Supramolecular Graft Copolymers Research Articles

Noncovalently connected supramolecular metathesis graft copolymers: One-pot synthesis and self-assembly

For the first time, noncovalently connected supramolecular polymers were prepared by ring-opening metathesis polymerization (ROMP) and host–guest interactions in a one-pot process. An adamantane-based oxanorbornene dicarboximide derivative was first prepared, and then ROMP was accomplished in a single operation, followed by efficient complexation between cyclodextrin and adamantane moieties to form amphiphilic supramolecular graft copolymers via a two-feed procedure in one-pot. Subsequently, amphiphilic supramolecular block and alternating graft copolymers were constructed using a similar technique via the copolymerization with cyclooctene in one-pot. Importantly, the degree of polymerization and molecular weight distribution of these supramolecular polymers were well controlled, and further they self-assembled into supramolecular nanostructures with diverse morphologies in aqueous solution. It is expected that this research will provide a new direction for designing and constructing noncovalently connected supramolecular metathesis polymers.

Responsive Emulsions Stabilized by Amphiphilic Supramolecular Graft Copolymers Formed in Situ at the Oil-Water Interface.

Amphiphilic supramolecular graft copolymers which can stabilize oil-in-water (o/w) emulsions and enable responsive demulsification were demonstrated in this study. Linear poly[( N, N-dimethylacrylmide)- stat-(3-acrylamidophenylboronic acid)] (PDMA- stat-PAPBA) copolymers with phenylboronic acid (PBA) groups and linear polystyrene homopolymers with cis-diol terminals (PS(OH)2) were synthesized by reversible addition-fragmentation chain transfer polymerization. By the homogenization of the biphasic mixtures of an alkaline water solution of PDMA- stat-PAPBA copolymer and a toluene solution of PS(OH)2 homopolymer, stable o/w emulsions could be generated, although neither PDMA- stat-PAPBA nor PS(OH)2 alone was able to stabilize the emulsion. It was verified that the dispersed oil droplets in the emulsions were stabilized by the amphiphilic PDMA- stat-PAPBA- g-PS supramolecular graft copolymers, which were formed in situ at the oil-water interface by the complexation between the lateral PBA groups of PDMA- stat-PAPBA and the diol terminals of PS(OH)2 during homogenization. These emulsions showed pH- and glucose-responsive demulsification because of the reversible B-O bonds between the PDMA- stat-PAPBA backbones and the PS side chains. The effects of polymer concentrations on emulsion formation were also investigated. The current study provides an alternative method for the facile preparation of responsive polymeric emulsifiers, which potentially may be extended to other polymer pairs containing PBA and cis-diol groups.

Periodic introduction of a Hamilton receptor into a polystyrene backbone for a supramolecular graft copolymer with regular intervals

The Hamilton receptor group (–DADDAD–; D = hydrogen donor; A = hydrogen acceptor) was periodically introduced into a polystyrene backbone, starting from the ruthenium-catalyzed living radical polymerization of styrene with the Hamilton receptor-based bifunctional initiator.

Construction of a artificial glutathione peroxidase with temperature-dependent activity based on a supramolecular graft copolymer.

A supramolecular artificial glutathione peroxidase (PNIPAM-CD-g-Te) was prepared based on a supramolecular graft copolymer. PNIPAM-CD-g-Te was constructed by supramolecular host-guest self-assembly. Significantly, PNIPAM-CD-g-Te displayed noticeable temperature-dependent catalytic activity and typical saturation kinetics behavior. It was also proved that the change in the self-assembled structure of PNIPAM-CD-g-Te during the temperature-dependent process played a significant role in the temperature-dependent catalytic behavior. The construction of PNIPAM-CD-g-Te based on supramolecular graft copolymer endows artificial GPx with temperature-dependent catalytic ability, enriched catalytic centers, and homogeneously distributed catalytic centers. This work bodes well for the development of other biologically related host-guest supramolecular biomaterials.

Facile construction of fluorescent polymeric aggregates with various morphologies by self-assembly of supramolecular amphiphilic graft copolymers

Facile construction of fluorescent polymeric aggregates with various morphologies was realized by self-assembly of supramolecular amphiphilic graft copolymers.

A pH-responsive amphiphilic supramolecular graft copolymer constructed by crown ether based molecular recognition

Based on the bis(m-phenylene)-32-crown-10/paraquat molecular recognition motif in water, we have successfully prepared an amphiphilic supramolecular graft copolymer by the combination of modified hydrophilic poly(ethylene oxide) and hydrophobic polystyrene. It could self-assemble into pH-responsive bilayer vesicles in water.

Chain extension of center-functionalized polystyrene via radical–radical coupling: Periodic introduction of complementary hydrogen bonding interaction site on polymer chain

In this work, our purpose was directed to syntheses of unique polystyrene (PSt) periodically carrying complementary hydrogen-bonded interaction sites in the chain. First, a bifunctional (bi-headed) initiator carrying three-point complementary hydrogen bonding sites (Cl–DAD–Cl: D=hydrogen donor; A=hydrogen acceptor) was employed for ruthenium-catalyzed living radical polymerization of styrene. Precise control of the polymerization allowed quantitative introduction of the DAD unit at the center and Cl capping group at the terminals for the resultant PSt chain as well as narrow molecular weight distribution. Generation of concentrated radical species from the C–Cl bonds at the both terminals in the absence of monomer induced radical–radical coupling reaction between the styryl radical species for “chain extension”. Since molecular weight distribution of the precursor was enough narrow (Mw/Mn<1.10) and the DAD unit was quantitatively incorporated at the central position, the resultant polymer chains carried the complementary interaction site at regular interval corresponding to the chain length (molecular weight) of the precursor. The position-controlled polystyrene chain interacted with poly(methyl methacrylate) having the complementary interaction unit (ADA) at the center to give supramolecular graft copolymer.

Study on the formation of a supramolecular conjugated graft copolymer in solution

The formation in solution of a supramolecular graft copolymer bearing conjugated blocks is demonstrated using diffusion ordered NMR spectroscopy (DOSY). A tailor-made poly(3-(2-ethylhexyl)thiophene) (P3EHT) with a phenol end group is synthesized. For this purpose, the chain-growth mechanism of the polymerization of 2-bromo-5-chloromagnesio-3-alkylthiophenes in the presence of a Ni(dppp) catalyst (dppp = 1,3-bis(triphenylphosphino)propane) is exploited, as it enables the use of functionalized initiators to introduce specific end groups. The so-obtained polythiophene was subsequently mixed in solution with poly(4-vinylpyridine) (P4VP) to enable phenol-pyridine hydrogen bonding. The formation of the supramolecular graft copolymer is studied using DOSY-measurements. Based on the results thereof, the amount of P3EHT attached to the P4VP is calculated and the association constant of the hydrogen bond is estimated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 804–809

Phase behaviors of supramolecular graft copolymers with reversible bonding

Phase behaviors of supramolecular graft copolymers with reversible bonding interactions were examined by the random-phase approximation and real-space implemented self-consistent field theory. The studied supramolecular graft copolymers consist of two different types of mutually incompatible yet reactive homopolymers, where one homopolymer (backbone) possesses multifunctional groups that allow second homopolymers (grafts) to be placed on. The calculations carried out show that the bonding strength exerts a pronounced effect on the phase behaviors of supramolecular graft copolymers. The length ratio of backbone to graft and the positions of functional groups along the backbone are also of importance to determine the phase behaviors. Phase diagrams were constructed at high bonding strength to illustrate this architectural dependence. It was found that the excess unbounded homopolymers swell the phase domains and shift the phase boundaries. The results were finally compared with the available experimental observations, and a well agreement is shown. The present work could, in principle, provide a general understanding of the phase behaviors of supramolecular graft copolymers with reversible bonding.

A novel supramolecular graft copolymer via cucurbit[8]uril-based complexation and its self-assembly

A novel supramolecular graft copolymer (SGP) composed of viologen-containing copolymer (P(DMA-co-diEV)) as the main chain and Np ended PNIPAM (Np-PNIPAm) as the grafts is prepared (DMA: N,N-dimethylacryamide, diEV: ethylviologen dimer, Np: naphthalene, PNIPAM: poly(N-isopropylacrylamide)). The grafting is based on the triple complexation among a host of cucurbit[8]uril (CB[8]) and two guests of diEV and Np, which is characterized by UV–vis spectra and ITC. Temperature sensitive property of PNIPAm moiety allows SGP to self-assemble into non-covalently connected micelle (NCCM) at high temperature. The micelles are sensitive to reducing agents, for example Na2S2O3, which breaks the current inclusion complex pair and induces aggregation.

Supramolecular graft copolymers in moderately polar media based on hydrogen-bonded aromatic oligoamide units

By exploiting hetero-complementary aromatic oligoamide units containing hextuple hydrogen bonds, supramolecular graft copolymers were successfully constructed in moderately polar media.

Supramolecular Pseudorotaxane Graft Copolymer from a Crown Ether Polyester and a Complementary Paraquat-Terminated Polystyrene Guest

The self-assembly of a polyester containing crown ether host repeat units and a paraquat-terminated polystyrene guest provides a supramolecular pseudorotaxane graft copolymer based on the bis(m-phenylene)-32-crown-10/paraquat recognition motif. NMR chemical shift changes in solution gave evidence of the complexation of the crown ether and paraquat moieties. Solutions of the two polymers at 1:1 host:guest stoichiometry (crown ether:paraquat), but only 3 mass % crown polymer, possessed an intrinsic viscosity 1.9 times that of the paraquat-terminated polystyrene and 2.7 times that of the polyester. Differential scanning calorimetry revealed only one glass transition for a solid from evaporation of a solution at 3:1 host:guest (crown ether:paraquat) stoichiometry; this indicated complete phase mixing, as confirmed by optical microscopy and small-angle laser light scattering.

Size and Morphology Control of Aggregates from Supramolecular Graft Copolymers Stabilized by Ionic Interaction

A series of SGPs composed of a PLL main and a PLGA side chain was synthesized with different DSs in a DMSO solvent. The addition of water induced the self-assembly of PLL/PLGA SPGs into spherical micelles. The size of the spherical micelles decreased with an increase in DS and core/shell structures, which was confirmed by XPS and zeta-potential measurements. The morphological transitions were under thermodynamic control when the solvents mixed. Consequently, further increases in water content caused the transition of the spherical micelles to vesicles, while the initial spherical micelles were reconstructed from vesicles when the DMSO was added. The content of water, the boundaries for the morphology transition, depended on the DS. pH and salt levels affected the stability of the aggregates.

Preparation of Supramolecular Graft Copolymers and the Subsequent Formation of pH-Sensitive Vesicles

A feasible methodology for the preparation of vesicles through self-assembly of supramolecular graft copolymers (SGPs) was developed. Two types of polymeric vesicles were prepared through self-assembly of two SGPs. For the first SGP, hydrophobic poly(4-vinylpyridine) (PVPy) were used as main chains, and hydrophilic poly(N-vinylpyrrolidone) with carboxylic end groups (PNVP-COOH) were grafted onto the main chains through ionic interaction between the carboxylic groups and pyridine groups. For the second SGP, hydrophobic poly(4-acrylamidobenzoic acid) (PABA) were used as main chains, and poly(N-vinylpyrrolidone) with amino end groups were grafted onto the main chains through ionic interaction between the amino groups and carboxylic groups. Both SGPs could self-assemble to form vesicles in aqueous solution. The size of the vesicles prepared from the PVPy/PNVP-COOH (or PABA/PNVP-NH2) system could be controlled through modulation of the mass ratio of PVPy and PNVP-COOH (or PABA and PNVP-NH2). Both vesicles were...

Supramolecular Graft Copolymers Based on 2,7-Diamido-1,8-naphthyridines

Supramolecular graft copolymers containing a quadruple hydrogen bond motif in the main chain have been prepared by acyclic diene metathesis (ADMET) polymerization of an α,ω-diene monomer containing a 2,7-diamido-1,8-naphthyridine (Napy) unit. During the ADMET polymerization, a supramolecular protection strategy was applied in order to prevent naphthyridine coordination to the ruthenium catalyst. The 2-ureido-4[1H]-pyrimidinone (UPy) derivatives used as protecting groups also allowed for detection of the supramolecular graft copolymer with size exclusion chromatography. Deprotection by simple treatment with a polar solvent afforded free Napy binding sites on the main chain. Reversible grafting of UPy derivatives of various sizes onto the free poly-Napy was demonstrated by diffusion-ordered NMR experiments.

Aqueous Micelles from Supramolecular Graft Copolymers

AbstractAqueous micelles have been prepared from amphiphilic supramolecular graft copolymers, in which poly(ethylene glycol) (PEG) side chains were linked to a poly(methyl methacrylate) (PMMA) backbone via ruthenium(II)‐terpyridine complexes. Three different graft copolymers were investigated, in which the average number of PEG branches (constant length) and the length of the PMMA backbone were varied. The successful formation of micelles was proven by dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). A good agreement was found between TEM and AFM observations, which show polydisperse spherical micelles. The hydrodynamic diameter measured by DLS was much larger, suggesting the formation of aggregates. No substantial difference in the micellar characteristic features was found between the three investigated samples.Schematic representation of the graft copolymer synthesis.magnified imageSchematic representation of the graft copolymer synthesis.