A Simple and Facile Approach to Aliphatic N-Substituted Functional Eight-Membered Cyclic Carbonates and Their Organocatalytic Polymerization

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• 作者：Shrinivas Venkataraman ; Victor W. L. Ng ; Daniel J. Coady ; Hans W. Horn ; Gavin O. Jones ; Tak Shun Fung ; Haritz Sardon ; Robert M. Waymouth ; James L. Hedrick ; Yi Yan Yang
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：November 4, 2015
• 年：2015
• 卷：137
• 期：43
• 页码：13851-13860
• 全文大小：509K
• ISSN：1520-5126

文摘

Aliphatic N-substituted functional eight-membered cyclic carbonates were synthesized from N-substituted diethanolamines by intramolecular cyclization. On the basis of the N-substituent, three major subclasses of carbonate monomers were synthesized (N-aryl, N-alkyl and N-carbamate). Organocatalytic ring opening polymerization (ROP) of eight-membered cyclic carbonates was explored as a route to access narrowly dispersed polymers of predictable molecular weights. Polymerization kinetics was highly dependent on the substituent on the nitrogen atom and the catalyst used for the reaction. The use of triazabicyclodecene (TBD), instead of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), as the catalyst for the N-alkyl substituted monomers significantly enhanced the rate of polymerizations. Computational studies were performed to rationalize the observed trends for TBD catalyzed polymerizations. With the optimal organocatalyst all monomers could be polymerized generating well-defined polymers within a timespan of 鈮? h with relatively high monomer conversion (鈮?0%) and low molar-mass dispersity (膼_M 鈮?1.3). Both the glass transition temperatures (T_g) and onset of degradation temperatures (T_onset) of these polymers were found to be N-substituent dependent and were in the range of about 鈭?5 to 35 掳C and 230 to 333 掳C, respectively. The copolymerization of the eight membered monomers with 6-membered cyclic comonomers including commercially available l-lactide and trimethylene carbonate produced novel copolymers. The combination of inexpensive starting materials, ease of ring-closure and subsequent polymerization makes this an attractive route to functional polycarbontes.