McCarthy Research Group
McCarthy Research Group
B.S. Chemistry, University of Massachusetts Amherst, 1978
Ph.D. Organic Chemistry, Mass. Institute of Technology, 1982
Room: A512, Conte Research Center
University of Massachusetts Amherst
120 Governors Drive
Amherst, MA 01003
The McCarthy group uses chemistry and pretty much any other tool we can find to try to understand and control materials properties. We have predilections for polymers, surfaces and interfaces so our labs are well equipped to address questions in these areas. But we don't hesitate to do organic, inorganic, polymer or organometallic synthesis if the situation requires it. Neither do we hesitate to use the expertise and strength of the other groups in PSE - many of our situations turn out requiring this. We've had particular interests over the past 3 decades that include (a) polymer surface modification, (b) polymer adsorption, (c) chemistry and processing of supercritical fluid - swollen polymers, (d) gas separation and barrier materials, (e) metal, metal oxide and graphite surface chemistry (usually involving polymer interfaces, but also covalently attached monolayers), (f) plasma polymerization and chemical vapor deposition, and (g) wetting physics. We've also dabbled in a few other areas including (h) small polymer objects, (i) magnetic particles/ferrofluids and (j) using ionic liquids for various tasks. Current interests include silicones, thermal spray coating, the surface chemistry of several inorganic materials, and using the controlled wetting of particles and surfaces to make new things.
Two Recent Research Highlights:
1. Peiwen Zheng, Ph.D. 2012, showed that anionic siloxane equilibration is a simple and obvious mechanism to effect self-healing in cross-linked PDMS-based silicones. "Living" network polymers were prepared by copolymerizing cyclic and polycyclic siloxanes with anionic initiators. The anionic (silanolate) chain ends persist in the product and react with polymer segments to open and close network junctions. Two samples of this type of material react with one another (co-equilibrate) when placed in contact because of this equilibration reaction – they form one object. When mechanical stress is applied to samples of these materials, they change shape in response to the stress and relieve the stress using this siloxane interchange reaction. Because "self-healing" is a topical research area Peiwen carried out detailed studies on this process, but also had some fun. After breaking, healing and rebreaking many dog bone – shaped objects, she cut up a dog bone and remolded into a dog.
2. Joe Krumpfer, another 2012 Ph.D., applied some wetting physics that was discovered in the McCarthy Group to form an array of individual salt crystals mounted on micrometer scale posts. When a water-repellent surface containing posts (it is water repellent because perfluoro-alkyl groups are covalently attached) is submerged and withdrawn from water, it emerges apparently completely dry. We predicted that it should, in fact, not be dry, but should have little drops of water on the top of each post. You don't see these drops because they evaporate very quickly. When you use salt water, however, the salt gets left behind. Because the drops are so small, only one nucleation event occurs and only one crystal forms on each post. There are about a million mounted crystals on a 1 cm2 area sample of this surface.