Vat photopolymerization (VP) is a high-throughput additive manufacturing modality that also offers exceptional feature resolution and surface finish; however, the process is constrained by a limited selection of processable photocurable resins. Low resin viscosity (<10 Pa·s) is one of the most stringent process-induced constraints on resin processability, which in turn limits the mechanical performance of printed resin systems. Recently, the authors created a VP-processable photosensitive latex resin, where compartmentalization of the high molecular weight polymer chains into discrete particles resulted in the decoupling of viscosity from molecular weight. However, the monomers used to form the hydrogel green body resulted in decreased ultimate material properties due to the high cross-link density. Herein, we report a novel scaffold that allows for facile UV-based AM and simultaneously enhances the final part’s material properties. This is achieved with a chemically labile acetal-containing cross-linker in conjunction with N-vinylpyrrolidone, which forms a glassy polymer after photocuring. Subsequent reactive extraction cleaves the cross-links and liberates the glassy polymer, which provides mechanical reinforcement of the geometrically complex VP-printed elastomer. With only a 0.1 wt % loading of photoinitiator, G′/G′′ crossover times of less than 1 s and green body plateau moduli nearing 105 Pa are obtained. In addition, removal of the hydrophilic and thermally labile scaffold results in decreased water uptake and increased thermal stability of the final printed part. Ultimate strain and stress values of over 650% and 8.5 MPa, respectively, are achieved, setting a new benchmark for styrene–butadiene VP elastomers.
Chain-transfer ring-opening metathesis polymerization (CT-ROMP) provided a route to carboxytelechelic polyethylene (PE) with subsequent incorporation into segmented copolymers.
Degradable poly(ethylene glycol) (PEG) hydrogels provide a versatile platform for drug delivery and tissue engineering, and acetal functionalization now enables photoprocessible PEG oligomers with selective and facile degradation in acidic environments. Tailored morphologies within acetal-functionalized hydrogels provided fundamental understanding of the multiphase network degradation. End group modification of poly(ethylene glycol) (M n = 2,000 g/mol) with 2-(vinyloxy)ethyl acrylate yielded polyether precursors with both pH-sensitive acetals and photo-curable acrylate end groups. UV-initiated binary thiolacrylate crosslinking of the acetal-functionalized PEG diacrylate with varied amounts of a thiolfunctionalized three-armed PEG provided pH-degradable networks. Controlled stoichiometric imbalance of thiol and acrylate functionalities ensured predictable plateau storage moduli from 2 × 10 5 to 8 × 10 5 Pa. Small-angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA) confirmed that the thiol/acrylate molar ratio provided hydrogels with varying network architectures and crosslink densities. Spectroscopic monitoring of an imbedded mobile dye (Direct Red-81) quantified hydrogel degradation rates. Degradable hydrogels exhibited bulk degradation in acidic solution. Gels with the lowest crosslink density fully degraded in aqueous solutions at pH 3.4 within 60 h, while the highly crosslinked gels fully degraded over 3 weeks. All hydrogels displayed long-term stability in phosphate-buffered saline (pH 7.4) beyond 3 mo, suggesting stable hydrogels for selective degradation and cargo release in low pH environments.
Vat photopolymerization (VP) is an advanced additive manufacturing (AM) platform that enables production of intricate 3D monoliths that are unattainable with conventional manufacturing methods. In this work, modification of amorphous poly(arylene ether sulfone)s (PSU) allows for VP printing. Post-polymerization telechelic functionalization with acrylate functionality yielded photocrosslinkable PSUs across a molecular weight range. 1 H NMR spectroscopy confirms chemical composition and quantitative acrylate functionalization. Addition of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) photoinitiator to 30 wt% PSU solutions in NMP provides a photocurable composition. However, subsequent photorheological studies elucidate rapid photodegradation of the polysulfone main chain, which is especially apparent in high M n (15 kg mol −1 ) PSU formulations. UV-light intensity and wavelength range are altered to reduce degradation while allowing for efficient crosslinking. The addition of 0.5 wt% of avobenzone photoblocker produces an ill-defined structure with 6 kg mol −1 PSU. For higher molecular weights (>12 kg mol −1 ), solutions with a low molar mass reactive diluent, i.e., trimethylolpropane triacrylate, enable the printing of an organogel with a storage modulus (>10 5 Pa) sufficient for vat photopolymerization. Employing multicomponent solutions provide well-defined parts with complex geometries through vat photopolymerization.
Water‐soluble polymers (WSPs) represent a diverse class of macromolecules, and this diversity arises from the breadth of functionality derived from both natural and synthetic sources. Nature provides abundant WSPs through biosynthetic pathways in plants, animals, and fungi, and biological processes yield precisely controlled and well‐defined structures. Polymer chemists strive to develop synthetic methods that mimic the precision of natural processes. Monomers that are derived from petroleum feedstocks together with naturally sourced monomers provide a rich catalog of WSP precursors. Monomer structure, reactivity, concentration, sequence control, and reaction conditions influence polymeric microstructures, solubility, and aqueous solution structure. This article provides an overview of WSP fundamentals and highlights recent advancements in natural, nonionic, ionic, associative, and high‐performance WSPs. Recent advances in the design and performance of WSPs have critically improved the technological impact of filtration processes, water purification, drilling efficiency, and pharmaceutical applications. From modulating the rheological and filtration properties to establishing novel drug delivery systems through controllable self‐assembly, WSPs represent a critical enabling field for many emerging and diverse applications. WSPs will help to address many of the emerging challenges of our times, from energy generation and storage to water availability and next‐generation life‐saving medical technologies. This article will point to the potential impacts based on fundamental structure‐property‐processing relationships.
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