Hydroxyethyl curdlan as a novel water soluble derivative: Synthesis,characterization, and antioxidant capacity

In this study, hydroxyethyl curdlans (HeCDs) with different molecular weights were successfully fabricated. The structure and properties of the synthesized HeCDs were measured by FTIR, ¹³C nuclear magnetic resonance (NMR), and Raman spectroscopy and compared with curdlan. The degree of crystallinity of HeCDs was measured with X-ray diffractometry (XRD). Differential scanning calorimetry and thermogravimetric analysis were performed to determine thermal properties of HeCs. Solubility of HeCDs was tested in water, common organic solvents, and NaOH solution. Antioxidant activities of HeCs were investigated using various in vitro assay systems. The HeCDs exhibited a dose-dependent free radical scavenging activity as shown by their DPPH radical, ABTS radical and superoxide anion radical inhibition, and ferrous chelating ability and reducing power. The improved water solubility property and antioxidant activity of these curdlan derivatives could have a wide range of applications, particularly its use as an antioxidant in food, food packaging, biomedical, and pharmaceutical industries.     

Copolymers of 2‐(3‐(6‐tetralino)‐3‐methyl‐1‐cyclobutyl)‐2‐Hydroxyethyl Methacrylate with Acrylonitrile and 4‐Vinylpyridine: Synthesis,Characterization, and Monomer Reactivity Ratios

The copolymerization of 2‐(3‐(6‐tetralino)‐3‐methyl‐1‐cyclobutyl)‐2‐hydroxyethyl methacrylate (TCHEMA), monomer with acrylonitrile and 4‐vinylpyridine were carried out in 1,4‐dioxane solution at 65°C using AIBN as an initiator. The copolymers were characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopic techniques. Thermal properties of the polymers were also studied by thermogravimetric analysis and differential scanning calorimetry. The copolymer compositions were determined by elemental analysis. The monomer reactivity ratios were calculated by the Fineman‐Ross and Kelen‐Tüdös method. Also, the apparent thermal decomposition activation energies were calculated by the Ozawa method with a Shimadzu TGA 50 thermogravimetric analysis thermobalance.     

Antibacterial cellulose acetate films incorporated with N‐halamine‐modified nano‐crystalline cellulose particles

Cellulose acetate (CA) membranes have been widely used as food packaging materials as well as reverse osmosis systems. This study presents the manufacturing of composite CA film with antibacterial properties which is essential for CA film applications in the industry. N‐Halamine precursor of polymethacrylamide‐modified nano‐crystalline cellulose particles (NCC‐PMAMs) were prepared and incorporated into CA film. The composite films with intercalated structure were formed via a solvent‐casting technique. After chlorination, the composite film CA/NCC‐PMAM‐Cl‐1.0 with 1.82 × 10¹⁶ atoms/cm² covalently bonded chlorine showed excellent antibacterial properties by inactivating 6.04 logs of Staphylococcus aureus and 6.27 logs of Escherichia coli within 10 and 5 min, respectively. According to X‐ray diffraction spectra, NCC‐PMAMs behaved as a facilitator for film crystallization. The mechanical strength of the composite film also increased compared with that of pure CA film. However, the composite film became brittle and the maximum decomposition temperature decreased slightly. Preliminary data of in vitro cytocompatibility evaluation indicate that the film is not toxic and has potential use in food packaging. Copyright © 2016 John Wiley & Sons, Ltd.     

1H NMR for quantifying sulfide trapping efficiency by using 1,3,5‐tris(2‐hydroxyethyl)‐1,3,5‐triazinane

Hydrogen sulfide (H₂S) is an extremely toxic colourless gas; it is corrosive and denser than air. It usually happens in oil and natural gas fields, refineries, coal mines, and in some industrial effluent treatment systems. This work presents an alternative method of monitoring and quantifying H₂S trapping efficiency by using 1,3,5‐tris(2‐hydroxyethyl)‐1,3,5‐triazinane as a sequestering agent, and sodium sulfide as a source of sulfide ion, through ¹H NMR spectroscopy. The results proved that the reaction occurs very quickly at 20 °C at pH 7 and 10. 3,5‐di(2‐hydroxyethyl)‐1,3,5‐thiodiazinane and 5‐(2‐hydroxyethyl)‐1,3,5‐dithiozinane were observed and quantified; it was evidenced that ¹H NMR spectroscopy can be applied as a fast and effective method to quantify H₂S trapping efficiency. Copyright © 2014 John Wiley & Sons, Ltd.     

New associative EHEC‐g‐PAam copolymers: Their syntheses,characterization, and rheological behavior

The syntheses and rheological behavior of ethyl hydroxyethyl cellulose (EHEC)‐based graft‐copolymers were studied. Copolymers were prepared by grafting EHEC with acrylamide (Aam) via reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyl groups of EHEC were esterified with a carboxylic acid functional chain transfer agent (CTA) to prepare EHEC‐macroCTAs with different degrees of substitution. EHEC‐macroCTAs were characterized by ATR‐FTIR, ¹³C NMR, and SEC, and elemental analysis was used to quantify the degree of CTA substitution. EHEC‐macroCTAs with different degrees of substitution were copolymerized with acrylamide by “grafting from” technique. Formation of new cellulose‐based copolymers was comprehensively confirmed by ¹H NMR, ATR‐FTIR, and SEC measurements. Further, the associations of EHEC‐g‐PAam copolymers in water were studied at various concentrations and temperatures by means of UV–vis spectroscopy, fluorescence spectroscopy, and rheological measurements. The results indicate that copolymers have both intra and intermolecular association in water depending on the amount of grafts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1869–1879, 2009     

Modelling of sorbic acid diffusion through bacterial cellulose-based antimicrobial films

Antimicrobial packaging protects the product from the external environment and microbial contamination, conferring numerous advantages on human health. Interest in biopolymers as packaging materials has considerably increased recently. Bacterial cellulose is an interesting biomaterial produced as nanofibrils by Acetobacter xylinium and is a promising candidate due to its remarkable properties. New composite materials with antimicrobial properties were developed in this work, containing poly(vinyl alcohol) (PVA) as polymer matrix and ground bacterial cellulose (BC) as reinforcing fibres. Sorbic acid was used as an antimicrobial agent because it is a preservative recognised in the food industry. The materials obtained were studied using Fourier-transformed infrared spectroscopy (FTIR). The swelling rate of the composites was also measured. Release experiments of sorbic acid from the composite films into water were performed and the mass transfer phenomena were investigated using Fick’s law of diffusion. The antimicrobial effect was tested against Escherichia coli K12-MG1655. The results obtained indicated that the new biocomposite films could be promising antimicrobial food packaging materials.     

Graft copolymerization ofN‐vinyl‐pyrrolidone and acrylamide on cellulose derivatives: synthesis,characterization and study of their biological effect

Graft copolymers of carboxymethyl cellulose and hydroxyethyl cellulose with N‐vinyl‐2‐pyrrolidone and acrylamide have been synthesized by grafting copolymer of N‐vinyl‐2‐pyrrolidone and acrylamide onto a mixture of carboxymethyl cellulose and hydroxyethyl cellulose by a solution polymerization technique using a redox initiation system. The graft copolymers were characterized by ¹³C‐NMR spectroscopy and scanning electron microscopy. These graft copolymers have been tested for their biodegradability and biological activity. None of the graft copolymer solutions shows any microbial degradation up to 10 days. The reported results are evidence of the possibility of anti‐fungi effect. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of O‐(2,3‐dihydroxypropyl) cellulose in NaOH/urea aqueous solution: As a precursor for introducing “necklace‐like” structure

O‐(2,3‐dihydroxypropyl) cellulose (DHPC) samples were synthesized by etherification of cellulose with glycidol (GLY) in a NaOH/urea aqueous solution system under different reaction conditions, so that they had different degrees of ether substitution (DS) in both the overall and regional distributions. The characterization was made by NMR spectroscopy in order to clarify the effects of the molar ratio of in‐fed GLY to anhydroglucose unit and of the reaction temperature not only on the total and regional DSs but also on the molar substitution (MS_dhp) for the multireactive dihydroxypropyl group. The evaluation of MS_dhp was performed after complete propionylation of each DHPC sample. Determination of molecular weights was also conducted on the propionylated DHPCs by GPC analysis. As a preliminary extension, butyralization of DHPC was undertaken in aqueous solution by using p‐toluenesulfonic acid as catalyst together with butyraldehyde (BuA). Two‐dimensional NMR (¹H–¹³C gHSQC) spectra measurements revealed that the products contained butyral groups, owing to dehydration‐cyclization between the BuA‐carbonyl and the duplicate hydroxyls in the side chain of DHPC. Such butyral derivatives of cellulose are expected to be a promising functional material parallel or superior to poly(vinyl butyral) available for safety glass interlayers, etc. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3590–3597     

Metal chelates with some cellulose derivatives; part IV. Structural chemistry of HEC complexes

Reactions of hydroxyethyl cellulose (HEC) with Cr ^III, Ni^II, Co^II, or Cu^II chlorides in aqueous medium yielded complexes with formulae [M(HEC)Cl _m .n H ₂O], wherem =1 or 2 and n=2 or 3. HEC acted as a uninegatively charged bidentate ligand in the case of Cr^III and Ni^II, and as a neutral ligand in the case of Co^II and Cu^II complexes. The spectra showed that the binding sites in Cr^III and Ni^II complexes were the ether oxygen between two ethoxyl groups and the oxygen of the hydroxyl group; while in the Co^II and Cu^II complexes the binding sites were the oxygen of ethoxyl groups and the primary alcoholic O atom of glucopyranose rings. These complexes would most likely exhibit octahedral geometry with Cr^III, Ni^II, and Co^II, but square planar configuration in the case of the Cu^II complex. The ligand parameters of the Cr^III, Ni^II, and Co^II metal chelates were calculated in different solvents and at different temperatures. The thermal stability of the above complexes was investigated and the overall thermodynamics functions G⁰, H⁰, and S⁰, associated with complex formation, were estimated.     

X‐ray diffraction study of the thermal expansion behavior of cellulose triacetate I

Highly crystalline samples of cellulose triacetate I (CTA I) were prepared from highly crystalline algal cellulose by heterogeneous acetylation. X‐ray diffraction of the prepared samples was carried out in a helium atmosphere at temperatures ranging from 20 to 250 °C. Changes in seven d‐spacings were observed with increasing temperature due to thermal expansion of the CTA I crystals. Unit cell parameters at specific temperatures were determined from these d‐spacings by the least squares method, and then thermal expansion coefficients (TECs) were calculated. The linear TECs of the a, b, and c axes were α_a = 19.3 × 10^?5 °C^?1, α_b = 0.3 × 10^?5 °C^?1 (T < 130 °C), α_b = ?2.5 × 10^?5 °C^?1 (T > 130 °C), and α_c = ?1.9 × 10^?5 °C^?1, respectively. The volume TEC was β = 15.6 × 10^?5 °C^?1, which is about 1.4 and 2.2 times greater than that of cellulose I_β and cellulose III_I, respectively. This large thermal expansion could occur because no hydrogen bonding exists in CTA I. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 517–523, 2009     

Binding cellulose and chitosan via click chemistry: Synthesis,characterization, and formation of some hollow tubes

A novel cellulose‐click‐chitosan polymer was prepared successfully in three steps: (1) propargyl cellulose with degrees of substitution (DS) from 0.25 to 1.24 was synthesized by etherification of bamboo Phyllostachys bambusoide cellulose with propargyl chloride in DMA/LiCl in the presence of NaH. The regioselectivity of propargylation on anhydrous glucose unit determined by GC‐MS was in the order of 2 >> 6 > 3; (2) the functional azide groups were introduced onto the chitosan chains by reacting chitosan with 4‐azidobenzoic acid in [Amim]Cl/DMF and the DS ranged from 0.02 to 0.46; (3) thus, the cellulose‐click‐chitosan polymer was obtained via click reaction, that is, the Cu(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, between the terminal alkyne groups of cellulose and the azide groups on the chitosan backbone at room temperature. The successful binding of cellulose and chitosan was confirmed and characterized by FTIR and CP/MAS ¹³C NMR spectroscopy. TGA analyses indicated that the cellulose‐click‐chitosan polymer had a higher thermal stability than that of cellulose and chitosan as well as cellulose–chitosan complex. More interestingly, some hollow tubes with near millimeter length were also observed by SEM. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Physical and Chemical Characterization of Cellulose Based Textiles Modified by Periodate Oxidation

Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state ¹³C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method.     

Comparative thermal analysis study of two biopolymers, starch and cellulose

The degradation of cellulose and starch samples in air and nitrogen has been investigated by thermal analysis techniques. The techniques employed were differential thermal analysis, rising temperature and temperature jump thermogravimetry. Rate data were obtained from these experiments and Arrhenius parameters calculated from these values. This data was used to determine the mechanism by which the cellulose and starch samples degraded. The Arrhenius parameters were also calculated. The behavior of starch and cellulose upon thermal analysis were compared and are reported.E _act for corn starch was found to be 474 kJ mol^–1 and for a cellulose 242 kJ mol^–1.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Effect of catalyst systems and reaction conditions on the synthesis of cellulose‐g‐PDMAam copolymers by controlled radical polymerization

Various copper‐based catalyst systems and reaction conditions were studied in the graft copolymerization of N,N‐dimethylacrylamide (DMAam) with a cellulose‐based macroinitiator by controlled radical polymerization. The cellulose macroinitiator with degree of substitution DS = 0.44 was synthesized from dissolving softwood pulp in a LiCl/DMAc solution. The graft copolymerizations of DMAam, using the cellulose macroinitiator and various copper‐based catalyst systems, were then carried out in DMSO solutions. The copolymerization kinetics was followed by ¹H NMR. Water‐soluble cellulose‐g‐PDMAam copolymers were comprehensively characterized by ATR‐FTIR and ¹H NMR spectroscopies and SEC analyses. DLS and steady‐shear viscosity measurements revealed that when the DP_graft of the cellulose‐g‐PDMAam copolymer is high enough, the copolymer forms a more compact structure in water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cold NaOH/urea aqueous dissolved cellulose for benzylation: Synthesis and characterization

Cold NaOH/urea aqueous dissolved cellulose was studied for the synthesis of benzyl cellulose by etherification with benzyl chloride. By varying the molar ratios of benzyl chloride to OH groups in cellulose (1.5–4.0) and reaction temperatures (65–70 °C), benzyl cellulose with a degree of substitutions (DS) in the range of 0.29–0.54 was successfully prepared under such mild conditions. The incorporation of benzyl groups into cellulose was evidenced by multiple spectroscopies, including FT IR, ¹H NMR, ¹³C NMR, CP/MAS ¹³C NMR and XRD. In addition, the thermal stability and surface morphology of the benzyl cellulose was also investigated with regard to the degree of substitution. The results indicated that the benzyl cellulose product with a low DS (0.51) in the present study reached the same solubility in many organic solvents as compared to those prepared in heterogeneous media. After benzylation, the sample decomposed at a lower temperature with a wider temperature range, which indicated that the thermal stability of benzyl cellulose was lower than that of the native cellulose. In addition, benzylation resulted in a pronounced reduction in crystallinity as well as a fundamental alteration of morphology of the native cellulose.     

Regioselective Dendritic Functionalization of Cellulose

Summary: A series of regioselectively dendronized cellulose derivatives has been prepared by the treatment of cellulose in a N,N‐dimethylacetamide/LiCl solvent system with dendrons possessing isocyanate focal substituents. These new materials were characterized using FT‐IR and ¹³C NMR spectroscopies, and thermogravimetric analysis; the products were highly soluble in a wide range of organic solvents.

Substitution pattern of the dendronized cellulose.     

Preparation,properties, and antibacterial behavior of a novel cellulose derivative containing lactam groups

Lactam groups were introduced onto the backbone of hydroxyethyl cellulose (HEC) to modify properties, such as solubility in organic solvents and solution viscosity and to introduce possible antibacterial activity. Functionalization was achieved using 1‐(hydroxymethyl)‐2‐pyrrolidinone (HMP), and the functionalization reactions were investigated using NMR spectroscopy. The covalent attachment between HEC and HMP was confirmed using ¹H‐¹³C correlated NMR experiments. Degrees of functionalization were calculated using integrated ¹³C NMR spectra, with values of up to 0.9 being demonstrated on the primary alcohol functionality of HEC. The functionalized HECs showed markedly different properties to unfunctionalized HEC, including the ability to swell considerably in water. Functionalized HEC displayed increased thermal stability and reduced solution viscosity compared with unfunctionalized HEC. Moreover, functionalization altered the bacterial adhesion characteristics compared with unfunctionalized HEC. © 2014 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 68–78     

ZnO/PBAT nanocomposite films: Investigation on the mechanical and biological activity for food packaging

Packaging of foods in high barrier materials is essential to attain food safety. Nanocomposite technology is leading in search of the earlier said kind of packaging materials. The role of zinc oxide (ZnO) loadings on poly(butylene adipate‐co‐terephthalate) (PBAT) structure were investigated, in addition to that packaging properties such as barrier, thermal, and mechanical properties were studied. Antimicrobial films are developed based on PBAT and ZnO nanoparticles. The nanocomposites exhibits a significant increase in the mechanical and thermal stability. The resulting PBAT/ZnO nanofilms show superior antimicrobial activity against Escherichia coli and Staphylococcus aureus. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,Characterization and Catalytic Behaviour of Silica Supported Zinc Salicylaldimine Complex

Zinc salicylaldimine complex immobilized on silica gel was used as a promising catalyst for the transesterification reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG).The catalyst was characterized by Fourier transform infra‐red spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). The product bis‐(2‐hydroxyethyl)terephthalate (BHET)was confirmed by mass and ¹H‐NMR studies. In comparison to zinc acetate i.e., homogeneous catalyst, a polymer supported catalyst showed better stability, catalytic activity and ease of separation from the reaction product. The catalyst can be reutilized during successive catalytic cycles.