CHAIN-LENGTH DEPENDENCE OF THE ELECTROPHORETIC MOBILITY IN RANDOM GELS

The electrophoretic mobility mu of a flexible N-segment probe polymer has been measured in cross-linked gels of concentration c. Assuming mu approximately N--alpha-c--gamma, alpha initially increases with N, reaches a maximum of approximately 2 in a crossover regime, and finally decreases to 1, the exponent of reptation. In accord with a semidilute-solution scaling argument, an analogous maximum in gamma is observed. Behavior at intermediate N and c is consistent with "entropic-barrier"-mediated transport, while larger N or c leads to reptation.