studied using PEI complexed with 30 mol% of fatty acids. Surprisingly, while PEI-OA and PEI-ISA complexes effectively adsorbed on TiO 2 nanoparticles until saturation, the amount of adsorbed PEI-SA increased continuously. Comparing the flow curves of TiO 2 /toluene suspensions under 1.4 mg/m 2 addition of PEI-fatty acid complexes, where PEI-OA and PEI-ISA were under saturated adsorption, it was confirmed that PEI-OA effectively stabilizes TiO 2 nanoparticles in toluene without imparting thixotropic properties up to 30 vol%, while the suspensions with PEI-SA and PEI-ISA were solidified at lower volume contents and had high thixotropic properties.

We report on a 2.5 Gbit/s transmission experiment at 645 nm wavelength using a PMMA–GI–POF with a core diameter of 500 μm reaching a record distance of 200 m. The result is obtained owing to the use of a very sensitive silicon APD receiver, a laser source with a narrow spectral width, a fiber with improved performance, and low‐loss optical interconnection between the components. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 163–166, 1999.

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