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Self-organization in Polymer Gel Systems Incorporated with Active Elements

含有活性元素的聚合物凝胶系统的自组织

基本信息

批准号：
10640376
负责人：
MIYAKAWA Kenji
金额：
$ 2.24万
依托单位：
Fukuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The poly (N-isopropyl acrylamide)(PNIPA) gel coupled with Belousov-Zhabotinsky (BZ) reaction was prepared by covalently bonding the catalyst ruthenium (Ru(bpy)_3) to the polymer chain. The chemical oscillation in the BZ reaction is found to induce periodical and autonomous swelling-shrinking volume changes of the gel. In this new type of gel, conversely a volume change of the PNIPA gel affects the propagation of the chemical wave. Our attention was focused on effects of mechanical changes on the chemical wave by utilizing the thermally driven volume phase transition of the PNIPA gel. Both the velocity and the frequency of the chemical wave increased with increasing the temperature, and abruptly decreased at the volume transition temperature of the gel. The diffusion of HBr0_2, which is essential for the wave propagation, was hindered with increasing the temperature. The diffusion of HBrO_2 through the gel network in the low temperature region was explained in the same way as a simple diffusion of inactive molecules through a restricted environment. At the high temperature, in contrast, the change of the wave velocity cannot be explained by the simple diffusion theory. This is probably because non-homogeneities in reactant concentrations and the increase in the amount of bulky catalyst hinder the diffusion and the rate of reaction.Depending on the ratio of concentration of the reducing agent to that of the oxidizing agent, reduction waves appears in contrast to usual oxidizing waves. The most striking behaviors observed are self-replication and preservation of reduction pulse waves. In the former dynamics, after the propagating reduction pulse wave vanishes, it splits into two counterpropagating pulses. In the latter dynamics, counterpropagating reduction pulse waves annihilate each other upon head-on collision and then reappear.

通过将催化剂钌(Ru(bpy)_3)共价键合到聚合物链上制备了与Belousov-Zhabotinsky (BZ)反应偶联的聚(N-异丙基丙烯酰胺)(PNIPA)凝胶。研究发现 BZ 反应中的化学振荡会引起凝胶周期性且自主的膨胀-收缩体积变化。相反，在这种新型凝胶中，PNIPA 凝胶的体积变化会影响化学波的传播。我们的注意力集中在利用 PNIPA 凝胶的热驱动体积相变来研究机械变化对化学波的影响。化学波的速度和频率都随着温度的升高而增加，并在凝胶的体积转变温度处急剧下降。对于波的传播至关重要的HBr0_2的扩散随着温度的升高而受到阻碍。 HBrO_2 在低温区域通过凝胶网络的扩散可以用与非活性分子通过受限环境的简单扩散相同的方式来解释。相反，在高温下，波速的变化不能用简单的扩散理论来解释。这可能是因为反应物浓度的不均匀性和大体积催化剂数量的增加阻碍了扩散和反应速率。根据还原剂与氧化剂浓度的比率，出现与通常的氧化波相反的还原波。观察到的最引人注目的行为是减少脉冲波的自我复制和保存。在前一种动力学中，传播的还原脉冲波消失后，它分裂成两个反向传播的脉冲。在后一种动力学中，反向传播的还原脉冲波在正面碰撞时相互湮灭，然后重新出现。