Poly methylene-l,3-

Structural characterization of crystalline phases of poly(methylene-l,3-cyclopentane) samples of different microstructures have also been reported (a) Ruiz de Ballesteros, O. Venditto, V. Auriemma, F. Guerra, G. Resconi, L. Waymouth, R. M. Mogstad, A. L. Macromolecules 1995, 28, 2383. (b) Ruiz de Ballesteros, O. Cavallo, L. Auriemma, F. Guerra, G. Macromolecules 1995, 28, 7355. 

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... 

The (co)polymerization of dienes can be a good method for the preparation of polymers with reactive vinyl groups, a method that enables the preparation of polymers possessing plural vinyl groups per polymer chain. A fluorinated bis(phenoxy-imine) Ti complex was shown by Coates and co-workers to convert 1,5-hexadiene to poly(methylene-l,3-cyclopentane-fti-3-vinyl tetramethylene), which contained multiple vinyl groups. As already discussed, Saito et al. and others revealed that bis(phenoxy-imine) Ti complexes favored secondary insertion. " This is probably responsible for the formation of 3-vinyl tetramethylene units. Likewise, the same catalyst system can form sPP-/ -poly(methylene-l,3-cyclopentane-z -3-vinyl tetramethylene) from propylene and 1,5-hexadiene. Very recently. 

In the case of the formation of a cycloaliphatic polymer with bicyclic units in the main chain, such as the polymer with poly[methylene-l,3-(2,5-methanocy-clohexane)] structural units obtained in the cyclopolymerisation of 3-vinyl-1,5-hexadiene, the intramolecular insertion, analogous to that presented in scheme (89), is followed by another intramolecular insertion involving a vinyl substituting group ... 

Cycloaliphatic polymers such as poly(methylene-l,3-cykloalkane)s... 

The microstructure of the discussed cycloaliphatic polymers concerns the cis-trans geometrical isomerism of the rings and the relative stereochemistry between the rings. A modified Bovey m-r nomenclature [507] provides a useful description of the microstructure of poly(methylene-l,3-cycloalkane)s, where capital letters (M for mesogenic, R for racemic) denote the stereochemistry of the rings and lower case letters ( m and r) denote the relative stereochemistry between the rings [503], Therefore, cA-isotactic, tram-isotactic, cA-syndiotactic and tram-syndiotactic cyclopolymers may be formed. As in many other cases, 13C NMR spectroscopy reveals information about both the tacticity of the polymer and the ratio of cis to treins rings. 

The cyclopolymerisation of unsymmetrical a, co-diolefins such as 2-methyl-1,5-hexadiene in the presence of catalysts such as Cp2 ZrMc2 M(Me)0 x, [Cp2 , ZrMe]+ [B(C6F5)4] or [Cp2 ZrMe]4 [McB(C6 F5)2] yields highly regiore-gular cyclopolymers [501]. The perfectly head-to-tail linked monomeric units in the formed poly[methylene-l,3-(l-methylcyclopentane)] arises from the chemo-selective insertion of the less hindered terminus of 2-methyl-1,5-hexadiene into the active Mt—P bond, followed by cyclisation involving the insertion of the disubstituted olefinic bond (Figure 3.50) [497]. The insertion of the disubsti-tuted olefinic bond is made easier by its intramolecular nature. 

The microstructure and the properties depend on the cis/trans ratio of the ring bonding and on the stereochemistry between the rings. Poly(methylene-l,3-cyclopentane) obtained by cyclopolymerization of 1,5-hexadiene shows four different structures from which the tram isotactic structure is predominant, when using simple biscyclopentadienyl compounds. Higher substituted (pen-tamethyl) zirconocenes yield mainly as-connected polymers which are highly crystalline and have melting points up to 190 °C. 

Cyclopolymerizations of functionalized 1,6-dienes such as 4-trimethylsilyloxy-1,6-heptadiene are also possible, using B(C6p5)3 as co-catalyst. After hydrolysis with HCl poly(methylene-l,3-5-hydroxycyclohexane) (eq. (4)) is formed [68]. 

Propylene-fr-poly(methylene-l,3-cyclopentane-co-propylene) was synthesized by the copolymerization of propylene with 1,5-hexadiene by MgCl2-supported Ziegler-Natta catalyst using a stopped-flow technique [118]. 

Chain Transfer to Organometallic Compounds. Hydroxy-terminated poly(methylene-l,3-cyclopentane) has been prepared by selective chain transfer to aluminum in the cyclopolymerization of 1,5-hexadiene with the sterically... 

Fig. 16. Poly(methylene-l,3-cyclopentane) structures of maximum order.

Coates, G. W. Waymouth, R. M. Enantioselective cyclopolymeiizatioii optically active poly(methylene-l,3-cyclopentane).7. Am. Chem. Soc. 1991,113, 6270-6271. 

Polymers with ring structures, interspaced with CH2 groups, can be obtained by polymerization of 1,5-dienes. 1,2-insertion of the terminal double bond into the zirconium-carbon bond is followed by an intramolecular cyclization forming a ring. Waymouth describes the cyclopolymerization of 1,5-hexadiene to poly(methylene-l,3-cyclopentene) [62, 63] of the four possible microstructures. The optically active trans-, isotactic structure (Fig. 39) is predominant (68%) when using a chiral pure enantiomer of [En(IndH4)2 Zr](BINAP)2 and MAO. 

Coates, G.W. and Waymouth, R.M. (1991)Enantioselective cyclopolymerization optically active poly(methylene-l,3-cyclopentane). Journal of the American Chemical Society, 113,6270-6271. 

---