Circular Polydiketoenamine Elastomers with Exceptional Creep Resistance via Multivalent Cross-Linker Design.

Elastomers are widely used in textiles, foam, and rubber, yet they are rarely recycled due to the difficulty in deconstructing polymer chains to reusable monomers. Introducing reversible bonds in these materials offers prospects for improving their circularity; however, concomitant bond exchange permits creep, which is undesirable. Here, we show how to architect dynamic covalent polydiketoenamine (PDK) elastomers prepared from polyetheramine and triketone monomers, not only for energy-efficient circularity, but also for outstanding creep resistance at high temperature.

Exciton Transfer Between Extended Electronic States in Conjugated Inter-Polyelectrolyte Complexes.

Artificial light harvesting, a process that involves converting sunlight into chemical potential energy, is considered to be a promising part of the overall solution to address urgent global energy challenges. Conjugated polyelectrolyte complexes (CPECs) are particularly attractive for this purpose due to their extended electronic states, tunable assembly thermodynamics, and sensitivity to their local environment. Importantly, ionically assembled complexes of conjugated polyelectrolytes can act as efficient donor-acceptor pairs for electronic energy transfer (EET).

Exceptional Electron-Rich Heteroaromatic Pentacycle for Ultralow Band Gap Conjugated Polymers and Photothermal Therapy.

Stable redox-active conjugated molecules with exceptional electron-donating abilities are key components for the design and synthesis of ultralow band gap conjugated polymers. While hallmark electron-rich examples such as pentacene derivatives have been thoroughly explored, their poor air stability has hampered their broad incorporation into conjugated polymers for practical applications. Herein, we describe the synthesis of the electron-rich, fused pentacyclic pyrazino[2,3-:5,6-']diindolizine (PDIz) motif and detail its optical and redox behavior.

Energy Transfer in Aqueous Light Harvesting Antennae Based on Brush-like Inter-Conjugated Polyelectrolyte Complexes.

Conjugated polyelectrolytes (CPEs) have the potential to serve as building blocks of artificial light-harvesting systems. This is primarily due to their delocalized electronic states and potential for hierarchical self-assembly. We showed previously that inter-CPE complexes composed of oppositely charged exciton-donor and exciton-acceptor CPEs displayed efficient electronic energy transfer.

Excitonically Coupled Simple Coacervates via Liquid/Liquid Phase Separation.

Viscoelastic liquid coacervate phases that are highly enriched in nonconjugated polyelectrolytes are currently the subject of highly active research from biological and soft-materials perspectives. However, formation of a liquid, electronically active coacervate has proved highly elusive, since extended π-electron interactions strongly favor the solid state. Herein we show that a conjugated polyelectrolyte can be rationally designed to undergo aqueous liquid/liquid phase separation to form a liquid coacervate phase.

Chain-Growth Sulfur(VI) Fluoride Exchange Polycondensation: Molecular Weight Control and Synthesis of Degradable Polysulfates.

Sulfur(VI) fluoride exchange (SuFEx) click chemistry has offered a facile and reliable approach to produce polysulfates and polysulfonates. However, the current SuFEx polymerization methods lack precise control of target molecular weight and dispersity. Herein, we report the first chain-growth SuFEx polycondensation process by exploiting the unique reactivity and selectivity of S-F bonds under SuFEx catalysis.

Solution-processable and functionalizable ultra-high molecular weight polymers via topochemical synthesis.

Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers. However, the totality of topochemical polymerization reactions has failed to produce ultra-high molecular weight polymers that are both soluble and display variable functionality, which are restrained by the crystal-packing and reactivity requirements on their respective monomers in the solid state. Herein, we demonstrate the topochemical polymerization reaction of a family of para-azaquinodimethane compounds that undergo facile visible light and thermally initiated polymerization in the solid state, allowing for the first determination of a topochemical polymer crystal structure resolved via the cryoelectron microscopy technique of microcrystal electron diffraction.

Modifying Cell Membranes with Anionic Polymer Amphiphiles Potentiates Intracellular Delivery of Cationic Peptides.

Rapid, facile, and noncovalent cell membrane modification with alkyl-grafted anionic polymers was sought as an approach to enhance intracellular delivery and bioactivity of cationic peptides. We synthesized a library of acrylic acid-based copolymers containing varying amounts of an amine-reactive pentafluorophenyl acrylate monomer followed by postpolymerization modification with a series of alkyl amines to afford precise control over the length and density of aliphatic alkyl side chains. This synthetic strategy enabled systematic investigation of the effect of the polymer structure on membrane binding, potentiation of peptide cell uptake, pH-dependent disruption of lipid bilayers for endosome escape, and intracellular bioavailability.

An anionic, endosome-escaping polymer to potentiate intracellular delivery of cationic peptides, biomacromolecules, and nanoparticles.

Peptides and biologics provide unique opportunities to modulate intracellular targets not druggable by conventional small molecules. Most peptides and biologics are fused with cationic uptake moieties or formulated into nanoparticles to facilitate delivery, but these systems typically lack potency due to low uptake and/or entrapment and degradation in endolysosomal compartments. Because most delivery reagents comprise cationic lipids or polymers, there is a lack of reagents specifically optimized to deliver cationic cargo.

Conformational Entropy as a Means to Control the Behavior of Poly(diketoenamine) Vitrimers In and Out of Equilibrium.

Control of equilibrium and non-equilibrium thermomechanical behavior of poly(diketoenamine) vitrimers is shown by incorporating linear polymer segments varying in molecular weight (MW) and conformational degrees of freedom into the dynamic covalent network. While increasing MW of linear segments yields a lower storage modulus at the rubbery plateau after softening above the glass transition (T ), both T and the characteristic time of stress relaxation are independently governed by the conformational entropy of the embodied linear segments. Activation energies for bond exchange in the solid state are lower for networks incorporating flexible chains; the network topology freezing temperature decreases with increasing MW of flexible linear segments but increases with increasing MW of stiff segments.

Gal8 Visualization of Endosome Disruption Predicts Carrier-Mediated Biologic Drug Intracellular Bioavailability.

Endolysosome entrapment is one of the key barriers to the therapeutic use of biologic drugs that act intracellularly. The screening of prospective nanoscale endosome-disrupting delivery technologies is currently limited by methods that are indirect and cumbersome. Here, we statistically validate Galectin 8 (Gal8) intracellular tracking as a superior approach that is direct, quantitative, and predictive of therapeutic cargo intracellular bioactivity through in vitro high-throughput screening and in vivo validation.

Excipients for the lyoprotection of MAPKAP kinase 2 inhibitory peptide nano-polyplexes.

Herein, excipients are investigated to ameliorate the deleterious effects of lyophilization on peptide-polymer nano-polyplex (NP) morphology, cellular uptake, and bioactivity. The NPs are a previously-described platform technology for intracellular peptide delivery and are formulated from a cationic therapeutic peptide and the anionic, pH-responsive, endosomolytic polymer poly(propylacrylic acid) (PPAA). These NPs are effective when formulated and immediately used for delivery into cells and tissue, but they are not amenable to reconstitution following storage as a lyophilized powder due to aggregation.

Combined, Independent Small Molecule Release and Shape Memory via Nanogel-Coated Thiourethane Polymer Networks.

Drug releasing shape memory polymers (SMPs) were prepared from poly(thiourethane) networks that were coated with drug loaded nanogels through a UV initiated, surface mediated crosslinking reaction. Multifunctional thiol and isocyanate monomers were crosslinked through a step-growth mechanism to produce polymers with a homogeneous network structure that exhibited a sharp glass transition with 97% strain recovery and 96% shape fixity. Incorporating a small stoichiometric excess of thiol groups left pendant functionality for a surface coating reaction.

A Biosynthetic Scaffold that Facilitates Chondrocyte-Mediated Degradation and Promotes Articular Cartilage Extracellular Matrix Deposition.

Articular cartilage remains a significant clinical challenge to repair because of its limited self-healing capacity. Interest has grown in the delivery of autologous chondrocytes to cartilage defects, and combining cell-based therapies with scaffolds that capture aspects of native tissue and allow cell-mediated remodeling could improve outcomes. Currently, scaffold-based therapies with encapsulated chondrocytes permit matrix production; however, resorption of the scaffold often does not match the rate of matrix production by chondrocytes, which can limit functional tissue regeneration.

Photopolymerizable nanogels as macromolecular precursors to covalently crosslinked water-based networks.

We present a strategy for directly and efficiently polymerizing aqueous dispersions of reactive nanogels into covalently crosslinked polymer networks with properties that are determined by the initial chemical and physical nanogel structure. This technique can extend the range of achievable properties and architectures for networks formed in solution, particularly in water where monomer selection for direct polymerization and the final network properties are quite limited. Nanogels were initially obtained from a solution polymerization of a hydrophilic monomethacrylate and either a hydrophilic PEG-based dimethacrylate or a more hydrophobic urethane dimethacrylate, which produced globular particles with diameters of 10-15 nm with remarkably low polydispersity in some cases.

Nanogels as a Basis for Network Construction.

Reactive nanogels with diverse chemical and physical compositions were synthesized using solution free radical polymerization. Conventional monomer resins show a reduction in polymerization shrinkage and stress as well as improved bond strength when nanogels are used as a filler. Nanogels dispersed in inert solvent at appropriate concentrations form macroscopic networks with chemical compositions that are not directly available from the starting monomers.