Efficient In Situ Nucleophilic Thiol-yne Click Chemistry for the Synthesis of Strong Hydrogel Materials with Tunable Properties

Synthetic hydrogel materials offer the ability to tune the mechanical properties of the resultant networks by controlling the molecular structure of the polymer precursors. Herein, we demonstrate that the nucleophilic thiol-yne click reaction presents a highly efficient chemistry for forming robust high water content (ca. 90%) hydrogel materials with tunable stiffness and mechanical properties. Remarkably, optimization of the molecular weight and geometry of the poly­(ethylene glycol) (PEG) precursors allows access to materials with compressive strength up to 2.4 MPa, which can be repeatedly compressed to >90% stress. Beyond this, we demonstrate the ability to access hydrogels with storage moduli ranging from 0.2 to 7 kPa. Moreover, we also demonstrate that by a simple precursor blending process, we can access intermediate stiffness across this range with minimal changes to the hydrogel structure. These characteristics present the nucleophilic thiol-yne addition as an excellent method for the preparation of hydrogels for use as versatile synthetic biomaterials

Tunable Thermoplastic Poly(ester–urethane)s Based on Modified Serinol Extenders

As a consequence of their mechanical properties, thermoplastic poly­(ester–urethane)­s (TPEUs) have been extensively examined for their potential applications in biomedical engineering. The incorporation of bio-derived small molecules, such as amino acid derivatives, as chain extenders may allow for more biodegradable hard segments, which result in nontoxic degradants. TPEUs were synthesized using modified 2-aminopropane-1,3-diol (serinol) extenders, ethyl (1,3-dihydroxy­propan-2-yl)­carbamate (C_3c), and 1-(1,3-dihydroxy­propan-2-yl)-3-ethylurea (C_3u) in order to determine the effect of extender side-group functionality on the properties of the resultant materials. The TPEUs were synthesized with varying percentage “hard” segment (%HS) using poly­(ε-caprolactone) (PCL) and 1-isocyanato-4-[(4-iso­cyanato­cyclohexyl)­methyl]­cyclohexane (H₁₂MDI) as the polyol and diisocyanate, respectively. It was found that by controlling the %HS and side group functionality, the thermal and mechanical properties of the materials could be tuned. Furthermore, the selection of extender was found to affect both the hydrophilicity and degradation profile of the materials

Efficient In Situ Nucleophilic Thiol-yne Click Chemistry for the Synthesis of Strong Hydrogel Materials with Tunable Properties

Synthetic hydrogel materials offer the ability to tune the mechanical properties of the resultant networks by controlling the molecular structure of the polymer precursors. Herein, we demonstrate that the nucleophilic thiol-yne click reaction presents a highly efficient chemistry for forming robust high water content (ca. 90%) hydrogel materials with tunable stiffness and mechanical properties. Remarkably, optimization of the molecular weight and geometry of the poly­(ethylene glycol) (PEG) precursors allows access to materials with compressive strength up to 2.4 MPa, which can be repeatedly compressed to >90% stress. Beyond this, we demonstrate the ability to access hydrogels with storage moduli ranging from 0.2 to 7 kPa. Moreover, we also demonstrate that by a simple precursor blending process, we can access intermediate stiffness across this range with minimal changes to the hydrogel structure. These characteristics present the nucleophilic thiol-yne addition as an excellent method for the preparation of hydrogels for use as versatile synthetic biomaterials

Efficient In Situ Nucleophilic Thiol-yne Click Chemistry for the Synthesis of Strong Hydrogel Materials with Tunable Properties

Synthetic hydrogel materials offer the ability to tune the mechanical properties of the resultant networks by controlling the molecular structure of the polymer precursors. Herein, we demonstrate that the nucleophilic thiol-yne click reaction presents a highly efficient chemistry for forming robust high water content (ca. 90%) hydrogel materials with tunable stiffness and mechanical properties. Remarkably, optimization of the molecular weight and geometry of the poly­(ethylene glycol) (PEG) precursors allows access to materials with compressive strength up to 2.4 MPa, which can be repeatedly compressed to >90% stress. Beyond this, we demonstrate the ability to access hydrogels with storage moduli ranging from 0.2 to 7 kPa. Moreover, we also demonstrate that by a simple precursor blending process, we can access intermediate stiffness across this range with minimal changes to the hydrogel structure. These characteristics present the nucleophilic thiol-yne addition as an excellent method for the preparation of hydrogels for use as versatile synthetic biomaterials

Efficient In Situ Nucleophilic Thiol-yne Click Chemistry for the Synthesis of Strong Hydrogel Materials with Tunable Properties

Synthetic hydrogel materials offer the ability to tune the mechanical properties of the resultant networks by controlling the molecular structure of the polymer precursors. Herein, we demonstrate that the nucleophilic thiol-yne click reaction presents a highly efficient chemistry for forming robust high water content (ca. 90%) hydrogel materials with tunable stiffness and mechanical properties. Remarkably, optimization of the molecular weight and geometry of the poly­(ethylene glycol) (PEG) precursors allows access to materials with compressive strength up to 2.4 MPa, which can be repeatedly compressed to >90% stress. Beyond this, we demonstrate the ability to access hydrogels with storage moduli ranging from 0.2 to 7 kPa. Moreover, we also demonstrate that by a simple precursor blending process, we can access intermediate stiffness across this range with minimal changes to the hydrogel structure. These characteristics present the nucleophilic thiol-yne addition as an excellent method for the preparation of hydrogels for use as versatile synthetic biomaterials

Improving the Performance of Photoactive Terpene-Based Resin Formulations for Light-Based Additive Manufacturing

Photocurable liquid formulations have been a key research focus for the preparation of mechanically robust and thermally stable networks. However, the development of renewable resins to replace petroleum-based commodities presents a great challenge in the field. From this perspective, we disclose the design of photoactive resins based on terpenes and itaconic acid, both potentially naturally sourced, to prepare photosets with adjustable thermomechanical properties. Biobased perillyl itaconate (PerIt) was synthesized from renewable perillyl alcohol and itaconic anhydride via a scalable solvent-free method. Photoirradiation of PerIt in the presence of a multiarm thiol and photoinitiator led to the formation of networks over a range of compositions. Addition of nonmodified terpenes (perillyl alcohol, linalool, or limonene) as reactive diluents allowed for more facile preparation of photocured networks. Photosets within a wide range of properties were accessed, and these could be adjusted by varying diluent type and thiol stoichiometry. The resins showed rapid photocuring kinetics and the ability to form either brittle or elastic materials, with Young’s modulus and strain at break ranging from 3.6 to 358 MPa and 15 to 367%, respectively, depending on the chemical composition of the resin. Glass transition temperatures (Tg) were influenced by thioether content, with temperatures ranging from 5 to 43 °C, and all photosets displayed good thermal resistance with Td,5% > 190 °C. Selected formulations containing PerIt and limonene demonstrated suitability for additive manufacturing technologies and high-resolution objects were printed via digital light processing (DLP). Overall, this work presents a simple and straightforward route to prepare renewable resins for rapid prototyping applications

Dual Catalysis for Selective Ring-Opening Polymerization of Lactones: Evolution toward Simplicity

Much work has been directed to the design of complex single-site catalysts for ring-opening polymerization (ROP) to enhance both activity and selectivity. More simply, however, cooperative effects between Lewis acids and organocatalytic nucleophiles/Lewis bases provide a powerful alternative. In this study we demonstrate that the combination of <i>N</i>-heterocyclic carbenes, 1,8-diazabicycloundec-7-ene (DBU) and 4-dimethylaminopyridine (DMAP) with simple Lewis acids enables the ROP of the macrolactone pentadecalactone in a rapid and efficient manner. Remarkably, regardless of the nature of the nucleophile, the order of activity was observed to be MgX₂ ≫ YCl₃ ≫ AlCl₃ and MgI₂ > MgBr₂ > MgCl₂ in every case. The minimal influence of the organobase on polymerization activity allows for the use of simple and inexpensive precursors. Furthermore, extension of the study to other cyclic (di)­ester monomers reveals the choice of Lewis acid to lead to monomer selective ROP activity and hence control over copolymer composition by choice of Lewis acid. This approach could lead to the realization of complex polymer structures with tunable physical properties from simple catalyst combinations

Synthesis of ω‑Pentadecalactone Copolymers with Independently Tunable Thermal and Degradation Behavior

ω-Pentadecalactone (PDL) was copolymerized with lactones of varying sizes (6-, 7-, 9-, and 13-membered rings) in order to characterize the properties of PDL copolymers throughout the lactone range for copolymerizations catalyzed by magnesium 2,6-di-<i>tert</i>-butyl-4-methylphenoxide (Mg­(BHT)₂(THF)₂). Kinetics of the copolymerization reactions were studied using quantitative ¹³C NMR spectroscopy, which revealed that the polymerization of the smaller, strained lactone monomer occurred rapidly before the incorporation of PDL into the polymer. Furthermore, all polymers were randomly sequenced as a consequence of transesterification side reactions that occurred throughout polymerization. The copolymers were all shown to cocrystallize to produce polymers with melting and crystallization temperatures that displayed a linear relationship with respect to monomer ratio. Differences in degradation behavior of the smaller lactones enabled the synthesis of PDL copolymer materials that displayed independently controllable thermal and degradation properties

Stereocomplexed Functional and Statistical Poly(lactide-carbonate)s via a Simple Organocatalytic System

The stereocomplexation of polylactide (PLA) has been widely relied upon to develop degradable, sustainable materials with increased strength and improved material properties in comparison to stereopure PLA. However, forming functionalized copolymers of PLA while retaining high crystallinity remains elusive. Herein, the controlled ring-opening copolymerization (ROCOP) of lactide (LA) and functionalized cyclic carbonate monomers is undertaken. The produced polymers are shown to remain crystalline up to 25 mol % carbonate content and are efficiently stereocomplexed with homopolymer PLA and copolymers of opposite chirality. Polymers with alkene and alkyne pendent handles are shown to undergo efficient derivatization with thiol–ene click chemistry, which would allow both the covalent conjugation of therapeutic moieties and tuning of material properties

Orthogonal Modification of Norbornene-Functional Degradable Polymers

Well-defined norbornene-functional poly­(carbonate)­s were prepared by ring-opening polymerization and utilized as multireactive polymeric scaffolds in a range of postpolymerization modifications. The norbornene-functional handles were shown to undergo facile reaction with azides via a 1,3-dipolar cycloaddition, tetrazines in the inverse electron demand Diels–Alder reaction and thiols via radical thiol-ene coupling. Furthermore, the above-mentioned chemistries were demonstrated in a sequential one-pot, three-step modification reaction illustrating the potential of these polymers as scaffolds to access multifunctionalized materials in an undemanding manner