Postpolymerization Functionalization of Copolymers Produced from Carbon Dioxide and 2-Vinyloxirane: Amphiphilic/Water-Soluble CO2-Based Polycarbonates

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• 作者：Donald J. Darensbourg ; Fu-Te Tsai
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：June 24, 2014
• 年：2014
• 卷：47
• 期：12
• 页码：3806-3813
• 全文大小：411K
• ISSN：1520-5835

文摘

Common CO₂-based polycarbonates are known to be highly hydrophobic, and this 鈥渋nert鈥?property makes them difficult for the covalent immobilization of bioactive molecules. A practical method for modifying polymers is to introduce various functional groups that permit decoration of polymer chains with bioactive substances. In this report, CO₂-based poly(2-vinyloxirane carbonate) (PVIC) with more than 99% carbonate linkages is isolated from the CO₂/2-vinyloxirane alternating copolymerization catalyzed by the bifunctional catalyst [(1R,2R)-SalenCo(III)(DNP)₂] (1) (DNP = 2,4-dinitrophenolate) bearing a quaternary ammonium salt on the ligand framework. It was also observed that the presence of propylene oxide significantly activates 2-vinyloxirane for incorporation into the polymer chain as well as inhibits the formation of cyclic carbonate in the terpolymerization process. DSC studies demonstrate that the glass transition temperature (T_g) decreases with the increase in the content of vinyl groups in the polycarbonate. By way of thiol鈥揺ne coupling, showing mainly 鈥渃lick鈥?characteristics and nearly quantitative yields, amphiphilic polycarbonates (PVIC-OH and PVIC-COOH) with multiple hydroxy or carboxy functionalities have been prepared, providing suitable reactivities for further modifications (ring-opening of l-aspartic acid anhydride hydrochloride salt and deprotonation by aqueous ammonium hydroxide (NH₄OH_(aq))) to successfully isolate the water-soluble CO₂-based polycarbonate PVIC-COONH₄, and the PVIC-OH-Asp polymer which shows particles dispersed in water with an average hydrodynamic diameter D_n = 32.2 卤 8.8 nm. It is presumed that this emerging class of amphiphilic/water-soluble polycarbonates could embody a powerful platform for bioconjugation and drug conjugation. In contrast to lower T_gs of PVIC, (PVIC-co-PC), PVIC-OH, and PVIC-COOH, the polycarbonates PVIC-OH-Asp and PVIC-COONH₄ show higher T_gs as a consequence of their intrinsic ionic property (ammonium salts).