Subvitrimers

Subvitrimers are a class of polymer networks that lie between conventional thermosets and vitrimers. Like vitrimers, subvitrimers employ dynamic covalent bonds capable of bond exchange, which can in principle allow network adaptability. In practice, however, the exchange processes in subvitrimers are more limited: exchange kinetics may be slower, less extensive, or restricted by factors such as network topology, catalyst availability, diffusivity, or steric hindrance. This leads to a material that can relax stress and undergo some remodeling, yet preserves crosslink density and overall network integrity under typical service conditions.

Chemistry and mechanism involve dynamic covalent chemistries such as transesterification, transimination, disulfide exchange, or boron–ester exchange. The key distinction from classic vitrimers is the reduced extent or slower rate of bond exchange, which results in higher activation barriers for topological rearrangement and a longer timescale for noticeable rearrangements at a given temperature.

Physical properties of subvitrimers reflect their intermediate behavior. They often exhibit a glass transition or softening behavior that allows limited flow or reshaping at elevated temperatures, but without the rapid, network-wide topology changes characteristic of vitrimers. Their stress relaxation and self-healing, when present, occur over longer times and higher activation energies compared with true vitrimers.

Applications of subvitrimers aim to balance reprocessability with mechanical performance. Potential uses include recyclable coatings, repairable composites, and adaptable adhesives, where partial network remodeling is desirable without compromising structural integrity. Subvitrimers are an area of ongoing research, with the line between subvitrimers and vitrimers continuing to evolve as understanding of dynamic covalent networks deepens.