Synthesis and properties of block polypseudorotaxanes by threading cucurbit[6]uril

A novel water-soluble block polypseudorotaxane (4) was synthesized in water from cucurbit[n]uril (n?=?6), designated as CB[6], and a block copolymer of methoxy poly(ethylene glycol)-b-poly-[N ¹-(4-vinylbenzyl)-pentane-1,5-diamine dihydrochloride]-b-methoxy poly(ethylene glycol) (P3). Driven by the hydrophobic/hydrophobic interaction and the association between the diamine and glycoluril units, CB[6] beads are localized on the pentamethylene units in the side chains of P3 as found by NMR studies. The degree of threading, i.e., the average number of CB[6] beads per repeat recognition unit of P3, can be controlled from 0.25 to 1.0 by varying the amount of CB[6] added. This molecular feature leads to interesting aggregation behavior of the polypseudorotaxanes in aqueous solutions, as revealed by dynamic light scattering measurements, transmission electron microscopy observations, ultraviolet/visible spectroscopy (UV?Cvis) and fluorescence spectrometry. The average hydrodynamic radius (R _h), the intensity of UV?Cvis absorption band and the fluorescence intensity (I _f) of the block polypseudorotaxanes in solution increase with the increasing of threaded CB[6]. With the solution temperature increasing, the size of the aggregates in water increased and the fluorescence intensity (I _f) of the solution decreased, which shows the polypseudorotaxanes can sensitively respond to temperature changes. This opens the door for the application of the block polypseudorotaxanes in various fields such as drug delivery and controlled release.     

Syntheses,crystal structures and properties of self-assembly supramolecular compound based on cucurbit[6]uril

A new cucurbit [6]uril based compound {[Cd₂Cl₂(INA)₂(HCOO)₂(H₂O)₂](CB [6])·2(HCOOH)·5H₂O}(CCUT-101) was synthesized by the solvothermal reaction of cadmium chloride, cucurbit[6]uril (CB[6]), and isonicotinic acid (HINA). X-ray diffraction analysis indicated that coordination of INA⁻ with the Cd^2 + resulted in the formation of some one-dimensional wave-like chains, which connected with CB[6] by π ⋯ π stacking and hydrogen bonding, and further extended to a 2D layer. The luminescence behaviors and sensing properties of CCUT-101 in different solvents were carried out.     

Side-chain pseudopolyrotaxanes by threading cucurbituril[6] onto quaternized poly-4-vinylpyridine derivative: Synthesis and properties

A novel side-chain pseudopolyrotaxanes 4 is synthesized from cucurbituril (CB[6]) and quaternized poly-4-vinylpyridine derivative 3 in water by simple stirring at room temperature. CB[6] beads are localized on hexamethylene units in side chains of 3 as found by NMR studies, and the hydrophobic and charge-dipole interactions are the driving force. The degree of threading (q/n, the average number of CB[6] beads per repeat recognition unit of 3) can be controlled from 0.2 to 1.0 by controlling the amount of CB[6] added. The reduced viscosity of pseudopolyrotaxanes in aqueous solution has smaller change with the change of the concentration or temperature, which is consistent with the hydrodynamic radius and more rigid chain conformation because of the threaded CB[6]. DLS results show the average hydrodynamic diameter (D_h) of the pseudopolyrotaxanes in solution increases with the increasing of CB[6] threaded. The pseudopolyrotaxanes have higher thermal stability and intensity of absorption band than the parent polymer 3 as found by TGA and UV-vis studies. The decomposition temperature and intensity of absorption increase with increasing amount of CB[6] threaded. The effect of NaI to pseudopolyrotaxanes is studied by the transmittance with UV-vis, and the result shows that NaI is the satisfied precipitant to the pseudopolyrotaxanes.     

Synthesis of ultrahigh molecular weight phenolic polymers by enzymatic polymerization in the presence of amphiphilic triblock copolymer in water

An enzymatic oxidative polymerization of phenols was investigated in the presence of poly(ethylene glycol) (PEG)-poly(propylene glycol) (PPG)-poly(ethylene glycol) (PEG) triblock copolymer (Pluronic) in water. The formation of micellar aggregate of phenol and Pluronic by hydrogen bonding interaction in an aqueous solution was verified by DLS measurement. The PEG content of Pluronic greatly affected the polymerization behaviors. Using Pluronic with high PEG content improved the regioselectivity of the polymerization of phenol to give the polymer mainly consisting of phenylene unit. The polymerization in the presence of Pluronic F68 (EG₇₆-PG₂₉-EG₇₆) produced the phenolic polymer with ultrahigh molecular weight (M_w > 10⁶). From other phenols, high molecular weight polymers were also obtained. In addition, the FT-IR, DSC, and XRD analyses exhibited the formation of miscible complex between the phenolic polymer and Pluronic by hydrogen bonding interaction.     

Novel block ionomers. III. Mechanical and rheological properties

Select rheological (dynamic viscoelastic) and mechanical properties of novel block cationomers and anionomers and their blends have been investigated. The block ionomers were linear di‐ and triblocks, and symmetric three‐arm stars comprising hydrophobic polyisobutylene (PIB) blocks attached to ionized poly(methacrylic acid) (PMAA^?X⁺, where X⁺ = Na⁺, Zn²⁺) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA⁺I^?) blocks. The specific structures investigated were the well‐defined diblocks PIB‐b‐PMAA^? and PIB‐b‐PDMAEMA⁺ and their blends, the triblocks PMAA^?‐b‐PIB‐b‐PMAA^? and PDMAEMA⁺‐b‐PIB‐b‐PDMAEMA⁺ and their blends, and the three‐arm star anionomer Φ(PIB‐b‐PMAA^?)₃. For comparison, the properties of the precursor PIBs and unionized blocks have also been studied. Hydrogen bonding between the carboxyl groups of the PMAA blocks in PIB‐b‐PMAA diblocks leads to inverse micelles. Neutralization of the PMAA by Zn(AcO)₂ and quaternization of the PDMAEMA segments by CH₃I in the triblock copolymers and star copolymers yielded ionic domains, which self‐assemble and produce physical networks held together by coulumbic interaction. The physical/chemical characteristics of the domains control the viscoelastic behavior and mechanical properties of these block ionomers. The mechanical properties of the various block ionomers were significantly enhanced relative to the precursors, and they were thermally stable below the transition temperature. Further, the thermomechanical properties of these novel materials were satisfactory even above 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1516–1525, 2003     

Aggregation behaviour of a water-soluble ammonium-functionalized polythiophene: Luminescence enhancement induced by bile-acid anions

The water-soluble poly{trimethyl-[7-(3-thienylsulfanyl)heptyl]ammonium iodide-co-thiophene} (PTN⁺Me₃) forms aggregates whose size span a large range of values, depending on solvent, concentration and film formation conditions. Larger aggregates were detected by atomic force microscopy and dynamic light scattering, smaller ones by DOSY NMR, UV–visible and fluorescence. All techniques indicate a reduced aggregation of PTN⁺Me₃ in DMSO relative to water and a marked de-aggregation of PTN⁺Me₃ in water following addition of bile-acid anions such as deoxycholate and ursodeoxycholate. The latter effect shows itself through a very large enhancement of the polymer photoluminescence likely caused by disruption of aggregated non-emissive exciton traps. A tailored combination of electrostatic and hydrophobic interactions between the polymer and the bile-acid anions seems to be necessary to achieve this effect. These observations suggest that this polythiophene might provide a basis for the development of fluorescent sensors suitable for the detection of medium-sized amphiphilic biomolecules.     

pH敏感聚合物微球的制备及其性能研究

通过原位聚合的方法制备了生物相容的、具有环境响应特性核壳型羟乙基纤维素／聚甲基丙烯酸(HEC／PMAA)聚合物微球。采用动态光散射法和荧光光谱法研究了HEC／PMAA聚合物微球的形成机理;采用红外光谱(FTIR)分析了微球中分子间相互作用;利用TEM观察了HEC／PMAA微球的形貌;考察了HEC／PMAA微球的pH敏感性能。     

Consequences of Protonation of Diamines in the Gas Phase and the Solid State

An interesting model class of compounds are proton sponges—aromatic diamines characterized by exceptional basicity, such as 1,8-bis(dimethylamino)naphthalene (DMAN). For these compounds, protonation causes substantial redistribution of electron density which may be traced by observing the changes of structural parameters as well as of the properties of electron density at bond critical points. On protonation, electron density in DMAN goes from the terminal atoms towards the center of the molecule. This redistribution can also be confirmed by good quality neutron structural data. An ionic complex of DMAN with triformylmethane (TFM) acid has been studied by X-ray diffraction. We propose a multicenter model of hydrogen bonding {[Me₂N–H^0.5….^0.5H–NMe₂]⁺… X⁻} in this complex. The influence of weak intermolecular interactions of the DMANH⁺ cation with the nearest electronegative atom from the counterion on the strong intramolecular [N–H···N]⁺ hydrogen bonding has been demonstrated. Such interactions affect the localization of the proton in the intramolecular [N–H···N]⁺ hydrogen bridge.     

Helical opposition in poly(2‐methoxyaniline) by tuning the concentration of salts in reaction solution

The synthesis and application of helical polyaniline derivatives (PANIs) have attracted much interest. However, most of these syntheses have been carried out in organic solutions. In our previous reports, helical PANIs were successfully realized in aqueous solution. Because helical architecture in the backbones of PANIs is an induced rather than the natural arrangement, it is significant to study the change in helicity in aqueous solution, especially opposition or reversion. One excess‐handed helicity was induced in poly(2‐methoxyaniline) (PMOA) by electrochemical polymerization of 2‐methoxyaniline at pH = 2.5 in the presence of protonated β‐cyclodextrin sulfate (CDS^? H⁺). When 0.04 mol L^?1 NaCl was added to the reaction solution, the PMOA backbone took on an opposite excess of one‐handed helicity, which was confirmed by induced circular dichroism. Such a result originates from the dynamic switch between electrostatic and hydrogen‐bonding interactions. The helix‐inducing process in PMOA depends on the interaction between PMOA and chiral CDS. Due to the competition of Na⁺ Cl^? with PMOA⁺ CDS^?, the electrostatic interaction between PMOA and CDS is limited or weakened. Thus, the slightly preferred interaction between them switches from electrostatic to hydrogen bonding. Simultaneously, the interaction positions and distance are changed. The changed steric hindrance induces PMOA into adopting an opposite excess‐handed helicity. Copyright © 2010 Society of Chemical Industry     

Association phenomena between copolymers of p-styrenesulfonate(Cs+)/3-methacryloxypropyltrimethoxysilane and hydroxypropylcellulose in aqueous solution and solvent-cast films

Association between copolymers of p-styrenesulfonate (Cs⁺)/3-methacryloxypropyltrimethoxysilane [copolySS(Cs⁺)/MAPTMS], and hydroxypropylcellulose (HPC) are shown to exist in dilute aqueous solution. Gels form at concentrations as low as 0.05 g/dL. The tendency to form gels is a function of mol % MAPTMS in the copolymer and molecular weight of HPC. Gels can be dispersed by the addition of dimethylformamide (DMF), a known disruptor of hydrogen bonding. Homopolymers of SS(Cs⁺) and MAPTMS were also prepared. PolyMAPTMS shows anamolous behavior with regards to association with HPC in that gels form to a lesser degree than the trend exhibited by the copolymers. This is rationalized on the basis of the lack of chain expansion due to the absence of salt groups and their intrapolymer repulsions. In addition to the hydrodynamic data, the phase relationship of blends of HPC with either copolySS(Cs⁺)/MAPTMS, polySS(Cs⁺), or polyMAPTMS cast from aqueous solution strongly suggests specific interactions between polymers.     

The role of hydrogen-bond in solubilizing drugs by ionic liquids: A molecular dynamics and density functional theory study

The solvation mechanisms of aspirin and etomidate in four combinations of [Emim]⁺ and [BuGun]⁺ paired with [OAc]⁻ and [NTf₂]⁻ were systematically studied by molecular dynamics simulations and DFT calculations. It was shown that the favorable solvation of aspirin and etomidate correlated well with hydrogen-bond (H-bond) basicity of anions and the H-bond acidity of cations, respectively. Wherein, the H-bond between aspirin and [OAc]⁻ anion with high H-bond basicity possessed covalent feature, so ILs containing [OAc]⁻ anion has the best effective in solubilizing aspirin. However, H-bond interactions between etomidate and cations exhibited an electrostatic dominant, and moderate cation–anion interaction could weaken it. Accordingly, for etomidate, the best ILs solvent comprised a weakly interacting anion and a cation with strong H-bond acidity, that is, [BuGun][NTf₂]. This solvation difference was because aspirin with carboxyl group displayed strongly H-bond donating characteristic, whereas etomidate with no active hydrogen protons mainly formed H-bond with cations. Additionally, we found that π–π stacking interactions were of secondary importance for the solubilization of etomidate, but little for aspirin. These simulations will be helpful for experimental design new ILs to solubilize some drugs with aspirin-like or etomidate-like structures.     

Molecular Containers Bind Drugs of Abuse in Vitro and Reverse the Hyperlocomotive Effect of Methamphetamine in Rats

We measured the affinity of five molecular container compounds (calabadions 1 and 2 , CB[7], sulfocalix[4]arene, and HP‐β‐CD) toward seven drugs of abuse in homogenous aqueous solution at physiological pH by various methods (¹H NMR, UV/Vis, isothermal titration calorimetry [ITC]) and found binding constants (K_a values) spanning from <10² to >10⁸ m ^?1. We also report X‐ray crystal structures of CB[7] ? methamphetamine and 1? methamphetamine. We found that 2 , but not CB[7], was able to ameliorate the hyperlocomotive activity of rats treated with methamphetamine. The bioavailability of the calabadions and their convergent building block synthesis suggest potential for further structural optimization as reversal agents for intoxication with nonopioid drugs of abuse for which no treatments are currently available.     

Effect of hydrophilic chain length on the aqueous solution behavior of block amphiphilic copolymers PMMA‐b‐PDMAEMA

A series of amphiphilic block copolymers, polymethyl methacrylate (PMMA)‐b‐poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA), were synthesized by atom transfer radical polymerization (ATRP) method. Surface tension, dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic force microscopy (AFM) studies were performed to investigate the aqueous micellar behavior of these block amphiphiles. At a fixed degree of polymerization (DP) of PMMA block (DP = 55), the PDMAEMA block length was found to have a significant influence on the critical micelle concentration (cmc) values and hydrodynamic size of aggregates. An increase in the DP of PDMAEMA from 11 to 337, resulted in a decrease in the cmc from 1.44 × 10^?5 to 5.81 × 10^?7 M (a factor of almost 24.8), and a decrease in the Z (2R_h) from 85.5 to 15.5 nm (pH = 4), respectively. TEM and AFM results indicated that by changing the soluble block lengths, spherical, short rod, crew‐cut, vesicles or large aggregates can be observed in the solution. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Competitive hydrogen bonding mechanisms underlying phase behavior of triple poly(N‐vinyl pyrrolidone)–poly(ethylene glycol)–poly(methacrylic acid‐co‐ethylacrylate) blends

Differential scanning calorimetry (DSC) of triple blends of high molecular weight poly(N‐vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA) demonstrates partial miscibility of polymer components, which is due to formation of interpolymer hydrogen bonds (reversible crosslinking). Because both PVP and PMAA‐co‐EA are amorphous polymers and PEG exhibits crystalline phase, the DSC examination is informative on the phase state of PEG in the triple blends and reveals a strong competition between PEG and PMAA‐co‐EA for interaction with PVP. The hydrogen bonding in the triple PVP–PEG–PMAA‐co‐EA blends has been established with FTIR Spectroscopy. To evaluate the relative strengths of hydrogen bonded complexes in PVP–PEG–PMAA‐co‐EA blends, quantum‐chemical calculations were performed. According to this analysis, the energy of H‐bonding has been found to diminish in the order: PVP–PMAA‐co‐EA–PEG(OH) > PVP–(OH)PEG(OH)–PVP > PVP–H₂O > PVP–PEG(OH) > PMAA‐co‐EA–PEG(? O? ) > PVP–PMAA‐co‐EA > PMAA‐co‐EA–PEG(OH). Thus, most stable complexes are the triple PVP–PMAA‐co‐EA–PEG(OH) complex and the complex wherein comparatively short PEG chains form simultaneously two hydrogen bonds to PVP carbonyl groups through both terminal OH‐groups, acting as H‐bonding crosslinks between longer PVP backbones. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The Mechanism of Cucurbituril Formation

This article begins by describing the synthesis and recognition properties of the cucurbit[n]uril homologues CB[5], CB[6], CB[7], CB[8], and CB[10]. Subsequently, we describe the state-of-the-art in understanding the mechanism of CB[n] formation. We describe the experiments that establish that glycoluril ( 1 _H) undergoes condensation with formaldehyde by a combination of chain-growth and step-growth polymerization processes. Chain-growth processes deliver methylene bridged glycoluril oligomers 2 C – 8 C as intermediates that may undergo macrocyclization to nor-seco-CB[n] when the oligomer is long enough ( 5 C – 8 C) and subsequently form CB[n]. Step-growth processes allow oligomers to condense to give longer oligomers connected by a single CH₂-bridge that undergo macrocyclization to deliver (±)-bis-nor-seco-CB[6] and bis-nor-seco-CB[10]. Lastly, we describe some of the exciting new recognition processes of the newly formed members of the CB[n] family. For example, bis-nor-seco-CB[10] undergoes homotropic allostery during ternary complex formation, (±)-bis-nor-seco-CB[6] exhibits moderately diastereoselective recognition processes (d.r. up to 88 : 12) with chiral ammonium ions in water, and nor-seco-CB[6] functions as an aldehyde reactive CB[n] synthon that can control the folding of alkanediammonium ions into a backfolded conformation in water.     

Absorption properties of an inverted cucurbit[7]uril-based porous coordination polymer induced by [ZnCl4]2 − anions

Coordination of an inverted cucurbit[7]uril (iQ[7]) with a series of alkali cations (A⁺), revealed that iQ[7] can interact with potassium to form iQ[7]-K⁺-based porous coordination polymer in the presence of [ZnCl₄]^2 − anions as a structure directing agent. Unexpectedly, isothermal titration calorimetry revealed no obvious interaction of iQ[7] with any A⁺ cation. Moreover, the iQ[7]-K⁺-based porous coordination polymer showed selective sorption of polar volatile organics, which may have potential applications for molecular sieves, sensors, and absorption and separation processes.     

Role of ionic liquids in the efficient transfer of lithium by Cyanex 923 in solvent extraction system

The solvent extraction of Li⁺ by Cyanex 923 was investigated upon the addition of different imidazolium-based ionic liquids (ILs). The results showed 1-hydroxylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HOEmim][NTf₂]) can improve the extraction of Li⁺ most effectively. The fundamental mechanism is that [HOEmim][NTf₂] can remarkably enhance the coordination ability of Cyanex 923 to Li⁺ to form more stable and hydrophobic ion-pair species [Li(Cyanex 923)_n][NTf₂] (n_max = 3) resulting from the electrostatic interaction and typical hydrogen bonding of IL, and thus facilitating the transfer of Li⁺ into organic phase. This work has revealed the transfer mechanism of Li⁺ in a solvent extraction system comprising of IL and neural ligand. The knowledge of the coordination environment of Li⁺ in the presence of IL also gives us a new insight into the separation of ⁶Li/⁷Li. The disadvantage of this process is the loss of IL. However, this study provides guidance for the design of better IL-based systems for the separation of metal ions.     

Synthesis of syndiotactic poly(methacrylic acid) by free‐radical polymerization of the pseudo‐divinyl monomer formed with methacrylic acid and catechol

Syndiotactic poly(methacrylic acid) (Syn‐PMAA, r diad = 91 mol %) was synthesized by free radical polymerization of methacrylic acid (MAA) with catechol. The pseudo‐divinyl monomer was formed with one catechol and two MAA molecules by the hydrogen bonding between OH groups of catechol and COOH group of MAA. When the free radical polymerization of the pseudo‐divinyl monomer was carried out, intra‐ and intermolecular addition proceeded with racemic addition. The hydrogen bonding was the driving force to control tacticity. We discussed the effects of solvent, temperature, and the concentrations of MAA and catechol on the pseudo‐divinyl monomer formation. The highly syndiotactic PMAA was successfully obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Screening of ionic liquids as entrainers for the separation of 1-propanol + water and 2-propanol + water mixtures using COSMO-RS model

The COSMO-RS model was used to screen potential ionic liquids for the separation of aqueous azeotropic mixtures 1-propanol?+?water and 2-propanol?+?water. A combination of 22 cations (involving imidazolium, pyridinium, pyrrolidinium, quinolinium, and ammonium) and 36 anions were investigated. The anions chloride [Cl] and dihydrogen phosphate [H₂O₄P] were found to strongly influence the vapor liquid equilibrium behavior, whereas the ammonium-based cations diethanol ammonium [(Et)₂AMM]⁺ and tetra methyl ammonium [M₄AMM]⁺ were the most promising cations. In addition, the study of mixing enthalpy and excess Gibbs free energy confirmed that the molecular interaction of ionic liquids with water was found to be much larger than that with alcohols 1-propanol and 2-propanol, indicating the presence of a strong hydrogen bonding between the ionic liquids and water. Further, the addition of ionic liquids to the alcohol–water mixture reduces the activity coefficient of water and increases the relative volatility of the mixture, facilitating easier separation. Ionic liquids [(Et)₂AMM][Cl], [(Et)₂AMM][H₂O₄P], [M₄AMM][Cl], and [M₄AMM][H₂O₄P] are expected to be effective entrainers for the separation of the industrially important 1-propanol?+?water and 2-propanol?+?water systems.     

Performance evaluation of poly (methacrylic acid) as corrosion inhibitor in the presence of iodide ions for mild steel in H2SO4 solution

The inhibition performance of poly (methacrylic acid) (PMAA) and the effect of addition of iodide ions on the inhibition efficiency for mild steel corrosion in 0.5 M H₂SO₄ solution were investigated in the temperature range of 303–333 K using electrochemical, weight loss, scanning electron microscopy (SEM), and water contact angles measurements. The results show that PMAA is a moderate inhibitor for mild steel in 0.5 M H₂SO₄ solution. Addition of small amount of KI to PMAA significantly upgraded the inhibition efficiency up to 96.7%. The adsorption properties of PMAA and PMAA + KI are estimated by considering thermodynamic and kinetic parameters. The results reveal that PMAA alone was physically adsorbed onto the mild steel surface, while comprehensive adsorption mode characterized the adsorption of PMAA + KI. Adsorption of PMAA and PMAA + KI followed Temkin adsorption isotherm. The SEM and water contact angle images confirmed the enhanced PMAA film formation on mild steel surface by iodide ions.