Light-initiated additive
manufacturing techniques typically rely
on layer-by-layer addition or continuous extraction of polymers formed
via nonliving, free radical polymerization methods that render the
final materials “dead” toward further monomer insertion;
the polymer chains within the materials cannot be reactivated to induce
chain extension. An alternative “living additive manufacturing”
strategy would involve the use of photocontrolled living radical polymerization
to spatiotemporally insert monomers into dormant “parent”
materials to generate more complex and diversely functionalized “daughter”
materials. Here, we demonstrate a proof-of-concept study of living
additive manufacturing using end-linked polymer gels embedded with
trithiocarbonate iniferters that can be activated by photoinduced
single-electron transfer from an organic photoredox catalyst in solution.
This system enables the synthesis of a wide range of chemically and
mechanically differentiated daughter gels from a single type of parent
gel via light-controlled modification of the parent’s average
composition, strand length, and/or cross-linking density. Daughter
gels that are softer than their parent, stiffer than their parent,
larger but with the same modulus as their parent, thermally responsive,
polarity responsive, healable, and weldable are all realized.
In the presence of light, variations in the trithiocarbonate (TTC) concentration provide a new approach for controllably tailoring the structure of polymer gels.
We study the kinetics of chiral phase transitions in quark matter. We discuss the phase diagram of this system in both a microscopic framework (using the Nambu-Jona-Lasinio model) and a phenomenological framework (using a Landau free energy). Then, we study the far-from-equilibrium coarsening dynamics subsequent to a quench from the chirally-symmetric phase to the massive quark phase. Depending on the nature of the quench, the system evolves via either spinodal decomposition or nucleation and growth. The morphology of the ordering system is characterized using the order-parameter correlation function, structure factor, domain growth laws, etc.
Using dissipative particle dynamics (DPD), we developed a computational approach to model the light-induced regeneration of a gel matrix when a significant portion of the material is severed. We considered photo-controlled radical polymerization (photo-CRP) within polymer networks with embedded iniferter groups: the "photo-growth" strategy. Absorption of light by the iniferter groups turns on the polymerization process, which inserts monomers and cross-linkers into the network strands. Photo-growth allows us to effectively regenerate a severed gel under the application of light even when the severed parts are not in direct contact. The growth process can be turned off once the polymerization is near completion to yield a new cross-linked gel that resembles the uncut material.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.