Self oscillating polymer, the most popular materia

Materials that will "drive crazy": self oscillating polymer

the so-called self oscillating polymer (hereinafter referred to as SOP) that promotes collaborative innovation demonstration refers to polymer materials driven by chemical self oscillating chemical reactions. This concept was first proposed by Japanese scientist Ryo Yoshida in 1995. It is a special stimulus response polymer. Traditional stimulus response polymers can only realize one-way changes in properties or states, while SOP can realize autonomous, reversible and periodic changes

at present, the stimulation source of self oscillating polymers generally adopts chemical reactions with self oscillating characteristics, such as Belousov zhabotinski reaction, Bray liebhafsky reaction, Briggs Rauscher reaction, pH oscillation reaction, etc. The basic design idea of self oscillating polymers is that polymers contain functional groups that respond to oscillating reactions, and the oscillating changes of reactants or products of oscillating reactions drive the oscillating changes of polymer properties

▲ BZ OSCILLATING REACTION, the color shows oscillating changes in the process of oscillating response

the research on SOP driven by BZ reaction is the most extensive and in-depth. At present, the research on SOP is mainly conducted by foreign scientific research institutions, mainly including the University of Tokyo, brandeisuniversity, University of Massachusetts, University of Pittsburgh, etc. So, what research have scientists done with self oscillating polymers

the following is a brief example

basic structure of self oscillating polymer

take the self oscillating polymer with temperature sensitive structure developed by Yoshida as an example for detailed analysis. The polymer is in the form of copolymer, which contains temperature sensitive unit NIPAAm and repetitive unit ruthenium containing monomer that responds to BZ reaction. The solubility of the polymer will change periodically with the progress of BZ reaction, and material systems such as vesicles, gel and polymer brushes with oscillating response can be obtained

▲ the structure of typical self oscillating polymer, each system has fine-tuning structure due to different needs

self oscillating polymer vesicles

stimulus response vesicles are important new nano particle materials. There are also many vesicular structures in human cells, which have attracted extensive interest of scientists because of their special functions. Yoshida uses the weight reduction value of the block polymer (structure is shown in Figure 1) that is responsive to the ions in the BZ reaction to compare the large bubbles, and controls the temperature between t0 and tr (t0 is the critical aggregation temperature when the polymer is in the oxidation state, and TR is the critical aggregation temperature when the polymer is in the reduction state). It can observe the automatic formation and fragmentation process of the bubbles

▲ due to the periodic formation and dissociation of vesicles, the solution system presents periodic turbidity and clarification

artificial cells

cells are the most recent structural and functional units of organisms, and their importance is self-evident. Yoshida reported a new SOP simulating cells. The mechanism is similar to the above vesicles, but the difference is that the system has a cross-linking structure, and the vesicles will not dissolve periodically, but will periodically change in volume and "self beating" phenomenon will occur

▲ periodic beating cell like structure

autonomous intestinal peristalsis

intestinal peristalsis plays an important role in the digestion and absorption of substances. In order to simulate such changes, Yoshida designed a self oscillating gel, which was designed into a tubular structure to achieve a bionic function similar to intestinal peristalsis. This tubular gel material immersed in the solution with BZ reaction can not only be similar to the volume contraction expansion change of block gel, but also observe the automatic transportation of bubbles in the self oscillating gel

▲ the movement of gel materials over time

phototaxis and photophobia movement

in nature, many organisms have phototaxis and photophobia behaviors, such as moths fighting the fire and sunflowers turning with the sun. Researchers have also simulated similar phototaxis and photophobia movements based on the frequent use of SOP. The principle used is that BZ reaction has a high degree of inhibition in the environment with high light intensity, and vice versa. Use SOP gel to observe the position change of gel under different light intensities. It is found that when irradiated with a light source with a wavelength of 460nm and a large light intensity, the self oscillation frequency of the gel in the dark field is higher than that of the gel in the bright field. The experimental standard is that the gel tends to be certain in the direction of the dark field, showing light avoidance

generally speaking, the research of SOP materials is still in the preliminary exploration stage of model establishment and simple application, and its application in bionics will be the trend and goal in this field. It can be predicted that through multidisciplinary and multidisciplinary cooperation, SOP materials will find a real application battlefield and develop into practical intelligent polymer materials