End‐group functionalization and postpolymerization modification of helical poly(isocyanide)s

Abstract

This contribution presents the synthesis of helical alkyne‐terminated polymers using a functionalized Nickel complex to initiate the polymerization of menthylphenyl isocyanides. The resulting polymers display low dispersities and controlled molecular weights. Copper‐catalyzed azide/alkyne cycloadditions (CuAAC) are performed to attach various azide‐containing compounds to the polymer termini. After azido‐phosphonate moiety attachment the polymer displays a signal at 25.4 ppm in the 31P NMR spectrum demonstrating successful end‐group functionalization. End‐group functionalization of a fluorescent dye allows to determine the functionalization yield as 89% (±8). Successful ligation of an azide‐functionalized peptide sequence (MKLA = 1547 g/mol) increases the Mn from 5100 for the parent polymer to 6700 for the bioconjugate as visualized by GPC chromatography. Analysis by CD spectroscopy confirms that the helical conformation of the poly(isocyanide) block in the peptide–polymer conjugate is maintained after postpolymerization modification. These results demonstrate an easy, generalizable, and versatile strategy toward mono‐telechelic helical polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2766–2773

Synthesis and Light‐Mediated Structural Disruption of an Azobenzene‐Containing Helical Poly(isocyanide)

“…This allows for the covalent functionalization of our light-triggerable poly(isocyanide) with numerous azide-containing molecules via copper-catalyzed click chemistry. [34] Alkyne-functionalization would also allow for the fabrication of stimuli-responsive block copolymers through post-polymerization ligation (PPL), thus enhancing our previously reported systems that featured structural domains similar to those found in Nature's proteins (i.e. coil and sheet).…”

“…The dispersity obtained through GPC (Ð = 1.32, M n = 5500 g/mol) is in line with dispersity values of poly(isocyanide)s in the literature. [12][13][14][15]34] CD spectroscopy was performed to study the handedness of the helix and to see if the conformation could be affected using light as stimulus (Figure 3). Alanine-based poly(isocyanide)s featuring an amide bond in their side-chains, as is the case in our system (Figure 1), are well-studied and are known to form stable helical structures due to both side-chain bulk and the hydrogen bonding network along the side-chains at repeat units n and n + 4.…”

“…Alanine-based poly(isocyanide)s featuring an amide bond in their side-chains, as is the case in our system (Figure 1), are well-studied and are known to form stable helical structures due to both side-chain bulk and the hydrogen bonding network along the side-chains at repeat units n and n + 4. [9,[33][34][35] Disruption of the hydrogen bonding network could, in turn, result in a disruption of the structure. A Cotton effect in the CD spectrum around 310 nm, which corresponds to the n-π* transition of the C=N backbone chromophore, indicates that a helix with the defined hydrogen bonding array was formed, while a Cotton effect around 280 nm indicates a system without a hydrogen-bonding array.…”

Coil‐helix and sheet‐helix block copolymers via macroinitiation from telechelic ROMP polymers

“…This method provides multiple advantages, such as high fidelity monomer incorporation, and a potential to tune block composition (e.g., random vs. true block vs. blocky); yet, the structures engineered using this methodology can be limited to a discrete set of monomers, pending the chosen polymerization method . Thus, post‐polymerization ligation strategies are an attractive route to connect individual polymer blocks resulting from multiple polymerization methods and initiators. Despite the wide use of this method in conjunction with click chemistry, post‐polymerization ligation of polymers can suffer not only from insufficient yields associated with conjugation, but also from purification challenges of the desired bcp from unreacted building blocks.…”

Supramolecular Diblock Copolymers Featuring Well‐defined Telechelic Building Blocks

“…Herein, we engineer supramolecular diblock copolymers (Scheme 1) comprised of topologically-diverse and welldefined telechelic polymers based upon sheet-forming poly(p-phenylene vinylene)s (PPV), [13] helical poly(methacrylamide)s [12] and poly(isocyanide)s, [15] and poly(norbornene) [11b] and poly(styrene) coils prepared via controlled polymerization routes such as ROMP,R AFT,A TRP,a nd palladium-initiated anionic polymerization. Hydrogen-bond and metal-coordination-driven assembly of the individual telechelic building blocks leads to main chain supramolecular AB sheet-helix, sheet-coil, and coil-helix polymers.T he block copolymers are characterized using NMR spectroscopy to determine binding constants,a sw ell as wide-angle X-ray scattering (WAXS), circular dichroism (CD) and fluorescence spectroscopy to gain insights into the assembled structures and evaluate if the secondary structures and individual polymer properties are prevalent in the block copolymer architecture.…”