In nature the synthesis of ordered siloxane structures, like those found in the spicula of sea sponges, is protein-mediated in water solution and at moderate temperature and pH. Procter & Gamble scientists have developed a process that produces cyclic siloxanes and silicone polymers through protein-mediated catalysis on a solid substrate. Moreover, these reactions occur under mild conditions and produce high yields. The researchers discovered that if organosilane monomers are combined on a solid substrate containing specifically sized pores, they polymerize into pieces no longer than the size of the pore. This reaction is assisted by two means. First, a protein catalyst (subtilisin protease) catalyzes the polymerization in the pores under mild conditions with very high efficiency. Second, solvents mediate the solubility of the monomer but cause precipitation of the polymer once it reaches the desired length. Purified polymers of uniform length can then be removed from the mixture for industrial use.
Protein catalyzed polymerization under mild temperatures and pHs is relatively non-toxic yet it produces high yields of the specific product. Since it does not require heating or the use of hazardous and caustic compounds, it is a much more sustainable process.
This process mimics the natural synthesis of cyclic siloxanes.
Industrial synthesis of polymeric silicones requires toxic organochlorides, high temperatures, and extreme pHs. This process produces large quantities of waste and is quite energy intensive.Edit Summary