Synthesis of new cyanosiloxanes
The aim of the work described in this thesis was to prepare polymers of structure I (SiMe2(CH2)yC(CN)2(CH2)ySiMe2O)n (y &'61 1, 2 or 3). Chapters 1 provides an introduction to the work. Methods for producing diadducts of malononitrile, which were central to the synthesis of I (y &'61 1, 2 or 3), are reported in Chapter 2. For the nucleophilic attack of allyl chloride by sodium, calcium and ammonium salts of malononitrile, polar aprotic solvents such as DMSO, sulpholane and liquid ammonia provided the best yields. During this work a GLC technique was developed for following the progress of the reaction. The results obtained revealed that both the mono- and diadducts of malononitrile were formed in the early stages of the reaction. This technique also demonstrated that calcium hydride gave better yields of diadduct than sodium hydride. The synthesis of I (y &61 3) is reported in Chapter 3. The stages were; i) synthesis of diallyl malononitrile, ii) hydrosilylation of the diadduct with dimethylchlorosilane, iii) hydrolysis of the resultant product to give (HOSiMe2CH2CH2CH2)2C(CN)2, and iv) the polymerization of the disilanol with various catalysts. Chapter 4 covers the attempt at the synthesis of I (y &'61 2). The diadduct (CH2&'61 CH)2C(CN)2 was synthesized by a variation on the Michael addition reaction. However, the both the yield and purity of the product were low. This led to poisoning of the platinum catalyst in the hydrosilylation reaction that followed. The attempts at the synthesis of polymer I (y &'61 1) are described in Chapter 5. Attempts to produce (HSiMe2CH2)2C(CN)2 were hindered by the low reactivity of HSiMe2CH2Cl. Further attempts were made to produce I (y &'61 1) by the ring-opening polymerization of a nitrile containing cyclic disiloxane.