Materials

Dr. Smith from the University of Illinois has developed a series of colloidal quantum dots that have precisely matched brightness among different colors. The brightness of the quantum dots is quantitatively equalized on single particle and ensemble level, using a core/shell/shell structure. Such brightness equalized quantum dots can be applied for quantitative and multiplex bio-imaging, as well as in optoelectronic devices and displays.

Researchers at the University of Illinois at Urbana-Champaign have developed a powerful new platform of polyureas that enable systems that are hydrolyzable, self-healing, and malleable, opening exciting applications in the packaging, coating, and adhesives industries.  In this new class of polyureas, a bulky substituent is attached to one of the nitrogen atoms of the urea bond and destabilizes the typically stable linkage leading to dynamic dissociation. The polymers can be built from the vast library of isocyanate monomers already developed for the polyurea and polyurethane industries, yielding a wide range of materials with varying, engineered characteristics.

Hydrolyzable Polyureas (TF14085)

Hydrolyzable polymers are currently used in the agriculture and food industries as environmentally friendly plastics and packaging materials and in the biomedical field as drug delivery systems, surgical sutures, and scaffolds for tissue engineering.  However, most hydrolyzable polymers, based on polyester materials or materials containing anhydride, acetal, ketal, or imine linkages, are synthesized via condensation or ring-opening polymerizations, often requiring high temperature conditions and catalysts and resulting in by-products.  In contrast, because polyureas are made via a simple and clean chemistry without catalysts or by-products, hydrolyzable polyureas offer users the ability to tune polymer systems to specific applications without involving complex chemistries.

In this platform of polyureas, the destabilization introduced by the bulky substituent on the nitrogen of the urea bond leads to dynamic dissociation to the corresponding amines and isocyanates, with the isocyanates further undergoing irreversible hydrolysis in aqueous solution and complete degradation of the polyurea.

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Polyureas That Love to Break Down
Chemical and Engineering News, December 8, 2014, http://cen.acs.org/articles/92/i49/Polyureas-Love-Break-Down.html

Self-Healing Polyureas (TF12136)

Incorporating the appropriate bulky substituents into polyureas enables polymers that can undergo autonomous, catalyst-free repair at room/low temperatures without the use of microcapsule healing agents, special precursors or customized laboratory/environmental conditions.  Commercially available materials are used to produce self-healing polymers with capabilities to re-heal multiple times.

Here the bulky substituents are chosen so that (i) the dissociation and reverse (polymer-forming) reactions are rapid and (ii) the polymer-forming reaction is highly favored, thereby insuring optimum bulk mechanical properties of the polymer.  Conventional  polyureas and poly(urethane-urea)s can thus readily be made dynamic and self-healing while maintaining their stability by replacing regular amines with amines containing bulky substituents.  By tuning the substituent, the dynamic properties of the polymer and its mechanical properties can be controlled. 

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Also see.

Malleable Polyureas (TF15006 / 2015-152)

The polyurea systems can also be made malleable and recyclable by exploiting the reversible nature of the urea bond with the bulky subsituent.  The cross-linked systems bearing the bulky substituents can be ground into powders and pressed/molded as shown below.

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Surface adhesion is a ubiquitous need for consumer, manufacturing, and industrial applications. Whether hanging art on the wall, enabling pick-and-place robotics, or rapidly attaching components to a system or building, the ability to create strong, temporary seals that are reusable and do not damage surfaces is cruicial. Existing solutions based on magnets, sticky adhesives, and suction cups have limitations regarding which surfaces they can be applied to (e.g., suction cups require a smooth surface; magnets require a metallic one), how reusable they are, and how strong a bond they can form (e.g., suction cups can only achieve 1 atmosphere (atm) of adhesion in air).  

Researchers at the University of Illinois Urbana-Champaign have developed a two-part dry adhesive system that is strong, reusable, and capable of gripping a wide variety of smooth, rough, and non-homogenous surfaces, both flat and curved. The system features an electrically conductive layer that triggers a thermoresponsive adhesive layer; re-application of voltage allows the adhesive to be removed with no damage or loss of function to either the surface or the adhesive. This technology bonds in seconds, is residue-free, is made from inexpensive materials, does not pick up debris over time like a traditional "sticky" adhesive surface, and has been demonstrated to work on a wide variety of surfaces and environments, including underwater. The bond formed is extremely strong, with researchers showing 18 atm adhesion in initial tests. The technology has also been demonstrated in conjuction with a robotic gripper arm. 

Benefits

• Reusable                                              
• Adhere to a range of surfaces, including smooth, rough, non-homogenous, non-magnetic, magnetic, fabric, etc.                                            
• No damage to surface the device adheres to                            
• Waterproof                                          
• Strong bond

Applications

Applications incude manufacturing (pick-and-place robotics that interface with a single surface of a component are often limited to materials that will respond to magnetic or suction adhesion), consumer (e.g., hanging things on walls), textiles (e.g., modifying and reusing uniforms), and myriad other industrial applications. 

Publication

Microstructured Shape Memory Polymer Surfaces with Reversible Dry Adhesion. Jeffrey D. Eisenhaure, Tao Xie, Stephen Varghese, and Seok Kim. ACS Applied Materials & Interfaces 2013 5 (16), 7714-7717

DOI: 10.1021/am402479f

Professors Jeffrey Moore, Nancy Sotos, and Scott White from the University of Illinois has developed a novel method to create composites that allows for much easier manufacturing and more design latitude.