Cyclization Insertion Research Articles

Synthesis and photophysical properties of polyethylene containing pyrenyl units in the side chain

Copolymerization of ethylene and diallyl-bis(pyren-1-yl)-silane (APyS) was investigated with zirconocene catalysts, rac-ethylenebis(indenyl)zirconium dichloride (1) and diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (2), using methylaluminoxane as a cocatalyst. APyS was copolymerized via both 1,2-insertion and cyclization insertion, and cyclization selectivity, ratio of cyclized insertion unit, of APyS in the copolymers obtained with Catalyst 1 was higher than that obtained with Catalyst 2. Catalyst 2 showed a higher reactivity for APyS than Catalyst 1. Photophysical properties of the copolymer were investigated by UV–vis and photoluminescence (PL) spectroscopy, and absorption and fluorescence derived from pyrenyl groups were detected in the copolymers. Chloroform solution of the copolymer showed emission derived from both monomer and eximer of pyrenyl units. Only the emission derived from eximer of pyrenyl units was observed in the cast film. The polarized PL spectrum of an oriented film showed anisotropy, and the polarization excitation parallel to the drawing direction showed high fluorescence intensity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis of polyethylene and polypropylene containing fluorene units in the side chain

Copolymerizations of ethylene or propylene and allyl monomers containing 9-fluorenyl group, diallyl-di-9-fluorenylsilane (DAFS), 9,9-diallylfluorene (DAF), and 9-allylfluorene (AF), were investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged zirconocene catalysts, especially a syndioselective catalyst, showed a higher reactivity for all the comonomers than the nonbridged catalysts. DAFS was mainly incorporated into the polymer chain via cyclization insertion, whereas DAF was copolymerized via both 1,2- and cyclization insertions. Cyclization selectivity, ratio of cyclized insertion unit, of DAF in the copolymerization with propylene was higher than that in the copolymerization with ethylene. Copolymerization with AF yielded low-molecular weight copolymer because of frequent chain transfer reaction. Optical properties of the propylene based-copolymers were investigated by UV-vis and photoluminescence spectroscopy, and absorption- and emission-derived from fluorenyl groups were detected in the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3542–3552, 2010

Copolymerization of propylene and disubstituted diallylsilanes involving intramolecular cyclization with stereoselective zirconocene catalysts

AbstractThe copolymerization of propylene and disubstituted diallylsilanes [(CH2 CHCH2)2R2Si (R = CH3 or C6H5)] was investigated with isoselective and syndioselective zirconocene catalysts with methylaluminoxane as a cocatalyst. The syndioselective catalyst showed a higher reactivity for disubstituted diallylsilanes than the isoselective catalysts. Diallyldimethylsilane was incorporated into the polymer chain via cyclization insertion preferentially and formed 3,5‐disubstituted dimethylsilacyclohexane units in the polypropylene main chain. In the copolymerization with diallyldiphenylsilane, diallyldiphenylsilane was copolymerized via both cyclization insertion and 1,2‐insertion, which formed a pendant allyl group. The structures of isolated silacyclohexane units, determined by 13C NMR and distortionless enhancement by polarization transfer spectroscopy, proved that the 1,2‐insertion of diallylsilanes proceeded with enantiomorphic site control; however, the diastereoselectivity of the cyclization reaction was independent of the stereoselectivity of the catalysts used, and cis‐silacyclohexane units were mainly formed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6083–6093, 2006

Cover Picture: Macromol. Chem. Phys. 19/2005

Cover: Copolymerizations of ethylene and disubstituted diallylsilanes (A2R2Si) (CH2CHCH2)2R2Si (R = CH3, C6H5) have been investigated with zirconocene catalysts. The stereospecific catalysts showed higher reactivity for A2R2Si monomers than the aspecific ones. A2R2Si monomers were incorporated in the polymer chain via cyclization insertion, and formed 3,5‐disubstituted silacyclohexane unit. Further details can be found in the Full Paper by N. Naga on page 1959.

Synthesis of Polyolefins Containing Silacycloalkane Units in the Main Chain, 1

AbstractSummary: Copolymerizations of ethylene and disubstituted diallylsilanes (CH2CHCH2)2R2Si (R = CH3, C6H5) have been investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged stereospecific catalysts showed a higher reactivity for disubstituted diallylsilanes than the non‐bridged aspecific catalysts. Disubstituted diallylsilanes were incorporated into the polymer chain via cyclization insertion preferentially, and formed 3,5‐disubstituted silacyclohexane units in the polyethylene main chain. A zirconocene catalyst, dimethylsilylenebis(indenyl)zirconium dichloride, produced a copolymer containing pendant allyl groups derived from the 1,2‐insertion of diallyldiphenylsilane without cyclization. magnified image

Cover Picture: Macromol. Rapid Commun. 18/2004

Cover: The cover picture summarizes the copolymerization mechanism of ethylene and 1,7‐octadiene (OD) with a constrained‐geometry catalyst 1. The inserted OD unit formed unexpected 1,5‐cyclononane units as well as 1,3‐cycloheptane units in the main chain of polyethylene. This characteristic cyclononane cyclic unit would be derived from a unique OD cyclization insertion mode: cyclization insertion of the OD unit in the penultimate position after a single ethylene insertion step.Further details can be found in the Communication by N. Naga* and A. Toyota on page 1623.

Unique Insertion Mode of 1,7‐Octadiene in Copolymerization with Ethylene by a Constrained‐Geometry Catalyst

AbstractSummary: The copolymerization of ethylene and 1,7‐octadiene (OD) was investigated with a constrained‐geometry catalyst. The 13C NMR spectrum of the copolymer indicated cyclization insertion of the OD unit in the penultimate position after a single ethylene insertion step. This unique insertion mode of OD forms a 1,5‐disubstituted cyclononane unit in the main chain of polyethylene.Copolymerization of ethylene and 1,7‐octadiene (OD) with a constrained‐geometry catalyst.magnified imageCopolymerization of ethylene and 1,7‐octadiene (OD) with a constrained‐geometry catalyst.