1061323-36-1Relevant articles and documents
Metallo-supramolecular cyclic polymers
Zhang, Ke,Zha, Yongping,Peng, Bo,Chen, Yongming,Tew, Gregory N.
, p. 15994 - 15997 (2013)
Cyclic brush polymers represent an exciting new macromolecular topology. For the first time, this new topology has been combined with metallo-supramolecular interactions to construct novel cyclic brush polymers. Here, ring-expansion metathesis polymerization was used to synthesize a universal cyclic template with a polynorbornene backbone, which was further modified with the metal-chelating synthon terpyridine. The terpyridine side chains served as the key supramolecular unit for the creation of cyclic polymer brushes and gels. This metallo-supramolecular functionality allowed direct visualization of the cyclic brush polymers by transmission electron microscopy for the first time. This demonstration should open a new area in which supramolecular interactions are used to build an array of novel cyclic brush copolymers as well as other cyclic-polymer-based architectures generating new materials.
Gels based on cyclic polymers
Zhang, Ke,Lackey, Melissa A.,Cui, Jun,Tew, Gregory N.
, p. 4140 - 4148 (2011)
Cyclic poly(5-hydroxy-1-cyclooctene) (PACOE) was synthesized by ring-expansion metathesis polymerization (REMP), and thiol-ene chemistry was used to cross-link the internal double bonds in the PACOE backbone. This created a novel network material (gels formed from cyclic polymers) with unique structural units, where the cyclic PACOE main chains, which serve as secondary topological cross-linkages, were connected by primary intermolecular chemical cross-linkages. The resulting properties were notably different from those of traditional chemically cross-linked linear PACOE gels, whose gel fraction (GF) and modulus (G) increased while the swelling ratio (Q) decreased with increasing initial polymer concentration in the gel precursor solution (C0). For the gels formed from cyclic polymers, however, the GF, Q, and G all simultaneously increased as C0 increased at the higher range. Furthermore, at the same preparation state (same C0), the swelling ability and the maximum strain at break of the gels formed from cyclic polymers were always greater than those of the gels formed from linear polymers, and these differences became more pronounced as C0 increased.
Universal cyclic polymer templates
Zhang, Ke,Lackey, Melissa A.,Wu, Ying,Tew, Gregory N.
, p. 6906 - 6909 (2011)
Two unique molecular templates for generating polymeric materials with a cyclic molecular architecture were developed by combining ring-expansion metathesis polymerization and click chemistry. These two universal cyclic polymers were used in three examples to demonstrate the wide range of potential materials enabled. They include functional cyclic polymers, cyclic polymer brushes, and cyclic gels.
Cyclic ruthenium-alkylidene catalysts for ring-expansion metathesis polymerization
Boydston, Andrew J.,Xia, Yan,Kornfield, Julia A.,Gorodetskaya, Irina A.,Grubbs, Robert H.
experimental part, p. 12775 - 12782 (2009/04/07)
A series of cyclic Ru-alkylidene catalysts have been prepared and evaluated for their efficiency in ring-expansion metathesis polymerization (REMP). The catalyst structures feature chelating tethers extending from one N-atom of an N-heterocyclic carbene (NHC) ligand to the Ru metal center. The catalyst design is modular in nature, which provided access to Ru complexes having varying tether lengths, as well as electronically different NHC ligands. Structural impacts of the tether length were unveiled through 1H NMR spectroscopy as well as single-crystal X-ray analyses. Catalyst activities were evaluated via polymerization of cyclooctene, and key data are provided regarding propagation rates, intramolecular chain transfer, and catalyst stabilities, three areas necessary for the efficient synthesis of cyclic poly(olefin)s via REMP. From these studies, it was determined that while increasing the tether length of the catalyst leads to enhanced rates of polymerization, shorter tethers were found to facilitate intramolecular chain transfer and release of catalyst from the polymer. Electronic modification of the NHC via backbone saturation was found to enhance polymerization rates to a greater extent than did homologation of the tether. Overall, cyclic Ru complexes bearing 5- or 6-carbon tethers and saturated NHC ligands were found to be readily synthesized, bench-stable, and highly active catalysts for REMP.
