Ph.D., 1983, Stanford
Experimental Atomic, Molecular, and Optical Physics,Experimental Chemical Physics,Experimental Condensed Matter Physics
Professor Bloomfield is studying borosilicones, remarkable materials that have been misunderstood for over 70 years. Dismissed as scientifically uninteresting and used as children's toys (e.g., Silly Putty), borosilicones are actually network liquids---dynamic macromolecules that appear elastic on short timescales but exhibit flow on longer timescales. Each borosilicone is a vast covalent network of silicone polymer chains joined by 3-attachment boron crosslinks. At any instant, a borosilicone is a highly-crosslinked elastic material. Because the boron crosslinks are temporary, however, the network evolves with time and the borosilicone exhibits liquid behavior. While the simplest borosilicones are elastic liquids, more complicated borosilicones are intermediate between elastic liquids and elastic solids. The dynamics of these non-simple borosilicones are well-described by differential equations of fractional-order (see fractional calculus). When the concentration of permanent crosslinks added to a borosilicone exceeds the gelation threshold, the borosilicone loses its ability to flow and becomes a viscoelastic silicone rubber (VSR). A VSRs is a dual-network system: a liquid network piggybacking on a solid network. It has an equilibrium shape dictated by the topology of its solid network, but exhibits the extreme viscoelastic behavior associated with its liquid network.
Shape Recovery in Viscoelastic Silicone Rubber and the Fractional Zener Model (L. A. Bloomfield), arXiv:1912.08889 [cond-mat.soft] (2019).
Rapid technique for preparing conductive graphene-borosilicone putty (L. A. Bloomfield), arXiv:1912.02116 [cond-mat.soft] (2019).
Laminar Flow and Backrind Formation in Molding of Viscoelastic Silicone Rubber (L. A. Bloomfield), arXiv:1905.06313 [cond-mat.soft] (2019).
Borosilicones and Viscoelastic Silicone Rubbers: Network Liquids and Network Solids (L. A. Bloomfield), arXiv:1801.09253 [cond-mat.soft] (2018).
Viscoelastic silicone rubber compositions (L. A. Bloomfield), U.S. Pat. No. 9,550,864 (2017).
Viscoelastic silicone rubber compositions (L. A. Bloomfield), EP 2545103 (2016).
Viscoelastic silicone rubber compositions (L. A. Bloomfield), U.S. Pat. No. 9,102,799 (2015).