In a semi-crystalline polymer, chains reside both within amorphous and crystalline domains, leading to a heterogeneous distribution of constraints. The heterogeneous distribution disappears upon melting. We make ultra-high molecular weight polyethylene with reduced connectivity between neighbouring crystals. This polymer, on melting, gives a non-equilibrium melt where equilibrium (fully entangled) state is achieved with time by mixing between chains followed by chain reptation. By using block copolymers with deuterated blocks and solution cast films with deuterated layers we can influence when scattering contrast arises during melting of the polymer or while annealing. In this proposal we aim to investigate the influence of molar mass, temperature and polymer structure on the structural evolution of the non-equilibrium polymer melt.