Remote control grubbs catalysts that modulate ring‐opening metathesis polymerizations
Nuyken 1 and S. Pask, Polymers 5, In fact most five- and six-membered carboxylic structures are more prone to undergo free radical ring-closing. Some exceptions are cyclopropane derivatives such as vinylcyclopropane and highly strained bi-cyclic olefins. Bailey et al.
Bailey, Polymer Journal , 17, 1, 85 - 95 The chain growth center of a ring-opening polymerization can be a free radical, an anion, or a cation. Most cyclic monomers that polymerize via ROP possess polarized bonds such as ester, amide, carbonate, urethane and phosphate. Examples of monomers that undergo ring-opening polymerization include cyclic ethers, lactones, lactams, epoxides, aziridenes, and cyclic siloxanes.
Polylactones and polylactides of high molecular weight are entirely produced by ring-opening polymerization ROP of the corresponding cyclic mononers.
The reactivity of cyclic monomers depends on the structural composition and the ring strain which decreases with increasing ring size. Rings with large ring strain like 3-, 4-, and 5-membered rings polymerize readily through ROP whereas 7 and 8 membered rings are less reactive. Principles of Ring-Opening Polymerization A ring-opening polymerization ROP is another form of chain-growth polymerization in which the terminal end group of a polymer chain acts as a reactive center where further cyclic monomers can be added by ring-opening and additon of the broken bond.
Two examples are caprolactam and caprolactone: To polymerize these moieties, one of the rings has to open prior polymerization. In the case of Ru and Os chlorides, there is a dramatic swing from high- trans to high- cis polymer in all cases where chelating diolefin is present, whereas IrCl 3 is unaffected in this respect. High- cis polymers of norbornene, made using RhCl 3 and endo -dicyclopentadiene-modified RuCl 3 , show a strong tendency for the small number of trans units that are present to occur in triplets and larger blocks, an unusual blockiness feature previously noted only when the OsCl 3 catalyst was used.
French ChemistL. Olefin Metathesis s — In the presence of various organometallo compounds, olefin metathesis where the R groups of olefins were swapped with the other.
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Ring Opening Metathesis (Polymerization) - ROM(P)