Are RAFT and ATRP Universally Interchangeable Polymerization Methods in Network Formation?
Julia Cuthbert, Shiwanka V. Wanasinghe, Krzysztof Matyjaszewski, Dominik Konkolewicz
Abstract
Polymer networks were synthesized by both ATRP and RAFT to evaluate whether the choice of reversible deactivation radical polymerization method impacted the materials’ characteristics at either the molecular or bulk property level. Since control in ATRP is gained through interactions of a small-molecule catalyst with the polymer chain end, rather than degenerative transfer between two polymer chain ends, ATRP could lead to better controlled networks, particularly after gelation. In general, both RAFT and ATRP gave better controlled materials than the corresponding FRP processes. In general, RAFT reached higher conversions with higher gel fractions. The molecular properties indicate relatively small differences in control over the primary polymer chain length and the dispersity of the primary chains at lower targeted chain lengths of 100 or 200 units. However, ATRP provided better controlled polymers at longer primary chain lengths of 500 units. Both RAFT and ATRP networks swelled to greater extents than their conventional radical analogs, with ATRP giving somewhat higher swelling ratios at longer primary chain lengths and lower crosslink densities. Rheological analysis indicates that both materials are similar, although RAFT gave materials with higher elastic moduli, consistent with the higher conversion and lower sol fraction in RAFT. Overall, both RAFT and ATRP formed materials with similar properties at lower chain lengths, with ATRP appearing to yield slightly better properties at longer chain lengths. The control in RAFT and ATRP is likely through soluble components, including the small-molecule catalyst in ATRP and soluble polymer fractions (sol) in RAFT.