Host Monomers Research Articles

Host-Guest recognition strengthened supramolecular preformed particle gel for conformance control in low-permeability fractured reservoirs

The conventional preformed particle gels (PPG) have problems of irreversibly shear-breakage after shearing actions during the application for conformance control in low-permeability fractured reservoirs. Herein, a novel host–guest recognition strengthened supramolecular PPG (S-PPG) was synthesized with synergistically non-covalent and covalent crosslinking structures, using host (allyl β-CD) and guest (cetyldimethylallyl ammonium chloride) monomers. Firstly, the chemical structures and micro-morphologies of S-PPG were systematically characterized by FTIR, Cryo-SEM, EDS and AFM methods. Then, the dispersion and thermal stability, swelling properties and rheological properties, including viscoelasticity, creep-recovery and shear self-healing abilities, of S-PPG were investigated, respectively. Finally, the low-permeability cores with fractures were used to identify the injectivity and plugging properties of S-PPG and conventional PPG. The results showed that the S-PPG exhibited strong crosslinking network, high dispersion and thermal stability. In addition, the S-PPG also displayed better swelling, viscoelasticity, creep-recovery and shear self-healing ability after equilibrated swelling process compared to those of conventional PPG. Finally, the S-PPG exhibited considerable compatibility with low-permeability cores with fracture width of 0.05 mm, and produced higher plugging rate (93.53 %) than conventional PPG (86.35 %). Therefore, the newly formulated supramolecular preformed particle gel (S-PPG) containing host–guest recognition can provide a new approach for solving the problems of irreversibly shear-breakage and improving the conformance control performance of PPG in low-permeability fractured reservoirs.

Polymer Hosts Containing Carbazole-Dibenzothiophene-Based Pendants for Application in High-Performance Solution-Processed TADF-OLEDs.

The film-forming capability of the host plays a crucial role in effectively forming a light-emitting layer through a solution process in organic light-emitting diodes (OLEDs). In this study, we synthesized two side-chain polymer hosts, PCz-DBT and P2Cz-DBT, consisting of carbazole and dibenzothiophene. The synthesis was carried out through radical polymerization using styrene-based host monomers. Their photophysical characteristics and molecular energy levels are similar to those of the reference small molecule hosts, namely, Cz-DBT and 2Cz-DBT. However, compared to the small-molecule hosts Cz-DBT and 2Cz-DBT, the two polymer hosts showed high thermal stability and good film-forming properties in the neat and host-emitter blend films. Specifically, bluish-green multiple-resonance (MR) thermally activated delayed fluorescence (TADF) OLEDs, fabricated via solution processing with an emissive layer based on P2Cz-DBT, exhibited remarkable performance. These devices achieved a maximum external quantum efficiency of 17.4% without utilizing a hole transport layer. This polymer host design strategy is considered to significantly contribute to enhancing the performance of TADF-OLEDs fabricated through solution processing.

Synthesis of Pyrrole-N-vinylcarbazole Neat Copolymer (Py-NVK) and ZnO Nanocomposite (Py-NVK_ZnO)

The present work focused on the synthesis of neat copolymer (Py-NVK) and ZnO Nanocomposite from their pyrrole (Py) and N-vinylcarbazole (NVK) host monomers and creating new conducting materials (Py-NVK & Py-NVK_ZnO). The choice of neat copolymer and ZnO Nanocomposite was motivated by the unique properties of their host monomers (Py & NVK). The neat and ZnO Nanocomposite copolymer was prepared by the sol-gel method using FeCl3 as an initiator. Structural analyses were performed using Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HRTEM), X-Ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).

Hybridizing a Dual-Cross Network and a Linear Glassy Polymer for Dynamic Contributions to High Mechanical Toughness Based on Phase-Separated Structures

Bulk copolymerization of alkyl acrylate and cyclodextrin (CD) host monomers forms a single movable cross network (SC), in which the CD units act as movable cross-linkers. Moreover, the bulk copolymerization of the CD monomer and main chain monomer in the presence of SC results in dual-cross-network (DC) elastomers. DC elastomers result in good toughness (Gf). Here, to improve Gf and Young’s modulus (E), we hybridized DC elastomers with tertiary glassy polymers, which are called DCP elastomers. We prepared the DCP elastomers by photopolymerization of N,N-dimethylacrylamide (DMAA) and poly(2-methoxyethyl acrylate) (MEA) in the presence of DC. A DCP elastomer with a suitable weight percent (wt %) of the glassy polymer shows high Gf (108.4 MJ m–3) and E (223.4 MPa) values. Dynamic mechanical analysis (DMA) and in situ small-angle X-ray scattering (SAXS) measurements under uniaxial stretching indicate multiple deformations based on phase-separated structures. We suggest that the phase-separated structures of DCP elastomers cause a large stress dissipation, which contributes to high toughness.

A novel collector for high-sulfur bauxite flotation desulfurization

ABSTRACT Effective desulfurization of high-sulfur bauxite is one of the major problems in the alumina production industry. To overcome this, a novel nanoparticle collector (NC) to improve the desulfurization performance during flotation process was synthesized via emulsion polymerization method, whereby lignin (natural polymer) was used as the host monomer. The NC’s syntheses, desulfurization performance, characterization tests, and adsorption on pyrite were studied. Results showed that the optimum conditions for the syntheses of NC (average particle size of 252.5 nm) were at mass ratio of lignin (host monomer), potassium butyl xanthate (functional group) and sodium dodecyl sulfate (emulsifier) of 1:20:2, and reaction temperature of 70°C. NC showed better flotation performance (maximum desulfurization), and shorter flowsheet, compared to common collectors. On a different note, tests suggested that NCs were uniformly adsorbed on the surface of pyrite via physico-chemical way.

Preparation of dual-cross network polymers by the knitting method and evaluation of their mechanical properties

Bulk copolymerization of alkyl acrylates and cyclodextrin (CD) host monomers produced a single movable cross-network (SC). The CD units acted as movable crosslinking points in the obtained SC elastomer. Introducing movable crosslinks into a poly(ethyl acrylate/butyl acrylate) copolymer resulted in good toughness (Gf) and stress dispersion. Here, to improve the Young’s modulus (E) and Gf of movable cross-network elastomers, the bulk copolymerization of liquid alkyl acrylate monomer swelling in SC gave another type of movable cross-network elastomer with penetrating polymers (SCPs). Moreover, the bulk copolymerization of alkyl acrylate and the CD monomer in the presence of SC resulted in dual cross-network (DC) elastomers. The Gf of the DC elastomer with a suitable weight % (wt%) of the secondary movable cross-network polymer was higher than those of the SCP or SC elastomers. The combination of suitable hydrophobicity and glass transition of the secondary network was important for improving Gf. Small-angle X-ray scattering (SAXS) indicated that the DC elastomers exhibited heterogeneity at the nanoscale. The DC elastomers showed a significantly broader relaxation time distribution than the SC and SCP elastomers. Thus, the nanoscale heterogeneity and broader relaxation time distribution were important to increase Gf. This method to fabricate SCP and DC elastomers with penetrating polymers would be applicable to improve the Gf of conventional polymeric materials.

Oxoanion Imprinting Combining Cationic and Urea Binding Groups: A Potent Glyphosate Adsorber.

The use of polymerizable hosts in anion imprinting has led to powerful receptors with high oxyanion affinity and specificity in both aqueous and non-aqueous environments. As demonstrated in previous reports, a carefully tuned combination of orthogonally interacting binding groups, for example, positively charged and neutral hydrogen bonding monomers, allows receptors to be constructed for use in either organic or aqueous environments, in spite of the polymer being prepared in non-competitive solvent systems. We here report on a detailed experimental design of phenylphosphonic and benzoic acid-imprinted polymer libraries prepared using either urea- or thiourea-based host monomers in the presence or absence of cationic comonomers for charge-assisted anion recognition. A comparison of hydrophobic and hydrophilic crosslinking monomers allowed optimum conditions to be identified for oxyanion binding in non-aqueous, fully aqueous, or high-salt media. This showed that recognition improved with the water content for thiourea-based molecularly imprinted polymers (MIPs) based on hydrophobic EGDMA with an opposite behavior shown by the polymers prepared using the more hydrophilic crosslinker PETA. While the affinity of thiourea-based MIPs increased with the water content, the opposite was observed for the oxourea counterparts. Binding to the latter could however be enhanced by raising the pH or by the introduction of cationic amine- or Na+-complexing crown ether-based comonomers. Use of high-salt media as expected suppressed the amine-based charge assistance, whereas it enhanced the effect of the crown ether function. Use of the optimized receptors for removing the ubiquitous pesticide glyphosate from urine finally demonstrated their practical utility.

A bioinspired mineral-organic composite hydrogel as a self-healable and mechanically robust bone graft for promoting bone regeneration

Despite advances in the development of osteo-regenerative biomaterials, current products are vulnerable to stress-induced formation of cracks, resulting in the loss of functionality and a limited lifespan. In the present study, a strategy based on host-guest assembly was developed to fabricate a silk fibroin-based inorganic-organic hybrid hydrogel (termed SF@HG@HA) in which silk fibroin was used as a polymer template to tether host (β-cyclodextrin) and guest (cholesterol) monomers, respectively. Due to dynamic host-guest interactions, the prepared hydrogel could repair itself spontaneously when damaged, without the assistance of any external stimuli, mimicking the self-healing characteristics of native bone tissue. Furthermore, the efficient energy dissipation mechanism provided by the host-guest crosslinking strategy endowed the hydrogel with robust mechanical properties to bear substantial mechanical loading. SF@HG@HA was shown to support cell proliferation and osteogenic differentiation in vitro and accelerate bone regeneration in critical-size rat femoral defects in vivo. Together, the silk fibroin-based self-healing hydrogel with robust mechanical properties shows potential applications in the reconstruction of bone defects, which may provide new directions for the design of functional biomaterials for tissue regeneration.

Urea-Based Imprinted Polymer Hosts with Switchable Anion Preference.

The design of artificial oxyanion receptors with switchable ion preference is a challenging goal in host–guest chemistry. We here report on molecularly imprinted polymers (MIPs) with an external phospho-sulpho switch driven by small molecule modifiers. The polymers were prepared by hydrogen bond-mediated imprinting of the mono- or dianions of phenyl phosphonic acid (PPA), phenyl sulfonic acid (PSA), and benzoic acid (BA) using N-3,5-bis-(trifluoromethyl)-phenyl-Ń-4-vinylphenyl urea (1) as the functional host monomer. The interaction mode between the functional monomer and the monoanions was elucidated by 1H NMR titrations and 1H–1H NMR NOESY supported by molecular dynamic simulation, which confirmed the presence of high-order complexes. PPA imprinted polymers bound PPA with an equilibrium constant Keq = 1.8 × 105 M–1 in acetonitrile (0.1% 1,2,2,6,6-pentamethylpiperidine) and inorganic HPO42– and SO42– with Keq = 2.9 × 103 M–1 and 4.5 × 103 M–1, respectively, in aqueous buffer. Moreover, the chromatographic retentivity of phosphonate versus sulfonate was shown to be completely switched on this polymer when changing from a basic to an acidic modifier. Mechanistic insights into this system were obtained from kinetic investigations and DSC-, MALDI-TOF-MS-, 1H NMR-studies of linear polymers prepared in the presence of template. The results suggest the formation of template induced 1–1 diad repeats in the polymer main chain shedding unique light on the relative contributions of configurational and conformational imprinting.

Addition of Thiourea Host Monomer to Polymer Flocculants to Improve Selectivity of Phosphate Sorption

Inorganic phosphate is a common nutrient that is applied as a fertilizer to both agricultural fields as well as urban settings such as private yards, public parks and other urban landscaping. While phosphate typically binds tightly to soil, movement of phosphate off of application sites can occur through soil erosion. The soil and its bound phosphate can then end up in surface waters such as rivers and lakes. Phosphate found in surface water bodies exists both as bound to the suspended clay as well as that free in solution. Elevated phosphate concentration in surface waters can lead to algal blooms and eutrophication. While the phosphate bound to clay in suspension in surface water bodies can be removed by commercially available polymer flocculants, the phosphate that is free in solution is more challenging as it is usually found in low concentrations and other anionic salts are generally present in higher concentrations. To remove phosphate from contaminated water systems, where other anions exist at higher concentrations, it is favorable to have a method of removal that is selective for phosphate. As a proof of principle, thiourea derivatized polymer flocculants were examined for the selective removal of phosphate in the presence of competing anions. The polymer flocculants exhibited selectivity for phosphate through hydrogen bonding and were effective at removing up to 43% of phosphate from simulated wastewater. Computational studies and 1H NMR were used to investigate the selectivity of the thiourea monomer for phosphate over competing anions such as chloride and sulfate.

High salt compatible oxyanion receptors by dual ion imprinting

Imprinting of an ion-pair in presence of mutually compatible anion and cation host monomers leads to polymers showing enhanced ion uptake in competitive high ionic strength buffers.

Selective Enrichment of Phosphorylated Peptides by Monolithic Polymers Surface Imprinted with bis-Imidazolium Moieties by UV-Initiated Cryopolymerization.

Reversible protein phosphorylation on serine, threonine, and tyrosine residues is essential for fast, specific, and accurate signal transduction in cells. Up to now, the identification and quantification of phosphorylated amino acids, peptides, and proteins continue to be one of the significant challenges in contemporary bioanalytical research. In this paper, a series of surface grafted monoliths in the capillary format targeting phosphorylated serine has been prepared by first synthesizing a monolithic core substrate material based on trimethylolpropane trimethacrylate, onto which a thin surface-imprinted layer was established by oriented photografting of a variety of mono- and bis-imidazolium host monomers at subzero temperature, using six different continuous or pulsed UV light sources. The imprinted monolith capillaries were evaluated in a capillary liquid chromatographic system connected to a mass spectrometer in order to test the specific retention of phosphorylated peptides. Site-specific recognition selectivity and specificity for phosphorylated serine was demonstrated when separating amino acids and peptides, proving that the optimized materials could be used as novel trapping media in affinity-based phosphoproteomic analysis.

Responsive surface adhesion based on host–guest interaction of polymer brushes with cyclodextrins and arylazopyrazoles

Polymer brushes functionalized with cyclodextrin host and arylazopyrazole guest monomers provide strong surface adhesion that is water resistent but can be deactivated by UV irradiation.

Werner type clathrates involving guest benzoic acid and benzoate in discrete Mn(II) hosts: Experimental and theoretical studies

Two Werner type clathrates, viz. [Mn(phen)2Cl2]·bzH (2) and [Mn(phen)2Cl(H2O)]·4–NO2bz·3H2O (3) [phen = 1,10-phenanthroline, bzH = benzoic acid 4–NO2bz = 4-nitrobenzoate], have been synthesized from a complex precursor [Mn(phen)2Cl2] (1). The synthesized compounds have been characterized by X-ray crystal structure analysis, FT-IR, electronic spectra, ESR and TGA. The crystal structure of the clathrates reveal the self-assembled inclusion of bzH and 4–NO2bz in discrete monomeric Mn(II) hosts. The enclathration of the guest molecules in the host monomers of the Mn(II) complexes brings rigidity to the structures. The supramolecular assemblies involving various non-covalent interactions observed in the solid state of compounds 1 and 2 have been analysed energetically using DFT calculations and rationalized using MEP surfaces and NCI plot index computational tools. The studies reveal the cooperativity between π–π and CH⋯Cl interactions in 1 and the stabilization of a self assembled bzH dimer in 2. The microbial activities have been investigated for the compounds.

A two-step process for capture and purification of human basic fibroblast growth factor from E. coli homogenate: Yield versus endotoxin clearance

A two-step purification process for human basic fibroblast growth factor (FGF-2) from clarified E. coli homogenate has been developed in which the impurity level after the second step is below the limit of quantification. Endotoxin content is cleared to 0.02 EU/μg FGF-2 and the overall yield is 67%. The performance of the cation exchanger Carboxymethyl-Sepharose Fast Flow (CM-SFF) was compared to the affinity resin Heparin-SFF regarding the impurity profile and product quality in the elution peak. The CM-SFF eluate was further purified using hydrophobic interaction resin Toyopearl-Hexyl-650C. The relative amounts of target product, host cell proteins (HCPs), dsDNA, endotoxin, monomer content, and high molecular weight impurities differed along the elution peak depending on the applied method. The bioactive monomer (>99%) was obtained with a yield of 48% for CM-SFF and 68% for Heparin-SFF. A half-load reduction in CM-SFF increased the yield up to 67% without deterioration of the impurity content. Assuming a dose of 400 μg FGF-2, endotoxin was reduced to 188 EU/dose, dsDNA <10 ng/dose, and HCP <2 ppm/dose using the cation exchanger. In the pooled eluate fractions, dsDNA was removed 4-fold (291 ng/mL) and endotoxin 14-fold (0.47 EU/μg FGF-2) more efficiently by CM-SFF than by affinity chromatography. In contrast, HCP clearance was 3-fold (13 ppm) more efficient with Heparin-SFF than CM-SFF. In contrast to process monitoring by UV280nm or SDS-PAGE, this characterization is the basis for a Process Analytical Technology attempt when correlated with online monitored signals, as it enables knowledge-based pooling according to defined quality criteria.

An unusual werner type clathrate of Mn(II) benzoate involving energetically significant weak C[sbnd]H⋯C contacts: A combined experimental and theoretical study

A new Werner type manganese(II) clatharate [Mn(Bz)2(H2O)4]∙(4–CNpy)∙2H2O (1), where Bz = benzoate and 4–CNpy = 4–cyanopyridine, has been synthesized at room temperature and characterized by X-ray crystal structure analysis, FT-IR, electronic spectrum and TGA. The crystal structure of cocrystal hydrate of 1 involves a discrete host monomer with enclathrated water and 4-CNpy molecules. Crystallographic studies on the compound 1 reveal that enclathration of guest water molecules in the Mn(II) host units results in a supramolecular tetramer in the crystal structure of 1 involving weak CH⋯C contacts. The geometry of the supramolecular host tetramer with the guest 4–CNpy molecules has been fully optimized using the crystallographic coordinates and the computational results suggest that the observed CH⋯C interactions are energetically quite significant. It is observed that both electrostatics as well as dispersion interactions are the most dominant contributors towards the stabilization of the CH⋯C interaction.

Self-Healing Supramolecular Hydrogel: Polyrotaxane Cross-Linked By Host-Guest Interactions

Self-healing materials, which can extend the service life of objects, have attracted much attention in efforts to create a sustainable society. One of the most important approaches to obtain self-healing materials is non-covalently bonded systems. Unlike covalently bonds, non-covalent interactions such as hydrogen bonds, π-π stacking interactions, metal-ligand coordination bonds, and host-guest interactions [1] are reversible. It has been recently reported that materials recover their original mechanical property when they are damaged. This self-healing property occurs by introducing a non-covalent interaction site into the end or side chain of a polymer. In this regard, the healing time is affected by the mobility of the polymer chain because self-healing occurs by the formation of non-covalent bonds between the responsible sites via non-covalent interactions in the polymer. To address the expected practical demands and requirements, the development of a self-healing material that recovers in a short time is in high demand. For this purpose, we employ polyrotaxanes (PRxs), which are a class of supramolecular threaded macromolecules in which cyclic molecules are threaded onto linear polymers.[2] The advantage of PRxs is that threaded cyclic compounds are freely mobile along the linear polymer because they are non-covalently assembled between the linear polymer and many cyclic molecules. Thus, compared to functional groups conjugated to a conventional polymer side chain, the functional group conjugated with the cyclic molecules in PRx can effectively bind to the target. Herein we report a self-healing material based on PRx through host-guest interactions. This material was prepared by radical copolymerization of acryl amide (AAm) and the host monomer in the presence of PRx introduced with guest molecules. The resulting material exhibits a self-healing property, and its healing speed is faster than a self-healing material without PRx. [1] (a) T. Kakuta, Y. Takashima, M. Nakahata, M. Otsubo, H. Yamaguchi, A. Harada, Adv. Mater. 2013, 25, 2849-2853. (b) M. Nakahata, Y. Takashima, A. Harada, Macromol. Rapid. Commun. 2016, 37, 86-92. [2] (a) Y. Kobayashi, Y. Nakamitsu, Y. Zheng, Y. Takashima, H. Yamaguchi, A. Harada, Chem. Commun. accepted (b) A. Harada, J. Li, M. Kamachi, Nature 1992, 356, 325-327. Figure 1. (a) Chemical structures of Ad(x)DMEDAPRx–βCD gel, Ad(x)–βCD gel, and AAm(x) gel. (b) Schematic illustration of the self-healing feature of Ad(x)DMEDAPRx–βCD gel. Here, x represents the mol% of the cross-linking unit. Figure 1

Lipophilic Polyelectrolyte Gels and Crystal Crosslinking, New Methods for Supramolecular Control of Swelling and Collapsing of Polymer Gels

Abstract This review focuses on our trial to control the swelling and collapsing of polymer gels by two different approaches. One is the introduction of ion-pairs from bulky and hydrophobic ions into hydrophobic polymers to form ionic polymer gels as “lipophilic polyelectrolyte gels”. Partial dissociation of these ion-pairs in nonpolar media, such as chloroform and THF, provides them a high swelling ability as superabsorbent polymers. Compatibility of the polymers with the media and ion dissociation are crucial for the superabsorbency. The other is preparation of polymer gels by controlling the size, shape and crosslinking points with the aid of nanoporous metal-organic frameworks (MOF). It includes polymerization between the organic ligands as host monomers fixed on the open framework and the guest monomers that penetrate into the nanopores. Thus, all the components in a crystal are polymerized, which is called “crystal crosslinking”. Hydrolysis of the coordination bonds produces insoluble polymer gels without metal ions. The shapes of the polymer gels are essentially identical to those of the template crystals, and the swelling ability is controlled by arrangements of the host monomers in the template crystals. These two approaches should be unique and effective for controlling the swelling ability of the polymer gels.

A photocontrollable supramolecular hyperbranched polymer based on host-guest recognition in aqueous solution

A novel supramolecular hyperbranched polymer had been fabricated conveniently through host-guest recognition based on Cucurbit[8]uril in aqueous solution. The three branched monomer contained an azobenzene unit and a viologen moiety on each of its branch. The polymerization of the supramolecular polymer in water could be controlled by tuning the isomer ratio of azobenzene groups of the guest monomers upon the competitive irradiation of lights. In addition, the strictness of the structure could be adjusted by varying the molar ratio between host and guest monomers. Planar supramolecular network had been constructed by drying the solvent of the solution of supramolecular hyperbranched polymers on smooth plane. The research provided a promising way to conduct dual-responsive supramolecular polymerization.

Cationic pTyr/pSer imprinted polymers based on a bis-imidazolium host monomer: phosphopeptide recognition in aqueous buffers demonstrated by μ-liquid chromatography and monolithic columns.

We report on the design and characterization of imprinted cationic host polymers for selective trapping of phosphoserine and phosphotyrosine peptides. A series of imidazolium host monomers were synthesized and characterized with respect to binding affinity and stoichiometry of interaction with salts of phenylphosphonic acid. The strongest binders were subsequently used for the preparation of imprinted polymers in the form of crushed monoliths, using Fmoc-phosphotyrosine-ethyl ester or Fmoc-phosphoserine-ethyl ester as templates in combination with a hydrophilic crosslinking monomer. The polymers were compared with respect to binding and its dependence on solvent, and whether charged or uncharged host monomers were used. The recipes were subsequently implemented in the capillary monolith format for evaluation by micro-liquid chromatography in both buffered and organic media. Results from both tested formats reveal that the cationic host polymers displayed enhanced recognition in polar and buffered media, in contrast to neutral urea-based hosts which showed best results in acetonitrile rich mobile phases.