From a thermodynamic view, the solidifying of polymers is a battle between entropy and enthalpy. Monomers naturally prefer chaos and high entropy. Forcing them into long, ordered chains requires energy and specific conditions. Once formed, their massive molecular weight limits how they can move. They form solids because their sheer physical length makes cooperative movement impossible without a lot of heat. This unique state of matter blurs the line between traditional liquids and crystalline solids.