Liquids, solids and elastic heresy in between - is there a 2½th state of matter?

Mark Warner
Cambridge University, England

Several materials seem to be elastic intermediates. Rubber extends by as much as 1000%, has a shear modulus 104 times smaller than its bulk modulus, and has liquid-like molecular mobility. Liquid crystals have orientational long-range order and thus (Frank) elasticity, but flow like liquids.

The elastic classification of matter is simple and strict:

Thus rubber is really a solid, and liquid crystals are really liquids.

I discuss (with demonstrations) new materials breaking these apparently so simple and inflexible rules. I explore the consequences of such new elasticity and how it is manifested in practice.