End-groups and telomers

For polymers of modest MW ( 5000), the most direct evidence concerning end-groups is provided by C NMR spectra such as that shown in Fig. 15.1 for a polymer made from cyclopentene in the presence of pent-l-ene. Such spectra show the presence of equal proportions of the two end-groups derived from M2 but do not give any information about the relative proportions of Q (Mi) Q, Q (Mi) Q, and Q (Mi) Q. Evidence for this comes fi om GC/MS investigation of the telomers (n = 1-5). An example is shown in Fig. 15.2 for the same system. All three groups 

By employing hex-l-ene as a chain transfer agent low-molecular-weight homopolymers of norbomadiene and copolymers with norbomene can be obtained. The products are freely soluble and afford high-quality NMR spectra, which are tmly representative of higher-molecular-weight polymers and which have been fully assigned to establish the detailed microstmcture (Bell, B. 1992). 

Olefin Metathesis and Metathesis Polymerization CH2fCHCK CH2CH2Cl4CHCH2CH2CH3 

In the reaction of cycloocta-1,5-diene (Mi) with oct-4-ene (M2), the proportion of any given linear polyene formed at equilibrium increases to a maximum and then declines as the ratio [Mi]/[M2] is increased. If the double bonds were distributed at random between Mi, M2, and the linear polyenes, the optimum content of double bonds in linear dienes should occur at [M2]/[Mi] = 2, and for trienes at [M2]/ [Ml] = 1. Experimentally, the maximum proportion of double bonds in the linear diene and triene species is found to occur at the somewhat higher values of [M2]/ [Ml] = 2.5-3 and 2-2.5, respectively (Pinazzi 1977a). This is a consequence of the 

The synthesis of a,co-difunctional telomers by cross-metathesis between cyclic olefins and acyclic functionalized olefins is possible in the presence of functional-group-tolerant catalysts. Thus, cross-metathesis of dimethyl hex-3-enedioate with cycloocta-1,5-diene (Pinazzi 1980 Reyx 1982b, 1990), cyclopentene (Reyx 1986, 1987), or norbomene (Cramail 1991a) in the presence of the catalyst system WCV Mc4Sn allows the synthesis of a,m-difunctional oligomers, e.g. reaction (2). 

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