■ Structures and Properties of Crystalline Polymer Solids■
Crystalline polymers such as polyethylene (PE) and polypropylene (PP) are widely used
materials in our daily life. It is thus important to understand their properties.
Especially, how the mechanical properties are determined is important because it is directly related to the material design.
Crystalline polymer solids consist of amorphous and crystal regions, and form hierarchical superstructures.
Amorphous and crystal regions show entropy and energy elasticities, respectively. Also, superstructures show the viscosity and plasticity. As a result, crystalline polymers show various nonlinear mechanical properties.

Typically, polymeric solids are used in nonlinear regions.
Therefore it is unknown how we can design polymeric materials for specific purposes.
The design is still based on the trial-and-error type approach.
The understanding of the relation between structures and properties of crystalline polymers is demanding.
To make the relation clear, one should first understand and analyze the nonlinear mechanical properties phenomenologically,
and then find the relation between the phenomenological parameters and molecular level mechanisms
Our research purpose is to clarify the mechanisms of nonlinear mechanical properties in
crystalline polymer solids, for which we have the elasticity, viscosity, and plasticity.
We aim to give guidelines for the material design for strong polymeric materials, based on the obtained knowledge
The followings are some of our research results.

1. Lamellar Clusters in Crystalline Polymers