Exploiting Ring-Opening Aminolysis–Condensation as a Polymerization Pathway to Structurally Diverse Biobased Polyamides

A pathway to biobased polyamides (PAs) via ring-opening aminolysis–condensation (ROAC) under benign conditions with diverse structure was designed. Ethylene brassylate (EB), a plant oil-derived cyclic dilactone, was used in combination with an array of diamines of diverse chemical structure, and ring-opening of the cyclic dilactone EB was revealed as a driving force for the reaction. The ROAC reactions were adjusted, and reaction conditions of 100 °C under atmospheric pressure using 1,5,7-triazabicyclo[4.4.0]­dec-5-ene (TBD) as a catalyst for 24 h were optimal. The structures of the polyamides were confirmed by mass spectroscopy, FTIR, and NMR, and the PAs had viscosity average molecular weights (<i>M</i>_η) of ∼5–8 kDa. Glassy or semicrystalline PAs with glass transition temperatures between 48 and 55 °C, melting temperatures of 120–200 °C for the semicrystalline PAs, and thermal stabilities above 400 °C were obtained and were comparable to the existing PAs with similar structures. As a proof-of-concept of their usage, one of the PAs was shown to form fibers by electrospinning and films by melt pressing. Compared to conventional methods for PA synthesis, the ROAC route portrayed a reaction temperature at least 60–80 °C lower, could be readily carried out without a low-pressure environment, and eliminated the use of solvents and toxic chemicals. Together with the plant oil-derived monomer (EB), the ROAC route provided a sustainable alternative to design biobased PAs

From Food Additive to High-Performance Heavy Metal Adsorbent: A Versatile and Well-Tuned Design

A biosourced, cross-linked hydrogel-type heavy metal adsorbent is presented. Various factors such as the highly efficient chemical interactions, the various network structures, the decreased energy consumption during cross-linking, and the negligible amount of generated waste are considered when designing the adsorbent. The widely applied, naturally occurring food additive δ-gluconolactone is studied as a building block for the adsorbent. Aminolysis reactions were applied to form linear dimer precursors between diamines and δ-gluconolactones. The abundant hydroxyl groups on the dimers from δ-gluconolactone were fully exploited by using them as the cross-linking sites for reactions with ethylenediaminetetraacetic dianhydride, a well-known metal-chelating moiety. The versatility of the adsorbent and its metal-ion binding capacity is well tuned using dimers with different structures and by controlling the feed ratios of the precursors. Buffers with different pH values were used as the conditioning media to examine the swelling properties and the mechanical properties of the hydrogels, revealing that both properties can be controlled. High heavy metal chelating performance of the adsorbent was determined by isothermal adsorption kinetics, titration, and thermal gravimetric analysis. The adsorbent exhibits an outstanding chelating ability toward the three tested heavy metals (Cu­(II), Co­(II), Ni­(II)), and the maximum adsorption capacity (<i>q</i>_m ∼ 121 mg·g^–1) is higher than that of the majority of the reported biosourced adsorbents

Isosorbide as Core Component for Tailoring Biobased Unsaturated Polyester Thermosets for a Wide Structure–Property Window

Biobased unsaturated polyester thermosets as potential replacements for petroleum-based thermosets were designed. The target of incorporating rigid units, to yield thermosets with high thermal and mechanical performance, both in the biobased unsaturated polyester (UP) and reactive diluent (RD) while retaining miscibility was successfully achieved. The biobased unsaturated polyester thermosets were prepared by varying the content of isosorbide, 1,4-butanediol, maleic anhydride, and succinic anhydride in combination with the reactive diluent isosorbide-methacrylate (IM). Isosorbide was chosen as the main component in both the UP and the RD to enhance the rigidity of the formed thermosets, to overcome solubility issues commonly associated with biobased UPs and RDs and volatility and toxicity associated with styrene as RD. All UPs had good solubility in the RD and the viscosity of the mixtures was primarily tuned by the feed ratio of isosorbide but also by the amount of maleic anhydride. The flexural modulus and storage modulus were tailorable by altering the monomer composition The fabricated thermosets had superior thermal and mechanical properties compared to most biobased UP thermosets with thermal stability up to about 250 °C and a storage modulus at 25 °C varying between 0.5 and 3.0 GPa. These values are close to commercial petroleum-based UP thermosets. The designed tailorable biobased thermosets are, thus, promising candidates to replace their petroleum analogs

Post-Electrospinning “Triclick” Functionalization of Degradable Polymer Nanofibers

4-Dibenzocyclooctynol (DIBO) was used as an initiator for the ring-opening copolymerization of ε-caprolactone and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO) resulting in a series of DIBO end-functionalized copolymers. Following deprotection of the ketone group, the polymers were derivatized with aminooxyl-containing compounds by oxime ligation. Mixtures of keto- and alkyne-derivatized polymers were co-electrospun into well-defined nanofibers containing three separate chemical handles. Strain-promoted azide alkyne cycloaddition (SPAAC), oxime ligation, and copper-catalyzed azide alkyne cycloaddition (CuAAC) were used to sequentially functionalize the nanofibers first with fluorescent reporters and then separately with bioactive Gly-Arg-Gly-Asp-Ser (GRGDS), BMP-2 peptide, and dopamine. This translationally relevant approach facilitates the straightforward derivatization of diverse bioactive molecules that can be controllably tethered to the surface of nanofibers

Enhanced Schwann Cell Attachment and Alignment Using One-Pot “Dual Click” GRGDS and YIGSR Derivatized Nanofibers

Using metal-free click chemistry and oxime condensation methodologies, GRGDS and YIGSR peptides were coupled to random and aligned degradable nanofiber networks postelectrospinning in a one-pot reaction. The bound peptides are bioactive, as demonstrated by Schwann cell attachment and proliferation, and the inclusion of YIGSR with GRGDS alters the expression of the receptor for YIGSR. Additionally, aligned nanofibers act as a potential guidance cue by increasing the aspect ratio and aligning the actin filaments, which suggest that peptide-functionalized scaffolds would be useful to direct SCs for peripheral nerve regeneration

Bioactive Surface Modification of Metal Oxides via Catechol-Bearing Modular Peptides: Multivalent-Binding, Surface Retention, and Peptide Bioactivity

A series of multivalent dendrons containing a bioactive osteogenic growth peptide (OGP) domain and surface-binding catechol domains were obtained through solid phase synthesis, and their binding affinity to hydroxyapatite, TiO₂, ZrO₂, CeO₂, Fe₃O₄ and gold was characterized using a quartz crystal microbalance with dissipation (QCM-d). Using the distinct difference in binding affinity of the bioconjugate to the metal oxides, TiO₂-coated glass slides were selectively patterned with bioactive peptides. Cell culture studies demonstrated the bioavailability of the OGP and that OGP remained on the surface for at least 2 weeks under in vitro cell culture conditions. Bone sialoprotein (BSP) and osteocalcein (OCN) markers were upregulated 3-fold and 60-fold, respectively, relative to controls at 21 days. Similarly, 3-fold more calcium was deposited using the OGP tethered dendron compared to TiO₂. These catechol-bearing dendrons provide a fast and efficient method to functionalize a wide range of inorganic materials with bioactive peptides and have the potential to be used in coating orthopaedic implants and fixation devices