The macromolecular chain in single-chain condensed state is of looped chain conformation because of van der Waals attractive interaction between the intra-chain monomer units along the chain. As the attractive interaction between intra-chain monomer units in multi-chain condensed state is shielded by the attractive interaction between inter-chain monomer units of the neighboring chains in inter-penetration

the molecular chain in multi-chain condensed state is of Gauss conformation. The methods of preparing samples of single-chain condensed state

the experimental observations of single-chain single crystals

single-chain glasses and the stretching of solvent swollen single-chain rubbery state are briefly discussed. The process of transition from a single-chain condensed state to a multi-chain condensed state

that is the process of polymer coil inter-penetration

is a problem lacking basic understanding at the present time.