We report supramolecular AB diblock copolymers comprised of well-defined telechelic building blocks. Helical motifs, formed via reversible addition-fragmentation chain-transfer (RAFT) or anionic polymerization, are assembled with coil-forming and sheet-featuring blocks obtained via atom-transfer radical polymerization (ATRP) or ring-opening metathesis polymerization (ROMP). Interpolymer hydrogen bonding or metal-coordination achieves dynamic diblock architectures featuring hybrid topologies of coils, helices, and/or π-stacked sheets that, on a basic level, mimic protein structural motifs in fully synthetic systems. The intrinsic properties of each block (e.g., circular dichroism and fluorescence) remain unaffected in the wake of self-assembly. This strategy to develop complex synthetic polymer scaffolds from functional building blocks is significant in a field striving to produce architectures reminiscent of biosynthesis, yet fully synthetic in nature. This is the first plug-and-play approach to fabricate hybrid π-sheet/helix, π-sheet/coil, and helix/coil architectures via directional self-assembly.
This contribution introduces main-chain supramolecular ABC and ABB'A block copolymers sustained by orthogonal metal coordination and hydrogen bonding between telechelic polymers that feature distinct secondary structure motifs. Controlled polymerization techniques in combination with supramolecular assembly are used to engineer heterotelechelic π-sheets that undergo high-fidelity association with both helical and coil-forming synthetic polymers. Our design features multiple advances to achieve our targeted structures, in particular, those emulating sheet-like structural aspects using poly(p-phenylenevinylene)s (PPVs). To engineer heterotelechelic PPVs in a sheet-like design, we engineer an iterative one-pot cross metathesis-ring-opening metathesis polymerization (CM-ROMP) strategy that affords functionalized Grubbs-II initiators that subsequently polymerize a paracyclophanediene. Supramolecular assembly of two heterotelechelic PPVs is used to realize a parallel π-sheet, wherein further orthogonal assembly with helical motifs is possible. We also construct an antiparallel π-sheet, wherein terminal PPV blocks are adjacent to a flexible coil-like poly(norbornene) (PNB). The PNB is designed, through supramolecular chain collapse, to expose benzene and perfluorobenzene motifs that promote a hairpin turn via charge-transfer-aided folding. We demonstrate that targeted helix-(π-sheet)-helix and helix-(π-sheet)-coil assemblies occur without compromising intrinsic helicity, while both parallel and antiparallel β-sheet-like structures are realized. Our main-chain orthogonal assembly approach allows the engineering of multiblock copolymer scaffolds featuring diverse secondary structures via the directional assembly of telechelic building blocks. The targeted assemblies, a mix of sequence-defined helix-sheet-coil and helix-sheet-helix architectures, are Nature-inspired synthetic mimics that expose α/β and α+β protein classes via de novo design and cooperative assembly strategies.
Two chemically distinct monotelechelic helical polymers were synthesized using anionic and reversible addition−fragmentation chain-transfer (RAFT) polymerizations. A chiral poly(isocyanide) block was obtained using a palladium−ethynyl complex modified with the N 1 ,N 3 -bis(6-butyramidopyridin-2yl)-5-hydroxyisophthalamide (Hamilton wedge) moiety as a catalyst employing anionic polymerization. A complementary barbiturate-functionalized chain-transfer agent was used to polymerize chiral N-(1-(naphthalen-2-yl)ethyl)methacrylamides by RAFT polymerization. The assembly into helix−helix supramolecular block copolymers in chloroform via hydrogen bonding was analyzed by 1 H NMR spectroscopy, resulting in an average measured association constant of (9.5 ± 0.5) × 10 3 M −1 . After block copolymer formation, the secondary structures of both helical polymers were maintained within the block copolymer, as evidenced by circular dichroism and infrared spectroscopies. Films were prepared from a 1:1 mixture of polymers in solution and were analyzed by WAXS and DSC to evaluate organization in the solid state. While diblock formation in the solution phase is readily obtainable, there was little evidence supporting a self-assembly assisted microstructure in the solid state. This work demonstrates a synthetic methodology for obtaining two telechelic helical polymers capable of supramolecular assembly in solution toward the goals of developing multifunctional polymeric ensembles.
The ability to precisely control the localization of enzymes on a surface is critical for several applications including biosensing, bionanoreactors, and single molecule studies. Despite recent advances, fabrication of enzyme patterns with resolution at the single enzyme level is limited by the lack of lithography methods that combine high resolution, compatibility with soft, polymeric structures, ease of fabrication, and high throughput. Here, a method to generate enzyme nanopatterns (using thermolysin as a model system) on a polymer surface is demonstrated using thermochemical scanning probe lithography (tc-SPL). Electrostatic immobilization of negatively charged sulfonated enzymes occurs selectively at positively charged amine nanopatterns produced by thermal deprotection of amines along the side-chain of a methacrylate-based copolymer film via tc-SPL. This process occurs simultaneously with local thermal quasi-3D topographical patterning of the same polymer, offering lateral sub-10 nm resolution, and vertical 1 nm resolution, as well as high throughput (5.2 × 104 μm2/h). The obtained single-enzyme resolution patterns are characterized by atomic force microscopy (AFM) and fluorescence microscopy. The enzyme density, the surface passivation, and the quasi-3D arbitrary geometry of these patterned pockets are directly controlled during the tc-SPL process in a single step without the need of markers or masks. Other unique features of this patterning approach include the combined single-enzyme resolution over mm2 areas and the possibility of fabricating enzymes nanogradients.
We demonstrate a high resolution and high-throughput patterning method to generate protein nanopatterns with sub-10 nm resolution by using thermochemical scanning probe lithography.
The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from their limited rheological tuneability and slow reactions kinetics. The direct ink write (DIW) 3D printing of a two‐part resin, Epon 828 and Jeffamine D230, using a self‐assembly approach is reported. Through the addition of self‐assembling, ureidopyrimidinone‐modified Jeffamine D230 and nanoclay filler, suitable viscoelastic properties are obtained, enabling 3D printing of the epoxy–amine pre‐polymer resin. A significant increase in viscosity is observed, with an infinite shear rate viscosity of approximately two orders of magnitude higher than control resins, in addition to, an increase in yield strength and thixotropic behavior. Printing of simple geometries is demonstrated with parts showing excellent interlayer adhesion, unachievable using control resins.
We report supramolecular AB diblockc opolymers comprised of well-defined telechelic building blocks.H elical motifs,f ormed via reversible addition-fragmentation chaintransfer (RAFT) or anionic polymerization, are assembled with coil-forming and sheet-featuring blocks obtained via atom-transfer radical polymerization (ATRP) or ring-opening metathesis polymerization (ROMP). Interpolymer hydrogen bonding or metal-coordination achieves dynamic diblock architectures featuring hybrid topologies of coils,h elices, and/or p-stacked sheets that, on ab asic level, mimic protein structural motifs in fully synthetic systems.T he intrinsic properties of eachb lock( e.g.,c ircular dichroism and fluorescence) remain unaffected in the wake of self-assembly.T his strategy to develop complex synthetic polymer scaffolds from functional building blocks is significant in af ield striving to produce architectures reminiscent of biosynthesis,y et fully synthetic in nature.This is the first plug-and-playapproach to fabricate hybrid p-sheet/helix, p-sheet/coil, and helix/coil architectures via directional self-assembly.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.
N-(Bis(4-(2-ethylhexyloxy)phenyl)(phenyl)-methyl) methacrylamide was synthesized and polymerized via reversible addition-fragmentation chain-transfer (RAFT) polymerization. The chain-transfer agent (4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPADB)), combined with a chiral additive, and a radical initiator yielded polymers with dispersities between 1.2 and 1.4. At low concentrations, the polymers are soluble in hexanes and chloroform while at higher concentrations they swell in these solvents. Characterization of the polymers by wide-angle X-ray scattering (WAXS) revealed an interplanar distance of 19.0 Å . The WAXS data combined with polarized optical microscopy support a lamellar crystallization and lyotropic liquid crystalline behavior in hexanes and chloroform.
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