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Cationic Zirconocene‐Mediated Catalytic H‐Shuttling Polymerization of Polar Vinyl Monomers: Scopes of Catalyst, Chain‐Transfer Agent, and Monomer
Author(s) -
He Jianghua,
Zhang Yuetao,
Chen Eugene Y.X.
Publication year - 2015
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201400018
Subject(s) - cationic polymerization , chain transfer , polymerization , monomer , chemistry , polymer chemistry , catalysis , living polymerization , chain termination , catalytic chain transfer , ring opening polymerization , radical polymerization , polymer , organic chemistry
Summary This study investigates the characteristics of the recently developed catalytic H‐shuttling polymerization (HSP) of polar vinyl monomers mediated by cationic zirconocenium catalysts, through examining the scopes of chain transfer agent, catalyst, and monomer. Amongst the three classes of chain transfer agents (metal hydrides, metal aryl/alkyls, organics) investigated for the MMA polymerization catalyzed by C s ‐ligated catalyst 1 , the Lewis acid B(C 6 F 5 ) 3 , metal hydrides MH (M = K, Na, Li) and the organic PhNMe 2 promote efficient catalytic polymerization, while metal alkyls such as Et 3 Al and Et 2 Zn serve only as the scavenger and/or monomer activator and thus do not promote chain transfer. In the presence of 5 equivalents of KH, both C s ‐ligated catalyst 1 and achiral C 2v ‐ligated catalyst 3 promote catalytic MMA polymerization through effective chain transfer, whereas C 2 ‐ligated catalyst 2 shows no chain transfer. Of several other conjugated polar vinyl monomers investigated, including acrylamides and α ‐methylene‐ γ ‐butyrolactones, only N,N ‐diphenylacrylamide (DPAA) exhibits catalytic polymerization behavior. Thus, in the presence of enantiopure pre‐catalyst ( S,S )‐ 4 and excess B(C 6 F 5 ) 3 , DPAA is polymerized catalytically and asymmetrically to optically active poly(DPAA) with a narrow MWD of 1.02.