Polyolefins-based Crystalline Elastomers

The objective of this project is the study of innovative elastomers based on polyolefins that present increased stiffness, with respect to conventional elastomers, thanks to the presence of non-negligible level of crystallinity. The novelty of this project is the definition of a new class of materials, the "crystalline elastomers", characterized by a combination of mechanical properties typical of crystalline materials (high mechanical strength and stiffness) and of elastomers (ease of deformability, ductility and perfect elasticity). According to basic knowledge of polymer science, these properties are considered irreconcilable in the same material, so that a basic principle of polymer physics sanctions that an elastomer cannot be highly crystalline. Studying crystalline elastomers represents, therefore, an absolutely novel topic in the field of science and technology of polymers. In crystalline materials elasticity can develop only if crystals play an active role in the elastic recovery through various mechanisms, such as occurrence of polymorphic transition of a metastable form into a more stable form during recovery (enthalpic elasticity) or reversible textural transformations. This project aims at the development of innovative crystalline elastomers by exploiting these novel concepts. Crystalline homo- and copolymers of propylene, ethylene, butene and other olefins, showing stress-induced phase and morphological transformations, will be prepared with metallorganic catalysts, which allow a fine control over stereoregularity, regioregularity and comonomer incorporation. The mechanical properties of these materials will be studied and related to the molecular structure. Understanding the relationships between material properties and the structure of used catalyst will allow designing and obtaining low cost elastomers with tailored stiffness and strength that depend on the constitution, stereoregularity and overall molecular architecture, which in turn can be controlled through the choice of the catalyst