Cationic Polymerization Of Cyclopentadiene And The Relationship Between The Reaction Conditions And Sub-Cluster Scales

With the rapid development of oil and coal industries, a great amount of cyclopentadiene and dicyclopentadiene is produced. By polymerization, they can be transformed into polymer or copolymer. However, some important properties of polymers or copolymers obtained thereby can not be predicted and therefore can not be controlled due to their complicated structures. In present study, the cationic polymerization was used to synthesize the polymers with well-defined and well-controlled structure. The resulted hydrogenated oligo(cyclopentadiene)(HOCP) can reduce permeability of iPP films to both oxygen and aroma and was used as reinforcing agent and heat-sealing promoter for iPP. The cyclopentadiene polymers synthesized from C₅ by-products in oil industries can improve the properties of commodity plastics.The cationic polymerization of cyclopentadiene is usually carried out below -20℃. In our study, the oligo(cyclopentadiene) with weight average molecular weight (Mw) between 2,000～15,000 was made using Lewis acid as catalyst at room temperature. From both technological and industrial points of view, this is very important for the cyclopentadiene polymerization initiated by Lewis acids.Two basic structural units (1,2- and 1,4-cyclopentene) of the polymer were obtained by cationic polymerization. Solvent is a very important factor in affecting both the molecular weight of the polymer and the content of 1,2-structure cyclopentene Polar solvents, such as methylene chloride and trichloromethane, were found to promote ion generation, reduce the activation energy and consequently increase the polymerization rate. In methylene chloride, the molecular weight of product synthesized was 15,000, while in cyclohexane it became 2,000. By using different catalysts, the difference in the molecular weight and 1,2-structure content of oligocyclopentadiene was apparent. The molecular weight was the highest for catalyst BF₃OEt₂ and the lowest for catalyst SnCl₄. The content of the 1,2-structure in the product decreased for catalysts from AlCl₃, SnCl₄, TiCl₄ to BF₃OEt₂. The results might be explained in terms of the tightness of the growing ion pairs. A more acidic catalyst gives an ion pair with weaker interaction and a less acidic catalyst with stronger interaction. The molecular weight of oligo(cyclopentadiene) decreased with the increase of polymerization temperature. The linear relationship between the reciprocal of degree of polymerization and the reciprocal of monomer concentration illustrated that the cationic centers were ion pairs. The chain transfer constant for catalyst SnCl₄ was the highest.For the first time, the "sub-cluster statistic theory" was applied to study the molecular weight distribution of oligo(cyclopentadiene). The relationship between the molecular weight distribution and sub-cluster scale (R₁^*R₂) was deduced based on the fourth statistic mechanics and the sub-cluster parameters R₁, R₂ were calculated. The molecular weight curves plotted against the R₁^*R₂ were linear. The polymerization conditions, such as reaction time, reaction temperature, monomer concentration, catalyst concentration, solvent dielectric constant, and co-catalyst concentration changed...