Separation of alcohol–water mixture by pervaporation through a novel natural polymer blend membrane–chitosan/silk fibroin blend membrane

A novel natural polymer blend membrane, namely chitosan/silk fibroin blend membrane, was prepared. The selective solubility and the pervaporation properties of alcohol–water mixture were studied. The results showed that the membrane was water selective and the separation factor of ethanol–water mixture could be improved compared to pure chitosan membrane, when silk fibroin content in blend membrane was no more than 40 wt %. The blend membrane exhibited a best performance, (i.e., the water in permeate was large than 99 wt % when silk content was 20 wt % and the crosslinking agent–glutaraldehyde content was 0.5 mol %). The mechanism of improvement on pervaporation properties was explained by reducing the free volume and freeing hydrophilic groups of chitosan because of the strong intermolecular hydrogen bond forming between chitosan and silk fibroin in blend membrane. In addition, the influence of operation temperature and feed concentration as well as the pervaporation properties of isopropanol–water mixture were also studied. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 975–980, 1999     

Physical properties of silk fibroin/chitosan blend films

Silk fibroin/chitosan blend films were examined through IR spectroscopy to determine the conformational changes of silk fibroin. The effects of the fibroin/chitosan blend ratios (chitosan content) on the physical and mechanical properties were investigated to discover the feasibility of using these films as biomedical materials such as artificial skin and wound dressing. The mechanical properties of the blend films containing 10–40% chitosan were found to be excellent. The tensile strength, breaking elongation, and Young's modulus were affected by the chitosan contents of the blend films, which were also related to the density and degree of swelling. The coefficient of water vapor permeability of the blend films increased linearly with the chitosan content, and the values of 1000–2000 g m^?2 day^?1 were comparable to those of commercial wound dressings. Silk fibroin/chitosan blend films had good oxygen and water vapor permeabilities, making them useful as biomaterials. In particular, the blend film containing 40–50% chitosan showed very high oxygen permeability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 928–934, 2001     

丝素/羧甲基壳聚糖共混膜的结构性能探讨

将含有甘油和戊二醛的丝素与羧甲基壳聚糖按一定比例混合,制得丝素/羧甲基壳聚糖共混膜,对共混膜的结构与性能进行了探讨。结果表明:随着羧甲基壳聚糖含量的增加,共混膜的透气率增大,加入交联剂戊二醛有效地改善了共混膜的力学性能,但其透气率有所降低;当丝素与羧甲基壳聚糖的质量比为4/1时,共混膜的断裂强度最大,力学性能较好,共混膜相容性较好,其断面光滑、致密。制备丝素/羧甲基壳聚糖共混膜的较佳条件为:丝素中的甘油质量分数为15%,戊二醛质量分数为0.075%,丝素与羧甲基壳聚糖质量比为4/1。     

Structure and physical properties of silk fibroin/polyacrylamide blend films

This article deals with the characterization of blend films obtained by mixing silk fibroin (SF) and polyacrylamide (PAAm). The DSC curves of SF/PAAm blend films showed overlapping of the main thermal transitions characteristic of the individual polymers. The exothermic peak at 218°C, assigned to the β‐sheet crystallization of silk fibroin, slightly shifted to a lower temperature by blending. The weight‐retention properties (TG) of the blend films were intermediate between those of the two constituents. The TMA response was indicative of a higher thermal stability of the blend films, even at low PAAm content (≤25%), the final breaking occurring at about 300°C (100°C higher than pure SF film). The peak of dynamic loss modulus of silk fibroin at 193°C gradually shifted to lower temperature in the blend films, suggesting an enhancement of the molecular motion of the fibroin chains induced by the presence of PAAm. Changes in the NH stretching region of silk fibroin were detected by FTIR analysis of blend films. These are attributable to disturbance of the hydrogen bond pattern of silk fibroin and formation of new hydrogen bonds with PAAm. The values of strength and elongation at break of blend films slightly improved at 20–25% PAAm content. A sea–island structure was observed by examining the air surface of the blend films by scanning electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1563–1571, 1999     

丝素/羧甲基壳聚糖共混膜的结构与性能

利用丝素(SF)与羧甲基壳聚糖(CMCS)共混制取不同比例的SF/CMCS共混膜。研究了CMCS诱导的丝素构象转变行为,测试了共混膜的吸湿性、透湿性和保水性。当CMCS的质量分数为5%时,共混膜中丝素的构象以β-折叠为主;当CMCS的质量分数为10%时,共混膜中丝素的构象由β-折叠向α-螺旋发生转变;当CMCS的质量分数达到15%时,共混膜中丝素的构象向无规卷曲发生转变。当CMCS质量分数小于15%时,共混膜中SF与CMCS具有良好的相容性,溶胀度较小,吸湿性随CMCS含量的增加而迅速降低。     

Structure and properties of silk fibroin/carboxymethyl chitosan blend films

The secondary structure of silk fibroin (SF) and the compatibility of the two components were associated with the carboxymethyl chitosan (CMCS) content in SF/CMCS blend films. A rather complete conformation transition of SF from random coil to β-sheet occurred after adding 5% CMCS into the SF film, and the blend film exhibited a high crystallinity and a good compatibility. The conformation of SF changed from β-sheet to α-helix when blending 10% CMCS. When the CMCS content was up to 15%, the conformation of SF in blend films showed a transformation from β-sheet to a random coil and their crystallinities decreased evidently; accordingly, there was a two-phase separation structure for the blend films containing 15% CMCS or more. However, the intermolecular interaction between the two polymers still existed in blend film with 15% CMCS or more. The blend films with 5–10% CMCS content showed the lower moisture absorption, swelling capacity, and solubility in water. These properties of blend films increased when adding CMCS more than 15%.     

Study on the properties of nano‐TiO2 particles modified silk fibroin porous films

Using the freeze‐drying method, Nano‐TiO₂/silk fibroin porous films were synthesized with different ratios of TiO₂ to silk fibroin solution. Through scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), tensile strain, and water‐solubility tests, the structures and properties of these porous films were characterized. The SEM results indicated that the pores of the nano‐TiO₂/silk fibroin porous films were uniformly distributed by the freeze‐drying method. The XRD analysis indicated that the formation of nano‐TiO₂ particles might induce a conformational transition of silk fibroin from the typical Silk I to the typical Silk II structure partly with an increase in the crystallinity of the porous films. Compared with the pure silk fibroin porous films, the mechanical properties of nano‐TiO₂/silk fibroin porous films were improved, and its heat transition temperature was also enhanced; however, the water‐solubility of this material was diminished. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rapid formation of flexible silk fibroin gel‐like films

Flexible silk fibroin gel‐like films with microporous morphology were prepared from B. mori silk fibroin fibers directly solubilized in formic acid/CaCl₂ solvent. These films were characterized by several analysis techniques to determine the structure and properties of films. The pore size of gel‐like films can be adjusted through SF concentration and Ca ions concentration. The controllable pore size in gel‐like films was grew from 3–5 μm to 100 μm under the increase of fibroin concentration from 1.0 wt % to 8.0 wt %. At the same time, the water content of silk fibroin gel‐like film decreased from 83.5 ± 3.4% to 68.2 ± 2.6%. With increasing Ca ions contents from 2.0 wt % to 10.0 wt % in dissolution process, the pore size and water content of silk fibroin gel‐like films grew larger, especially its water content values reached 86.2 ± 4.0% at 10.0 wt % Ca ions concentration. At wet condition, the gel‐like film with β‐sheet structure showed higher breaking stress (4.26 ± 0.31 MPa) and elongation (45.45 ± 15.79%) at 8.0 wt % concentration. With the preparation method, the membrane is hydrophilic and the pore size is adjustable, which contributes to high toughness and favorable cell growth environment, suggesting that these silk fibroin gel‐like films can be a potential candidate scaffold for biomedical applications, such as wound dressing, facial mask, contact lenses, etc. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41842.     

Development of a novel glucosamine/silk fibroin–chitosan blend porous scaffold for cartilage tissue engineering applications

Silk fibroin–chitosan blend is reported to be an attractive scaffold material for tissue engineering applications. In our earlier study, we developed a scaffold having an optimal silk fibroin–chitosan blend ratio of 80:20 and proved its potentiality for cartilage tissue engineering applications. Glucosamine is one of the major structural components of cartilage tissue. The present work investigates the effect of glucosamine components on the physicochemical and biocompatibility properties of this scaffold. To this end, varied amounts of glucosamine were added to silk fibroin–chitosan blend with the aim of improving various scaffold properties. The addition of glucosamine components did not show any significant change in physicochemical properties of silk fibroin–chitosan blend scaffolds. The composite scaffold showed an open pore structure with desired pore size and porosity. However, cell culture study using human mesenchymal stem cells derived from umbilical cord blood revealed an overall increase in cell supportive properties of glucosamine-added scaffolds. Cell viability, cell proliferation and glycosaminoglycan assays confirmed enhanced cell viability and proliferation of mesenchymal stem cells. Thus, this study demonstrated the beneficial effect of glucosamine on improving the cell supportive property of silk fibroin–chitosan blend scaffolds making it more potential for cartilage tissue regeneration. To the best of our knowledge, this is the first report on the study of glucosamine-added silk fibroin–chitosan blend porous scaffolds seeded with mesenchymal stem cells derived from umbilical cord blood.     

Blend films from chitosan and konjac glucomannan solutions

Blend films were prepared by blending 7 wt % konjac glucomannan (KGM) aqueous solution with 2 wt % chitosan (CH) in acetate solution and dried at 40°C for 4 h to obtain the transparent films. Their structure and properties were studied by infrared (IR), wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Crystallinities of the blend films decreased with the increase of konjac glucomannan. The thermostability, tensile strength, and breaking elongation of the blend films in dry state were obviously higher than those of both konjac glucomannan and chitosan films. Tensile strength of the dry blend film achieved 73.0MPa when the weight ratio of chitosan to konjac glucomannan was 7:3. The structure analysis indicated that there is a strong interaction between konjac glucomannan and chitosan resulted from intermolecular hydrogen bonds. The water solubility of the blend films was improved by blending with konjac glucomannan, so they have promising applications to soluble antiseptic coating of pills. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 509–515, 2000     

Preparation and characterization of low‐density polyethylene/banana starch films containing compatibilizer and photosensitizer

Composite films containing various percentages of banana starch and low‐density polyethylene (LDPE) were prepared. The effects of the compatibilizer, banana starch content, and photosensitizer content on the thermal and tensile properties of these films were investigated. The banana starch content was varied from 5 to 20 wt % of LDPE, whereas benzophenone was added as a photosensitizer in three different amounts (0.25, 0.5, and 1 wt %) based on LDPE. In these films PE‐graft‐maleic anhydride (PE‐g‐MA) was used as a compatibilizer at 10 wt % banana starch. It was found that the thermal stability of the composite films remained unchanged with respect to the amount of banana starch and benzophenone content. The addition of banana starch had no effect on the melting temperature and degree of crystallinity of the films. Similarly, PE‐g‐MA had no effect on the melting temperature but decreased the degree of crystallinity of the LDPE phase. Benzophenone caused an increase in the melting temperature but decreased the degree of crystallinity of LDPE in the films. Increasing the amount of banana starch decreased the tensile properties of the composite films. The addition of PE‐g‐MA as a compatibilizer increased the tensile properties compared with the uncompatibilized films. However, benzophenone had no effect on the tensile properties of the blend films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2717–2724, 2006     

丝素与聚氨酯共混膜的热压条件探讨

采用热压法，对丝素粉体与水性聚氨酯的共混物进行热压处理，并研究了丝素粉体与水性聚氨酯的共混物在不同时间和不同压力的热压条件下制得共混膜的性能。结果表明：热压法制得的共混膜结构致密，手感柔软光滑，透明度较高；当热压压力为35MPa，热压时间为10min时，得到的共混膜断裂强度和杨氏模量最高，断裂伸长率最低，吸水性也较好。     

Deduction of a facile method to construct Antheraea mylitta silk fibroin/gelatin blend films for prospective biomedical applications

Blend films of two types (I and II) were prepared by mixing Antheraea mylitta silk fibroin (AMF) and gelatin solution in various blend ratios via the solution casting method. Two different crosslinkers, namely glutaraldehyde and genipin, were used during blend preparation. The structural characteristics and thermal properties of the blend films were examined by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), Thermogravimetric analysis (TGA) and Diffrential scanning calorimetery (DSC). The FTIR spectra showed conformational alterations in type I blend films while type II films attained high β‐sheet crystallinity. The XRD diffractograms presented a high degree of crystallinity in type II blend films compared to type I, which showed an almost amorphous structure. Further, thermal and biological studies were conducted on type II films. According to the TGA thermograms, the degradation temperature of the crosslinked blend films shifted compared to pure gelatin and pure AMF films. Partial miscibility of the two components was indicated by DSC thermograms of the blends. The high water uptake capacity of type II blend films was found to imitate hydrogel behaviour. The blend films did not show any toxicity in 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay and supported L929 fibroblast cell spreading and proliferation. The biodegradation of the blend films was significantly faster than the pure silk film. © 2020 Society of Industrial Chemistry     

Characterization of films from chitosan and quaternized poly(4‐vinyl‐N‐butyl) pyridine solutions

All Blend films were prepared from a mixture of 2 wt % chitosan in acetate solution and 4 wt % quaternized poly(4‐vinyl‐N‐butyl) pyridine (QPVP) in aqueous solution and dried at room temperature for 72 h to obtain the films. Their structure and properties were studied by infrared (IR), wide‐angle X‐ray diffraction (WXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). Crystallinities of the blend films decreased with the increase of QPVP when weight of QPVP content was less than 15.0 wt %. The thermostability, tensile strength, and breaking elongation of the films in dry state were better than those of chitosan film. Tensile strength of the blend film dried at 40°C under vacuum for 24 h achieved 56.38 MPa when the weight ratio of chitosan to QPVP was 9 : 1. The structural analysis indicated that there was a strong interaction between chitosan and QPVP resulting from strong adhesion between both polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 559–566, 2004     

Preparation and characterization of soy protein isolate–carboxymethylated konjac glucomannan blend films

To improve the mechanical and water vapor barrier properties of soy protein films, the transparent films were prepared by blending 5 wt % soy protein isolate (SPI) alkaline water solution with 2 wt % carboxymethylated konjac glucomannan (CMKGM) aqueous solution and drying at 30 °C. The structure and properties of the blend films were studied by infrared spectroscopy, wide‐angle X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and measurements of mechanical properties and water vapor transmission. The results demonstrated a strong interaction and good miscibility between SPI and CMKGM due to intermolecular hydrogen bonding. The thermostability and mechanical and water vapor barrier properties of blend films were greatly enhanced due to the strong intermolecular hydrogen bonding between SPI and CMKGM. The tensile strength and breaking elongation of blend films increased with the increase of CMKGM content: the maximum values achieved were 54.6 MPa and 37%, respectively, when the CMKGM content was 70 wt %. The water vapor transmission of blend films decreased with the increase of CMKGM content: the lowest value achieved was 74.8 mg · cm^?2 · d^?1 when the CMKGM content was 70 wt %. The SPI–CMKGM blend films provide promising applications to fresh food packaging. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1095–1099, 2003     

Biodegradation of Bombyx mori silk fibroin fibers and films

The in vitro biodegradation of Bombyx mori silk fibroin was studied by incubating fibers and films with proteolytic enzymes (collagenase type F, α‐chymotrypsin type I‐S, protease type XXI), for times ranging from 1 to 17 days. The changes in sample weight and degree of polymerization of silk fibers exposed to proteolytic attack were negligible. However, tensile properties were significantly affected, as shown by the drop of strength and elongation as a function of the degradation time. Upon incubation with proteolytic enzymes, silk films exhibited a noticeable decrease of sample weight and degree of polymerization, the extent of which depended on the type of enzyme, on the enzyme‐to‐substrate ratio, and on the degradation time. Protease was more aggressive than α‐chymotrypsin or collagenase. Film fragments resistant to enzymatic degradation were enriched in glycine and alanine. FT‐IR measurements showed that the degree of crystallinity of biodegraded films increased. Soluble degradation products of silk films consisted of a range of peptides widely differing in size, deriving from the amorphous sequences of the silk fibroin chains. Biodegraded fibers showed an increase of surface roughness, while films displayed surface cracks and cavities with internal voids separated by fiber‐like elements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2383–2390, 2004     

Grafting of methyl methacrylate onto silk fibers initiated by tri-n-butylborane

Structural characteristics of the methyl methacrylate (MMA)-grafted silk fibers using tri-n-butylborane as an initiator were analyzed by infrared spectroscopy and differential scanning calorimetry (DSC), and their refractive index and tensile properties were measured. Graft polymerization was promoted by FeCl₃ pretreatment of the silk. The graft yield reached a maximum by the immersion in 4% FeCl₃ solution for 1 min at 25°C. The infrared spectrum of poly(MMA)-grafted silk fibers showed overlapped absorption bands of silk fibroin with the β structure and of the grafted MMA polymer. A grafted silk fiber with graft yield of more than 140% exhibited two endothermic peaks at 321°C and 396°C on the DSC curve, attributed to the thermal decomposition of silk fibroin and grafted poly(MMA) chain, respectively. Refractive index measurements suggested that the molecular orientation and the crystallinity of the silk fiber decreased with increasing graft yield. Electron photomicrographs showed that silk was coated by grafted PMMA. The tensile strength of the grafted silk decreased rapidly by the grafting even at a lower level.     

Effects of addition of condensed tannin on the structure and properties of silk fibroin film

Condensed tannin is a polymeric polyphenol compound, which has considerable protein‐binding ability and a variety of bioactivities, such as anti‐inflammatory, antithrombotic and antimicrobial activities. In this study, silk fibroin film was modified by adding condensed tannin. It was found that strong intermolecular interactions occurred between silk fibroin and tannin, and incorporation of 1–10% (w/w) tannin in the blend films resulted in more compact, stiffer but less elastic films. Swelling and dissolution trials showed that the addition of tannin significantly reduced the swelling and solubility of the films. The mechanical properties, swelling and solubility of the blend films varied as a function of tannin concentration, showing optimum values when containing 10% (w/w) tannin. The silk fibroin–tannin films all showed significant antioxidant activity and antibacterial activity against Gram‐positive bacteria, and the activities were positively related to the concentration of tannin. The results emphasized that the addition of condensed tannin could simultaneously improve the structural stability of silk fibroin film and impart functional properties. © 2016 Society of Chemical Industry     

新型仿生化纤维的制备与纤维性能评价

为提高纤维素纤维和壳聚糖纤维的生物相容性能并保持纤维原有的力学机械强度,在其单纤维纺丝溶液中添加原胶原蛋白、丝素蛋白、甲壳素等,经湿法纺丝,考察了各种混合纤维的密度、直径、纤度、强度、伸长率等性能的变化。研究结果表明:壳聚糖纤维中混合原胶原蛋白后,纤维纤度增加,但对纤维的伸长和强度影响不大;当原胶原蛋白含量达10%时,纤维伸长率最大。纤维素纤维因添加了丝素后,强度、伸长下降,但添加第三组分甲壳素后表现出优异的机械性能。扫描电镜对混合纤维的形貌分析证实了生物材料与甲壳素、壳聚糖及纤维素间存在着良好的共混相容性,对纤维性能起到改善的作用。     

Miscibility and mechanical properties of sulfonated polystyrene–polyurethane blends

A sulfonated polystyrene (SPS) and a polyurethane containing a tertiary amine group (NPU) were blended in solution. The effect of blend composition was studied in the blend of SPS with 9.83 mol % of sulfonation (SPS-9.83) and NPU with 33 mol % of MDEA (NPU-33). As the SPS concentration increases, a significant improvement of miscibility is observed. The tensile strength of the blends is greater than either pure NPU or SPS. A maximum strength and a maximum density occur at 50 wt % SPS. The stress–strain curve shows a well-defined yield when the SPS concentration in the blend is 30 or 50 wt %. The yield is more dramatic in the blend with 50 wt % SPS than that of 30 wt % SPS. At a lower SPS concentration, the blend behaves like a rubber, while a higher SPS concentration in the blend results in a brittle failure before yield. An increase in the sulfonation level of SPS in the SPS–NPU-33 (30/70) blends leads to an improved miscibility. A significant enhancement of tensile strength is observed as the sulfonation increases. A clear yield point on the stress–strain curves occurs when the sulfonation of SPS in the blend is 4.79 mol % or greater. Increasing the MDEA content of NPU up to 8.3 mol % can lead to an enhancement of tensile strength. A further increase in the MDEA content has little influence on the tensile strength, but a clear yield on the stress–strain curve occurs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2035–2045, 1998