1,6-Heptadiynes, polymerization

A number of Mo carbene catalysts, bearing various modified ligands, have been reported and proven to elegantly induce living polymerization of acetylene monomers. The first example is the cyclopolymerization of 1,6-heptadiynes catalyzed by Mo carbenes Mo carbenes ligated by bulky imido and alkoxy groups are quite effective. In... 

Although the polymerization of diene monomers is most familiar for 1,3-dienes, as in the production of rubbers, the polymerization of 1,6-dienes to yield polymers containing six-membered rings ( cyclopolymerization ) has been well established for many years43. Gibson et al.441 have used cyclopolymerization of 1,6-diynes to prepare polymers which are effectively substituted polyacetylenes, the archetype being the polymerization of 1,6-heptadiyne ... 

Abstract Metathesis-based polymerizations of 1-alkynes and cyclopolymerizations of 1,6-heptadiynes using late transition metal catalysts are reviewed. Results obtained with both binary, ternary, and quaternary catalytic systems and well-defined molybdenum- and ruthenium-based catalysts are presented. Special consideration is given to advancements in catalyst design and mechanistic understanding that have been made in this area over the last few years advancements that have facilitated tailor-made syntheses of poly(ene)s. In addition, the first supported ruthenium-based cyclopolymerization-active systems are summarized. Finally, selected structure-dependent properties will be outlined where applicable. 

The cyclopolymerization of 1,6-heptadiynes represents a powerful alternative to 1-alkyne polymerization [81, 94]. Cyclopolymerizations may be accom-... 

In order to understand the polymer structures that are obtained in the polymerization of 1,6-heptadiynes, one needs to consider all possible polymerization mechanisms. If 1,6-hep tadiynes are subject to cyclopolymerization using well-defined Schrock catalysts, polymerization can proceed via two mechanisms. One is based on monomer insertion, where the first alkyne group adds to the molybdenum alkylidene forming a disubstituted alkylidene, which then reacts with the second terminal alkyne group to form poly(ene)s consisting of five-membered rings. Analogous to 1-alkyne polymerization, one refers to this type of insertion as a-insertion (Scheme 4). 

While classical catalysts usually result in ill-controlled polymerization systems, well-defined Schrock initiators cyclopolymerize 1,6-heptadiynes in a living manner - in most cases a class VI living manner (according to Matyjaszewski [84]). Polymers based on one single repetitive unit (poly(cyclopent-l-enylene-... 

Regioselective Polymerization of 1-Alkynes and Stereoselective Cyclopolymerization of a,co-Heptadiynes... 

Poly(1,6-heptadiyne)-Based Materials by Metathesis Polymerization... 

Heptadiyne and its homologues of substituted acetylenes are very interesting examples of substituted acetylenes, which can be susceptible to the ringforming polymerization to give a new type of conjugated polymer backbone system. The present review deals with the comprehensive research results in the field of poly(1.6-heptadiyne)-based conjugated polymer chemistry. 

Heptadiyne was first chosen for polymerization since this monomer could be expected to give the most facile polymerization reaction via an internal head-to-tail propagation which would lead to a six-membered carbocyclic recurring unit. Stille and Frey first reported the study on the polymerization of nonconjugated diynes, especially 1,6-heptadiyne with Ziegler type catalysts. ... 

Table 2. Effect of Catalyst Composition Ti(OC4H9-n)4 Plus AIR3 for the Polymerization of 1,6-Heptadiyne ...

The attempted polymerization of 1,6-heptadiyne with NbCls and TaCls yielded a mixture of cyclotri-mer (15%) and polymer (25% for NbCls, 20% for TaCls), having a relatively low conversion (40% for NbCls, 35% for TaCls). In most cases, the resulting poly(l,6-heptadiyne)s, besides a low molecular weight of oligomers, were insoluble in any organic solvents... 

Cyclopolymerization of 1,6-heptadiyne having bulky substituents was effectively carried out by the MoCls-based catalysts, and their optimized polymerization results are summarized in Table 6. ° In most cases, the polymer yields were quantitative. And the result-... 

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