Bio-based polymer networks by thiol-ene photopolymerization of allylated l-glutamic acids and l-tyrosines

Influence of Vanillin Acrylate-Based Resin Composition on Resin Photocuring Kinetics and Antimicrobial Properties of the Resulting Polymers

The investigation of the influence of vanillin acrylate-based resin composition on photocuring kinetics and antimicrobial properties of the resulting polymers was performed in order to find efficient photocurable systems for optical 3D printing of bio-based polymers with tunable rigidity, as well as with antibacterial and antifungal activity. Two vanillin derivatives, vanillin diacrylate and vanillin dimethacrylate, were tested in photocurable systems using phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator. The influence of vanillin acrylate monomer, amount of photoinitiator, presence and amount of dithiol, and presence of solvent on photocuring kinetics was investigated by real-time photoreometry. Polymers of different rigidity were obtained by changing the photocurable resin composition. The photocuring kinetics of the selected vanillin acrylate-based resins was comparable with that of commercial petroleum-based acrylate resins for optical 3D printing. Polymers based on both vanillin acrylates showed a significant antibacterial activity against Escherichia coli and Staphylococcus aureus. Vanillin diacrylate-based polymer films also demonstrated an antifungal activity in direct contact with Aspergillus niger and Aspergillus terreus. Vanillin diacrylate-based dual curing systems were selected as the most promising for optical 3D printing of bio-based polymers with antibacterial and antifungal activity.

Durable, acid-resistant copolymers from industrial by-product sulfur and microbially-produced tyrosine

The search for alternative feedstocks to replace petrochemical polymers has centered on plant-derived monomer feedstocks. Alternatives to agricultural feedstock production should also be pursued, especially considering the ecological damage caused by modern agricultural practices. Herein, l-tyrosine produced on an industrial scale by E. coli was derivatized with olefins to give tetraallyltyrosine. Tetraallyltyrosine was subsequently copolymerized via its inverse vulcanization with industrial by-product elemental sulfur in two different comonomer ratios to afford highly-crosslinked network copolymers TTS x (x = wt% sulfur in monomer feed). TTS x copolymers were characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis (DMA). DMA was employed to assess the viscoelastic properties of TTS x through the temperature dependence of the storage modulus, loss modulus and energy damping ability. Stress-strain analysis revealed that the flexural strength of TTS x copolymers (>6.8 MPa) is more than 3 MPa higher than flexural strengths for previously-tested inverse vulcanized biopolymer derivatives, and more than twice the flexural strength of some Portland cement compositions (which range from 3-5 MPa). Despite the high tyrosine content (50-70 wt%) in TTS x , the materials show no water-induced swelling or water uptake after being submerged for 24 h. More impressively, TTS x copolymers are highly resistant to oxidizing acid, with no deterioration of mechanical properties even after soaking in 0.5 M sulfuric acid for 24 h. The demonstration that these durable, chemically-resistant TTS x copolymers can be prepared from industrial by-product and microbially-produced monomers via a 100% atom-economical inverse vulcanization process portends their potential utility as sustainable surrogates for less ecofriendly materials.

Implementation of two distinct wavelengths to induce multistage polymerization in shape memory materials and nanoimprint lithography

Here, a process is introduced for forming dual stage thiol-Michael/acrylate hybrid networks photocured by two different wavelengths, demonstrating its use in nanoimprint lithography (NIL) and shape memory materials. Initiated with a visible light sensitive photobase and a UV-sensitive radical initiator, thiol-Michael-acrylate hybrid polymerizations were programmed to proceed sequentially and orthogonally, with base-catalyzed thiol-Michael photopolymerization as the first stage and radical mediated acrylate photopolymerization as the second stage. By regulating the photopolymerization formulations, i.e. thiol-to-acrylate ratios, initiator loadings and irradiation conditions, a series of materials with highly tunable mechanical performance was achieved, with ultimate Tg values ranging from 23 to 70 °C. With a photopatternable first stage and a readily reconfigurable second stage, its implementation in nanoimprint lithography (NIL) enabled surface features on the scale of 10 nm to be formed on a photopatterned substrate. Additionally, the dual stage polymer results in a relatively homogenous polymer network with a narrow glass transition temperature (Tg), which enables rapid response in applications as shape memory materials, with shape-fixity values above 95% and shaperecovery values above 99%. With its unique photocuring process and programmable mechanical properties, the two color light controlled photopolymerization can be exploited as a useful tool in a wide range of materials science applications.