Overcoming a Tight Coil To Give a Random 鈥淐o鈥?Polymer Derived from a Mixed Sandwich Cobaltocene

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• 作者：Mahboubeh Hadadpour ; Yuqing Liu ; Preeti Chadha ; Paul J. Ragogna
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：September 23, 2014
• 年：2014
• 卷：47
• 期：18
• 页码：6207-6217
• 全文大小：524K
• ISSN：1520-5835

文摘

Reversible addition鈥揻ragmentation transfer (RAFT) polymerization of a 畏⁵-cyclopentadienylcobalt-畏⁴-cyclobutadiene (CpCoCb) containing monomer under a wide variety of experimental conditions (e.g., different solvents, temperatures, RAFT agents, concentrations, and [RAFT agent]/[initiator]) was examined. In all cases the results revealed that although the monomer was being consumed over the course of the reaction, there was no significant increase in the molecular weight of the resulting polymer. It was determined that as the polymer chain grows (DP 鈮?10), a tight coil morphology was adopted, which hinders the approach of an additional, sterically demanding CpCoCb-containing monomer. This resulted in premature termination/chain transfer reactions rather than an increase in the polymer chain length. To address this problem, methyl acrylate (MA) with its lower steric demand was copolymerized with the bulky CpCoCb-containing monomer to act as a spacer. This provided the necessary steric relief and an opportunity for the metallopolymer to grow. This copolymerization resulted in dramatic improvements in the polydispersity and molecular weight of the end material. In subsequent experiments, the random copolymer was used as a macro-RAFT agent to prepare diblock copolymers, with good control over the molecular weight, allowing for an examination of the self-assembly behavior of the block copolymer in the solid state.