Synthesis of Well-Defined Amphiphilic Poly(蔚-caprolactone)-b-poly(N-vinylpyrrolidone) Block Copolymers via the Combination of ROP and Xanthate-Mediated RAFT Polymerization

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• 作者：Avnish Kumar Mishra ; Vijay Kumar Patel ; Niraj Kumar Vishwakarma ; Chandra Sekhar Biswas ; Manoj Raula ; Arvind Misra ; Tarun Kumar Mandal ; Biswajit Ray
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：April 26, 2011
• 年：2011
• 卷：44
• 期：8
• 页码：2465-2473
• 全文大小：990K
• 年卷期：v.44,no.8(April 26, 2011)
• ISSN：1520-5835

文摘

Well-defined amphiphilic poly(蔚-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-b-PNVP) block copolymers were successfully prepared via the combination of ring-opening polymerization (ROP) and xanthate-mediated reversible addition鈭抐ragmentation chain transfer (RAFT) polymerization. Well-defined poly(蔚-caprolactone) (PCL鈭扥H) was synthesized by ROP in bulk at 110 掳C using benzyl alcohol as initiator and stannous octate [Sn(Oct)₂] as catalyst . The 鈭扥H end group was then converted into its corresponding xanthate (PCL鈭扻) via the conversion to its corresponding bromide (PCL鈭払r). These are verified by ¹H NMR spectroscopy. PCL-b-PNVP block copolymers were synthesized via RAFT polymerization in tetrahydrofuran (THF) at 80 掳C using PCL鈭扻 as macro-chain transfer agent and characterized by ¹H NMR spectroscopy and gel permeation chromatography (GPC). The amphiphilic diblock copolymer PCL₆₃-b-PNVP₉₀ forms spherical micelles of 34 nm diameter in water as shown by transmission electron microscopy (TEM), supported by ¹H NMR spectroscopy, and light scattering. The critical micellar concentrations were determined by fluorescence spectroscopy using pyrene as probe. The critical micelle concentration (cmc) value of the block copolymers increases with the increase in the chain length of PNVP block. The overall hydrodynamic radius (R_h) of the micelles remains almost constant over the concentration range above the cmc value and over the angles of scattering measurement.