Polyalkenamers metathesis ring-opening polymerization

The metathesis products, the polyalkenamers, exhibit excellent properties as polymeric fillers for elastomers. The interests of the rubber industry stimulate research orientation to this kind of ring-opening polymerization (see, for example, refs. 344-346). 

Among others, it can be used in ring-opening metathesis polymerization to produce polynorbomene the oldest polyalkenamer (see Section 12.3). Cycloaddition of... 

Z/E Isomerism (generally indicated by cis/trans). This is found in polymers obtained from conjugated dienes or by ring-opening metathesis polymerization of cycloalkenes (polyalkenamers). The example illustrated hereafter is that of 1,4-polyisoprene (or 2-methylbuta-l,3-diene). It is important from an economical point of view—in particular, in the industry of natural and synthetic elastomers. 

A type of ring opening addition polymerization using transition metal catalysts not unlike Ziegler-Natta catalysts is called metathesis polymerization." Metathesis polymers, first made in the 1960s, are called polyalkenamers. Polymers made from cyclooctadiene and norbornadiene have applications as specialty elastomers. The polymerization of norbornadiene can be summarized as follows ... 

Another common feature of most ring-opening schemes is the low heat of polymerization. Polybutadiene has a very similar structure to polypentenamer, but the isothermal conversion of butadiene to polymer requires removal of 74.9 kJ/mol, whereas conversion of cyclopentene to polymer requires removal of only 18.4 kJ/mol. A commercial polyalkenamer and other polymers made from metathesis and ringopening metathesis polymerization are described in Section 16.4. 

Most cyclic alkenes (cyclohexene being the notable exception because of its stability) undergo metathesis, but instead of dimerizing to form cyclodienes (equation 11.19), they usually polymerize instead to form polyalkenamers (path c, Scheme 11.1). Because this kind of metathesis involves rupturing the C=C and opening up the ring, the process is called ROMP. 

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