6. Conclusion

To summarize, it is necessary to note that metathesis polymerization with cycle opening has proved to be a powerful method of synthesizing polymers. Materials obtained with this method possess good exploitation characteristics and have already proved effective on the market of polymer goods. Development of carbene complexes based on ruthenium has made it possible to synthesize polymers from ester of 5-norbornene-2,3-dicarboxylic acid using ROMP. To obtain polymer materials by described process, a technology of injection molding in which polymerization rate matters most. Largely, polymerization rate is defined by the structure of catalyst and monomer. The activity of ruthenium catalyst complexes is well studied and apart from the structure of the complex itself it depends on a number of external factors including temperature, solvent polarity, presence of acceptor or donor compounds, etc. The structure of monomer also affects polymerization rate. It is known that steric factor during polymerization of dicyclopentadiene and oxygenated derivatives of norbornene contribute greatly to the reaction rate.

In most studies, the researchers used kinetic correlations to estimate reaction capacity of different compounds. As a rule, kinetic data are obtained with NMR method, studying polymerization in-situ. The technique of such experiments is well adjusted by many scholars and has proved to be effective.

Implementing this approach, it is shown how the structure of esters of 5-norbornene-2,3-dicarboxylic acid affects their reaction capacity and activation parameters in metathesis polymerization with cycle opening initiated by ruthenium complex of Hoveyda-Grubbs type II with N-chelating ligand. Taking the values of activation parameters, it is assumed that there may exist active ruthenium in chelated form, which is proved in the following studies [28, 36, 45].

It was established that the increase in the length of hydrocarbon radical does not affect greatly the reactivity, but it influences substantially the activation parameters. Branching aliphatic radical affects greatly both reactivity and activation parameters of polymerization. Based on the change in activation parameters, it might be assumed that active form of ruthenium complex forms intramolecular complex with different stability of this complex.

It was stated that mutual position of ester substituents in relation to norbornene ring affects both reactivity and activation parameters of 2,3-dicrabomethoxy-5-norbornenes. The presence of a substituent for the monomer molecule in endo-position reduces reaction capacity of this monomer [46]. Activation parameters are directly depended on the ability of monomer to form intramolecular complex with active form of ruthenium.

Based on NMR-spectra, we estimated the structures of the obtained polymers. Based on the correlation of cis- and trans-fragments, it was established that the length and branching aliphatic radical of exo,exo-2,3-dicarboxy-5-norbornenes and exo,endo-orientation of ester substituents of 2,3-dicarbomethoxy-5-norbornene do not affect the structure of the obtained polymers. Endo,endo-orientation of two ester substituents of 2,3-dicarbomethoxy-5-norbornene increases the number of trans-units in the polymer, which is attributed to more substantial steric hindrances caused by carbonyl oxygen of monomer ester group and H2IMes-ligand of catalyst when forming cis-structure if compared with hindrances caused by methylene bridge of norbornene ring and H2IMes-ligand of catalyst when forming trans-structure.
