Synthesis and Analysis of Telechelic Polyisobutylenes for Hydrogen-Bonded Supramolecular Pseudo-Block Copolymers

The Hamilton Receptor in Supramolecular Polymer Sciences

Supramolecular polymers are polymeric materials of monomeric fragments, held jointly by reversible and directional non-covalent interactions such as multiple hydrogen-bonding, charge transfer effects, host-guest interactions, metal coordination, and aromatic stacking. This review article on the Hamilton-based supramolecular polymers aims to shed light on the molecular recognition achievements by the Hamilton-based polymeric systems, evaluate Hamilton receptor's future prospects, and capitalize its potential applications in supramolecular chemistry. To the best of our knowledge, this is the first elaborative and sole manuscript in which polymeric Hamilton receptors are being exposed in detail. The first portion of this manuscript is related to the importance and urgency of polymers along with the historic background of Hamilton receptors. The middle section discloses the potential applications of Hamilton-type receptors in various fields, e.g., dendrimers, mechanically polymeric rotaxanes, and self-assemblies. The final section of the manuscript discloses the future aspects and the importance of novel polymer-based Hamilton-type receptors in the modern era. We believe that this first review in this emerging yet immature field will be useful to inspire scientists around the world to find the unseen future prospects, thereby boosting the field related to this valued artificial receptor in the province of supramolecular chemistry and also in other domains of scientific fields and technology, as well.

Nucleobase-containing polymer architectures controlled by supramolecular interactions: the key to achieve biomimetic platforms with various morphologies

Challenges and opportunities in supramolecular self-assembly of synthetic nucleobase-containing copolymers.

3D Printing of Solvent-Free Supramolecular Polymers

Additive manufacturing has significantly changed polymer science and technology by engineering complex material shapes and compositions. With the advent of dynamic properties in polymeric materials as a fundamental principle to achieve, e.g., self-healing properties, the use of supramolecular chemistry as a tool for molecular ordering has become important. By adjusting molecular nanoscopic (supramolecular) bonds in polymers, rheological properties, immanent for 3D printing, can be adjusted, resulting in shape persistence and improved printing. We here review recent progress in the 3D printing of supramolecular polymers, with a focus on fused deposition modelling (FDM) to overcome some of its limitations still being present up to date and open perspectives for their application.

Supramolecular Triblock Copolymers Through the Formation of Hydrogen Bonds: Synthesis, Characterization, Association Effects in Solvents of Different Polarity

Anionic polymerization techniques were employed for the synthesis of linear polystyrene (PS) and block copolymer of PS and polyisoprene (PI) PS-b-PI bearing end hydroxyl groups. Following suitable organic chemistry transformation, the –OH end groups were converted to moieties able to form complementary hydrogen bonds including 2,6-diaminopurine, Dap, thymine, Thy, and the so-called Hamilton receptor, Ham. The formation of hydrogen bonds was examined between the polymers PS-Dap and PS-b-PI-Thy, along with the polymers PS-Ham and PS-b-PI-Thy. The conditions under which supramolecular triblock copolymers are formed and the possibility to form aggregates were examined both in solution and in the solid state using a variety of techniques such as ¹H-NMR spectroscopy, size exclusion chromatography (SEC), dilute solution viscometry, dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), and differential scanning calorimetry (DSC).

Chelation-assisted CuAAC in star-shaped polymers enables fast self-healing at low temperatures

The achievement of self-healing (SH) under ambient conditions (low temperature, no external input of energy) still presents a significant area of research, and is enabledvia“click”-type crosslinking reactions.

Utilising alternative modifications of α-olefin end groups to synthesise amphiphilic block copolymers

Amphiphilic block copolymers comprised of polyisobutylene (PIB) and poly(2-(dimethylamino)ethyl methacrylate) (DMAEMA) have been synthesised.

Entropic Effects on the Supramolecular Self-Assembly of Macromolecules

We report the transfer of entropic chain length effects into the realm of supramolecular chemistry and thereby demonstrate a macromolecular method to tune the reaction equilibria of hydrogen bonding motifs via the application of substituents of differing lengths and masses while not altering the actual recognition units to achieve a difference in the degree of association. The supramolecular adducts are characterized via temperature-dependent nuclear magnetic resonance (NMR) spectroscopy.

Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends

The supramolecular blend of complementary nucleobase-functionalized ABA triblock copolymers self-assemble into a microphase-separated morphology with enhanced mechanical performance and thermal responsiveness.

Direct Chain End Functionalization of Living Polyisobutylene Using Phenoxyalkyl (Meth)acrylates

Phenoxyalkyl acrylates and methacrylates were studied as quenching (capping) agents for living carbocationic polymerization of isobutylene (IB) at -70 °C in 40/60 (v/v) hexane/methyl chloride, catalyzed by TiCl₄. Quenching reactions were carried out by reactivation by TiCl₄ of preformed difunctional tert-chloride-terminated polyisobutylene (PIB) or by a one-step method in which IB polymerization and quenching were conducted sequentially in the same reactor. Chain-end concentrations ranged from 0.02 to 0.1 M, and quenchers were used at concentrations of 1.5-2.5 times the chain ends. The phenoxyalkyl (meth)acrylates were synthesized by reaction of (meth)acryloyl chloride with the corresponding phenoxyalkanol; alkylene tethers from two to eight carbons were examined. Quenched polymers were characterized by ¹H and ¹³C NMR, MALDI-TOF mass spectrometry, and size exclusion chromatography (SEC). Alkylation was observed to occur exclusively at the para position of the phenoxy moiety, and SEC showed no coupling or molecular weight degradation as a result of quenching. For short tethers of two or three carbons, quenching was slow and incomplete due to competing loss of living chain ends presumably by carbocation rearrangement. For tethers of four, six, or eight carbons, quenching was much faster and yielded quantitative (meth)acrylate chain-end functionality (number-average functionality ≥1.98 by ¹H NMR). MALDI-TOF-MS results were consistent with the expected end group structures. The carbonyl group of the quencher consumes one equivalent of Lewis acid in formation of a 1:1 complex; thus, the highest rate of quenching at a given Lewis acid concentration is achieved by using only a modest excess of quencher relative to living chain ends.

Self-assembly of an interacting binary blend of diblock copolymers in thin films: a potential route to porous materials with reactive nanochannel chemistry

Self-assembly of a binary mixture of poly(styrene)336-block-poly(4-vinyl pyridine)25 (PS336-b-P4VP25) and poly(ethylene glycol)113-block-poly(4-hydroxy styrene)25 (PEG113-b-P4HS25) is shown to give rise to a cylindrical morphology in thin films through pyridine/phenol-based hetero-complementary hydrogen bonding interactions between the P4VP and P4HS copolymer segments. Removal of the cylindrical phase (PEG-b-P4HS) allowed access to porous materials having a pore surface decorated with P4VP polymer blocks. These segments could be transformed into cationic polyelectrolytes through quaternization of the pyridine nitrogen atom. The resulting positively charged nanopore surface could recognize negatively charged gold nanoparticles through electrostatic interactions. This work, therefore, outlines the utility of the supramolecular AB/CD type of block copolymer towards preparation of ordered porous thin films carrying a chemically defined channel surface with a large number of reactive sites.

Isophthalic Acid-Pyridine H-Bonding: Simplicity in the Design of Mechanically Robust Phase-Segregated Supramolecular Polymers

We report a new series of supramolecular polymeric networks based on the isophthalic acid-pyridine (IPA-Py) H-bonding motif. The IPA units were attached as end-groups to telechelic poly(ethylene-co-butylene) to create a tetrafunctional macromonomer, which was cross-linked by the addition of various bispyridines. Some of the supramolecular polymer networks thus made display surprisingly good mechanical characteristics. We show that their structure and properties are strongly influenced by the nature of the bispyridine motif and by the fact that some of the IPA-Py motifs aggregate into particularly well-defined hard phases.

Facile preparation of supramolecular (ABAC)n multiblock copolymers from Hamilton wedge and barbiturate-functionalized RAFT agents

The facile preparation of novel supramolecular (ABAC)_n multiblock copolymers from Hamilton wedge and barbiturate functionalized H-bonding RAFT agents is reported.

Binding and supramolecular organization of homo- and heterotelechelic oligomers in solutions

Solvent can subtly influence the organization of supramolecular polymers.

Facile Preparation of Supramolecular H-Shaped (Ter)polymers via Multiple Hydrogen Bonding

A well-defined Hamilton wedge (HW) midchain functionalized block copolymer, i.e., polyethylene glycol-b-polystyrene (PEG-HW-PS, M_n,GPC = 5600 Da, PDI = 1.03), was successfully synthesized via a combination of atom transfer radical polymerization (ATRP) and copper-catalyzed azide alkyne cycloaddition (CuAAC). An α,ω-cyanuric acid (CA) difunctional linear homopolymer poly(n-butylacrylate) (CA-PnBA-CA, M_n,GPC = 8100 Da, PDI = 1.09) was concomitantly prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Supramolecular H-shaped macromolecules were-for the first time-prepared through supramolecular self-assembly between HW and CA recognition motifs to generate (PS-b-PEG)·PnBA·(PS-b-PEG) and (PS-b-PS)·PnBA·(PS-b-PS) in CH₂Cl₂ or dichloromethane-d₂ at ambient temperature. The self-assembly process (at a total concentration of the two species of close to 4.5 mM) was evidenced by proton nuclear magnetic resonance (¹H NMR) spectroscopy, diffusion-ordered NMR spectroscopy (DOSY), and dynamic light scattering (DLS) analyses. The results derived via DOSY NMR experiments and DLS combined with a Job plot analysis and in-depth NMR titration experiments indicate that the formation of supramolecular H-shaped macromolecules in 2:1 stoichiometry is efficiently occurring via the employed complementary recognition motifs with high binding constants (between 1.2 and 1.5 × 10⁵ L mol^-1 at ambient temperature).

Studies on the orthogonal assembly of β-cyclodextrin-poly (ε-caprolactone) and ferrocene-poly (ethylene oxide)

A biodegradable multi-arm polymer β-cyclodextrin-poly (ε-caprolactone) (CD-PCL) with a ``jellyfish-like'' structure was obtained, in which flexible and hydrophobic PCL arms were selectively grafted to the wide side of the hydrophilic torus-shaped β-CD. The amphiphilic "jellyfish-like'' polymer with a hollow cavity and hydrophobic tails could orthogonally self-assemble into a new amphiphilic supramolecular copolymer CD-PCL/FcPEG with poly (ethylene oxide) end-decorated by ferrocene (FcPEG) in aqueous solution based on terminal hydrophobic interactions. The chemical structures of CD-PCL and CD-PCL/FcPEG were characterized by IR, NMR and UV and their self-assembled structures in water were investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). CD-PCL alone self-assembled into nano vesicles in water, while CD-PCL/FcPEG into nanospheres. The supramolecular nanospheres were further investigated by cyclic voltammogram. The results indicated that the ferrocenyl groups which were embedded into the hydrophobic core of the supramolecular nanospheres could not transmit electrons or carry out electrochemical oxidation and reduction reaction.

Star and miktoarm star block (co)polymers viaself-assembly of ATRP generated polymer segments featuring Hamilton wedge and cyanuric acid binding motifs

The self-assembly of well-defined ATRP prepared polymers with terminal and mid-chain Hamilton wedge as well as cyanuric acid binding motifs is demonstrated to be an efficient avenue to star and miktoarm star block copolymers.