STUDIES IN NETWORK FORMATION .6. POPULATIONS OF SPECIES PRODUCED ON CROSS-LINKING PREFORMED POLYMER - RANDOM AND NONRANDOM CROSS-LINKING

This paper examines the populations of simple cross-linked species formed during the cross-linking of a preformed polymer by a free radical process. Reaction conditions are identified under which gelation kinetics are ideal and where cross-linking is assumed to be random and intermolecular; semidilute solutions and low rates of radical formation. Deviations from ideal kinetics found under other reaction conditions dilute solutions and high rates of radical formation, are attributed to excess intramolecular cross-linking. Weight fractions of simpler cross-linked species, determined by gel-permeation chromatography under various reaction conditions and extents of cross-linking, are consistent with these generalizations and mechanisms are proposed to account for deviations in those weight fractions from values calculated from simple gelation theory.