Stereochemistry and stoichiometry in aliphatic polyester photopolymers for 3D printing tailored biomaterial scaffolds

Abstract

Stereoselective aliphatic polyesters were synthesized through the ring opening copolymerization of cyclic anhydrides and epoxides using a tin catalyst to yield Mn ~ 10-13 kDa macromolecules (Đ < 1.6). Isomerization...

Ring-Opening Copolymerization of Four-Dimensional Printable Polyesters Using Supramolecular Thiourea/Organocatalysis

“…ASTM Type IV dogbones were elongated at 5 mm x min −1 until failure (Figure 6), with only the oligomeric (0.4 kDa) sample displaying low moduli and strength. The elastic moduli of this oligomeric samples was ∼56 MPa (Table 2), while the stronger 25.5 kDa samples displayed an elastic moduli of nearly 400 MPa, similar to results published with the Becker groups free-radical crosslinked poly(propylene fumarate) system or to Brooks's stereochemistry controlled poly(malate/fumarate) polyesters 49 Importantly, molecular weight does not seem to play a significant role in tensile properties for polymers longer than this oligomeric length (Figure 7). Statistically, there appears to be no significant difference in the strain-at-break samples (except for the 15 kDa sample) after M n = 1 kDa.…”

“…ASTM Type IV dogbones were elongated at 5 mm x min –1 until failure (Figure ), with only the oligomeric (0.4 kDa) sample displaying low moduli and strength. The elastic moduli of this oligomeric samples was ∼56 MPa (Table ), while the stronger 25.5 kDa samples displayed an elastic moduli of nearly 400 MPa, similar to results published with the Becker groups free-radical cross-linked poly­(propylene fumarate) system or to Brooks’s stereochemistry controlled poly­(malate/fumarate) polyesters…”

3D Printing of Green and Renewable Polymeric Materials: Toward Greener Additive Manufacturing

“…Photopolymers used in SLA, DLP, and similar methods are traditionally required to be Newtonian fluids with low viscosities and high reactivity rates. − This allows for the resin to flow around the solid, gelled parts during photoirradiation and then to flow out of the negative space as the stage is raised (when the light source is off) but rapidly solidify upon irradiation. However, this restriction to liquid resins still encompasses a variety of achievable thermal and mechanical characteristics, and there are some advances that are broadening the material library …”

“…Among natural and naturally derived materials, terpenes and terpenoids are some of the most useful in polymer synthesis and applications, such as the production of degradable polyesters, high T g and performance polymers, and 3DP. − These monomers are widely available from sources such as essential oils, tree sap and materials, and citrus fruit, as byproducts from other manufacturing processes, or simply through the processing of citrus fruits and other renewable resources. ,, The alkene and other functional groups inherent to terpenes make them great candidates for sustainably sourced photoresins (Figures and ). These alkenes are useful in thiol–ene “click” and radical photopolymerizations, and the variation in structure and substitution means that residual alkenes may remain without requiring off-stoichiometric imbalances or uncured materials. ,,,− For example, Weems et al demonstrated the use of the terpenes limonene, terpinene, geraniol, nerol, and linalool to create photoresins for stereolithography (SLA) 3DP via thiol–ene photoclick reactions (Figure ), making use of these natural functional handles, but requiring a two-step prepolymerization process similar to those used in polyurethane foam synthesis. ,− Weems et al further demonstrated poly­(β-myrcene) as a viable photoresin, while Constant et al expanded upon this concept through copolymerization of limonene and myrcene as a means of tailoring the resultant thermoset material properties while still achieving DLP-3D printing (Figure ). …”

Postfabrication Functionalization of 4D-Printed Polycarbonate Photopolymer Scaffolds

“…In efforts to address these limitations, recent work with thiol-ene, thiol-yne, reversible deactivation radical polymerization, and free-radical cross-linking using in-chain alkenes has been attempted with varying degrees of success. ,,, A recent study by Roppolo et al focused on a thiol-yne-type method of digital light processing (DLP) printing, where excess functional groups would allow for postpolymerization modification . This method, while successful, was limited by the achievable resolution of the scaffold but successfully demonstrated that high concentrations of either residual alkene or thiol functional groups could be incorporated into the structure .…”