Papers by Author: Rumana A. Jahan

Abstract: In this paper, we investigated the influence of the temperatureand the initial concentrations of malonic acid on the transmittance self-oscillation for a novel nonthermoresponsivepolymer chain. The amplitude of the self-oscillation hardly changes while change in the temperature and the concentration of malonic acid. The period of the self-oscillation does not decrease with increase in the concentration of malonic acid at 14, 16 and 18 °C.

Abstract: In this paper, theeffect of the initial concentrationof nitric acidon the soluble-insoluble self-oscillation for a novel polymer chainwith nonthermoresponsive nature was investigated. The self-oscillationoccurs induced by the Belousov-Zhabotinsky (BZ) reaction. In the condition of [HNO₃] = 0.1 M, no transmittance self-oscillation occurs. In addition, in thecondition of [HNO₃] = 0.2 M, the life-time of the self-oscillation is significantly short. This is because the solution pH much affects the BZ reaction. Moreover, we demonstrated that the period of the transmittance self-oscillation decreases with the increase in the temperaturein accordance with the Arrenius equation.

Abstract: In this paper, we investigated the effect ofthetemperatureand the initial concentration of sodium bromateon the soluble-insoluble self-oscillation of a nonthermoresponsiveself-oscillatingpolymer chain. The polymer chain consisted of Acrylamide (AM) main-chain covalently bonded to Ru (bpy)₃as a catalyst of the Belousov-Zhabotinsky (BZ) reaction. The amplitude of the transmittance self-oscillation is hardly affected by the concentration of sodium bromate and the temperature.

Abstract: We synthesized a self-oscillating polymer chain with a negatively charged moiety. The polymer chain caused the aggregation-disaggregation self-oscillation under the constant temperature induced by the Belousov-Zhabotinsky (BZ) reaction. In this study, we investigated the influence of temperature and the concentration of sodium bromate on the aggregation-disaggregation self-oscillation of the polymer solution (1.0 wt%) in a strongly acidic condition. As a consequence, we clarified that the life-time of the self-oscillation increased with decrease in the concentration of sodium bromate. On the other hand, the lifetime of the self-oscillation decreased with increase in temperature. In high temperature condition (48 and 60 °C), the amplitude of the self-oscillation was significantly inhomogeneous. Moreover, the frequency of the self-oscillation increased with increasing temperature. On the other hand, the frequency decreased with increase in the concentration of sodium bromate. This tendency was opposite to that in the acid-free condition and the 2.0 wt% AMPS-containing polymer solution.

Abstract: In this paper, we studied the effect of the temperature and the initial concentration of sodium bromate (NaBrO3) on the aggregation-disaggregation self-oscillation for a polymer chain. The polymer chain consisted of N-isopropylacrylamide (NIPAAm), Ru catalyst of the BZ reaction and Acrylamide-2-methylpropanesulfonic acid (AMPS) as a solubility control site. The concentration of sodium bromate and the temperature significantly affected the self-oscillating behavior and the period of the aggregation-disaggregation self-oscillation. Moreover, the amplitude of the aggregation-disaggregation self-oscillation of the AMPS-containing polymer solution decreased with time. The damping behavior is originating from the increase in the size of the polymer chain. In addition, this study clarified that the period of the self-oscillation of the AMPS-containing polymer solution in the strongly acidic condition was significantly shorter than that in the acid-free condition.