Reversible self-assembled structures balance two competing attractions to enable stimuli-responsive materials.
Scientists devised a new approach that balances attractions between particles and promises to become a useful tool to create designer materials that can repair damage. The discovery of a cross point between temperature-dependent interactions between particles – not previously thought possible – opens the doors for more nimble synthesis. The crosspoint exploits the temperature-dependent behavior (solubility and adsorption) of a polymer. Researchers discovered that a liquid polymer-colloid mixture on cooling and heating forms different solid phases reversibly. These solids are formed by two distinct pathways: (1) at low temperature, pressure from collisions with the surrounding non-adsorbing polymer forms a colloidal crystal and (2) at high temperature, the polymer sticks (adsorbs) to particles, forming a random aggregate.
This research opens a new pathway to stimuli-responsive self-assembled structures. Using the crosspoint pathway, it may now be possible to (1) thermally control viscoelastic properties, (2) heal defects that occur during assembly, (3) more controllably sequester and release objects, and (4) exert fine control over inter-particle interactions for sequential assembly of two- and three-dimensional materials with precisely organized optical and mechanical functions.
A new approach that balances attractions between particles promises to become a useful tool to fine-tune self-assembly and add functionality, such as error correction during assembly and damage repair. Previous polymer-directed routes for particle self-assembly were in stark contrast to biological systems that can form, reconfigure, and repair complex assemblies within cells by balancing assembly and disassembly processes.
In this research, understanding of the pathways for both assembly and disassembly was developed. The transformative aspect is the identification by researchers at New York University of a crossing point between the two pathways for a polymer-colloid mixture previously thought impossible; the crossing point mimics the biological assembly-disassembly capability. Adsorption properties of polymers change with temperature. At low temperature, colloidal crystals are formed due to pressure from collisions with surrounding non-adsorbing polymer. Actually, the colloids are squeezed together to increase the volume available to the non-adsorbing polymer. This mechanism for forming colloidal crystals was well known, but what was observed next was quite surprising. On heating, the colloidal crystal melted to form a liquid polymer-colloid mixture. Beyond this point, the solubility of the polymer decreased as the temperature increased; eventually, the polymer was able to weakly stick (adsorb) to the particles, creating bridges that solidify the liquid to a random aggregate gel.
At the crossover point between colloidal crystal deformation and gel formation, these new attractions (so-called enthalpic attraction, in thermodynamic terminology) completely balance the forces exerted by the volume available to the polymer from the particles being squeezed together (so-called entropic attraction). The crossing point depends on the change in solubility of the non-adsorbing polymer, resulting in a liquid-to-solid transition on cooling and heating. Most importantly, this process is thermally reversible at each stage of assembly and disassembly, which could allow entry into and out of the particles. As a result, it may be possible to heal defects in assembled structures, and to fabricate two- and three-dimensional materials with desired optical and mechanical properties. The general nature of these interactions suggests that they can be applied over a broad range of self-assembly approaches, such as the DNA-directed assembly of particle networks, to stimuli-responsive functional materials.
The Latest on: Stimuli-responsive materials
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The Latest on: Stimuli-responsive materials
- Rising temperatures: Sukhishvili and team develop novel biomedical soft materialson October 16, 2019 at 5:00 pm
“Developing stimuli-responsive materials that can deliver antibiotics only when needed is critical for the prevention of the spread of antimicrobial resistance, a rapidly increasing problem” said ...
- 4D printing makes lattice that turns into a faceon October 8, 2019 at 8:06 am
This design approach and multimaterial 4D-printing method could be extended to other stimuli-responsive materials and be used to create scalable, reversible, shape-shifting structures with ...
- Harnessing power of CRISPR to control behavior of DNA-responsive materialson August 22, 2019 at 11:22 pm
demonstrates the use of CRISPR as a control element in a new type of stimuli-responsive "smart" materials. Upon activation by specific natural or user-defined DNA stimuli, a CRISPR-Cas enzyme enables ...
- Yifei Jinon July 11, 2019 at 8:19 am
His primary research interests mainly involve 3D bioprinting of living tissue constructs, 3D printing of hydrophobic functional materials, yield-stress fluids for 3D printing applications, ...
- NMSU professor gets $315K to study membrane technologies for advanced water treatmenton June 29, 2019 at 2:43 pm
Reza Foudazi, a chemical and materials engineering assistant professor at New Mexico State University, has received a three-year, nearly $315,000 grant from the National Science Foundation for his ...
- R&D Profile: Stimuli-Responsive Polymers in bioMEMS Devices: F. Montagne, Swiss Center for Electronics and Microtechnology, CHon June 27, 2019 at 5:00 pm
Stimuli-responsive polymers, also referred to as "smart" polymers, are a very interesting class of materials since they exhibit ... two examples of real case application of stimuli-responsive polymers ...
- RUI: Solution and Thin Film Properties of Dually Stimuli-Responsive Molecular Brush Block Copolymerson May 29, 2019 at 5:00 pm
The stimuli-responsive functionality of PDMAEMA will be combined with block and branched copolymer architectures in order to generate new materials with expected unique solution and thin film ...
- Physical Stimuli Responsive Polymers Market Will Reflect Significant Growth Prospects during 2019 to 2026on May 10, 2019 at 6:25 am
8.5.1 Advanced Polymer Materials (Canada) Company Details 8.5.2 Company Description and Business Overview 8.5.3 Production and Revenue of Physical Stimuli Responsive Polymers 8.5.4 Physical Stimuli ...
- Muscle-Like Material Contracts When Illuminatedon April 5, 2019 at 2:21 pm
ST. LOUIS, April 5, 2019 — Researchers at Washington University in St. Louis (WUSTL) developed the material that in experiments showed the ability to lift a weight by simply shining a light on it.
- Muscle-like material expands and contracts in response to light (video)on April 2, 2019 at 12:51 pm
“The beauty of our system is that we can take a little bit of our polymer, called a polyviologen, and put it in any type of 3D network, turning it into a stimuli-responsive material,” Barnes says.
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