Stereochemistry-Controlled Mechanical Properties and Degradation in 3D-Printable Photosets

Abstract

Stereochemistry provides an appealing handle by which to control the properties of small molecules and polymers. While it is established that stereochemistry in linear polymers affects their bulk mechanical properties, the application of this concept to photocurable networks could allow for resins that can accommodate the increasing demand for mechanically diverse materials without the need to significantly change their formulation. Herein, we exploit cis and trans stereochemistry in pre-resin oligomers to create photoset materials with mechanical properties and degradation rates that are controlled by their stereochemistry and molecular weight. Both the synthesis of stereopure (cis or trans) acrylate-terminated pre-polymers and the subsequent UV-triggered cross-linking occurred with a retention of stereochemistry, close to 100%. The stereochemistry of a 4 kDa oligomer within the resin enabled the tuning of the formulation to either a fast eroding, soft cis elastomer or a stiff trans plastic that is more resistant to degradation. These results demonstrate that stereochemistry is a powerful tool to modify the stiffness, toughness, and degradability of high-resolution, three-dimensional printed scaffolds from the same formulated ratio of components.

Sugar-Based Polymers with Stereochemistry-Dependent Degradability and Mechanical Properties

“…In that study, the cis / trans stereoisomerism indeed influenced the mechanical properties of the materials, but the effect was modest and all unsaturated polymers displayed plastic-like behavior irrespective of the stereoisomer. This behavior has also been observed in polymers that contain double bonds, synthesized by nucleophilic thiol-yne addition, in which the materials retain a yield point and hence display plastic deformation, even despite significant differences in mechanical behavior. − To our knowledge, the only exceptions from this behavior are natural rubber and gutta percha (poly­( cis -isoprene) and poly­( trans -isoprene), respectively) and a recent report of a cross-linked photoset material in which constraints imposed by the network formation prevent association of the oligomeric chains when low molar mass oligomers are used …”

“…33−36 To our knowledge, the only exceptions from this behavior are natural rubber and gutta percha (poly(cis-isoprene) and poly(trans-isoprene), respectively) and a recent report of a cross-linked photoset material in which constraints imposed by the network formation prevent association of the oligomeric chains when low molar mass oligomers are used. 37 Encouraged by the divergent mechanical behavior of the isomeric polymers, we then examined the influence of stereochemistry on the thermal properties. Annealed thin films of IIPU and IMPU were compared using differential scanning calorimetry (Figure 1b, Figure S33).…”

Click Step-Growth Polymerization and E/Z Stereochemistry Using Nucleophilic Thiol–yne/–ene Reactions: Applying Old Concepts for Practical Sustainable (Bio)Materials

“…In a later study, we employed the same E - and Z- alkene monomers to synthesize stereopure telechelic oligomers with molar masses ranging from 4 to 10 kDa. 76 Importantly, the oligomers possessed acrylate end-groups as the stoichiometry of the acrylate monomer to thiol was biased. The alkene-containing oligomers were then orthogonally cross-linked into networks via acrylate photopolymerization.…”

“…The simple polymerization method allowed us to precisely make polymers of mixed stereochemistry to access intermediate properties between the two stereopure samples. In a later study, we employed the same E - and Z- alkene monomers to synthesize stereopure telechelic oligomers with molar masses ranging from 4 to 10 kDa . Importantly, the oligomers possessed acrylate end-groups as the stoichiometry of the acrylate monomer to thiol was biased.…”

The Mechanics of Forming Ideal Polymer–Solvent Combinations for Open-Loop Chemical Recycling of Solvents and Plastics

“…The process described herein considers the use of polymer–solvent slurry as the feedstock material for further processing, with the immediate example being the synthesis of carbon nanomaterials [ 21 ]; however, there may be advantages to reconstituting the polymer from the solvent instead [ 27 ]. This process of cleaning the polymer and solvent in a dissolution–reprocessing technique [ 28 ] would require additional operational units that incur greater energy demand.…”