Radical ring‐opening polymerization and copolymerization with expansion in volume

Abstract

Abstract Although ring‐opening polymerization involving ionic intermediates and Ziegler catalysts are quite extensively used in polymer chemistry, free radical ring‐opening polymerization is extremely rare. We have been able to show that unsaturated spiro ortho carbonates will undergo double ring‐opening polymerization under radical conditions. In addition these monomers will undergo ready copolymerization with common monomers, such as styrene, methyl methacrylate, and diallyl carbonate. Since this process involves a double ring‐opening, a slight expansion in volume occurs. For a number of industrial applications, such as precision castings, strain‐free composites, binders for solid propellants, high strength adhesives, dental fillings, and rock‐cracking materials, it is highly desirable to have monomers that expand on polymerization. In the formation of composites, such a monomer might minimize poor adhesion between the matrix and the reinforcing agent or eliminate microcracks. Formation of additional polymers usually involves shrinkage since the monomer undergoes a transition from a van der Waals distance to a covalent distance in the polymeric material. Ring‐opening polymerization usually involves somewhat less shrinkage because for every new bond that is formed involving a shift from a van der Waals distance to a covalent distance, another bond is broken involving a shift from a covalent distance to a near van der Waals distance. Thus, if monomers are utilized in which two bonds are broken for every new bond that is formed in the polymerization process, near zero shrinkage or expansion takes place.