Polymerizations by Metathesis

Macromonomers with norbornene end groups were synthesized by living anionic polymerization. The norbornene groups were polymerized by molybdenum catalysts. A series of other a>-nor-bornenyl macromonomers were synthesized and polymerized by metathesis polymerization. 

Substitution of the donor Cl in WC16 (tungsten is the most frequently used transition metal in centres of metathesis) by a carbanion produces a grouping which is capable of further cycloalkene polymerization by metathesis [253]... 

Most polymerizations of cyclic monomers are ionic processes. Coordination catalysts are effective only for some heterocycles (oxirane and its derivatives, lactones). Ziegler-Natta catalysts can only be used for cycloalkene polymerization by metathesis heterocycles act as a catalytic poison. Smooth radical polymerization of hydrocarbon monomers with ring strain is unsuccessful [304], The deep-rooted faith that ring strain represents a major contribution to the driving force in ring opening (polymerization) has to be revised [305, 306]. 

In Table 10.1 are simimarized the alkylacetylenes that have been polymerized by metathesis catalysts. The halides NbCls, TaCls, M0CI5, and WCl can be used without a cocatalyst because acetylenes themselves react readily with the halide to generate an initiating metal carbene complex, perhaps through a sequence such as eqns. (23a) or (23b) (Weiss 1986b). 

Substituted phenylacetylenes that have been polymerized by metathesis catalysts also include those with the following substituents 2- and 4-methyl- (Yamaguchi 1991 Mizumoto 1995 Vijayaraj 1995), various 2-alkyls (Abe 1989, 1994), 2,5-di-... 

EtsAl. Only the C5 ring is opened. As expected, the analogous compound in which the double bond in the C5 ring has been hydrogenated, cannot be polymerized by metathesis (Dall Asta 1968c). The reaction does not proceed to completion but only to an equilibrium monomer concentration (Ofstead 1972). 

Following the observations by Oshika (1968) and Dall Asta (1969) that DCPD could be polymerized by metathesis catalysts, it was shown by Devlin (1970) that it could be polymerized by M0OCI3 to a gel at 35°C and then cured to a hard brown resin at 140°C. Initially attention was concentrated on finding conditions for producing substantially gel-free polymers and copolymers of DCPD through careful control of the order of mixing, the use of chain-transfer agents, e.g. but-1-... 

Norbomene, or bicyclo[2.2.1]hept-2-ene, is one of the better-known monomers that can be subjected to ring-opening polymerization by metathesis catalysts. This monomer, or its derivatives, produces polymers with both a ring and a site of unsaturation in the main chain repeat unit. 

Norbomene can also be polymerized by metathesis catalysts to polyno-... 

The main monomers that can be polymerized by metathesis polymerization are the following ones ... 

Ionic, Ziegler-Natta and Ring-Opening Metathesis Polymerization By V. Dragiitan and R. Streck... 

Poly(l,4-naphthylenevinylenes) have been prepared by metathesis polymerization of benzobarrelenes [181,182] and the photoluminescence properties of homopolymers and block-copolymers have been studied in some detail [183]. PPV also has been prepared via ROMP of [2.2]paracyclophane-l,9-diene [184] and ROMP of a paracyclophene that contains a solubilizing leaving group [185]. The resulting polymer is converted to PPV upon acid catalysis at room temperature. ADMET of 2,5-dialkyl-l,4-divinylbenzenes using Mo or W catalysts has... 

An unusual synthetic approach to PF copolymers was demonstrated by Bunz and coworkers [370], who prepared poly(fluorene ethynylene) 281a-e by metathesis polymerization reaction (Scheme 2.44) [370], The aggregation of polymers 281 in concentrated solutions and in solid state is manifested in slight (up to 10-20 nm) red shift of the absorbance and emission peaks, although solutions and films emit pure blue light. 

Trimmel, G., Riegler, S., Fuchs, G., Slugovc, C. and Stelzer, F. Liquid Crystalline Polymers by Metathesis Polymerization. Vol. 176, pp. 43-87. 

The properties of siloxide as ancillary ligand in the system TM-O-SiRs can be effectively utilized in molecular catalysis, but predominantly by early transition metal complexes. Mono- and di-substituted branched siloxy ligands (e.g., incompletely condensed silsesquioxanes) have been employed as more advanced models of the silanol sites on silica surface for catalytically active centers of early TM (Ti, W, V) that could be effectively used in polymerization [5], metathesis [6] and epoxidation [7] of alkenes as well as dehydrogenative coupling of silanes [8]. 

It is worth noting that 6,7-dihydro-2(3//)-oxepinone is an unusual lactone because it can be polymerized by two distinct mechanisms ROP of the cyclic esters by aluminum alkoxides, and the ring-opening metathesis polymerization (ROMP) of endocyclic olefins by the Schrock s catalyst (Fig. 28) [121]. 

Such reactions of cycloolefins are called metathesis polymerization by analogy with the transalkylidenation reaction of linear olefins which proceed under comparable conditions and in which the double bonds of the olefins are broken and new double bonds are formed (metathesis) ... 

---