Issue 37, 2017

Monomer-induced switching of stereoselectivity and limitation of chain growth in the polymerization of amine-containing para-substituted phenylacetylenes by [Rh(norbornadiene)Cl]2

Abstract

A series of para-substituted phenylacetylenes bearing various amine-containing pendant groups 1–4 can serve as both a monomer and cocatalyst in the polymerization catalyzed by [Rh(norbornadiene)Cl]2 alone in CH2Cl2, affording polyphenylacetylenes (PPAs) with different stereoselectivities and molecular weights. The polymerization of monomer 4 having a long and flexible pendant group produces high molecular weight PPAs with high cis-transoid configurations, similar to those obtained from the coordination–insertion polymerization of these monomers 1–4 by using the [Rh(norbornadiene)Cl]2/cocatalyst systems. However, the stereospecific transformation from the cis-transoid to the trans-cisoid configuration and the growth limitation of the polymer chain are observed in the polymerization of monomers 1–3 containing short and rigid pendant groups. The resulting PPAs have trans-cisoid selectivities of up to 66% and low molecular weights. A metathesis mechanism is suggested, in which the steric repulsion between the pendant group of the monomer and the propagation chain originates from the successive 1,2-insertion of monomers 1–3 to the Rh–carbene active species gives a rational explanation for the tendency of stereospecific transformation and the growth limitation of the polymer chain.

Graphical abstract: Monomer-induced switching of stereoselectivity and limitation of chain growth in the polymerization of amine-containing para-substituted phenylacetylenes by [Rh(norbornadiene)Cl]2

Supplementary files

Article information

Article type
Paper
Submitted
19 Jul 2017
Accepted
22 Aug 2017
First published
22 Aug 2017

Polym. Chem., 2017,8, 5761-5768

Monomer-induced switching of stereoselectivity and limitation of chain growth in the polymerization of amine-containing para-substituted phenylacetylenes by [Rh(norbornadiene)Cl]2

Y. Tian, X. Li, J. Shi, B. Tong and Y. Dong, Polym. Chem., 2017, 8, 5761 DOI: 10.1039/C7PY01201B

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