Hans-Joachim Hähnle

A Modular Approach for the Synthesis of Nanostructured Hybrid Materials with Tailored Properties: The Simultaneous Twin Polymerization

Twin polymerization (TP) has been shown to be an elegant method for the template-free synthesis of nanostructured hybrid materials and nanoscale porous inorganic oxides. In TP two different polymers are formed in a single step from the so-called twin monomer (TM). These polymers can be organic or inorganic in nature. In twin monomers, polymerizable building blocks are bonded together covalently. These covalent bonds are cleaved during the polymerization process. It is thus guaranteed that the growth of the two different polymer chains can become coupled in a reaction volume, which is limited both in terms of space, and mechanistically. TP is therefore clearly differentiated from the polymerization of hetero-bifunctional monomers in which the two polymerizable groups polymerize independently of each other or in which one of the groups initially remains completely intact during the polymerization. In theory in TP various different polymer strands can be situated next to each other, on the molecular length scale, immediately after their formation. Therefore, in the case of certain TP, compact nanostructured hybrid materials with a very small length scale (1–2 nm) of both homopolymer domains are formed within a defined time frame. The TP of the twin monomer 2,2’-spirobi[4H-1,3,2-benzodioxasiline] (SBS), which has already been investigated, leads to nanostructured hybrid materials consisting of silicon dioxide and a phenolic resin in a single process step (Scheme 1). In general, the TP of n molecules of the twin monomer, A-(C)m leads, by definition, to the formation of two homopolymers, -(A)nand -(C)n·m(Scheme 2). [1a]