A research group at the Institute for Solid State Physics, University of Tokyo has achieved the synthesis of an extremely uniform gel that overturns the common sense of soft materials.
Polymer gel materials such as jelly are soft materials that are common around us.Its applications are wide-ranging, such as water-absorbing and water-retaining materials for diapers and cosmetics, separation membranes for DNA and proteins, and sustained-release carriers for anticancer agents.
Gels are made by pinning (crosslinking) macromolecules with each other in solution.Since this cross-linking reaction proceeds stochastically between macromolecules that move randomly in solution, it has been thought that the polymer cross-linking structure formed is inevitably non-uniform.
On the other hand, in this study, we found that by densely filling the polymer in the solution before gelation, it is possible to maintain a uniformly dispersed state even after gelation.By proceeding with the cross-linking reaction in a state where the space in the solution is always uniformly filled, it is said that the final cross-linking structure has succeeded in creating an extremely uniform gel.
Since the network structure of a normal gel is non-uniform, random interference spots (speckles) are detected when a laser beam is applied.On the other hand, when this gel was evaluated by light scattering or X-ray scattering, no speckle of scattered light showing spatial non-uniformity was found.Not only that, because the spatial and temporal correlations of the polymer chains before and after gelation were exactly the same, gelation could no longer be detected by the general scattering method, and it was a solution until you actually touched it. It is said that it cannot be determined whether it is a gel or a gel. It overturns the common sense that "gel has a non-uniform network structure" and even redefines the state of gel.
Since this gel does not cause anomalous scattering of light due to structural non-uniformity, it achieves the theoretical upper limit of transparency that can be achieved as a soft material, and is expected to be applied to optical fibers and the like.In addition, since this method can be applied to a wide range of polymer species regardless of the type and reaction mode of the polymer, it is expected to have a ripple effect in various fields such as medicine, pharmacy, chemistry, optics, and electronic engineering.
Paper information:[Science Advances] Polymer gel with a flexible and highly ordered three-dimensional network synthesized via bond-percolation
