Synthesis and characterization of grafting β‐cyclodextrin with chitosan

Two new adsorbents [β‐cyclodextrin–chitosan (β‐CD–CTS) and β‐cyclodextrin‐6–chitosan (β‐CD‐6‐CTS)] were synthesized by the reaction of β‐cyclodextrin (β‐CD) with epoxy‐activated chitosan (CTS) and the sulfonation of the C‐6 hydroxyl group of β‐cyclodextrin with CTS, respectively. Their structures were confirmed by IR spectral analysis and X‐ray diffraction analysis, and their apparent amount of grafting was determined by ultraviolet spectroscopy. The adsorption properties of β‐CD‐CTS and β‐CD‐6‐CTS for p‐dihydroxybenzene were studied. The experimental results showed that the two new adsorbents exerted adsorption on the carefully chosen target. The highest saturated capacity of p‐dihydroxybenzene of β‐CD‐CTS and β‐CD‐6‐CTS were 51.68 and 46.41 mg/g, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 860–864, 2004     

Synthesis of Thiiranes from Oxiranes in the Presence of β‐Cyclodextrin in Water

A mild and highly efficient, user‐friendly procedure has been developed for the conversion of oxiranes to thiiranes under supramolecular catalysis in the presence of β‐cyclodextrin in water at ambient temperature in excellent yields. The use of β‐cyclodextrin in this transformation overcomes the use of heavy metal halides as promoters and chlorinated hydrocarbons and other hazardous organic solvents.     

Synthesis of a novel linear water‐soluble β‐cyclodextrin polymer

A novel linear water‐soluble β‐cyclodextrin polymer has been prepared by grafting β‐cyclodextrin on poly[(methyl vinyl ether)‐alt‐(maleic anhydride)]. First, lithium hydride was used to obtain the mono‐alkoxide β‐CD. Grafting of β‐CD derivatives to the polymer backbone was then carried out by an esterification method. Using this method, polymers containing various amounts of β‐CD were synthesized. The resulting grafted polymers were characterized by two complementary methods, ¹H NMR and IR spectroscopy. The first was used to calculate the degree of substitution for the low amounts of β‐CD. The second method was very useful to evaluate the degree of substitution and the molar ratio of CD especially for high amounts of grafting. Our results indicate good agreement between both methods for intermediate rates. Copyright © 2004 Society of Chemical Industry     

Novel Aqueous Phase Supramolecular Synthesis of 3‐Pyrrolylindolin‐2‐ones and Pyrrolylindeno[1,2‐b]quinoxalines

Various 3‐pyrrolylindolin‐2‐ones and pyrrolylindeno[1,2‐b]quinoxaline were synthesized for the first time in high yields in water under neutral conditions by supramolecular catalysis involving β‐cyclodextrin. The β‐cyclodextrin can be recovered and reused a number of times without any loss of activity.     

Concentrated emulsion polymerization for preparation of β‐cyclodextrin‐supported chromatography columns

Concentrated inverse emulsion polymerization was used for making chromatography columns (based on crosslinked polystyrene divinylbenzene (PS‐DVB)) with pore sizes less than 10 μm. According to DSC‐thermal gravimetry thermograms, it was confirmed that the residual monomer concentration after polymerization process is negligible. For application of these columns in chiral chromatography, the β‐cyclodextrin is chemically fixed on the PS‐DVB resin pore surface. The presence of hydroxyl groups in the PS‐DVB resin after chemical modification was confirmed by FTIR spectroscopy. By chemical modification of the PS‐DVB resin, thermal stability increased up to 446°C. The structure of columns was analyzed by scanning electron microscopy (SEM). SEM evaluations showed that the porous structure of PS‐DVB resin was maintained intact after the chemical modification with β‐cyclodextrin. According to X‐ray data, presence of the crystalline domain that is related to β‐cyclodextrin is confirmed.© 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 857–863, 2006     

Preparation and characterization of β‐cyclodextrin‐linked chitosan microparticles

Hydrophobically modified chitosan containing β‐cyclodextrin (CD) units was synthesized by using tosylated β‐CD. The final product was characterized by Fourier transform infrared (FTIR) spectroscopy, elemental analysis and TGA, and rheometry. The polymer bearing β‐CD moieties was used to obtain crosslinked microparticles by spray‐drying which could then be used in a controlled release system for drugs. FTIR confirmed the formation of an amide linkage between cyclodextrin and chitosan. As fluorescence spectroscopy demonstrated, hydrophobic microenvironments were formed by chitosan bearing cyclodextrin in solution at lower concentrations than for chitosan. Rheometry and FTIR showed the crosslinking of the new polymer using genipin, a molecule of natural origin. Microspheres (MS) obtained by spray‐drying showed narrow size distribution when β‐CD was grafted onto chitosan and ξ‐potential of MS was slightly lower although it remained positive. In conclusion, β‐CD linked chitosan polymer can be considered as a very promising controlled drug delivery system for drugs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A facile and practical approach to randomly methylated β‐cyclodextrin

BACKGROUND: Because of its high demand for use in pharmaceutical products, cosmetics, soil remediation technologies, etc., randomly methylated β‐cyclodextrin (RM‐β‐CD) is one of the most important cyclodextrin (CD) derivatives. The aim of this present work is to use a green and commercially available approach to obtain RM‐β‐CD. Compared with other methylated CDs, RM‐β‐CD with an asymmetric molecular structure has higher water solubility. When the degree of substitution (DS) is about 1.8, the solubility tends to increase with increasing temperature and is suitable for pharmaceutical applications. RESULTS: RM‐β‐CD was synthesized using a green approach with ideal DS equal to 1.79. The one step process of β‐cyclodextrin methylation by CH₃Cl instead of (CH₃)₂SO₄ at mild temperature (80 °C) and pressure (1.60 MPa) with a good yield (78%), is convenient and environmentally friendly. The mixture of RM‐β‐CD obtained contained five compounds with various DS, from which the main compound with a DS equal to 1.8 was separated by column chromatography. The compounds were carefully characterized by infra‐red, NMR and mass spectrometry. CONCLUSIONS: The one‐step process to RM‐β‐CDs with CH₃Cl is more economical, more efficient and less noxious than the usual method using (CH₃)₂SO₄. Moreover, this approach avoids some poisonous residual materials and meets the demand for protecting the environment. Copyright © 2009 Society of Chemical Industry     

Permanent fixation of β‐cyclodextrin on cotton surface—An assessment between innovative and established approaches

Attachment of β‐cyclodextrin (β‐CD) molecules on cotton textile provides hosting cavities that can include a large variety of guest molecules for specific functionality. Five different new and existing techniques were evaluated for connecting β‐CD and its derivatives to cotton surface. A comparison has been made in terms of maximum attachment of β‐CD on cotton surface. Novel chemical based crosslinking with homo‐bi‐functional reactive dye (C.I. reactive black 5) and grafting with reactive monochlorotriazinyl‐β‐cyclodextrin show maximum attachment to cotton surface. Innovative, enzymatic coupling of especially synthesized 6‐monodeoxy‐6‐mono(N‐tyrosinyl)‐β‐cyclodextrin was performed on cotton textile surface. Enzymatic coupling was also carried out in a homogeneous system and attachment confirmed by UV–vis spectroscopy. This tyrosinase mediated coupling is low temperature and very specific technique. A phenolphthalein based analytical method was partially modified to reliably measure the amount of attached β‐CD on cotton surface. Atomic force microscopy and scanning electron microscopy techniques were used for surface characterization of the treated and untreated cotton surfaces. Alteration in surface topography has been observed for β‐CD treated samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Negative effect of stretching on the development of β‐phase in β‐nucleated isotactic polypropylene

On the premise that shear in the slit die of an extruder was minimized as far as possible, β‐nucleated isotactic polypropylene (iPP) was extruded. Simultaneously, once the extrudate (in the melt state) left the die exit, it was stretched at various stretching rates (SRs). For iPP with a low content of β‐nucleating agent (β‐NA), the crystallinity of β‐phase (X_β) initially increases with increasing SR, and then decreases slightly with further increase in SR. However, for iPP containing a higher content of β‐NA, with increasing SR, X_β decreases monotonically, indicating a negative effect of SR on β‐phase formation. Small‐angle X‐ray scattering and polarized optical microscopy experiments reveal that, when SR is less than 30 cm min^?1, the increasing amount of row nuclei induced by increasing SR is mainly responsible for the increase of X_β. In contrast, when SR exceeds 30 cm min^?1, the overgrowth of shish structures unexpectedly restrains the development of β‐phase, and spatial confinement is considered as a better explanation for the suppression of β‐phase. Copyright © 2011 Society of Chemical Industry     

Effect of β‐cyclodextrin on the solid‐state synthesized polyaniline doped with hydrochloric acid

Polyaniline (PANI) salts doped with hydrochloric acid were prepared by using solid‐state polymerization in the presence of β‐cyclodextrin (β‐CD) at room temperature. The fourier transform infrared (FTIR) spectra, ultraviolet‐visible absorption spectra, X‐ray diffraction patterns were used to characterize the molecular structures of these polymers. Cyclic voltammetry study and conductivity measurements were done to investigate their electrochemical behaviors. The morphology of polymers was studied by the scanning electron microscopy and transmission electron microscopy. The results showed that PANI salts prepared in the presence of β‐CD had different physicochemical characteristics compared with PANI salt prepared in the absence of β‐CD. When the molar ratio of aniline to β‐CD was 80/20, the obtained PANI salt displayed higher crystallinity, conductivity and electrochemical properties. However, these properties were opposite on condition that the molar ratio of aniline to β‐CD was 50/50. The results also revealed that the morphology of PANI salt was affected by β‐CD, especially at aniline/β‐CD molar ratio in the feed of 50/50, in which PANI salt displayed rodlike structure morphology with a diameter of near 80–100 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A concise synthesis of single‐enantiomer β‐lactams and β‐amino acids using Rhodococcus globerulus

BACKGROUND: Pharmaceutical companies continue to evaluate β‐amino acids and β‐lactams in a range of drug candidates. The development of a highly efficient and selective bioresolution of cyclic β‐lactam substrates could yield enantiopure lactams and β‐amino acids with medicinal potential. The aim of this work was to discover and develop a biocatalyst capable of selectively hydrolysing β‐lactam substrates. RESULTS: Screening of our in‐house culture collection led to the discovery of a microorganism, Rhodococcus globerulus (NCIMB 41042) with β‐lactamase activity. Whole‐cell bioresolutions of the β‐lactams 1–4 were successfully carried out and in all cases enantiomeric excesses of the residual lactam and amino acid product were found to be greater than 98%. For one example, the bioresolution was optimised to operate at 60 g L^?1 substrate concentration with a 20% wt/wt cell paste loading. CONCLUSION: A microorganism, Rhodococcus globerulus (NCIMB 41042), capable of selectively hydrolysing a range of cyclic β‐lactams, has been discovered. A scalable whole‐cell bioresolution process has been developed, leading to the synthesis of multigram quantities of enantiomerically pure β‐lactams and β‐amino acids. Copyright © 2007 Society of Chemical Industry     

Synthesis,characterization, and degradation investigation of water‐soluble β‐cyclodextrin‐based epoxy resins

A series of β‐cyclodextrin‐based epoxy resins were synthesized with different epoxy equivalent weights. Their chemical structures were characterized with Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance Spectroscopy (NMR) examination. These epoxy resins were cured using L ‐arginine as a curing agent, and the degradation behavior of the cured resins was evaluated under different acidic buffer solutions at 37°C. The degradable behavior of such epoxy resins suggested potential applications as environment friendly materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Highly Enantioselective Phase‐Transfer Catalytic α‐Alkylation of α‐tert‐Butoxycarbonyllactams: Construction of β‐Quaternary Chiral Pyrrolidine and Piperidine Systems

A new enantioselective α‐alkylation of α‐tert‐butoxycarbonyllactams for the construction of β‐quaternary chiral pyrrolidine and piperidine core systems is reported. α‐Alkylations of N‐methyl‐α‐tert‐butoxycarbonylbutyrolactam and N‐diphenylmethyl‐α‐tert‐butoxycarbonylvalerolactam under phase‐transfer catalytic conditions (solid potassium hydroxide, toluene, −40 °C) in the presence of (S,S)‐3,4,5‐trifluorophenyl‐3,3′,5,5′‐tetrahydro‐2,6‐bis(3,4,5‐trifluorophenyl)‐4,4′‐spirobi[4H‐dinaphth[2,1‐c:1′,2′‐e]azepinium] bromide [(S,S)‐NAS Br] (5 mol%) afforded the corresponding α‐alkyl‐α‐tert‐butoxycarbonyllactams in very high chemical (up to 99%) and optical yields (up to 98% ee). Our new catalytic systems provide attractive synthetic methods for pyrrolidine‐ and piperidine‐based alkaloids and chiral intermediates with β‐quaternary carbon centers.     

Effect of nucleating duality on the formation of γ‐phase in a β‐nucleated isotactic polypropylene copolymer

BACKGROUND: It is a challenge for polymer processing to promote the formation of γ‐phase under atmospheric conditions in isotactic polypropylene (iPP) copolymer containing chain errors. Incorporation of an α‐nucleator in iPP copolymer seems reasonable since it can enhance non‐isothermal crystallization. Up to now, however, the issue regarding a β‐nucleated iPP copolymer still remains unclear, which is the subject of this study. RESULTS: The results indicate that the γ‐phase indeed occurs in a β‐nucleated random iPP copolymer with ethylene co‐unit (PPR) sample and becomes predominant at slow cooling rates (e.g. 1 °C min^?1) where the formation of the β‐form is suppressed to a large extent. With detailed morphological observations the formation of γ‐phase in the β‐nucleated PPR sample at slow cooling rate is unambiguously attributed to the nucleating duality of the β‐nucleator towards α‐ and β‐polymorphs. The α‐crystals, induced by the β‐nucleator, serve as seeds for the predominant growth of the γ‐phase. Moreover, the presence of the β‐nucleator, acting as heterogeneous nuclei, promotes the formation of γ‐phase in the nucleated PPR sample, at least to some extent. CONCLUSION: The findings in this study extend our insights into the formation of γ‐phase in β‐nucleated iPP copolymer and, most importantly, provide an alternative route to obtain iPP rich in γ‐phase. Copyright © 2008 Society of Chemical Industry     

Associations between a hydrophobically modified,degradable, poly(malic acid) and a β‐cyclodextrin polymer in solution

A new associating system has been elaborated from mixing a degradable polymer, poly(β‐malic acid‐co‐β‐ethyladamantyl malate), and a β‐cyclodextrin polymer in aqueous solution. Viscosity and dynamic light scattering measurements have been made on solutions of the single copolyester and of mixtures of both polymers. Studies on copolyesters with different percentages of hydrophobic groups (0–7.5%) show that a small proportion of the chains (less than 5% in weight) are aggregated in large structures (100 nm) which dominate the scattering intensity. The mixtures exhibit slow diffusive relaxation modes which correlate with a large viscosity enhancement at low concentration. These effects, which depend sensitively on pH, are attributed to the presence of polydisperse complexes of copolyester and β‐cyclodextrin polymer. The influence of pH, ionic strength, medium composition, and concentration were examined on the mixture of copolymers. It was found that the association properties are controlled by the net charge on the amphiphilic copolyester. © 2001 Society of Chemical Industry     

Adsorption of guanosine,cytidine, and uridine on a β‐cyclodextrin derivative grafted chitosan

A β‐cyclodextrin derivative grafted chitosan (CDD‐C) was synthesized with chitosan and carboxymethyl‐β‐cyclodextrin (β‐CD). Its structure was characterized by elemental, infrared spectra, and X‐ray diffraction analyses. The degree of substitution by the carboxymethyl‐β‐CD moiety achieved 0.27 with the addition of DMF to the reaction solution. The results are in agreement with the expectations. The static adsorption properties for guanosine, cytidine, and uridine were studied. Experimental results demonstrated that CDD‐C had higher adsorption capability for guanosine than cytidine and uridine, and the adsorption capacity for guanosine was 74.20 mg/g. The adsorption capacity was greatly influenced by pH, time, and temperature. The introduction of chitosan enhanced the adsorption ability and adsorption selectivity of β‐CD for guanosine. This novel derivative of chitosan is expected to have wide applications in separation, concentration, and analysis of guanosine, cytidine, and uridine in biological sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3050–3055, 2007     

Michael Reaction of Nitroalkanes with β‐Nitroacrylates under a Solid Promoter: Advanced Regio‐ and Diastereoselective Synthesis of Nitro‐Functionalized α,β‐Unsaturated Esters and 1,3‐Butadiene‐2‐carboxylates

A new class of nitro‐functionalized α,β‐unsaturated esters has been prepared by a regio‐ and diastereoselective Michael addition of nitroalkanes to β‐nitroacrylates, performed at room temperature, under carbonate on polymer as promoter, and in the presence of ethyl acetate as eco‐friendly solvent. Moreover, by the modular choice of the reaction conditions the method allows the synthesis of 1,3‐butadiene‐2‐carboxylates.     

Immobilization of a functionalized poly(ethylene glycol) onto β‐cyclodextrin‐coated surfaces by formation of inclusion complexes: Application to the coupling of proteins

The aim of this study was the immobilization of COOH‐modified poly(ethylene glycol) (PEG) layers onto β‐cyclodextrin‐coated surfaces by formation of inclusion complexes, in view of biosensors applications. To this end, PEGs with one phenyladamantyl and one carboxylic end group (Ad‐PEG‐COOH) were prepared according to a three‐step procedure. After modification of PEG with 4‐toluenesulfonylchloride, the reaction of the tosyl intermediate with the alcoholate of 4‐(1‐adamantyl)‐phenol was carried out in tetrahydrofuran to avoid the formation of by‐products. Then, it was shown by high performance liquid chromatography that the association between β‐cyclodextrin cavities and Ad‐PEG‐COOH polymers was not hindered by the presence of the COOH group. Last, the Ad‐PEG‐COOH polymer was immobilized onto β‐cyclodextrin‐coated gold surfaces by formation of inclusion complexes. The immobilization was performed in water, at room temperature, with a rapid kinetics. After activation of COOH groups with N‐hydroxysuccinimide, β‐lactoglobulin was coupled to the biocompatible PEG layer. Functionalization of the gold surface with β‐cyclodextrin cavities, immobilization of Ad‐PEG‐COOH onto the surface, and coupling of the protein to the reactive PEG layer were followed in real time by surface plasmon resonance imaging system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2362–2370, 2006     

Preparation and electrorheological characteristics of β‐cyclodextrin–epichlorohydrin–starch polymer suspensions

Three environment friendly β‐cyclodextrin polymer electrorheological (ER) particles (NS‐β‐CDP, WSS‐β‐CDP, and CLS‐β‐CDP) were synthesized by copolymerization through a mixture of β‐cyclodextrin (β‐CD) and epichlorohydrin in the absence of starch or in the presence of water‐soluble and water‐insoluble starch, respectively. The electrorheological properties of suspensions in silicone oil were then investigated under direct current (dc) electric fields. It was found that the yield stress of the typical WSS‐β‐CDP ER fluid was 6.2 kPa in 4 kV/mm, which is 35% higher than that of NS‐β‐CDP and similar to that of CLS‐β‐CDP. In the meantime, it can display a high ER performance even over a range of 65–95°C. The structures of these polymers were characterized by FT‐IR and Raman spectrometry, respectively. The results demonstrated that all of these polymers keep the original structural character of β‐CD and the copolymerizations between starch and β‐CD indeed occur. Furthermore, it was found that there was some relationship between the characteristic strength of polymers and their dielectric properties. Hence, the improvement of copolymer dielectric properties resulted in the enhancement of ER effects. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1681–1686, 2004     

Photocatalytic degradation of 2,2‐bis(4‐hydroxy‐3‐methylphenyl) propane (BPP) based on molecular recognition interaction

BACKGROUND: Endocrine disruptors in the aquatic environment and their potential adverse effects are currently issues of concern. One of these endocrine disruptors is 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane (BPP). In this work the molecular recognition interaction of BPP with β‐cyclodextrin (β‐CD) was studied using IR spectroscopy and steady state fluorescence spectroscopy, and the photocatalytic degradation behaviour of BPP based on molecular recognition interaction was investigated in a TiO₂/UV–visible (λ_max = 365 nm) system. This might provide a new method for the treatment of some organic pollutants in wastewater. RESULTS: β‐CD reacts with BPP to form a 1:1 inclusion complex, the formation constant of which is 4.94 × 10³ L mol^?1. The photodegradation rate constant of BPP after molecular recognition by β‐CD showed a 1.42‐fold increase in the TiO₂/UV–visible (λ_max = 365 nm) system. The photodegradation of BPP depended on the concentration of β‐CD, the pH value, the gaseous medium and the initial concentration of BPP. The photodegradation efficiency of BPP with molecular recognition was higher than that without molecular recognition. After 100 min of irradiation the mineralisation efficiency of BPP after molecular recognition by β‐CD reached 94.8%, whereas the mineralisation efficiency of BPP before molecular recognition by β‐CD was only 40.6%. CONCLUSION: The photocatalytic degradation of BPP after molecular recognition by β‐CD can be enhanced in the TiO₂/UV‐visible (λ_max = 365 nm) system. This enhancement is dependent on the enhancement of the adsorption of BPP, the moderate inclusion depth of BPP in the β‐CD cavity and the increase in the frontier electron density of BPP after molecular recognition. Copyright © 2008 Society of Chemical Industry