Chitosan Composite Multifilament Fibers with Two-Switch

Subscriber access provided by Washington University | Libraries

Article

Cellulose/Chitosan Composite Multifilament Fibers with Two-switch Shape Memory Performance Kunkun Zhu, Yang Wang, Ang Lu, Qiang Fu, Jinlian Hu, and Lina Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06691 • Publication Date (Web): 01 Mar 2019 Downloaded from http://pubs.acs.org on March 2, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Cellulose/Chitosan Composite Multifilament Fibers with Two-switch Shape Memory Performance

Kunkun Zhu1,2, Yang Wang1, Ang Lu1,Qiang Fu,3 Jinlian Hu2*, Lina Zhang1*

1

College of Chemistry and Molecular Sciences, Wuhan University, No. 299, Bayi Road, Wuhan

430072, China 2

Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon,

Hong Kong, China 3 College

of Polymer Science and Engineering, Sichuan University, No.24, South Section-1, Yihuan

Road Chengdu 610065, China

Correspondence to: E-mail: [email protected] (L. Zhang), [email protected] (J. Hu)

1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 31

ABSTRACT Facing the serious pollution caused by non-degradable plastic waste, environmentally benign materials from sustainable polymers have attracted tremendous research interest. Specially, functional fibers with good mechanical properties, shape memory behavior and biodegradability have been required in the fields of smart textiles, sensors and intelligent robot. Here, a new solvent, 4.5 wt% LiOH/7.5 wt% KOH/11.5 wt% urea aqueous solution, was developed to prepare stable cellulose/chitosan composite solution. Subsequently, cellulose/chitosan composite (CLS) fibers were spun successfully from the mixture solution on a lab-scale spinning machine. The CLS fibers exhibited good mechanical properties with tensile strength of 3.2 cN/dtex in the dry state and 2.9 cN/dtex in the wet state, as a result of the combination of good miscibility between two components and their nanofiber self-assembly driven by self-aggregation force through hydrogen bonding interactions. Interestingly, the CLS fibers showed a two-switch shape memory behaviors under water and acid stimulations. By changing the external stimulation, the strong self-aggregation force between cellulose and chitosan could be destroyed partly and then restructured to fix and recover, resulting in a designed shape. This work provided a new method for fabricating high strength and functional fiber in industry, which will promote the development of smart textiles.

KEYWORDS: cellulose, chitosan, functional fiber, shape memory, environmentally benign material

INTRODUCTION 2


Page 3 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Textiles, one of the largest volume consumer products globally, have been identified as a significant source of carbon emissions by the United Nations.1, 2 As the elementary units of textiles, fibers can be divided into synthetic fibers came from petroleum and regenerated fibers derived from natural polymers. However, the development of synthetic fibers have been restricted by their inherent non-biodegradability, serious pollution and the nonrenewable of petroleum. It is worth noting that more than 8 million tons of plastic enter the ocean every year, leading to the serious marine pollution.3 To protect environment, researchers have focused on replacing fossil raw materials with renewable alternatives that can be biodegraded in soil and ocean.4-6 Natural polymers such as cellulose and chitin have attracted tremendous research interest due to their renewability and environmentally benign.7-11 However, viscose rayon, accompanied by hazardous by products including CS2, H2S and heavy metals, has still occupied the most important position in industry ever since 1892.12 Thus, it is significant to develop a new fiber for viscose rayon substitute. At the end of the last century, an environmentally benign solvent called N-methylomorpholine-N-oxide (NMMO) has been proposed, from which a new regenerated cellulose fiber with the generic name of Lyocell was invented.13 Subsequently, ionic liquid, another environmentally benign solvent for cellulose, has become a new avenue for fabricating regenerated cellulose fibers.14 In our laboratory, a series solvent of alkali/urea aqueous solutions with cooling have been developed to dissolve cellulose, chitin and chitosan.15-17 Meanwhile, mechanical strong cellulose fibers and chitin fibers were spun successfully via environmentally benign process.18 Chitosan, derived from chitin, is a unique functional alkaline polysaccharide and has potential applications in various fields, including water treatment, agriculture, biomedicine and smart materials.19-22 Moreover, cellulose/chitosan composite (CLS) hydrogels, films and microspheres have been constructed by mixing cellulose alkali solution with chitosan alkali solution directly.23, 24 However, the CLS fibers have not yet been reported, as a result of t the poor 3



Page 4 of 31

stability of the cellulose/chitosan composite solution mixed directly from their alkali solution. Recently, smart materials such as piezoelectric materials, shape memory materials (SMMs) and self-healing materials have attracted much attention for their wide applications in electronic devices, aerospace, smart textiles, tissue engineering, etc.25-28 SMMs are materials that can be deformed and fixed in temporary shapes and then return to their original shapes under external stimulations such as temperature, water, pH value and light.29-33 Compared with shape memory alloys and shape memory ceramics, shape memory polymers (SMPs) have the unique advantages such as light weight, good manufacturability, high shape deformability, good biodegradability and low cast.34 Therefore, the fabrication of various SMPs materials, including hydrogel, foam, film, fiber, etc has attracted researchers.35-39 Nevertheless, the large-scale fabrications of polymer materials with shape memory have been not yet reported. In this work, 4.5 wt%LiOH/7.5 wt%KOH/11.5 wt%urea aqueous solution, was developed to prepare CLS system, for the first time. On the basis of the good stability of this composite solution, an ultra-strong CLS fiber was fabricated by wet-spinning on a lab-scale spinning machine. The structure and properties of the CLS fibers were characterized by scanning electron microscopy (SEM), two-dimensional wide-angle X-ray diffraction (2D WAXD), small angle X-ray scattering (SAXS) and tensile testing. It was demonstrated that the CLS fibers had good stimulate-response to both water and acid solutions, showing a two-switch shape memory behavior. The shape memory functionalized CLS multifilament would be significant for building smart textiles via green pathway.

EXPERIMENTAL SECTION Materials. Cellulose (CL, cotton linter pulp) with an viscosity-average molecular weight Mη = 10.0×104 measured with an Ubbelohde viscometer in cadoxen at 25 oC was provided by the Hubei 4


Page 5 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Chemical Fiber Co. Ltd. (Xiangyang, China).40 Chitosan (CS, commercial grade, degree of deacetylation about 89%) with an apparent weight-average molecular weight value Mw = 36.0×104 measured using laser light scattering was purchased from Ruji Biotechnology Co., Ltd. (Shanghai, China).41 All other chemical reagents were purchased from Sinopharm Chemical Reagent Co., China and used without further purifications. Preparation of CLS Solution and Wet Spinning. The aqueous solutions containing LiOH/urea/H2O of 4.5:15:80.5 and LiOH/KOH/urea/H2O of 4.5:7:8:80.5 by weight were used as solvent of cellulose and chitosan, respectively. Clearly, cellulose solution was directly prepared by dissolving the cotton linter pulp in the alkaline aqueous solvent pre-cooled to -12 oC with stirring, while the chitosan solution was obtained through a freezing/thawing cycle after dispersing the chitosan powders in the solvent. The CLS solution was achieved by mixing the cellulose solution and chitosan solution in a weight ratio of 1:1. Simultaneously, concentrated KOH solution was added during the mixing process to improve the stability of the composite solution. The final concentration of KOH in the CLS solution was 7.5 wt%. Transparent CLS dope with 5 wt% concentration (2.5 wt% cellulose and 2.5 wt% chitosan) was obtained after centrifugation. The wet-spinning process was carried out according to previous report on a lab-scale machine.18 Clearly, the dope was extruded through a spinneret cylinder (50 orifices; diameter, 160 μm) into 15 wt% phytic acid aqueous solution at 5 oC with a flow rate of 7.46 m/min by using a gear pump under nitrogen pressure (0.15 MPa). The fibers were first taken up on roller I after regenerating, drawn to roller II in hot water (60 oC), washed in another water (room temperature), dried at 60 oC, and then collected on the take-up roller. The multi-drawing processes were performed by adjusting the rotational speeds of rollers I and II. Research of Shape Memory Ability. The CLS fibers were immersed in water for 1 h then in 1 M HCl solution for 1 h at room temperature. To study the shape memory ability of the CLS fibers under 5



Page 6 of 31

acid, the acid soaked fibers were bent to a certain angle of θs (0°, 45°, 90°, 135°), immerged in 1 M NaOH solution, and then in water to fix an uncertain angle (θf). The shape fixation ratio (Rf) was calculated by equation 180 ― 𝜃𝑓

(1)

𝑅𝑓(%) = 180 ― 𝜃𝑠 × 100

The fixed fibers were immerged in 1 M HCl solution again to allow its recovery to another angle (θr). The shape recovery ratio (Rr) was calculated by equation 𝜃𝑟

(2)

𝑅𝑟(%) = 180 × 100

Similarly, the shape memory ability of the CLS fibers to water was investigated by wetting, blending, drying and rewetting. Characterization. SEM images at 5kV accelerating voltage were taken on a scanning electron microscope (FESEM, Zeiss, SIGMA). XRD spectra were recorded on a Rigaku Miniflex600 diffractometer in reflection mode with Cu Kα radiation (λ= 0.154 nm) operated at 40 kV and 40 mA. 2D WAXD patterns were recorded on a Bruker D8 Advance diffractometer via the Debye-Scherrer method operated at 40 kV and 0.65 mA with a Cu anode. SAXS patterns were recorded on the GeniX 3D beam delivery system using a MP-Xeuss 2.0 SAXS (BRUKER AXS, Inc.) with Cu Kα radiation (λ= 0.154 nm). Rheological analysis was carried out on a rheometer (DHR-2, TA instruments, USA) by using a parallel plate of 40 mm diameter under temperature sweep mode with constant frequency of 1 Hz, strain of 10%, and constant heating rate of 1-2 oC/min. Thermo-gravimetric analysis (TGA) of the hydrogels were carried out after freeze drying on a Pyris TGA linked to a Pyris diamond TA Lab System (Perkin-Elmer) at a heating rate of 10 oC/min from room temperature to 600 oC under nitrogen atmosphere. X-ray photoelectron spectroscopy (XPS) of the hydrogels were recorded on a Thermo Fisher ESCALAB 250Xi X-ray photoelectron spectroscopy. The optical micrographs of the cross-section of the CLS fibers were observed on an optical microscope (Leica DMLP, Germany). 6


Page 7 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Mechanical properties of the CLS fibers were tested using an LLY-06ED tensile tester (Laizhou Electronic Instrument Co., Ltd. China) at 23°C and humidity of 65%. The CLS fibers in wet state were tested after immerging in water for 5 min. Each fiber prototype were tested at least 10 independent specimens.

RESULTS AND DISCUSSION Preparation of CLS Solution and Wet-spinning. Both the cellulose and chitosan alkali solutions showed good fluidity after heating for 16 h at 37 oC (Figure S1), however, their mixing solution gelled after heating for only 5 h at the same temperature, showing a bad spinnability (Figure 1a). Thus, improving the solution stability is the key to spin the composite fibers. Considering the similar of cellulose and chitosan solvents,42, 43 namely 4.5 wt% LiOH/15 wt% urea and 4.5 wt% LiOH/7 wt% KOH/8 wt% urea, respectively, the effect of KOH and urea concentration on the solution stability was studied. By changing the urea concentration form 14 wt% to 8 wt%, the stability of cellulose solution was slightly influenced (Figure S2a), and the stability of chitosan solution also slightly enhanced with the increase of the urea concentrations (Figure S2b). These results indicated that urea concentration had light influence on the stability of both cellulose and chitosan solution. Figure 1b shows the storage modulus G′ and loss modulus G″ versus temperature of the CLS solutions with different KOH concentrations. The crossover point of G′ and G″ was defined as the gelation point, which increased with the raising KOH concentration and reached the best when the solution contained 7.5 wt% KOH. This solution can also flow well after heating for 16 h at 37 oC, showing its spinnability (Figure 1c). Actually, the CLS fibers were spun successfully by choosing phytic acid solution as a coagulation bath (Figure 2a, b). The CLS fibers exhibited good flexibility and a silk-like luster in their appearance (Figure 2c). According to the draw ratio of 1.0, 1.3 and 1.6 during the 7



Page 8 of 31

spinning process, the fibers were coded as CLS-1.0, CLS-1.3 and CLS-1.6, respectively. Surprisingly, the CLS fibers exhibited excellent mechanical properties both in the dry and wet state, as shown in Figure 2d and Table S1. The tensile strength increased from 2.3 to 3.2 cN/dtex in the dry state and 2.0 to 2.9 cN/dtex in the wet state with the increase of drawing ratio from 1.0 to 1.6. The tensile strength of CLS-1.6 was much higher than those reported CLS fibers, such as that spun from ionic liquids system (1.86 cN/dtex in the dry state and 1.75 cN/dtex in the wet state).44 Moreover, the mechanical properties of the CLS fiber were also better than viscose (1.8-2.5 cN/dtex in the dry state and 1.0 cN/dtex in the wet state).45, 46 The results also reflected the good miscibility of cellulose and chitosan in 4.5 wt%LiOH/7.5 wt%KOH/11.5 wt%urea aqueous solution. Figure 3 shows scanning electron microscopy (SEM) images of the surface and cross-section of the CLS fibers. The fibers exhibited smooth surface and a non-circular cross-section, similar with the cellulose fibers fabricated by spinning the dope into 15 wt% phytic acid coagulation.47 The apparent average diameter of the fibers could vary from 95 to 62 μm by drawing from 1.0 to 1.6. From the high-magnification SEM images of the cross-section, homogeneous reticular structure along the perpendicular to the longitudinal direction (Figure 3d and l) and homogenous oriented structure parallel to the longitudinal direction (Figure 3h) were observed clearly, indicating that both tangle and orientation existed in the CLS fibers. Moreover, the fabrication process of this CLS fibers was environmentally benign, low cost and short production cycle,18 showing great potentials in the textile industry. Two-switch Shape Memory Performance. Interestingly, the CLS fibers exhibited a two-switch shape recovery behavior, as shown in Figure 4. Actually, the dry fiber cut from the coil (Figure 2c) showed a little bent as a fixing result of the dense packing structure formed in the drying process (Figure 2a and b). In our findings, the wet and acid soaked fibers exhibited non-straight (Figure 4a). This could be explained that the strong self-aggregation force among neighboring cellulose and 8


Page 9 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


chitosan molecules could permanently locked the bent shape of the dry fiber from heating roll.48 As shown in Figure 4a, a wet fiber (original shape) was fixed on the surface of a test tube and dried in air for 30 min to fix as a C-shape. After immerging in water, the C-shaped fiber (temporary shape) could easily recovery to the original shape, showing a water-induce shape memory effect. Similarly, an acid soaked fiber was bent by a right-angle mold and immerged in alkali solution for 5 min to fix as an L-shape. By soaking in acid solution again, the L-shaped fiber could recover to the original shape, showing an acid-induce shape memory effect. Specially, another acid soaked fiber was first bent through two glass rods, and a loose S-shaped fiber could be obtained after fixing by alkali solution. After washing in pure water, the resulted loose S-shaped fiber was second bent through another two finer glass rods, and a compact S-shaped fiber could be obtained after drying. This compact S-shaped fiber could recovery to an uncompact S-shape and the original shape in turn after immerging in water and then adding acid in the water in turn, showing a two-switch shape memory effect. The fixation and recovery efficiencies of the two-switch shape memory fibers were studied by using an angle-controlled method. As shown in Figure 4b, the CLS fibers have the measured fixing ratio (Rf ) values more than 95%, which increased with an increase of set folded angles (θs), similar to natural animal hairs,49 indicting the less effect of folding process when the set angle is enlarged. The relationship of recovery ratio (Rr) and θs also displayed the increasing tendency for both waterinduce and acid-induce shape memory and all the Rr values were larger than 85% (Figure 4c). Moreover, the recovery process exposed upon water stimulation are recorded and presented in Figure 4d and Video S1. The fiber was able to recover 83% within initial 30s (Figure 4e), showing a quick recovery. Reasons of Good Mechanical Properties. To understand the effects of drawing on the strength of the CLS fibers, three kinds of fibers with different draw ratios were observed by slicing along the 9



Page 10 of 31

fiber axis, as shown in Figure 5a-c. The fibers exhibited homogeneous structure, further confirming the good miscibility between cellulose and chitosan in the LiOH/KOH/urea aqueous system. Additionally, the height of directional ridges decreased with the drawing process, suggesting the increased density of the fibers. The 2D-WAXD patterns of the CLS fibers exhibited narrower equatorial arcs at higher draw ratios, indicated that the cellulose and chitosan chains were preferentially oriented with the drawing direction,50 supported by the results in Figure 3h and 5a-c. Nanofibers with an average apparent diameter of 27 nm were clearly observed arranging in a parallel pattern when draw ratio was 1.6. It has been demonstrated that the hydronium ions (H3O+) of phytic acid can diffuse into the cellulose solution slowly to destroy the alkali-urea complex shell, and the exposed cellulose and/or chitosan chains aligned in parallel to form nanofibers via strong selfaggregation force.18, 48 The orientation degree of the fibers were evaluated through the strongest equatorial reflection of the WAXD patterns. The orientation index (π) of the crystals in the fibers was obtained via azimuthal breadth analysis by using the following equation51 𝜋=

180 ― 𝑑ℎ

(3)

180

where dh is the half-width of the azimuthal distribution curve along the strongest equatorial reflection in the X-ray diffractograms (see inset curves in Figure 5d-f). The π value increased from 0.78 to 0.84 with the increasing of the draw ratio from 1.0 to 1.6 (Table S1), which is much higher than the cellulose nanofibril/guar gum filament (π = 0.13-0.55).52 The long equatorial streaks while short meridional peaks of all SAXS patterns (Figure 5g-i) indicated that needle-shaped voids or fibrillary structure were aligned parallel to the fiber direction, and crystalline and amorphous existed as a periodic lamellar arrangement.53 In additionally, cellulose, chitosan and CLS hydrogels (coded as RCL, RCS and CLS, respectively) were prepared to investigate the interaction between cellulose and 10


Page 11 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


chitosan chains and molecular bundles. The bonding environment of cellulose and chitosan chains and molecular bundles during mixture was ascertained by using XRD, TGA and XPS. As shown in Figure S3, the spectrum of chitosan powders had three peaks of (020), (110) and (130) lattice diffraction of chitosan, while the regenerated chitosan hydrogel had only two reflection peaks of (020) and (110) (Figure 6a). Three peaks were observed for RCL hydrogel at 2θ=12.4°, 20.4° and 21.9°, _

corresponding to the (110), (110) and (200) crystal planes of cellulose II,54 different from the cellulose I (Figure S3). These results indicated that cellulose and chitosan chains and molecular bundles were restructured during the dissolve and regeneration process. Moreover, the diffraction peaks of the CLS hydrogel were mainly at 12.1° and 20.4° and the crystallinity was between the corresponding values of cellulose and chitosan, due to the reformation of hydrogen bonds between cellulose and chitosan during dissolution and regeneration process.55 From their DTG curves, the maximum decomposition rates were recorded at 367 and 298 oC for cellulose and chitosan hydrogels, respectively (Figure 6b and S4). However, the CLS hydrogel showed two well-resolved degradation peaks at 301 and 336 oC , being slightly shifted from the peak temperatures recorded for the pure chitosan and cellulose hydrogels, as a result of the complementary interaction between cellulose and chitosan chains.56 Furthermore, XPS results indicated that C, N and O co-existed in the chitosan and CLS hydrogels, whereas only C and O appeared in the cellulose hydrogel (Figure 6c). However, the peak of N in the CLS hydrogel was obviously shifted to a higher binding energy (399.6 eV) compared with the chitosan hydrogel (399.1 eV), indicating that the amino group of chitosan led to more hydrogen bonds in the composite hydrogel. In view of these results, the good miscibility between cellulose and chitosan, the dense structure, the high degree of orientation and the more hydrogen bonds led to the mechanically strong of the CLS fibers. Mechanism of Shape Memory Performance. To investigate the two-switch shape memory 11



Page 12 of 31

behavior of the fiber, three states (dry, wet, acid) of the CLS fibers, coded as CLS-dry, CLS-wet and CLS-acid, respectively, were evaluated by fourier transform infrared (FTIR) spectroscopy, as shown in Figure 6d. A broad absorption band at around 3400 cm-1 corresponding to free water was introduced to the FTIR curve of wet state, suggesting that intermolecular hydrogen bonds occurred between the glucose residues and aqueous molecules during the hydration.57 The absorption band at 3400 cm-1 become broader after immerging in acid, suggesting more hydrogen bonds formed. This could be caused by the interaction between the chitosan and acid. Moreover, tensile strength and Young’s modulus of the CLS fiber decreased from 2.1 cN/dtex to 1.0 cN/dtex and 88.5 to 12.0 cN/dtex, respectively after contacting with water, and sharply decreased to 0.2 cN/dtex and 0.7 cN/dtex after immerging in acid, respectively (Figure 6e). These changes of modulus proved the influence of drive force of shape memory behavior.58 This could be explained that hydrogen bonds and nanofibers were partly destroyed in water and acid solution, resulting in a decrease of the modulus. Due to the anisotropic structure, the CLS-dry fiber exhibited a pattern with colors when viewed between the cross polarizers (Figure 6f). While the colors of the fiber lighten a lot after wetting, and completely disappeared following acid soak. This could be explained that the anisotropic and compact structure of the fiber weakened, when their hydrogen bonding interactions were partly destroyed by infiltration of the water and acid molecules. Meanwhile, the CLS-wet fiber had a larger cross section than the CLS-dry fiber and the cross section of the CLS-acid fiber showed an explosive growth but still remained the fiber state. In view of the above results of the CLS fibers and hydrogels, a model to describe the mechanism of the two-switch shape memory performances of the CLS fibers is proposed, as shown in Figure 7. As we known, both cellulose and chitosan exist as extended wormlike chains in alkali/urea aqueous solution15, 17 and can easily arrange in parallel to form nanofibers via strong self-aggregation force 12


Page 13 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


between molecules driven by abundant hydrogen bonds.18, 40, 48 Thus, the CLS fiber consisted of cellulose and chitosan nanofibers, which tangled and arranged to form fibers, supported by the results of Figure 3 and 5c. According to the net-point/switch model, the elastic recovery force from physical/chemical net-points and intermolecular forces from attractive and/or covalent bonds as switch are in necessity in a shape memory materials.59 As shown in Figure 7a, the existence of tangle and strong self-aggregation force played a role of net-points in the fiber. To discuss the “switch” of the shape memory fibers under water and acid stimulations, three states (dry, wet, acid) models of the CLS fibers were built. In the dry state of the fiber, hydrogen bonds formed between the nanofibers (Figure 7b). Meanwhile, the hydrogen bonds will be partly destroyed by the interactions of the infiltrated water molecules in the wet state of the fiber,60 leading to light swelling of the fibers (Figure 7c), supported by the results of Figure 6d, e and f. Moreover, the hydrogen bonds can be easily reformed by removing the water under dry, similar to the dry process during the spinning (Figure 2b). The destroy and reform of the hydrogen bonds between the wet and dry state of the fiber serve as the switch of water-induce shape memory behavior, supported by the result of Figure 4a. On the basis of the strong self-aggregation force between cellulose and chitosan chains/bundle of the nanofibers and the unique amino group of chitosan, the nanofibers in the fibers was unsteady in acid solution. The hydrogen ion can infiltrate in the nanofibers and ionize the amino group of chitosan chain, leading to partly disassembly of the nanofibers in the fibers (Figure 7d). This made the sharp decrease of the tensile strength, Young’s modulus and the great swelling of the fibers that further proved the drive force of shape memory behavior,31, 58, 61 supported by the results of Figure 6e and f. Similarly, the nanofibers can be restructured by neutralizing in alkali solution, similar to the regeneration of fiber during the spinning.18 The disassembly and restructure of the hydrogen bonds between the acid and wet state of the fiber serve as the switch of acid-induce shape memory behavior, also supported by 13



Page 14 of 31

the result of Figure 4a. On the basis of the two-switch shape memory performance, we can design an ideal new programmable material for the expanded application of various fabrics. For example, after immerging in acid solution, fabrics can be given desired shape and pattern by neutralizing the acid and drying. This work proved a unique strategy for processing fabrics. The two-switch shape memory behavior mechanism reported here offers a universal and simple strategy for designing and fabricating high performance fibers suited for developing actuator, wrinkle-free fabrics and biomaterials.62, 63

CONCLUSION In summary, the stability of the cellulose/chitosan solution in LiOH/KOH/urea aqueous system was improved by adjusting the KOH concentration to 7.5 wt%. From the cellulose/chitosan aqueous solution, a functional fiber was spun on a lab-scale spinning machine through a simple and environmentally benign approach. By the combination of good miscibility between the two components and their nanofibers self-assembly driven by self-aggregation force through hydrogen bond interactions, the cellulose/chitosan composite fibers exhibited excellent mechanical properties. Moreover, the composite fiber showed a two-switch shape memory behavior under water and acid stimulations, By changing the external stimulation, the strong self-aggregation force between cellulose and chitosan could be destroyed partly and then restructured to fix and recover, resulting in a designed shape. This work provide a new method for fabricating functional fiber in industry.

ASSOCIATED CONTENT Supporting Information Supporting Information is available free of charge on the ACS Publications website at DOI: Photograph of the stability of the cellulose and chitosan solution; Temperature dependence of the 14


Page 15 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


storage modulus G′ and loss modulus G″ for cellulose and chitosan alkali solution with different urea concentrations; XRD spectra of cotton linter pulp and chitosan powders; thermogravimetric plot for cellulose, chitosan and CLS hydrogels; orientation parameter, and mechanical properties of the CLS fibers (PDF) Video of the recovery process exposed upon water stimulation (MP4)

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (L. Zhang) *E-mail: [email protected] (J. Hu) ORCID Lina Zhang: 0000-0003-3890-8690 Jinlian Hu: 0000-0001-7084-8048 Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work was supported by the Major Program of National Natural Science Foundation of China (21334005), the Major International (Regional) Joint Research Project (21620102004), Funds for International Cooperation and Exchange of the National Natural Science Foundation of China (21811530006), and the National Natural Science Foundation of China (51373147).

REFERENCES 15



Page 16 of 31

(1) World Trade Organization, I. T. S., Geneva, 2015. (2) The Role of Technology and Innovation in Inclusive and Sustainable Industrial Development, I. D. R., United Nations Industrial Development Organization, Vienna, 2015. (3) MacArthur,

E.

Beyond

Plastic

Waste.

Science

2017,

358,

843-843

DOI:

10.1126/science.aao6749. (4) Zhu, Y.; Romain, C.; Williams, C. K. Sustainable Polymers from Renewable Resources. Nature 2016, 540, 354-362 DOI: 10.1038/nature21001. (5) Munhoz, D. R.; Moreira, F. K. V.; Bresolin, J. D.; Bernardo, M. P.; De Sousa, C. P.; Mattoso, L. H. C. Sustainable Production and In vitro Biodegradability of Edible Films from Yellow Passion Fruit Coproducts via Continuous Casting. ACS Sustainable Chem. Eng. 2018, 6, 9883-9892 DOI: 10.1021/acssuschemeng.8b01101. (6) Chandra, S.; Karak, N. Environmentally Friendly Polyurethane Dispersion Derived from Dimer Acid

and

Citric

Acid.

ACS

Sustainable

Chem.

Eng.

2018,

6,

16412-16423

DOI:

10.1021/acssuschemeng.8b03474. (7) Duan, B.; Huang, Y.; Lu, A.; Zhang, L. Recent Advances in Chitin Based Materials Constructed via Physical Methods. Prog. Polym. Sci. 2018, 82, 1-33 DOI: 10.1016/j.progpolymsci.2018.04.001. (8) Wan, J.; Zhang, J.; Yu, J.; Zhang, J. Cellulose Aerogel Membranes with a Tunable Nanoporous Network as a Matrix of Gel Polymer Electrolytes for Safer Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 24591-24599 DOI: 10.1021/acsami.7b06271. (9) Shahid ul, I.; Sun, G. Thermodynamics, Kinetics, and Multifunctional Finishing of Textile Materials with Colorants Extracted from Natural Renewable Sources. ACS Sustainable Chem. Eng. 2017, 5, 7451-7466 DOI: 10.1021/acssuschemeng.7b01486. (10)Wu, H.-C.; Quan, D. N.; Tsao, C.-Y.; Liu, Y.; Terrell, J. L.; Luo, X.; Yang, J.-C.; Payne, G. F.; 16


Page 17 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Bentley, W. E. Conferring Biological Activity to Native Spider Silk: A Biofunctionalized Proteinbased Microfiber. Biotechnol. Bioeng. 2017, 114, 83-95 DOI: 10.1002/bit.26065. (11)Chen, Z.; Zhang, J.; Xiao, P.; Tian, W.; Zhang, J. Novel Thermoplastic Cellulose Esters Containing Bulky Moieties and Soft Segments. ACS Sustainable Chem. Eng. 2018, 6, 4931-4939 DOI: 10.1021/acssuschemeng.7b04466. (12)Beer, E. J. The Birth of Viscose Rayon. Transactions of the Newcomen Society 1962, 35, 109116. DOI: org/10.1179/tns.1962.007. (13)Woodings, C. Regenerated Cellulose Fibres. Woodhead Publishing, Cambridge, England, 2001. (14)Zhang,

H.;

Wang,

Z.;

Zhang,

Z.;

Wu,

J.;

Zhang,

J.;

He,

J.

Regenerated‐Cellulose/Multiwalled‐Carbon‐Nanotube Composite Fibers with Enhanced Mechanical Properties Prepared with the Ionic Liquid 1‐Allyl‐3‐methylimidazolium Chloride. Adv. Mater. 2007, 19, 698-704 DOI: org/10.1002/adma.200600442. (15)Cai, J.; Zhang, L.; Liu, S.; Liu, Y.; Xu, X.; Chen, X.; Chu, B.; Guo, X.; Xu, J.; Cheng, H. Dynamic Self-assembly Induced Rapid Dissolution of Cellulose at Low Temperatures. Macromolecules 2008, 41, 9345-9351 DOI: 10.1021/ma801110g. (16)Fang, Y.; Duan, B.; Lu, A.; Liu, M.; Liu, H.; Xu, X.; Zhang, L. Intermolecular Interaction and the Extended Wormlike Chain Conformation of Chitin in NaOH/Urea Aqueous Solution. Biomacromolecules 2015, 16, 1410-1417 DOI: 10.1021/acs.biomac.5b00195. (17)Duan, J.; Liang, X.; Cao, Y.; Wang, S.; Zhang, L. High Strength Chitosan Hydrogels with Biocompatibility

via

New

Avenue

Based

on

Constructing

Nanofibrous

Architecture.

Macromolecules 2015, 48, 2706-2714 DOI: 10.1021/acs.macromol.5b00117. (18)Zhu, K.; Qiu, C.; Lu, A.; Luo, L.; Guo, J.; Cong, H.; Chen, F.; Liu, X.; Zhang, X.; Wang, H.; Cai, J.; Fu, Q.; Zhang, L. Mechanically Strong Multifilament Fibers Spun from Cellulose Solution 17



Page 18 of 31

via Inducing Formation of Nanofibers. ACS Sustainable Chem. Eng. 2018, 6, 5314-5321 DOI: 10.1021/acssuschemeng.8b00039. (19)Son, E.-B.; Poo, K.-M.; Mohamed, H. O.; Choi, Y.-J.; Cho, W.-C.; Chae, K.-J. A Novel Approach to Developing a Reusable Marine Macro-algae Adsorbent with Chitosan and Ferric Oxide for Simultaneous Efficient Heavy Metal Removal and Easy Magnetic Separation. Bioresour. Technol. 2018, 259, 381-387 DOI: org/10.1016/j.biortech.2018.03.077. (20)Xing, K.; Zhu, X.; Peng, X.; Qin, S. Chitosan Antimicrobial and Eliciting Properties for Pest Control in Agriculture: A Review. Agron. Sustainable Dev. 2015, 35, 569-588 DOI: 10.1007/s13593014-0252-3. (21)Farrugia, B. L.; Mi, Y.; Kim, H. N.; Whitelock, J. M.; Baker, S. M.; Wiesmann, W. P.; Li, Z.; Maitz, P.; Lord, M. S. Chitosan-Based Heparan Sulfate Mimetics Promote Epidermal Formation in a Human

Organotypic

Skin

Model.

Adv.

Funct.

Mater.

2018,

28,

1802818

DOI:

10.1002/adfm.201802818. (22)Cui, X.; Guan, X.; Zhong, S.; Chen, J.; Zhu, H.; Li, Z.; Xu, F.; Chen, P.; Wang, H. Multi-Stimuli Responsive Smart Chitosan-Based Microcapsules for Targeted Drug Delivery and Triggered Drug Release. Ultrason. Sonochem. 2017, 38, 145-153 DOI: org/10.1016/j.ultsonch.2017.03.011. (23)He, M.; Chen, H.; Zhang, X.; Wang, C.; Xu, C.; Xue, Y.; Wang, J.; Zhou, P.; Zhao, Q. Construction of Novel Cellulose/Chitosan Composite Hydrogels and Flms and Their Applications. Cellulose 2018, 25, 1987-1996 DOI: 10.1007/s10570-018-1683-9. (24)Luo, X. G.; Zeng, J.; Liu, S. L.; Zhang, L. N. An Effective and Recyclable Adsorbent for the Removal of Heavy Metal Ions from Aqueous System: Magnetic Chitosan/Cellulose Microspheres. Bioresour. Technol. 2015, 194, 403-406 DOI: 10.1016/j.biortech.2015.07.044. (25)Zheng, T.; Wu, J.; Xiao, D.; Zhu, J. Recent Development in Lead-Free Perovskite Piezoelectric 18


Page 19 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Bulk Materials. Prog. Mater Sci. 2018, 98, 552-624 DOI: org/10.1016/j.pmatsci.2018.06.002. (26)Zhang, Q.; Liu, L.; Pan, C.; Li, D. Review of Recent Achievements in Self-Healing Conductive Materials and Their Applications. J. Mater. Sci. 2018, 53, 27-46 DOI: 10.1007/s10853-017-1388-8. (27)Yanju, L.; Haiyang, D.; Liwu, L.; Jinsong, L. Shape Memory Polymers and Their Composites in Aerospace Applications: A Review. Smart Mater. Struct. 2014, 23, 023001. (28)Lendlein, A. Fabrication of Reprogrammable Shape-Memory Polymer Actuators for Robotics. Sci. Rob. 2018, 3, eaat9090 DOI: 10.1126/scirobotics.aat9090. (29)Fang, Z.; Zheng, N.; Zhao, Q.; Xie, T. Healable, Reconfigurable, Reprocessable Thermoset Shape Memory Polymer with Highly Tunable Topological Rearrangement Kinetics. ACS Appl. Mater. Interfaces 2017, 9, 22077-22082 DOI: 10.1021/acsami.7b05713. (30)Tan, L.; Hu, J.; Ying Rena, K.; Zhu, Y.; Liu, P. Quick Water-Responsive Shape Memory Hybrids with Cellulose Nanofibers. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 767-775 DOI: 10.1002/pola.28429. (31)Zhang, Y.; Liao, J.; Wang, T.; Sun, W.; Tong, Z. Polyampholyte Hydrogels with pH Modulated Shape Memory and Spontaneous Actuation. Adv. Funct. Mater. 2018, 28, 1707245 DOI: 10.1002/adfm.201707245. (32)Wang, W.; Shen, D.; Li, X.; Yao, Y.; Lin, J.; Wang, A.; Yu, J.; Wang, Z. L.; Hong, S. W.; Lin, Z.; Lin, S. Light-Driven Shape-Memory Porous Films with Precisely Controlled Dimensions. Angew. Chem. Int. Ed. 2018, 57, 2139-2143 DOI: 10.1002/anie.201712100. (33)Gao, H.; Li, J.; Xie, F.; Liu, Y.; Leng, J. A Novel Low Colored and Transparent Shape Memory Copolyimide and Its Durability in Space Thermal Cycling Environments. Polymer 2018, 156, 121127 DOI: org/10.1016/j.polymer.2018.10.001. (34)Guo, J.; Wang, Z.; Tong, L.; Lv, H.; Liang, W. Shape Memory and Thermo-Mechanical 19



Page 20 of 31

Properties of Shape Memory Polymer/Carbon Fiber Composites. Compos. Part A: Appl. S. 2015, 76, 162-171 DOI: org/10.1016/j.compositesa.2015.05.026. (35)Zhang, Y.; Gao, H.; Wang, H.; Xu, Z.; Chen, X.; Liu, B.; Shi, Y.; Lu, Y.; Wen, L.; Li, Y.; Li, Z.; Men, Y.; Feng, X.; Liu, W. Radiopaque Highly Stiff and Tough Shape Memory Hydrogel Microcoils for Permanent Embolization of Arteries. Adv. Funct. Mater. 2018, 28, 1705962 DOI: 10.1002/adfm.201705962. (36)Xie, R.; Hu, J.; Hoffmann, O.; Zhang, Y.; Ng, F.; Qin, T.; Guo, X. Self-Fitting Shape Memory Polymer Foam Inducing Bone Regeneration: A Rabbit Femoral Defect Study. BBA-Gen. Subjects 2018, 1862, 936-945 DOI: org/10.1016/j.bbagen.2018.01.013. (37)Xiang, Z.; Zhang, L.; Yuan, T.; Li, Y.; Sun, J. Healability Demonstrates Enhanced ShapeRecovery of Graphene-Oxide-Reinforced Shape-Memory Polymeric Films. ACS Appl. Mater. Interfaces 2018, 10, 2897-2906 DOI: 10.1021/acsami.7b14588. (38)Bai, Y.; Zhang, J.; Chen, X. A Thermal-, Water-, and Near-Infrared Light-Induced Shape Memory Composite Based on Polyvinyl Alcohol and Polyaniline Fibers. ACS Appl. Mater. Interfaces 2018, 10, 14017-14025 DOI: 10.1021/acsami.8b01425. (39)Meng, Q.; Hu, J. A Temperature-Regulating Fiber Made of PEG-Based Smart Copolymer. Sol. Energy Mater. Sol. Cells 2008, 92, 1245-1252 DOI: org/10.1016/j.solmat.2008.04.027. (40)Zhu, K.; Duan, J.; Guo, J.; Wu, S.; Lu, A.; Zhang, L. High-Strength Films Consisted of Oriented Chitosan Nanofibers for Guiding Cell Growth. Biomacromolecules 2017, 18, 3904-3912 DOI: 10.1021/acs.biomac.7b00936. (41)Duan, J.; Xichao, L.; Kunkun, Z.; jinhua, G.; Lina, Z. Bilayer Hydrogel Actuators with Tight Interfacial Adhesion Fully Constructed from Natural Polysaccharides. Soft Matter 2017, 13, 345-354 DOI: 10.1039/C6SM02089E. 20


Page 21 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(42)Yang, Q.; Qi, H.; Lue, A.; Hu, K.; Cheng, G.; Zhang, L. Role of Sodium Zincate on Cellulose Dissolution in NaOH/Urea Aqueous Solution at Low Temperature. Carbohydr. Polym. 2011, 83, 1185-1191 DOI: org/10.1016/j.carbpol.2010.09.020. (43)Liang, X.; Duan, J.; Xu, Q.; Wei, X.; Lu, A.; Zhang, L. Ampholytic Microspheres Constructed from Chitosan and Carrageenan in Alkali/Urea Aqueous Solution for Purification of Various Wastewater. Chem. Eng. J. 2017, 317, 766-776 DOI: org/10.1016/j.cej.2017.02.089. (44)Denis, I.; Frank, H.; Karl, B.; Franz, E. Novel Cellulose/Polymer Blend Fibers Obtained Using Ionic Liquids. Macromol. Mater. Eng. 2012, 297, 585-594 DOI: org/10.1002/mame.201100432. (45)Kreze, T.; Malej, S. Structural Characteristics of New and Conventional Regenerated Cellulosic Fibers. Text. Res. J. 2003, 73, 675-684 DOI: 10.1177/004051750307300804. (46)Fink, H.-P.; Weigel, P.; Purz, H.; Ganster, J. Structure Formation of Regenerated Cellulose Materials from NMMO-Solutions. Prog. Polym. Sci. 2001, 26, 1473-1524 DOI: 10.1016/S00796700(01)00025-9. (47)Qiu, C.; Zhu, K.; Zhou, X.; Luo, L.; Zeng, J.; Huang, R.; Lu, A.; Liu, X.; Chen, F.; Zhang, L.; Fu, Q. Influences of Coagulation Conditions on the Structure and Properties of Regenerated Cellulose Filaments via Wet-Spinning in LiOH/Urea Solvent. ACS Sustainable Chem. Eng. 2018, 6, 4056-4067 DOI: 10.1021/acssuschemeng.7b04429. (48)Ye, D.; Yang, P.; Lei, X.; Zhang, D.; Li, L.; Chang, C.; Sun, P.; Zhang, L. Robust Anisotropic Cellulose Hydrogels Fabricated via Strong Self-aggregation Forces for Cardiomyocytes Unidirectional Growth. Chem. Mater. 2018, 30, 5175-5183 DOI: 10.1021/acs.chemmater.8b01799. (49)Xiao, X. L.; Hu, J. L. Animal Hairs as Water-Stimulated Shape Memory Materials: Mechanism and Structural Networks in Molecular Assemblies. Sci. Rep. 2016, 6, 26393 DOI: 10.1038/srep26393. (50)Chen, X.; Burger, C.; Wan, F.; Zhang, J.; Rong, L.; Hsiao, B. S.; Chu, B.; Cai, J.; Zhang, L. 21



Page 22 of 31

Structure Study of Cellulose Fibers Wet-Spun from Environmentally Friendly NaOH/Urea Aqueous Solutions. Biomacromolecules 2007, 8, 1918-1926 DOI: 10.1021/bm061186i. (51)Tang, H.; Butchosa, N.; Bulone, V.; Zhou, Q. Transparent, Hazy and Strong Macroscopic Ribbon of Oriented Cellulose Nanofibrils Bearing Poly (Ethylene Glycol). Adv. Mater. 2015, 27, 2070-2076 DOI: org/10.1002/adma.201404565 (52)Lundahl, M. J.; Klar, V.; Ajdary, R.; Norberg, N.; Ago, M.; Cunha, A. G.; Rojas, O. J. Absorbent Filaments from Cellulose Nanofibril Hydrogels through Continuous Coaxial Wet Spinning. ACS Appl. Mater. Interfaces 2018, 10, 27287-27296 DOI: 10.1021/acsami.8b08153. (53)Cai, J.; Zhang, L.; Zhou, J.; Qi, H.; Chen, H.; Kondo, T.; Chen, X.; Chu, B. Multifilament Fibers Based on Dissolution of Cellulose in NaOH/Urea Aqueous Solution: Structure and Properties. Adv. Mater. 2007, 19, 821-825 DOI: org/10.1002/adma.200601521. (54)Xu, D.-f.; Cai, J.; Zhang, L.-n. High Strength Cellulose Composite Films Reinforced with Clay for Applications as Antibacterial Materials. Chin. J. Polym. Sci. 2016, 34, 1281-1289. DOI: org/10.1007/s10118-016-1840-2 (55)Lin, S.; Chen, L.; Huang, L.; Cao, S.; Luo, X.; Liu, K. Novel Antimicrobial Chitosan–Cellulose Composite Films Bioconjugated with Silver Nanoparticles. Ind. Crops Prod. 2015, 70, 395-403 DOI: org/10.1016/j.indcrop.2015.03.040. (56)Stefanescu, C.; Daly, W. H.; Negulescu, I. I. Biocomposite Films Prepared from Ionic Liquid Solutions

of

Chitosan

and

Cellulose.

Carbohydr.

Polym.

2012,

87,

435-443

DOI:

org/10.1016/j.carbpol.2011.08.003. (57)Du, H.; Zhang, J. Solvent Induced Shape Recovery of Shape Memory Polymer Based on Chemically

Cross-linked

Poly(vinyl

alcohol).

Soft

Matter

10.1039/B922220K. 22


2010,

6,

3370-3376

DOI:

Page 23 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(58)Hu, X.; Zhang, D.; Sheiko, S. S. Cooling‐Triggered Shapeshifting Hydrogels with Multi‐Shape Memory Performance. Adv. Mater. 2018, 1707461 DOI: org/10.1002/adma.201707461. (59)Xiao, X.; Hu, J.; Gui, X.; Qian, K. Shape Memory Investigation of α-Keratin Fibers as MultiCoupled Stimuli of Responsive Smart Materials. Polymers 2017, 9, 87 DOI: 10.3390/polym9030087. (60)Hu, J.; Wu, Y.; Zhang, C.; Tang, B. Z.; Chen, S. Self-adaptive water vapor permeability and its hydrogen bonding switches of bio-inspired polymer thin films. Materials Chemistry Frontiers 2017, 1, 2027-2030 DOI: 10.1039/C7QM00170C. (61)Wan, H.; Li, X.; Zhang, L.; Li, X.; Liu, P.; Jiang, Z.; Yu, Z.-Z. Rapidly Responsive and Flexible Chiral Nematic Cellulose Nanocrystal Composites as Multifunctional Rewritable Photonic Papers with

Eco-Friendly

Inks.

ACS

Appl.

Mater.

Interfaces

2018,

10,

5918-5925

DOI:

10.1021/acsami.7b19375. (62)Weng, M.; Zhou, P.; Chen, L.; Zhang, L.; Zhang, W.; Huang, Z.; Liu, C.; Fan, S. Multiresponsive Bidirectional Bending Actuators Fabricated by a Pencil‐on‐Paper Method. Adv. Funct. Mater. 2016, 26, 7244-7253 DOI: org/10.1002/adfm.201602772. (63)Jinlian, H.; Harper, M.; Guoqiang, L.; Samuel, I. I. A review of stimuli-responsive polymers for smart textile applications. Smart Mater. Struct. 2012, 21, 053001.

23



Page 24 of 31

Figure 1. Stability of the CLS solution with different KOH concentrations. (a) The CLS solution with 3.5 wt% KOH gelled after heating at 37 oC for 5 h. (b) Temperature dependences of the storage modulus G′ and loss modulus G″ for CLS solutions with different KOH concentrations. (c) The CLS solution with 7.5 wt% KOH showed good fluidity after heating at 37 oC for 16 h.

24


Page 25 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Photographs and mechanical properties of the CLS fibers. (a) The heating roll and heating process in the wet-spinning process. (b) When the fiber gel dried on the surface of heating roll, water went out from the fiber gel, the dense packing constructed from cellulose and chitosan macromolecules formed in the dry fiber, and the bent shape kept by strong self-aggregation force through their abundant hydrogen bonds. (c) Photograph of the CLS fibers. (d) Stress-strain curves of the CLS fibers in the wet and dry state.

25



Page 26 of 31

Figure 3. SEM images of the CLS fibers. (a, e, i) Bundles of filaments, (b, f, j) the surface, (c, g, k) the cross section and (d, h, l) high-magnification SEM images of (a-d) CLS-1.0, (e-h) CLS-1.3 and (i-l) CLS-1.6.

26


Page 27 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. Shape memory behaviors of the CLS fibers. (a) Photographs of the CLS fibers with twoswitch shape memory behavior: top) water induced process, middle) acid induced process, and bottom) water and acid induced two-switch process. Fix. and Rec. are abbreviations of fixing and recovery, respectively. The dry fiber, wet fiber and acid soaked fiber were coded here as dry state, wet state and acid state, respectively. (b) Fixing ratio (Rf) and (c) shape recovery ratio (Rr) of the CLS fibers during the water and acid induced process. (d) Photographs of water induced the recovery of the folded CLS fiber at different times. (e) The shape recovery ratio over time during the water induced process. 27



Page 28 of 31

Figure 5. Effects of drawing process on the structure of the CLS fibers. (a-c) SEM images of the inner structure, (d-f) WAXD patterns and (g-i) SAXS patterns of (left) CLS-1.0, (middle) CLS-1.3 and (right) CLS-1.6. The fibers were epoxy-resin-embedded, sliced along the fiber axis by microtome, and then observed by SEM, scale bar: 200 nm. Azimuthal intensity distribution of the strongest equatorial reflection from the WAXD patterns are shown in the inset.

28


Page 29 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. Structural characterization of the CLS fibers. (a) XRD spectra of the RCL, CLS and RCS hydrogels, (b) the first derivative weight loss (DTG) curves, (c) XPS peak fitting curves, (d) FTIR spectra and (e) stress-strain curves of the CLS fibers in different states, and (f) Polarized optical micrographs of the CLS fiber in different states, optical micrographs of the cross section is presented in the inset.

29



Page 30 of 31

Figure 7. Schematic illustration of the two-switch shape memory behavior of the CLS fiber. (a) Structure schema of the CLS fiber and the hydrogen bond between cellulose and chitosan. (b) The dry state of the fiber, hydrogen bonds formed between the cellulose and chitosan nanofibers. (c) The wet state of the fiber, water partly destroyed the hydrogen bonds between nanofibers, while the nanofibers remained as strong self-aggregation force. (d) The acid state of the fiber, hydrogen ion infiltrate in and partly destroyed the nanofibers.

30


Page 31 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of content

Cellulose/chitosan multifilament fibers with outstanding mechanical properties and good shape memory performance were prepared via an environmentally friendly method.

31


Chitosan Composite Multifilament Fibers with Two-Switch

Recommend Documents