Effect of the composition ratio of copolymerized poly(carbonate) glycol on the microphase‐separated structures and mechanical properties of polyurethane elastomers

Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C₆) and tetramethylene (C₄) units between carbonate groups in various composition ratios (C₄/C₆ = 0/100, 50/50, 70/30, and 90/10), and the number‐average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass‐transition temperature of the soft segment in the PUEs and the glass‐transition temperature of the original glycol polymer decreased and the melting point of the hard‐segment domain increased with an increasing C₄ composition ratio. The microphase separation of the poly(carbonate) glycol‐based PUEs likely became stronger with an increasing C₄ composition ratio. Young's modulus of these PUEs increased with an increasing C₄ composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C₄ composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase‐separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase‐separated structure and mechanical properties of the PUEs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4448–4458, 2004     

Equilibrium processes of oxygen diffusion between bulk and (100) surface of tantalum

The diffusion exchange by oxygen atoms between bulk and (100) surface of tantalum at the earliest stages of oxygen adsorption was studied by high-temperature Auger electron spectroscopy (AES), whereby the spectra were recorded immediately in the course of heating the sample up to 2500 K. A difference of the potential barriers for the inward and outward diffusion of oxygen was determined, and an equilibrium character of these processes in the temperature interval from 1000 to 2000 K was demonstrated. Heating to higher temperatures results in the intense thermodesorption of oxygen.     

SOA Direct Modulation in Wavelength-Selectable Laser Array Light Sources

We demonstrated, for the first time, 2.5-Gb/s SOA direct modulation in the wavelength-selectable DFB laser array. The SOA direct modulation was achieved in the wide tuning range of 22.7nm by selecting arrayed laser and tuning the temperature. 40-km transmission was also confirmed..     

A new approach for the formation of fused cyclooctane or cyclohexane rings

The intramolecular regioselective addition of unsymmetrical allylsilanes to conjugated dienones is shown to permit facile entry into 5-6, 6-6, 5-8, and 6-8 bicyclic ring systems.