A sample of the novel homogeneous polymer gel. Image: 2019 Li et al.Gel-like materials have a wide range of applications, especially in chemistry and medicine. However, their usefulness is sometimes limited by their inherent random and disordered nature. Researchers at the University of Tokyo's Institute for Solid State Physics in Japan have now found a way to produce a new kind of gel that overcomes this limitation. As they report in a paper in Science, the new gel is still malleable and adaptable like existing gels, but has a more ordered structure, which can open up a new range of possible uses in various fields.
The word ‘gel’ usually conjures up images of something wobbly and viscous like hair gel or the inside of a memory-foam mattress. But in the world of scientific research, gels have a more specific definition: strictly speaking, gels are three-dimensional networks of polymers with microscopic pores between the individual polymer strands. The nature and arrangement of these polymer strands give gels different functions leading to various applications, such as chemical filtration or drug delivery.
The creation of polymer network gels is difficult to control, so they are very disordered and contain many structural inconsistencies or defects. They are said to be heterogeneous, meaning their form varies widely throughout their structure. However, research associate Xiang Li and his colleagues have found a novel way to maintain a high level of order while fabricating polymer gels. The result is a homogeneous gel, one that has a more consistent structure whilst still providing the benefits of a highly porous and malleable material.
"We demonstrated that it's actually quite easy to synthesize an extremely homogeneous gel network," said Li. "First, we tightly packed some star-shaped polymers together in a solvent and added some chemicals which, when activated, join these star polymers together. We activated the joining or 'cross-linking' chemicals in a controlled manner; this in turn led to a more ordered polymer gel network than one might ordinarily expect from this kind of process."
The fabrication process, based on a concept known as bond percolation, is very effective at producing ordered gel networks – so much so that the researchers feel it forces them to redefine what actually constitutes a gel. Previously a gel was assumed to contain disorder and defects, but these no longer appear to be key properties.
"Ordered yet flexible gel networks could be used in applications like high-performance chemical filters, flexible sensors, mechanical actuators, controlled drug release and even ultraclear optical fibers," explained Li. "We want to encourage others to build on our work here and find other ways to synthesize new polymer gels based on what we have started. Although our method was very specific, it lays the foundations for a more general experimental platform."
This story is adapted from material from the University of Tokyo, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.