Silicones and Siloxanes (Oils, Gums, Rubbers, Coatings)

Siloxane compounds have very special properties which lead to their usage for many industrial applications including as foaming agents, defoamers, lubricants, mold releases (low surface energy) and electrical tranformers (high thermal stability, high electrical resistivity). Our group has experience in preparing silicones and modifying their molecular weight profile. We are also active in the development of new strategies to incorporate functional organic sidechains that lead to surface activity, and enhanced biocompatibility.

Our expertise: New routes to silicones with precise structures using both novel silicone chemistry and organic chemistry.

Silicone Elastomers / Rubbers

Silicone elastomers are used as sealants, electrical insulants, release coatings, biomedical applicaitons and many others.  Our research examines strategies to control both the internal structure and external interfaces to change compatibility.  We are also active in the development of alternative cure chemistry (see next section).  In addition to standard potting and sealing elastomers, foamed structures can be created.

Our expertise: Synthesis and characterization of elastomers with well-defined and controlled modulus, surface roughness, tackiness (also including gels), silicone/organic polymer copolymers and interpenetrating networks.

Silicone Cure Chemistry

RTV Cure

Room temperature vulcanization cure or moisture cure silicones are often used in sealing applications (e.g., bathtub caulking). The presence of water in the atmosphere and catalysts (typically tin or titanium based) in the one part system effect the cure.

Our expertise: Manipulating moisture cure processes to control surface and internal structuring, for example, to manipulate drug release profiles and dope the silicone with structured silica.

Addition (Platinum) Cure

Two part systems usually rely on hydrosilylation catalyzed by platinum catalysts (hydrosilation involves the coupling of an Si-H containing compounds with an alkene RCH=CH₂). Silicones produced this way are of use as potting compounds, sealants, silicone rubbers and paper coating among other applications. They are also widely used in biomedical devices: we have published about the chemistry of platinum in devices.

New cure systems

Click chemistry (alkyne + azide) will operate in absence of any metal catalyst.  Piers-Rubinsztajn condensation is catalyzed by boron Lewis acids. These two protocols offer new, metal-free strategies to create silicone elastomers.

Our expertise: Hydrosilylation catalysts and processes (e.g., platinum chemistry), metal free routes to elastomers, silicone/organic polymer copolymers and interpenetrating networks.

Surface Active Silanes

Silanes are active at interfaces.  They are used as surfactants, foam stabilizers (e.g., polyurethane foams), as defoamers (e.g., in antacid preparations) and adjuvants (superwetters) in delivery of agricultural chemicals.  Most of these compounds are based upon silicone-polyether (e.g., poly(ethylene glycol)(PEG) graft copolymers.  We are currently preparing new materials based on silicones grafted to PEG, and natural products including proteins, polysaccharides and DNA.  These materials can be utilized to structure silicone elastomers and to hydrophilize silicone and other surfaces.

Our expertise:Preparation of organofunctional silicones and silicone elastomers with controlled wettability, including permanent wettability by water.

Silane Coupling Agents

Organofunctional silanes (silane coupling agents) are used to stabilize inorganic materials in organic matrices and as adhesion promotors (e.g., fiberglass reinforced polyester, use of silica as a filler, improved silicone (or other material) adhesion to a metal surface). Different functional species are available, including bases, thiols, radically active groups, etc. 

Our expertise:New multifunctional coupling agents and their use in the modification of monolithic and colloidal silica both to change the chemical nature and the electrostatic charge on the surface.