Literatur

Ohne Zusammenfassung     

Zur fluorimetrischen Bestimmung von Oestrogenen im Harn

Ohne Zusammenfassung     

Dynamic mechanical and rheological properties of binary S–(S/B)–S triblock copolymer blends

The rheology and dynamic mechanical properties of binary block copolymer blends consisting of a symmetrical triblock copolymer with thermoplastic elastomeric behavior (LN4) and an asymmetrical thermoplastic triblock copolymer (LN3) were investigated. TEM images of the blends show a systematic variation in the morphologies from worms (～20–0 wt % LN3) to cylinders (～60–30 wt % LN3) to lamellae (100–70 wt % LN3) as a function of LN3 content. DMA analysis has revealed that the increase in LN3 content leads to a decrease in miscibility between the PS end blocks and the S/B middle block. The frequency and temperature dependence of the storage modulus (G′), loss modulus (G″), and complex viscosity (|η*|) has been studied for LN4 (weakly segregated) and LN3 (strongly segregated) from their master curves. By comparing the rheological properties of these blend compositions at low‐frequency regime, it is observed that with the increase in LN3 content the shear modulus and complex viscosity increase. Blend compositions with 70–100 wt % of LN3 show nonterminal behavior at reduced frequencies due to the presence of highly ordered microdomains when compared to blends with ～0–20 wt % of LN3 content. van Gurp–Palmen plots were constructed to observe the transition from liquid‐ to solid‐like behavior in the vicinity of order‐to‐disorder transition (ODT) temperature. ODT temperature increases as the thermoplastic LN3 content increases which are also confirmed by the Han plots. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 329–343, 2008     

Über das Molekulargewicht und die Viskosität von Hochpolymeren

Ohne Zusammenfassung187. Mitteilung über hochpolymere Verbindungen. 186. Mitteilung: W. Kern, Z. physik.Chem. Abt. A, im Druck.A. Dobry, Kolloid-Z.81, 190 (1937).     

Enhancement of mechanical properties of triblock copolymers by random copolymer middle blocks

Symmetric styrene-b-styrene-co-butadiene-b-styrene (S-SB-S) tri-block copolymers with varying middle and outer block composition have been studied. We report our findings based on a systematic variation of the effective interaction parameter (χ) by adjusting the composition of the random copolymer in the middle block and of the outer blocks (in terms of PS-chain length) which allows us to explore the χ-parameter space with regard to molecular architecture more thoroughly than in SBS triblock copolymers. A variation in the S/B middle block composition or in the PS outer block content leads to a change in phase behaviour and morphology simultaneously accompanied by significant changes in mechanical properties, varying from elastomeric to thermoplastic property profile. Despite high PS contents of 55-75 wt.% these S-SB-S triblock copolymers reveal high strain at break values between 650% and 350% which is in striking contrast to the conventional SBS triblock copolymers where only about 10% strain at break have been reported to be achieved with similar PS-content (∼75 wt.%).     

Application of enhancement mode FET technology for wirelesssubscriber transmit/receive circuits

Single-supply power amplifiers have become the new paradigm in portable phone handsets due to the recent availability of heterojunction bipolar transistor (HBT) and pseudo enhancement mode PHEMT technology. We have developed a true enhancement mode heterostructure insulated-gate FET device (HIGFET) which is suitable for use in both saturated and linear power amplifiers. A three-stage power amplifier designed for 1900-MHz NADC application delivered +30-dBm output power and 41.7% power-added efficiency with an adjacent channel power of -29.8 dBc and alternate adjacent channel power of -48.4 dBc. In addition to this, we have demonstrated excellent noise figure and linearity performance for small-signal applications. At 900 MHz and bias conditions V_DS=1.0 V and I_DSQ=1 mA, a single-stage amplifier achieved a noise figure of 1.17 dB with an associated gain of 18.5 dB. These results make the technology an ideal candidate for application in both transmitter and receiver circuits