Are RAFT and ATRP Universally Interchangeable Polymerization Methods in Network Formation?

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.

Fully degradable polymer networks from conventional radical polymerization of vinyl monomers enabled by thionolactone addition

“…14 Unfortunately, networks prepared by FRP are almost exclusively nondegradable, even if cleavable crosslinkers with labile bonds are employed. [15][16][17] This is due to the mechanism of gelation in FRP which involves rapid formation of polymers with very high molecular weights, leading to microgelation and a highly clustered, heterogeneous internal structure of the network. [18][19][20] Reversible deactivation radical polymerization (RDRP) techniques can overcome this problem as they afford more homogeneous networks thanks to the linear growth of welldefined, uniform chains.…”

“…[18][19][20] Reversible deactivation radical polymerization (RDRP) techniques can overcome this problem as they afford more homogeneous networks thanks to the linear growth of welldefined, uniform chains. 18,20 Indeed, copolymerization of vinyl monomers with crosslinkers containing degradable or reversible bonds by RDRP can impart the resulting networks with degradability 16,17,21 or vitrimer-like properties. 22,23 Konkolewicz, Matyjaszewski et al compared polyacrylate gels synthesized using a degradable disulfide diacrylate crosslinker by RDRP and FRP, and noticed that while the former could be degraded, the latter could not.…”

Living polymer networks prepared by controlled radical polymerization techniques

“…3B). 35 There was very little difference between the two techniques for the most part. Most of the differences occurred at networks above a DP of 500, where ATRP had slightly better control while RAFT reached higher conversion and gel fractions.…”

“…30 Diagram of polymer networks made through RAFT and ATRP with corresponding polydispersity of gels made using ATRP and RAFT. 35 Polymer Chemistry Minireview ditional polymerization scenarios. 33 However, there are very few examples of comparison between polymer networks prepared by ATRP and RAFT pathways.…”

“…Recent work from 2018 has shifted towards RAFT based parent networks containing ATRP inimers (Dual CRP technique). 1,35,46 These have been mainly explored by the Matyjaszewski group under the name structurally tailored engineered macromolecular (STEM) gels. The initial STEM gel works use RAFT pathways for the parent networks (STEM-0) with the post-production growth performed through the ATRP inimers (STEM-1).…”