press release

Assembly of colloidal latex particles leads to innovation in fabrication of porous materials

Assembly of colloidal latex particles leads to innovation in fabrication of porous materials

Porous materials that have an interconnected network of pores are an interesting class of materials and have drawn attention in the area of separation science. The ability to fabricate robust so-called open cellular materials with control of the porosity remains a scientific challenge. The ability of regulating the interconnected network determines how a fluid (liquid or gas) can flow through the system. Think for example of how water runs through soil, or how water can be taken up through capillary action into a sponge. In addition, one can foresee that matter which flows through the porous material can temporarily be adhered/adsorbed onto the surface of the porous monolithic structure. The ability to easily control the surface functionality of the walls of the pores therefore is important.

In collaborative work with Chris Desire, a talented PhD student from the group of prof. Emily Hilder at the University of South Australia, we in the BonLab describe in Green Chemistry that we can use polymer latex particles as colloidal building blocks to form robust open cellular porous monolithic materials by simply stacking them onto each other. This assembly process is triggered by colloidal instability of a polymer latex dispersed in water which leads to the formation of a colloidal gel. The structure of the gel can then be made permanent by cross-linking through polymerization.

BonLab does PISA with RAFT-agent version 0.1

BonLab does PISA with RAFT-agent version 0.1

Call them plastics, polymers, elastomers, thermoplasts, thermosets, or macromolecules. What’s in the name? Despite the current negative press in view of considerable environmental concerns on how we deal with polymer materials post-use, it cannot be denied that polymers have been a catalyst in the evolution of human society in the 20st century, and continue to do so.

One of the synthetic pathways toward polymer molecules is free radical polymerization, a process known since the late 1800s and conceptually developed from the 1920s-1930s onwards. Since the 1980s it gradually became possible to tailor the chemical composition and chain architecture of a macromolecule. The process is called reversible deactivation radical polymerization (RDRP), also known as controlled or living radical polymerization. By grabbing control on how individual polymer chains are made, with the ability to control the sequencing of its building blocks, known as monomers, true man-made design of large functional molecules has become reality. This architectural control of polymer molecules allows for materials to be formulated with unprecedented physical and mechanical properties.

One interesting phenomenon is that when we carry out an RDRP reaction using a “living” polymer (a first block) dissolved in for example water and try to extend the macromolecule by growing a second block that does not dissolve in water, it is possible to arrange the blockcopolymer molecules by grouping them together into a variety of small (colloidal) structures dispersed in water. More interestingly, these assembled suprastructures have the ability to dynamically change shape throughout the polymerization process, for example to transform from spherical, to cylindrical, to vesicle type objects. This Polymerization Induced Self-Assembly process has been given the acronym PISA.

BonLab makes hydrogel beads communicate

BonLab makes hydrogel beads communicate

Hydrogels are soft objects that are mainly composed of water. The water is held together by a 3D cross-linked mesh. In our latest work we show that hydrogel beads made from the bio-sustainable polymer alginate can be loaded up with different types of molecules so that the beads can communicate via chemistry.

Chemical communication underpins a plethora of biological functions and behaviours. Plants, animals and insects rely on it for cooperative action, your body uses it to moderate its internal environment and your cells require it to survive.

A key goal of materials science is to mimic this biological behaviour, and synthetic objects that are able to communicate with one another by the sending and receiving of chemical messengers are of great interest at a range of length scales. The most widely explored platform for this kind of communication is between nanoparticles, and to a lesser extent, vesicles, but to date, very little work explores communication between large (millimetre-sized), soft objects, such as hydrogels.

In our work published in the Journal of Materials Chemistry B, we present combinations of large, soft hydrogel objects containing different signalling and receiving molecules, can exchange chemical signals. Beads encapsulating one of three species, namely the enzyme urease, the enzyme inhibitor silver (Ag+), or the Ag+ chelator dithiothreitol (DTT), are shown to interact when placed in contact with one another. By exploiting the interplay between the enzyme, its reversible inhibitor, and this inhibitor’s chelator, we demonstrate a series of ‘conversations’ between the beads.