A set of polystyrenes of varying molecular weights was synthesized by anionic polymerization under identical conditions, and their molecular weight distributions were critically examined. Polymerization of styrene was initiated with 2-butyllithium in cyclohexane at 45 °C. During the polymerization, seven aliquots of the reaction mixture were taken out at various reaction times using a cannula and terminated. The polymerization time varying molecular weights and molecular weight distributions of the polystyrenes were analyzed by temperature gradient interaction chromatography (TGIC) as well as size exclusion chromatography. The molecular weight distribution of the polystyrene approaches the Poisson distribution in the late stages of the polymerization, in accordance with the early prediction of Flory. We also confirmed that the molecular weight distribution of polystyrenes determined by TGIC is close to the true value.

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We have fabricated Si-based micromachined DNA polymerase chain reaction (PCR) chips with different groove depths. The platinum thin-film micro heater and the temperature sensor have been integrated on the chip. The volume of the PCR chamber in the chip is about 3.6 µl and the chip size is 17 × 40 mm2. The effects of groove geometry, including width, depth and position, on the thermal characteristics of the PCR chip have been investigated by numerical analysis and experimental measurement. From the results, the power consumption required for the PCR chip is reduced with the increase of groove depth. Compared with results for the case of no groove, the power consumption of the chip with a groove of 280 µm is reduced by 24.0%, 23.3% and 25.6% with annealing, extension and denaturation, respectively. The heating rate is increased rapidly with the increase of the groove depth. In particular, it is revealed that this effect is predominant for depths in the region above 280 µm. For a more precise control of chip temperature, the nonlinear feedback proportional-integral control scheme is used. The obtained heating and cooling rates are about 36 °C s−1 and 22 °C s−1, respectively. The overshoot and the steady state error are less than 0.7 °C and ±0.1 °C, respectively. In the experiment, the effects of the PCR buffer and the bubbles in the chamber on the temperature uniformity have also been studied. From the temperature measurement, it is revealed that the temperature difference between the thin-film sensor (on the lower plate) and the PCR buffer can be neglected if there is no air bubble in the PCR buffer. With such a high performance control scheme, we could implement a remarkable thermal cycling of conducting 30 cycles for 3 min. Finally, the chip PCR of plasmid DNA was successfully performed with no additives using the temperature control system.

The glass transition temperature (Tg) of poly(tert-butyl methacrylate) (PtBMA) Langmuir-Blodgett (LB) films relative to that of spin-coated films on a silicon substrate is investigated by ellipsometry and X-ray reflectivity. The Tg of spin-coated films on an oxide-free silicon wafer decreases as the film thickness decreases, which is consistent with the majority of the previous reports in the literature. However, the transition temperature of the LB films is nearly independent of the total thickness, that is, the number of accumulated layers, which is much different from the case for spin-coated films. After sufficient thermal annealing of the LB film, it recovers the thermal transition behavior of the spin-coated film with an equivalent thickness. The layer structure of the LB film is deemed to be responsible for the departure from the behavior of the spin-coated film.