Experimental and Theoretical Study of the Living Polymerization of N-Silylphosphoranimines. Synthesis of New Block Copolyphosphazenes

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• 作者：Silvia Su谩rez Su谩rez ; David Presa Soto ; Gabino A. Carriedo ; Alejandro Presa Soto ; Anne Staubitz
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 9, 2012
• 年：2012
• 卷：31
• 期：7
• 页码：2571-2581
• 全文大小：412K
• 年卷期：v.31,no.7(April 9, 2012)
• ISSN：1520-6041

文摘

The sequential living polymerization of N-silylphosphoranimines for the synthesis of polyphosphazene-b-polyphosphazene diblock copolymers (PP-b-PP) has been studied both experimentally and theoretically. For the experiments, BrMe₂P鈺怤鈥揝iMe₃, [Cl₃P鈺怤鈺怭Cl₃][X] (X = PCl₆^{鈥?/sup>, Cl鈥?/sup>), Cl₃P鈺怤鈥揝iMe₃, ClMe₂P鈺怤鈥揝iMe₃, and [Me₃P鈺怤鈺怭Me₂Cl]+ were used as representative model reagents. Density functional theory (DFT) calculations in the gas phase adjusted for solvent effects on ClMe₂P鈺怤鈥揝iMe₃, [Cl₃P鈺怤鈺怭Cl₃]+, Cl₃P鈺怤鈥揝iMe₃, and ClMe₂P鈺怤鈥揝iMe₃ confirmed the experimental observations. The results have shown the necessity of starting with mono-end-capped initiators to avoid the formation of triblock chains. It was also demonstrated that the nature of the nucleophilic N-silylphosphoranimines and the electrophilic cationic end groups of the living polyphosphazenes strongly affects the polymerization reaction, imposing limits to its synthetic potential. Thus, good electron donor N-silylphosphoranimines, i.e. XR₂P鈺怤鈥揝iMe₃, react better with electron-deficient cationic end groups such as 鈺怤鈥揚Cl₃+, probably by molecular orbital (MO) control. The results led to the designed synthesis of well-defined PP-b-PP block copolymers with narrow molecular weight distributions of formula [N鈺怭(Ph)(Me)]_n-b-[N鈺怭(OCH₂CF₃)₂]_m and [N鈺怭(Ph)(Me)]_n-b-[N鈺怭(O₂C₁₂H₈)]_m, which are excellent candidates for micellation studies.}