Synthesis of Polycarbonate Precursors

Srivastava, R. Srinivas, D. Ratnasamy, P. Synthesis of Polycarbonate Precursors over Titanosihcate Molecular sieves. Catal. Lett. 2003, 91, 133-137. 

Mercuric-5-nitrotetrazole [Structure (2.13)] was prepared according to the methods reported by Gilligan et al. [14] and Redman and Spear [15]. Thus, 5-aminotetrazole was treated with sodium nitrite and copper sulfate to obtain Cu(NT)2HNT-4H20 (where NT nitrotetrazole). The copper salt was subsequently converted to the ethylene diamine complex MNT was then obtained by treating the complex with mercuric nitrate in HN03 medium. The precursors and final product were air dried. The synthesis of these compounds is carried out in a fume hood behind a protective polycarbonate shield in a stainless steel reaction vessel. 

Scheme 6.12 Examples of titanium precursors for the synthesis of aliphatic polycarbonates.

The synthesis of SiC nanofibers (5-20 nm in diameter) by using sol-gel and polymer blend techniques was achieved by Raman et cd. [119]. In this case, tetra-ethoxysUane and methyltriethoxysUane were used as a Si source, and polycarbonate as a carbon source. A polymer solution containing alkoxide, water, and a suitable solvent was stirred and freeze-dried to produce an intimate mixture of polycarbonate and sol-gel-derived sUica. The dried precursor was then pyrolyzed at 1400 °C in an argon atmosphere to obtain nanostructmed SiC. 

S Polycarbonate (PC). Although the first reported synthesis of aromatic polycarbonates from bisphenol-A can be traced back to Einhom in 1898, there were no additional investigations into this polymer for the next 50 years. Despite numerous investigations into polycarbonates derived from other aromatic diols, the foundation of the polycarbonate industry lies on bisphenol-A. Hereafter, the term PC will refer only to bisphenol-A polycarbonate. Eigure 9.8 shows the structures of the PC polymer and its monomer precursors. 

The sol-gel method is a low temperature synthesis route for complex oxides [42]. It can be used to make complex functional oxide nanowires inside the pores of templates. In addition to the sol-gel method precursor-based solution deposition routes can also be used for nanostructure formation [43]. In both cases a postdeposition high temperature anneal (>500-600 °C) is needed to form the required stoichiometric phase. Due to the requirement of a high temperature anneal, alumina templates are used as the polycarbonate membranes decompose at a much lower temperature. For chemical solution deposition the membrane is dipped directly into the precursor solution. For sol-gel growth generally the required sol is prepared and the template is put into the sol for a required period (e.g. 0.5-1 h). After removing the membrane from the sol it is dried and then annealed at higher temperature before the required phase is formed. A schematic of the sol-gel route is shown in Figure 21.10. 

Another polyester type, i.e., polycarbonate, is rather seldom solvolytically depolymerized because of losing (at least partially) carbonate groups/bonds obtained via phosgene route synthesis. Troev et al. [29] recently described PC chemical degradation with dialkyl phosphonates (dimethyl or diethyl) or triethyl phosphate. The products, oligomeric carbonates containing phosphorus atoms, can be considered as precursors for the modification of various polymers by improving their flame-retardant properties, thermal stability, and adhesion. 

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