Photopolymerizable semi-crystalline polymers for thermally reversible, 3D printable cast molds.

Objectives: This study demonstrates the use of photopolymerization to create semi-crystalline linear polymers suitable for thermally reversible materials in dental cast moldings produced from 3D printing.

Methods: An aromatic diallyl, aliphatic dithiol chain extender, and monofunctional thiol were used in a photoinitiated system. The photopolymerization and crystallization kinetics as a function of chemistry and temperature were investigated using spectroscopy and calorimetry.

Vat Photopolymerization Additive Manufacturing of Tough, Fully Recyclable Thermosets.

To advance the capabilities of additive manufacturing, novel resin formulations are needed that produce high-fidelity parts with desired mechanical properties that are also amenable to recycling. In this work, a thiol-ene-based system incorporating semicrystallinity and dynamic thioester bonds within polymer networks is presented. It is shown that these materials have ultimate toughness values >16 MJ cm, comparable to high-performance literature precedents.

Catalytic Control of Crystallization in Dynamic Networks.

The effect of catalysts with varying nucleophilic strength on thiol-thioester bond exchange dynamics and concomitant crystallization was studied in a model semicrystalline polymer network. It was found that the characteristic time scale of covalent bond exchange, τ, could be tuned over a ∼10-10 s range simply by changing the nucleophilicity of the catalyst. Using isothermal crystallization measurements via differential scanning calorimetry, thermodynamic and kinetic features of crystallization were considered.

Controlled Diels-Alder "Click" Strategy to Access Mechanically Aligned Main-Chain Liquid Crystal Networks.

Aligned liquid crystal polymers are materials of interest for electronic, optic, biological and soft robotic applications. The manufacturing and processing of these materials have been widely explored with mechanical alignment establishing itself as a preferred method due to its ease of use and widespread applicability. However, the fundamental chemistry behind the required two-step polymerization for mechanical alignment has limitations in both fabrication and substrate compatibility.

Formation of rolls from liquid crystal elastomer bistrips.

Formation of desired three-dimensional (3D) shapes from flat thin sheets with programmed non-uniform deformation profiles is an effective strategy to create functional 3D structures. Liquid crystal elastomers (LCEs) are of particular use in programmable shape morphing due to their ability to undergo large, reversible, and anisotropic deformation in response to a stimulus. Here we consider a rectangular monodomain LCE thin sheet divided into one high- and one low-temperature strip, which we dub a 'bistrip'.