a method of separating a mixture of biopolymers of various lengths using a blend of two linear hydrophilic polymers , particularly polyacrylamides or substituted polyacrylamides , one with high weight - average molecular mass and another with low weight - average molecular mass , each present at a low concentration but wherein the concentration of the high weight - average molecular mass lpa is above its entanglement threshold , is disclosed . the matrix is excellent for use in methods of nucleic acid analysis , particularly long read length dna sequencing .