Supramolecular ABC Triblock Copolymers via One-Pot, Orthogonal Self-Assembly

Abstract

A heterotelechelic poly(norbornene imide) containing two terminal and orthogonal hydrogen-bonding receptors, N,N'-bis[6-(alkanoylamino)pyridin-2-yl] isophthalamide (often referred to as the Hamilton receptor or Wedge) and 2,7-diamido-1,8-naphthyridine (DAN), at the opposite ends of the polymer was synthesized via ring-opening metathesis polymerization (ROMP) through the employment of a Hamilton receptor-functionalized ruthenium initiator and a DAN-based chain-terminator. In parallel, two monotelechelic polymers containing either cyanuric acid (CA)- or ureidoguanosine (UG)-end groups that are complementary to the hydrogen-bonding receptors along the poly(norbornene imide) were synthesized either also via ROMP by terminating the polymerization of norbornene octyl ester with a CA-based chain-terminator or by the reaction of poly(ethylene oxide) with UG. Complete incorporations of the hydrogen-bonding receptors at the chain-ends of all polymers were confirmed by (1)H NMR spectroscopy. The telechelic polymers can be self-assembled into ABC triblock copolymers following either a stepwise or a one-pot, orthogonal self-assembly protocol. The self-assembly process was monitored by (1)H NMR spectroscopy, revealing full orthogonality of the two recognition pairs, Hamilton receptor-CA and DAN-UG. The resulting supramolecular ABC triblock copolymers were further characterized by a series of methods including 2-D NOESY, isothermal titration calorimetry, and viscometry, proving that the two orthogonal hydrogen-bonding interactions are strong enough to hold the three polymer chains together. We suggest that a self-assembly methodology solely based on the fully orthogonal hydrogen-bonding recognition motifs will allow for an easy and rapid synthesis of architecturally controlled supramolecular polymeric assemblies with a high degree of complexity.

Synthesis of a smart Janus-like supramolecular polymer based on the host–guest chemistry and its self-assembly

“…[2][3][4][5][6][7][8] Typical Janus particles were micro-or nano-sized particles composed of two hemispheres with distinct chemical or physical properties. [11][12][13][14][15][16][17] However, the difficulties in synthesizing Janus supramolecular polymers were enormous. 9,10 These unique properties also made Janus-type supramolecular polymers very promising in biomedical applications including mimicking primitive biological membranes, conguring into biomimetic nanocapsules, fabricating functional nanomedicines, and so on.…”

Single‐Chain Polymer Self‐Assembly Using Complementary Hydrogen Bonding Units

“…Figure S1 (Supporting Information) shows a partial 1 H NMR spectrum for the titration of S14 to 2 in DMSO‐d 6 . The signals of the interacting protons on the small molecules remain at the same chemical shifts even up to 3.0 equivalents of S14 (Figure S1A, Supporting Information), contrary to the characteristic downfield shifting demonstrated in CHCl 3 (vide infra) . The 1 H NMR spectrum of the triblock copolymer following dialysis in DMSO shows the removal of the UG‐protecting group (Figure S2, Supporting Information).…”

“…An acylated guanosine‐derivative ( S14 ) was synthesized to serve as a receptor as well as a protecting group to the recognition motifs of 2 , potentially circumventing the coordination of 2 to the ruthenium catalyst. We monitored the titration of the protecting group (2.0 equivalents) to 2 by 1 H NMR spectroscopy and observed the characteristic downfield shifts of the DAN amide protons from 8.93 to 11.45 ppm, and the downfield shifts of the UG–NH protons from 10.20 and 12.09 ppm to 11.50 and 13.58 ppm, respectively . Excess of the protecting group was added to ensure that the pyridine was fully protected.…”

Bioresorbable vascular scaffolds: The shape of things to come?

“…Especially within the field of supramolecular chemistry, the introduction of complex functional groups at the specific positions of a polymer chain is an important task to be fulfilled precisely 4. Among the many supramolecular moieties known, hydrogen bonding moieties have gained special interest since they can be used to transform a random chain assembly into an ordered supramolecular structure 5. Thus, we have accomplished the introduction of complex hydrogen‐bonding moieties via a combination of ROMP with “click”‐chemistry methods,6–8 as the direct copolymerization of many monomers with complex functional groups, such as hydrogen bonds or nitroxide‐moieties often leads to uncontrolled polymerization reactions with sometimes broad molecular weight distributions 9, 10.…”

“…Thus, we have accomplished the introduction of complex hydrogen‐bonding moieties via a combination of ROMP with “click”‐chemistry methods,6–8 as the direct copolymerization of many monomers with complex functional groups, such as hydrogen bonds or nitroxide‐moieties often leads to uncontrolled polymerization reactions with sometimes broad molecular weight distributions 9, 10. A still challenging task however, is the introduction of a functionalized end group via ROMP to one or both sides of a polymer chain, which can be achieved with different methods often including the reaction of the respective living chain end with functionalized enolethers5, 11–18 or oxygen 19. Other approaches to such telechelic polymers rely on the use of functionalized catalysts,17 chain transfer agents,20, 21 sacrificial synthesis22, 23 or the quench with vinyllactones 24.…”