Acylation of silk and wool with acid anhydrides and preparation of water-repellent fibers

Silk and wool fibers were acylated with two acid anhydrides, dodecenylsuccinic anhydride (DDSA) and octadecenylsuccinic anhydride (ODSA), at 75°C with N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) as the solvent, the latter of which allowed higher weight gains to be reached. The weight gain and acyl content of wool was always higher than that of silk. Tensile properties of silk remained unchanged regardless of weight gain, whereas wool displayed a noticeably higher extensibility at high weight gain. Fine structural changes of acylated wool were detected by DSC analysis. Moisture regain and water retention of acylated silk and wool decreased significantly, whereas water repellency increased. SEM analysis showed the presence of foreign material firmly adherent to the surface of both silk and wool, whose amount increased with increasing weight gain. These deposits were attributed to the presence of the modifying agents at the fiber surface on the basis of the characteristic IR bands. The possible application of silk and wool fibers acylated with DDSA or ODSA for the preparation of water-repellent textile materials is discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2832–2841, 2001     

Chemical modification of silk with aromatic acid anhydrides

Bombyx mori silk fibers were chemically modified by acylation with aromatic acid anhydrides, such as phthalic and o-sulfobenzoic anhydrides. We examined the reactivity of these modifying agents toward silk fibers, the physical and thermal properties, and the dyeing behavior with acid and cationic dyes. The o-sulfobenzoic anhydride was more reactive toward silk fibroin than phthalic anhydride. The amount of both basic and acidic amino acid residues decreased after modification with aromatic acid anhydrides. The moisture regain of silk treated with phthalic anhydride remained almost unchanged, while that of the samples modified with o-sulfobenzoic anhydride increased linearly as the weight gain increased. Chemically modified silk fabrics showed improved crease recovery behavior, even though phthalic anhydride seemed more effective at comparatively low weight gain. The modification of silk with o-sulfobenzoic anhydride caused a drastic a reduction of acid dye uptake and enhanced the affinity of silk for cationic dye. Silk fibers did not show any significant change in thermal behavior, regardless of the modification with o-sulfobenzoic anhydride. Silk fibers modified with phthalic anhydride showed on differential scanning calorimetry (DSC) curves a minor and broad endothermic peak at around 210°C, attributed probably to the breaking of the crosslinks formed between adjacent fibroin molecules.     

Chemical modification of silk with itaconic anhydride

Bombyx mori silk fibers were chemically modified by acylation with itaconic anhydride. The reactivity of the modifying agent toward silk fibroin was investigated on the basis of the amino acid analysis. We examined the physical properties, the structural characteristics, and the thermal behavior of modified silk fibers as a function of the weight gain. Silk fibers with a weight gain of 9%, corresponding to an acyl content of 68.9 mol/10⁵g, were obtained at the optimum reaction conditions for silk acylation (75°C for 3 h). The amount of basic amino acid residues (Lys, His, and Arg) decreased linearly as the weight gain increased. The alkali solubility increased proportionally with the weight gain, probably due to the dissolution of the modifying agent reacted with silk fibroin, and not to the degradation of the fibers induced by the chemical modification. The birefringence value, related to the molecular orientation, slightly decreased when the weight gain increased. The isotropic refractive index, associated with the crystallinity, increased when the weight gain ranged from about 5 to 7% and then remained unchanged. The moisture regain did not change regardless of the chemical modification, and the crease recovery behavior of modified silk fabrics did not show significant improvement. The thermal behavior of silk fibers was affected by the modification with itaconic anhydride. The decomposition temperature shifted up to 322°C, 10°C higher than the control silk fibers, suggesting a higher thermal stability induced by chemical modification.     

Chemical modification of tussah silk with acid anhydrides

Tussah silk fibroin was chemically modified by acylation with aliphatic, aromatic, and hydrophobic acid anhydrides. The tussah silk fibers were pretreated by immersing them in a lithium thiocyanate (LiSCN) solution and then acylated in dimethylformamide (DMF) at elevated temperatures. Using this method, acylated tussah silk fibers with weight gains of 8–22% could be obtained. The pretreatment with LiSCN was necessary to promote the acylation. Without it, the reaction did not proceed. The optimum temperature and reaction time of the pretreatment was 55°C and 60 min, respectively. When examining the physical properties and the thermal behavior of both pretreated and acylated tussah silk, it was found that the mechanical properties and the position of the major DSC endothermic peak remained unchanged, regardless of pretreatment and acylation. The moisture regain of the pretreated tussah silk increased slightly while the moisture regain of the acylated silk decreased linearly with increasing weight gain. The chemical modification allows for a wide control of the tussah silk fiber's properties, making it possible to use tussah silk for the development and production of novel textile and biomaterials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 382–391, 2000     

Structure and properties of bombyx mori silk fibers grafted with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA)

Silk fibers were graft-copolymerized with methacrylamide (MAA) and 2-hydroxyethyl methacrylate (HEMA) in aqueous media, using a chemical redox system as an initiator. High weight gains (300%) were obtained with both monomers, the weight gain being linearly related to the amount of monomer contained in the reaction system. The reaction efficiency attained 95–100%. The extent of homopolymerization was negligible for the MAA grafting system, while large amounts of poly-HEMA covered the surface of silk fibers beyond 70% weight gain. The fiber size increased linearly with the weight gain. The moisture content of MAA-grafted silk fibers was highly enhanced by grafting. The severe grafting conditions caused a partial degradation of the tensile properties of silk fibers, as well as of the degree of fiber whiteness. Following grafting, the breaking load slightly increased, while elongation at break and energy decreased. The decomposition temperature of grafted silk fibers shifted upwards. The Raman spectra of untreated silk fibers showed strong lines at 1667 (amide I), 1451, 1227 (amide III), 1172 and 1083 cm⁻¹. Overlapping of the lines characteristic of both silk fibroin and grafted polymer was observed in the spectra of grafted silk samples. The vibrational mode of the amide III lines of silk fibroin was significantly modified by grafting. © 1996 John Wiley & Sons, Inc.     

Covalent immobilization of biological molecules to maleic anhydride and methyl vinyl ether copolymers—A physico‐chemical approach

The covalent grafting of biological molecules to copolymers of maleic anhydride and methyl vinyl ether (MAMVE) has been used in various applications in diagnostics. To tentatively elucidate the phenomena involved in the control of the immobilization of oligodeoxynucleotides and proteins, the physico‐chemical properties of MAMVE copolymers were investigated. Because the grafting mixture contains water, to allow dissolution of the biomolecules without loss of biological properties, the anhydride‐based copolymer evolves from a neutral to a negatively charged macromolecule due to hydrolysis of the anhydride moities. The properties of both hydrolyzed and nonhydrolyzed polymers were investigated. As demonstrated by light‐scattering measurements in batch, the copolymers showed some level of aggregation in DMF, DMSO, and aqueous DMSO. The presence of aggregates was confirmed by size‐exclusion chromatography in DMF. However, partial deaggregation occurred for the lowest molecular weight sample, on adding 1% w/v of LiBr. The nonhydrolyzed copolymers exhibited a rigid conformation in a 5% water/DMSO mixture, as well as their hydrolyzed counterpart at a low ionization degree. The rate of the hydrolysis reaction was shown to be dependent on the pH of the reaction medium and on temperature. The activation energy of the hydrolysis reaction was 14 kJ/mol, and the rate constant in the order of 10⁻⁴ s⁻¹. On the basis of these data, the effect on the grafting reaction of biomolecules of different parameters such as ionic strength and the nature of the solvent, along with some other results were interpreted in terms of interactions between the synthetic and bioactive macromolecules. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 927–936, 1999     

Synthesis of ultrafine poly(styrene‐maleic anhydride) and polystyrene fibers by electrospinning

Fiber formation from atactic polystyrene (aPS) and alternating poly(styrene‐maleic anhydride) (PSMA) synthesized by free radical polymerization (AIBN, 90°C, 4 h) were investigated by electrospinning from various solutions. aPS was soluble in dimethylformamide (DMF), tetrahydrofuran (THF), toluene, styrene, and benzene, whereas PSMA was soluble in acetone, DMF, THF, dimethylsulfoxide (DMSO), ethyl acetate, and methanol. aPS fibers could be electrospun from 15 to 20% DMF and 20% THF solutions, but not from styrene nor toluene. PSMA, on the other hand, could be efficiently electrospun into fibers from DMF and DMSO at 20 and 25%, respectively. Few PSMA fibers were, however, produced from acetone, THF, or ethyl acetate solutions. Results showed that solvent properties and polymer–solvent miscibility strongly influenced the fiber formation from electrospinning. The addition of solvents, such as THF, generally improved the fiber uniformity and reduced fiber sizes for both polymers. The nonsolvents, however, had opposing effects on the two polymers, i.e., significantly reducing PSMA fiber diameters to 200 to 300 nm, creating larger and irregularly shaped aPS fibers. The ability to incorporate the styrene monomer and divinylbenzene crosslinker in aPS fibers as well as to hydrolyze PSMA fibers with diluted NaOH solutions demonstrated potential for post‐electrospinning reactions and modification of these ultrafine fibers for reactive support materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of alkenyl succinic anhydrides from methyl esters of high oleic sunflower oil

Alkenyl succinic anhydrides (ASA) have been prepared by ene‐reaction of high‐oleic sunflower oil methyl esters with maleic anhydride in a 50% xylene medium. Response surface methodology (RSM) was used to investigate the influence of two factors: reaction temperature and molar ratio between maleic anhydride (MA) and methyl esters (SME). The studied parameters in 8‐h reactions were the methyl oleate conversion, the distillation yield in ASA, and responses allowing the indirect estimation of side reaction products: clarity index and dynamic viscosity. The highest yield in ASA (>70%; clarity index ≈10) was reached for a temperature of 240–250 °C with a molar ratio of 1.5–1.7. But for an industrial application requiring minimized side products (clarity index >40), the optimal synthesis conditions were: temperature between 220 and 235 °C and molar ratio of 1.2–1.35 (yield ≈55%). Such conditions did not provide a medium free of side products, even if xylene decreased their formation. Compared to solvent‐free synthesis, conversion was lower with xylene. With solvent, higher temperatures were needed to reach the same yields. Supplementary heating compensated the reagent dissolution effect that slows down the kinetics of the ene‐reaction. The influence of reaction time at 220 °C with a MA/SME ratio of 1.2 in a 50% xylene medium was studied. A reaction time of 8–10 h provided a good compromise between ASA yield and side products.     

Physical properties of wool fibers modified with isocyanate compounds

Wool fibers were chemically modified with various kinds of isocyanates and diisocyanates. The reactivity of these modifying agents was examined as a function of the reaction solvent, temperature, time, and isocyanate chemistry. The use of dimethyl sulfoxide as the solvent, aliphatic mono and bifunctional isocyanates, such as dodecyl isocyanates and hexamethylene diisocyanate, and a temperature of 75°C resulted in higher weight gains. The moisture content of wool fibers tended to decrease with increasing the weight gain, the extent of which depended on the isocyanate used. Monofunctional isocyanates caused a sharp drop of tensile strength and an increase of elongation at break, while bifunctional isocyanates preserved the intrinsic tensile properties of wool. The FTIR spectra showed changes in the amide I, II, and III ranges, in the CO stretching range at 1750–1700 cm^?1, and in the CH stretching and bending regions at 3000–2800 and 1500–1350 cm^?1, respectively, attributable to the incorporation of the modifying agent. DSC measurements highlighted remarkable changes in the thermal behavior of acylated wool fibers. The bimodal melting endotherm at 230–240°C shifted to lower temperature, and the relative intensity of the constituent peaks changed as a function of the weight gain. Foreign deposits adhering to the surface of chemically modified wool fibers were detected by SEM analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1390–1396, 2003     

Absorption of metal cations by modified B. mori silk and preparation of fabrics with antimicrobial activity

Silk fabrics were modified by treatment with tannic acid (TA) solution or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of modification with TA and acylation with EDTA–dianhydride was investigated. The physico‐mechanical properties of silk fabrics acylated with EDTA–dianhydride remained unchanged regardless of chemical modification. The absorption of metal cations (Ag⁺, Cu²⁺) by untreated and modified silk fabrics was studied as a function of the kind of modifying agent, weight gain, and pH of the metal solution. The absorption of Cu²⁺ at alkaline pH was not significantly influenced by chemical modification of the silk substrate. The absorption of Ag⁺ by acylated silk remained at a level as low as untreated silk, while was enhanced by TA. The higher the content of TA, the higher the absorption of Ag⁺. With respect to the pH of the metal solution, the acylation with EDTA–dianhydride enabled silk to absorb and bind metal cations even in the acidic and neutral pH range, where tannic acid had no effect. Medium to high levels of metal desorption were exhibited by untreated and modified silk fabrics towards the metal cations, with the only exception of the silk–tannic acid–Ag complex, which displayed an extraordinary stability. All metal‐containing silks exhibited significant antibacterial activity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 297–303, 2001     

Studies on the δ‐form complex in the syndiotactic polystyrene–organic molecule system. II. Structural investigation of the δ‐form with p‐ and m‐xylene isomers

Syndiotactic polystyrene (sPS) membranes containing different mole fractions of p‐xylene were prepared by a solution‐casting procedure. Complex formation between sPS and xylene was studied by thermogravimetric analysis and Fourier transform infrared spectroscopy. The stability and desorption behavior of the sPS–guest solvent and phase transitions were studied by differential scanning calorimetry. The formation of the δ‐form complex in the presence of different mole fractions of xylene isomers was analyzed and confirmed. The mole fraction of p‐xylene in the dried membrane was found to be higher than that of the corresponding mole fraction in the isomer solvent solution used for casting. This was attributed to the preferential complexing ability of p‐xylene with sPS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2882–2887, 2003     

Effect of mixed solvents on phase inversion of polymeric membranes

The thermodynamics of phase inversion of polyvinylidene fluoride membrane with mixed solvents (N,N‐dimethyl formamide (DMF) and acetone) were modeled using Flory–Huggins theory. The kinetics of phase inversion were studied by measuring solvent concentration in the precipitation bath. A model was proposed to predict the time‐dependent solvent concentration profile in the precipitation bath. Depending on solvent volatility, the duration of the kinetics‐dominated regime and the evaporation‐dominated regime varies. A comparative analysis of thermodynamic and kinetic factors was used to predict membrane morphology and it was observed that the system under consideration was thermodynamics dominated. The membrane porosity exhibited decreasing porosity up to the Ac60 membrane (acetone to DMF ratio 60) and thereafter the membrane sublayer showed small pores. Addition of acetone resulted in increased crystallinity and surface hydrophilicity. The mean flow pore diameter measured using a liquid–liquid porometer decreased from 105 nm for an Ac0 membrane (acetone to DMF ratio 0) to 17 nm for an Ac60 membrane. Correspondingly, the molecular weight cut‐off of the membranes decreased from 135 kDa (for the Ac0 membrane) to 104 kDa (for the Ac60 membrane). The model proposed in this work can be used as a tool to predict the properties of intermediate compositions and prepare tailor‐made membranes with desired properties. © 2020 Society of Chemical Industry     

Preparation of metal‐containing protein fibers and their antimicrobial properties

Bombyx mori silk, Antheraea pernyi silk, and wool fibers were chemically modified by treatment with tannic acid (TA) or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of TA loading or acylation with EDTA‐dianhydride varied from fiber to fiber. B. mori silk and wool displayed the highest weight gains with TA and EDTA‐dianhydride, respectively. The uptake of different metal ions (Ag⁺, Cu²⁺, Co²⁺) by protein fibers, either untreated or chemically modified, was studied as a function of weight gain and pH of the aqueous metal solution. Below pH 7, absorption of metal ions by untreated and TA‐treated fibers was negligible. Acylation with EDTA‐dianhydride enabled protein fibers to absorb and bind significant amounts of metal ions in the acidic and neutral pH range. The levels of metal desorption at acidic pH depended on the fiber‐metal combination. Untreated protein fibers usually displayed the lowest stability of the metal complex. Metal complexes with protein fibers exhibited prominent antimicrobial activity against the plant pathogen Cornebacterium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 638–644, 2003     

The influence of solvent properties on the performance of polysulfone/β‐cyclodextrin polyurethane mixed‐matrix membranes

This study investigates the effect of solvent properties on the structural morphology and permeation properties of polysulfone/β‐cyclodextrin polyurethane (PSf/β‐CDPU) mixed‐matrix membranes (MMMs). The membranes were prepared by a modified phase‐inversion route using four different casting solvents [dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), dimethyl acetamide (DMA), and N‐methyl‐2‐pyrrolidone (NMP)]. While DMSO‐based membranes demonstrated particularly high permeability (ca 147 L/m²h.bar), their crystallinity was low compared to MMMs prepared using DMA, DMF and NMP due to the formation of thin active layers on their surfaces. Cross‐sectional morphology revealed that the MMMs have a dense top skin with finger‐like inner pore structures. Membranes prepared using NMP displayed the highest hydrophilicity, porosity, and crystallinity due to the low volatility of NMP; DMF membranes exhibited superior mechanical and thermal stability due to its (DMF) high hydrogen bonding (δH) values. Thus, the morphological parameters, bulk porosity, and flux performance of MMMs have a significant inter‐relationship with the solubility properties of each solvent (i.e., δH, density, volatility, solubility parameter). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2005–2014, 2013     

Diffuse reflectance Fourier transform infrared spectra of wood fibers treated with maleated polypropylenes

The esterification reaction between wood fibers and maleated polypropylenes was investigated. The reaction was conducted in a reactor in the presence of xylene used as a solvent and sodium hypophosphite as catalyst. The reaction between wood fibers and pure maleic anhydride was also investigated. The appearance of an infrared absorption band near 1730 cm⁻¹ indicated that maleated polypropylene chemically reacted by esterification with bleached Kraft cellulose. However, no direct evidence of an esterification reaction was obtained between thermomechanical pulp and maleated polypropylene. The Fourier transform infrared (FTIR) studies showed also that both bleached Kraft cellulose and thermomechanical pulp reacted with maleic anhydride with the formation of ester links. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1163–1173, 1997     

Changes in physical properties of methacrylonitrile (MAN)-grafted silk fibers

Changes in physical properties of silk fibers, grafted with methacrylonitrile (MAN), were investigated as a function of the weight gain. The weight gain increased steadily during the first 60 min of reaction and gradually attained an equilibrium value (60%) after about 4 h. The initial tensile resistance of silk fibers decreased by MAN grafting. The crystalline structure of silk fibers remained unchanged, regardless of MAN grafting, however. a minor and broad peak appeared in the X-ray diffraction curves of MAN-grafted silk fibers with a weight gain of 60%, corresponding to the unoriented MAN polymer attached inside the fibers. Molecular orientation of silk fibroin chains in the crystalline regions, evaluated from X-ray diffraction curves, did not change significantly, while both birefringence and isotropic refractive index decreased as the weight gain increased, implying that MAN polymer attached preferentially to the amorphous and not to the crystalline regions. Dynamic vis-coelastic measurements showed that the position at which the E′ value began to decrease shifted to a lower temperature as the weight gain increased. These findings suggest that the thermal movement of silk fibroin molecules was accelerated by the presence of the poly-MAN chains attached to the amorphous regions of silk fibroin fibers. © 1993 John Wiley & Sons, Inc.     

Optimization of solvent crystallization process in obtaining high purity anthracene and carbazole from crude anthracene

Solvent crystallization is the main method used for preparing anthracene and carbazole from the crude anthracene. The key to the optimization of this method is improving the solubility selectivity of the solvent by means of solvent modulating and process optimization. In this study, the solubility of anthracene, phenanthrene, and carbazole in xylene, dimethylformamide (DMF), DMF with amine/amide, isopropanolamine, and chlorobenzene is examined and the solid‐liquid ternary anthracene–carbazole–DMF/(DMF+19.96% isopropanolamine) system phase diagram is determined and applied in the solvent crystallization process. The results showed that the solubility selectivity of xylene increases with increased temperature. Also, selectivity increases with an increase of the amount of isopropanolamine in the mixture of DMF and isopropanolamine, while decreases with increased temperature. Through multiple washings of crude anthracene with xylene, DMF+19.96% isopropanolamine, and chlorobenzene, it was possible to obtain anthracene and carbazole of purity higher than 98 wt %. © 2013 American Institute of Chemical Engineers AIChE J, 60: 275–281, 2014     

相转移催化法合成3-巯基丙酸(4-乙烯基苯基)甲酯

对氯甲基苯乙烯(CMS)在相转移催化剂(PTC)催化下,与3-巯基丙酸钾进行亲核取代反应,制备了标题化合物。研究了溶剂、催化剂及反应温度对反应的影响,实验结果表明:以二甲苯为溶剂,以三乙胺为相转移催化剂,催化剂与CMS的物质的量之比为1∶10,80℃下反应8 h,3-巯基丙酸(4-乙烯基苯基)甲酯的产率达60.7%,HPLC分析得到产物纯度>98%,1HNMR分析确证了产物结构。     

Fluorescence quenching of phenanthrene and anthracene by maleic anhydride and n‐octadecenylsuccinic anhydride in solution and in bulk polypropylene

Fluorescence quenching of phenanthrene (Ph) and anthracene (An) fluorophores by maleic anhydride (MAH) and n‐octadecenylsuccinic anhydride (ODSA) quenchers in solid polypropylene (PP) films were studied. Results were compared with fluorescence quenching of the same fluorophores by MAH and ODSA quenchers in chloroform solution. Contrary to the results obtained in solution, it was observed that fluorescence emission of Ph fluorophore in PP films was more efficiently quenched by ODSA than by MAH. This was due to the better miscibility of Ph with ODSA than with MAH. When An fluorophore was used instead of Ph, it was observed that its fluorescence intensity in PP films was notably reduced by the addition of MAH. This was mainly due to the Diels–Alder reaction, which consumed a part of the An molecule. However, fluorescence intensity of An strangely increased with the addition of ODSA instead of MAH. Because of short lifetime of An (around 6 ns), ODSA had no quenching effect on An. POLYM. ENG. SCI., 47:192–199, 2007. © 2007 Society of Plastics Engineers     

Structure and physical properties of epoxide-treated tussah silk fibers

The structural characteristics and physical properties of epoxide-treated tussah silk fibers from Antheraea pernyi silkworm are discussed in relation to the increasing weight gain values. Ethyleneglycol diglycidylether (E) and glycerin diglycidylether (G) were used as modifying agents. The noticeably high weight gain values (about 140%) obtained were attributed to the catalytic effect of SCN^? anion absorbed by the fibers during the pretreatment under reduced pressure conditions. The amino acid analysis showed that epoxide G exhibited a slightly higher reactivity toward tyrosine, while arginine preferably reacted with epoxide E. The peak of loss modulus (E″) determined by dynamic viscoelastic measurements became broader and its position linearly shifted to lower temperature when the weight gain increased, and a minor peak appeared in the low-temperature region below 50°C. Differential scanning calorimetry (DSC) thermograms showed that the position of the decomposition peak of modified silk fibers shifted to lower temperature with increasing weight gain values. The minor and broad endothermic peaks, appearing in the reference sample at about 234 and 290°C, disappeared by epoxide treatment. X-ray diffraction patterns of tussah silk fibers suggested that the epoxide treatment does not affect directly the crystalline regions but causes a decrease of molecular orientation in the amorphous regions. Both briefringence (Δn) and isotropic refractive index (n_iso) of tussah silk fibers decreased by the reaction with epoxides, although with different rate and extent, confirming the decrease of average molecular orientation. The extent of decrease of strength and elongation depends on the kind of epoxide and on the weight gain value. Epoxide-treated tussah silk fibers did not show significant changes of surface characteristics as the weight gain values attained up to 60%.