Super Strong All-Cellulose Composite Filaments by Combination of

Subscriber access provided by NAGOYA UNIV

Article

Super Strong All-Cellulose Composite Filaments by Combination of Inducing Nanofiber Formation and Adding Nanofibrillated Cellulose Cuibo Qiu, Kunkun Zhu, Weixing Yang, Yi Wang, Lina Zhang, Feng Chen, and Qiang Fu Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.8b01262 • Publication Date (Web): 28 Sep 2018 Downloaded from http://pubs.acs.org on October 1, 2018

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

Biomacromolecules

Super Strong All-Cellulose Composite Filaments by Combination of Inducing Nanofiber Formation and Adding Nanofibrillated Cellulose †

†

†

†

†

Cuibo Qiu , Kunkun Zhu‡, Weixing Yang , Yi Wang , Lina Zhang‡*, Feng Chen * and Qiang Fu *

†

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

Road, Chengdu 610065, P. R. China ‡

College of Chemistry and Molecular Sciences, Wuhan University, No. 16 Luojiashan Street, Wuhan

430072, P. R. China Corresponding author E-mail: [email protected] (Q. Fu) E-mail: [email protected] (F. Chen) E-mail: [email protected] (L. Zhang)

Abstract: In this work, super strong all-cellulose multifilaments were obtained from cellulose dissolved in LiOH/urea system by inducing nanofiber formation, and were simultaneously reinforced by the introduction of TEMPO-oxidized nanofibrillated cellulose (NFC) with mean diameter of 20nm. The all-cellulose composite filaments (CF) containing only 3 wt% NFC exhibits a high orientation that Herman's parameter is 0.89. Importantly, the NFC can simultaneously reinforce and toughen the CF, with a tensile strength and elongation at break of 3.92 cN/dT and 14.6%, respectively, which make the obtained CF to become super strong. The strengthened mechanism of CF is considered as the nanofibril-induced crystallization and orientation, which makes up for the deficits and constructs a flawless structure in the regenerated cellulose filaments. Of note, the

ACS Paragon Plus Environment

Biomacromolecules 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

stability of spinning dope was also effectively improved by adding small amount of NFC, which is very important for fiber spinning on industry. This finding contributes to the preparation of high performance regenerated cellulose multifilaments by a simple, energy-efficient, and eco-friendly route.

Keywords: wet spinning, nanofibrillated cellulose (NFC), composite filaments, orientation, super strong all-cellulose multifilaments

Introduction With the arising of environmental pollution and resource depletion, wide attention has been attracted to environmentally friendly and sustainable materials.1 Cellulose, as the most luxuriant and renewability natural resource on earth,2 shows noticeable characteristics, including high hydrophilicity, biodegradability and wide availability, which points the way to develop sustainable materials in advanced field.3, 4 However, due to the highly ordered aggregate structure and extensive hydrogen bonding network, cellulose can’t be melted and dissolved in commonly used organic solvents. Alkali/urea aqueous solution dissolving cellulose at −12 °C is a completely novel and green way, so it is widely concerned by researchers in the neotype regenerated cellulose multifilament fibers.5-7 However, the metastability of spinning dope makes it difficult to prepare a high concentration of cellulose solution, thus to achieve their extraordinary mechanical properties still remains a challenge. In other words, the urgent issue need solving for expanding applications of cellulose filaments regenerated from alkali/urea solution is to improve their mechanical properties.8


Page 2 of 31

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

Biomacromolecules

Recently, cellulose nanofibers were expected to break the bottleneck of traditional materials and open up the new class of nature-derived nanomaterials thanks to its remarkable strength (6–7 GPa) and extraordinary modulus (120–140 GPa), transcending those of carbon and Kevlar filaments.9-12 Besides, nanofibers have high aspect ratio, low density and highly crystalline, especially the hydroxyl groups that furnish abundent chemical and physical reactive sites. Therefore, nanofibers were extensively applied in biosensor, biofilter, intelligent electronics, and optics.13-17 Based on this, various strategies have been used to obtain strong cellulose macrofibers from nanofibers,18-20 particularly, Hu et al. reported that bacterial cellulose nanofibers were successfully transformed from nanoscale to a super-strong and super-stiff macrofibers.10 However, the sophisticated process of preparing for ultralong bacterial cellulose nanofibers and only 2% in strain would impede its industrial application in some fields. In previous work,21, 22 it was found that there were inclusion complexs, consisted with single cellulose chains surrounding by NaOH hydrate and urea hydrate, as well as their aggregates co-exist in the cellulose dissolved in alkali/urea solution. Based on this, largely enhanced intensity of cellulose multifilaments was achieved via an efficient and green approach for directly constructing nanofibrous structure from alkali/urea aqueous solution in mild coagulation condition. The novel regenerated cellulose filaments with dense nanofibers formed by naked cellulose molecules exhibited excellent mechanical properties with a tensile strength of 3.43 cN/dtex and breaking elongation of 10.6%,23,

24

which is near to that of filaments from ionic liquid solution(3.68±0.22 cN/dtex),25

breaking a new ground in the traditional textile field. They are indeed strong but not super strong, thus applications in some advanced fields are still limited. Additionally, the poor solution stability of cellulose in LiOH-urea system is still an obstacle and need to be considered, particularly, for



industrial manufacture. Herein, we report a high-efficiency method to synchronously improve solution stability and filaments mechanical properties, make it become super strong (named super fiber that strength above 3.5 cN/dtex in textile industy26). Compared to previous work, in this study, a small amount of TEMPO-oxidized nanofibrillated cellulose (NFC) is added to the cellulose solution at ambient temperature and embedded in regenerated cellulose filaments via wet spinning. NFC is added for three reasons: (1) NFC is beneficial to improve the stability of the spinning dope by the means of both electrostatic repulsion and amphipathy.27,28 (2) NFC themselves are super strong and stiff thus can strengthen composite filaments.11 (3) NFC can be easily arranged in parallel under external forces and then induce orientation of cellulose molecular chains dissolved in LiOH/urea. Additionally, new hydrogen bonds could be formed by carboxyl groups on NFC with the hydroxyl groups supplied by the regenerated cellulose molecules, contributing to crystallization.29 That is, NFC is very helpful for the formation of high orientation and flawless multi-filaments. On the basis of the above, we prepared spinning dope with proper amount of NFC and solidified it in 15 wt% phytic acid/5 wt% phytic acid lithium at 5 °C then stretched it in deionized water at 60 °C, to obtain high-performance regenerated cellulose multifilaments. Because the matrix and reinforcing phase are cellulose, the similar nature facilitates the interfacial interaction, which makes nanocomposite multifilaments be fully biocompatible and biodegradable, combined with high strength and high toughness.30, 31 This finding provides strong evidence that the enhancement of nanofibers structure in novel regenerated cellulose multi-filaments, which lays the foundation of building blocks for future multifunctional textiles.


Page 4 of 31

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

Biomacromolecules

Experimental Section Materials. The macrofibrillated cellulose (Celish MFC KY100-S) and experimental drug 2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO, 98 wt%) including Sodium hypochlorite (NaClO), Lithium hydroxide (LiOH) as well as urea were purchased. The viscosity-average molecular weight (MZ ) of the cotton linter pulp (α-cellulose content ≥95%) was 7.1×10 4g·mol

-1

(degree of polymerization,

DP=460). Preparation of NFC. According to the previous literature,32 the microfibrillated cellulose (MFC, 4g) was suspended in water (1000 mL) via severe stirring. Firstly, TEMPO (0.08g) and sodium bromide (0.5g) were feed to the suspension. Secondly, 0.1 mol/L HCl was used to adjust the pH of 12 wt% NaClO solution to 10. The mixture continued to be stirred for 6h at 25 °C and the pH was maintained at 10 by dropwise adding 0.5 mol/L NaOH. Finally, the TEMPO-oxidized cellulose was thoroughly washed with deionized water by suction filtration and centrifuged to remove unoxidized MFC. The charge density (carboxylic acid content) of the NFC is 1.20 mmol/g.33 Preparation of Composite Multi-filaments. After the preparation of NFC, quantitative LiOH, urea and distilled water were mixed to prepare the cellulose solvent.34 A suitable cellulose cotton pulp was weighed and completely immersed into 500ml solvent precooled to −12 °C. Nextly, the mixed solution was vigorously stirred to accelerate the dissolution of cellulose to obtain a transparent cellulose solution. Then 0−210g of alkali aqueous NFC suspension (solid content, 1%) was added into the dissolved cellulose solution and stirred for 10 min at room temperature. In order to remove clutter and air bubbles, the spinning dope was centrifuged via 8000 r/min at 10 °C. Finally, moderate spinning dope was squeezed out from spinneret cylinder at a constant rate under the control of electric pump and immersed directly into the first coagulation basin (15 wt% phytic acid mixed with



5 wt% salt) where LiOH was consumed through the neutralization with the hydrogen ions from acid, resulting in gelation fibers. The nascent fibers were immediately towed into the 60 °C deionized water, in which the salt produced by the neutralization reaction and redundant acid could be removed thus to effective stretching. After plasticizing and stretching, the filaments were washed out, dried and wound on a spool to obtain composite filaments (CFs). The terse process of composite filaments is shown in Figure 1. With an increase of NFC, CFs were coded as CF-0, CF-1, CF-3, CF-5 and CF-7 (0,1,3,5,7 represents the mass ratio of NFC to all cellulose in the spinning dope), respectively.

Figure 1. Preparation schematic of cellulose nanocomposite filaments.

Characterization. The morphology of dissolved cellulose as well as TEMPO-oxidized NFC was observed by a transmission electron microscope (TEM, Tecnai G2 F20). Firstly, diluted cellulose solution and NFC aqueous were dropped onto a copper grid to prepare the samples. After natural drying, the TEM test was performed on an acceleration voltage 200 KV. Ultima IV diffractometer (Rigaku, Japan) was used to determinate the crystallographic form of the nanocomposite multifilaments. The scanning rate and region were 2°/min and 2θ from 5° to 50°,


Page 6 of 31

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

Biomacromolecules

severally. Depending on the XRD patterns, crystal regions (Sc) and amorphous regions (Sa) can be calculated by peak splitting software MDI Jade 6. And then the specific value of crystallinity (χc) can be obtained by the following formula:

χc =

Sc × 100% Sc + Sa

(1)

FTIR test was conducted on a Nicolet FTIR 6700 spectrometer (Thermo Electron Co., USA) at room temperature. The data of dry samples was collected from 4000 to 400 cm−1 with a resolution of 4 cm−1 under reflection mode. The rheological behavior and stability of the mixed cellulose solution were characterized on Haake rheometer (RV20/CVN, M10, Germany). Tablet mode was used to determinate the gel points of mixing dope. The diameter of the parallel plate was 40mm and the heating rate was 2 oC/min. While the viscosity was measured through the cylinder model under a constant shear rate of 20 s-1 and the solution was maintained for 20min at 35 °C. Scanning electron microscopy was performed on a NOVA NANOSEM 450 microscope to observe the cross-section morphological features of filaments and the prepared dried filament samples at an accelerating voltage of 5 kV. The determination of moisture content and thermal decomposition temperature was achieved on a Q500 analyzer (TA Instruments). Around 4mg of nanocomposites specimen was used for each analysis at a heating rate of 10 °C/min under a constant nitrogen flow rate. In order to obtain the two-dimensional wide-angle X-ray diffraction (2D-WAXD) patterns, a Bruker D8 Discover X-ray diffractometer was used. Straight specimens of fiber fasciculus were perpendicularly placed to the beam and the radiation passed vertically through the sample. The crystal orientation of fibers was quantified on the basis of Herman’s orientation parameter (f), which



Page 8 of 31

symbolises the degree of parallelism to the axial direction of the fibril and f ranges from 0 to 1. It can be calculated from the following equations:24 f =

= 2

∫

3 − 1 2

(2)

π

2 0

I ( ϕ ) si n ϕ cos2 ϕd ϕ

∫

π

2 0

(3)

I ( ϕ ) si n ϕd ϕ

Where φ is the azimuthal angle defined as zero at the meridian and I is the corresponding integral intensity. To thoroughly investigate the microstructure of CFs, two-dimensional small angle X-ray scattering (2D SAXS) patterns were obtained from the GeniX 3D beam delivery system. The test sample was a small bundle of dried stretched fibers with polyimide tape. During the testing process, a HI-STAR detector was used and the image acquisition time was 45 s. The mechanical properties of CFs were tested on a LLY-06 electronic monofilament strength tester (Textile Instruments Laizhou co., LTD., China). The test condition was with reference to the standard of GB/T 6505-2008 with a humidity of 65% as well as a temperature of 23°C. For each prototype, dtex was used to represent the thickness of the filaments and at least 20 independent specimens were measured to ensure that σb and εb values are credible under a constant pretension.

Results and Discussion Structure and morphology of NFC. The NFC was prepared by TEMPO-mediated oxidation of MFC, in which the -CH2OH on the MFC was oxidated to -COOH. As Figure S1(a) illustrated, a strong band is exhibited at 1725cm-1 (-C=O) but the intensity of absorption peak at 3300-3500 cm-1 (-OH) appears a sharp fall in the NFC. Besides, both patterns of MFC and NFC (Figure S1 b) show


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

Biomacromolecules

same broad peaks of the cellulose I crystalline form, which proves that the crystal type doesn’ t change during the TEMPO oxidation.35, 36 TEM observation (Figure 2a) displays the typical fibrous structure, with a diameter of about 20nm and a length of several micrometers. As shown in Figure 2b, the cellulose dissolved in the LiOH/urea solution exhibits a worm-like pattern with a mean diameter of approx. 30nm. An inclusion complex (IC) associates cellulose, LiOH, urea and water and its aggregates co-exist in the cellulose dilute solution, which is consistent with that reported in literatures.37-39 When the NFC is added into the alkali/urea-cellulose solution, there are two kinds of nanofibers in the solution and they intertwine with each other (Figure 2c). This result confirms that NFC is stable in alkali/urea solution at room temperature,29 and the miscibility between NFC and cellulose is good due to the amphiphilic and electrostatic repulsion of NFC, as discussed later. The worm-like cellulose chains easily aggregate in parallel to form nanofibers, which can significantly enhance the strength of the cellulose materials.40

Figure 2. TEM images of (a) TEMPO-oxidized NFC with concentration of 0.01 mg/mL;(b) cellulose solution at 0.06 mg/mL in 4.6wt% LiOH/15 wt% urea aqueous solution and (c) mixed cellulose solution at 0.1 mg/mL.

The stability and rheological properties of the mixed solutions were determined and the results are presented in Figure 3. It is observed that all the cellulose solutions are optically transparent (Figure



3a top), after standing for 48 h at 25 °C , the color of mixed dope changes (Figure 3a bottom).This can be explained that the LiOH and urea hydrates bound on the cellulose chains are perturbed, suggesting the breaking of the junction between cellulose molecules as a result of the self-association force of cellulose.41 Interestingly, only slight yellow occurs in the cellulose solution with 3wt% NFC yet huge color variation can be seen in that with 7wt% NFC, which represents that small amount of NFC is in favor of improving the stability of cellulose in the alkali/urea. In order to further prove this inference, the temperature dependence of G’ and G” was analyzed in 5 wt% cellulose solutions with different concentration of NFC. The gelation temperature increases from 56.4 to 65.5 °C with the increase of NFC from 0 wt% to 3wt% but decreases slightly by further adding NFC (Figure 3b). This may be explained that NFC with strong electrostatic repulsion can hinder the semiflexible cellulose from gathering.28 However, superabundant NFC will self-aggregate, crippling the effect of stability. Besides, as the temperature rises, the apparent viscosity of solution declines. And the apparent viscosity decreases with the increasing content of NFC (Figure 3c). This can be ascribed to the shear-thinned effect of NFC caused by the relatively high local shear action on the polymer thin layer.42 In addition, when the NFC content is 3wt%, the hybrid solution exhibits the best stability (Figure 3d), corresponding to the change of gel points. Thus it can be concluded that a small amount of NFC can enhance the spinnability of the cellulose, which is very important for industrial application.


Page 10 of 31

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

Biomacromolecules

Figure 3. (a) Photograph of 5wt% cellulose solution with NFC different loading, from left to right is 0wt%, 1wt%, 3wt%, 5wt% and 7wt% NFC, respectively (Top) as well as photograph of solution standing for 48 h at 25 °C (Below); (b) The changes of the storage modulus G’ and loss modulus G’’ depending on temperature for mixed solution;(c) Viscosity of mixed dope depended on temperature with a shear rate of 20 s-1 and (d) the time when the viscosity of the mixed solution starts to rise with a shear rate of 20 s-1 at 30 °C.

Structure and physical properties of CFs. Here, nanaocomposite multifilaments were successfully spun from the mixed cellulose solution containing different concentration of NFC on a laboratory wet spinning machine. The surface structure of the obtained filaments was examined by SEM, as shown in Figure 4 a−c. At a low magnification, filaments exhibit smooth surface. Under a higher magnification (top right), the surface of CF-0 is still smooth, while the surfaces of CF-3 and



CF-7 filaments display slightly wrinkled. We infer that it results from the sequence difference between NFC and fiber alignment. For the purpose of more detailed information, filaments are cut along the axis to observed the internal structure. As shown in Figure 4 d−f, all the composite filaments contain nanofiber structure (the mean diameter of 20−25nm) but have different density of nanofibers in the same field of vision. Obviously, with the increasing addition of NFC, more nanofibers can be seen from the CF-0 to CF-7 cellulose filaments. Compared with CF-0, CF-3 is closely packed with significantly decreased microvoid sizes, indicating a more homogeneous and compact structure being formed (Figure 4e). However, with further increasing the NFC loading, for CF-7 (Figure 4f), some flaws appear because excessive NFC is difficult to uniformly disperse in the spinning dope. Obviously, NFC is beneficial to construct a perfect structure of CFs but requires homogeneous dispersion of NFC in the regenerated cellulose network.43

Figure 4. SEM images of the surfaces for the representativeness filaments: (a) CF-0, (b) CF-3, and (c) CF-7, as well as the inner structure of (d) CF-0, (e) CF-3, and (f) CF-7.


Page 12 of 31

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

Biomacromolecules

In order to get more information about the structure of CFs, the cross sections of representative CFs were observed. As presented in Figure 5, the form of cross profile of the cellulose filaments is nearly circular, which is discriminative to the shape of the cross section for viscose rayon, but similar to that of Lyocell and Tencel.44 At high magnification, the pure regenerated cellulose multifilaments (CF-0) shows a loose cross section with numerous micrometer-sized open pores. As the increase of NFC, the pores are significantly reduced and structure approaches to dense in filaments, as if CF-3. Uniform dispersion of NFC in the matrix leads to a homogeneous and compact structure in CF-3. In addition, NFC with mean diameter ~20nm is observed in CF-3. However, with further increasing addition of NFC (CF-7), a lot of flaws appear in the filaments. This is because the increased NFC concentration induces their aggregates thanks to the effect of extended-chain conformation and mutual association of cellulose molecule abates, resulting in more defects, echoing to the image of the fiber profile.

Figure 5. SEM images of fracture surfaces of the representativeness filaments: (a,d) CF-0, (b,e) CF-3 and (c,f) CF-7.



Figure 6 a−c show the X-ray scattering (SAXS) patterns of some CFs. The intensity distribution of equatorial streak is sharp and elongated while that of meridional streak is weak and short. For wet spinning fibers, previous studies have pointed out that the narrow equatorial stripe in the SAXS is ascribed to two possibilities: (1) the formation of a fibrillar superstructure or (2) the presence of microporous.45-47 Zhang et al. believed that the equatorial streak in SAXS is mainly caused by the microvoids in the filaments during the dual diffusion process in wet-spinning.48 Obvious elongated shape of the equatorial streak can be observed in all the SAXS patterns, confirming that the needle-shaped microholes parallelly arrange to the filaments axial direction in the CFs. Based on the Guinier plots along the equatorial direction via the analysis software Foxtrot-Academic-Edition, the radius of the microvoids (R), average microvoids’ length (l) and misorientation BΦ relative to the fiber axis can be obtained by Guinier functions.24,49 The specific value of them is presented in the Table 1, obviously, a small fluctuation is observed in R (28−35nm) and R reduces little by little with the increase of NFC and reach the minimum value when the concentration is 3 wt%. Besides, l of CFs fluctuates in the range of 115−141 nm and has the similar trend as R following the variety of NFC content. However, a reversal appears in the CF-3, CF-5, and CF-7. In other words, CF-3 has the lowest void fraction, symbolizing a tight internal structure, which echoes to the SEM images.


Page 14 of 31

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

Biomacromolecules

Figure 6. SAXS patterns of some representativeness filaments: (a) CF-0, (b) CF-3 and (c) CF-7. 2D WAXD patterns of (d) CF-0, (e) CF-3, and (e) CF-7.

What’s more, the orientation of CFs can be observed from the SAXS patterns. The stronger the equatorial streak, the higher the orientation of filaments.7 It is found that CF-3 and CF-5 have the higher orientation compared to CF-0, yet the precise figure can’t be gotten from Figure 6 a−c. Therefore, 2D-WAXD tests were recorded to measure the orientation degree of CFs. As illuminated in Figure 6 d−f, all CFs presents the cellulose II structure, which is different from the crystalline form in cellulose pulp, indicating that the crystalline form of cellulose has changed during the process of regeneration.50 It's worth noting that the crystalline form of NFC is cellulose I but it can’t be obviously observed from the 2D-WAXD patterns due to the amount of NFC being bare. Besides, the appearance of broad arcs indicates an oriented structure in CFs. It is obvious that the range of arcs is related to the NFC concentration. The reflection of WAXD pattern in the CF-3 exhibits narrow equatorial arcs (Figure 6e), indicating a highest crystal orientation in this case. Compared with CF-0 (weak arcs), the addition of NFC leads to higher degree of orientation. However, CF-7



shows broad arcs, suggesting that too much NFC is not conducive to induce crystal orientation. Moreover, the degree of orientation (Π) and Hermans’ orientation divisor (f) by integrating the (020) crystal are also listed in Table 1. The value of Hermans orientation parameters (f) for CF-0 is 0.76, which is lower than those of CFs. This is probably due to the lack of NFC that is easy to parallel arrangement, which confirms the notion that NFC (0.89 for CF-3) results in a higher crystal orientation. The results of 2D-WAXD are consistent with SAXS as well as SEM results. The X-ray diffraction patterns of the CFs are presented in Figure S2 (a). The diffraction peaks at 2θ =12.2°, 20.2°, and 21.9° for (11̅0), (110), and (020) planes are ascribed to cellulose II crystal. Those at 2θ =12.1, 19.8, 22.0°and 34.5°for (110), (110), (200) and (004) planes are characteristic peaks for cellulose I crystal

51, 52

. A light peak at 34.5° can be observed in CFs except for CF-0,

which suggests cellulose I exists in the nanocomposite filaments. However, the intensity of diffraction peak at 34.5° is weak because of only a little exposed crystal area in the surface of NFC.53 As shown in Figure S2 (b), a mild C=O stretching band of CF-7 appears at ∼1732 cm−1, which can be explained that protonated carboxyl groups on NFC form hydrogen bonds with one or two hydroxyl groups of the regenerated cellulose.29 Depending on the XRD patterns, the crystallinity (χc) values are calculated and there is a fluctuations of 51% to 67%. With NFC increasing, a slight increase of χc values is seen in CF-0(55±3.3%), CF-1(58±2.4%) and CF-3(64±2.9%), suggesting NFC contributes to the crystallization.54 Nevertheless, a slight reduced χc value is seen in Table 1 when the concentration of NFC increases from 3 wt% to 7 wt%, this may be the agglomeration of NFC, leading to phase separation and reducing the number of newly formed hydrogen bonds by carboxyl groups on NFC with hydroxyl groups.


Page 16 of 31

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

Biomacromolecules

Table 1. The Structural Parameters of Regenerated Nanocomposite Filaments

Sample

R (nm)

l (nm)

χc（%））

Π（（%））

f

CF-0

35

138

55±3.3

77

0.76

CF-1

32

127

58±2.4

83

0.82

CF-3

28

64±2.9

86

0.89

CF-5

30

115 132

62±1.7

85

0.84

CF-7

33

141

57±2.7

82

0.79

Figure 7 illustrates the forming process of regenerated cellulose filaments reinforced with NFC. The cellulose dissolved in alkali/urea aqueous solution exhibits extended worm-like chains co-existed with their aggregates as nanofibers. It is proposed that NFC without alkali coating is easier to be straight than alkali-urea complexes cellulose. During regeneration of the mixed cellulose solution in the first coagulation bath, compared with pure alkali-urea complexes cellulose (Figure 7a), the stretching by roller makes NFC straighten and orient firstly (Figure 7b), which is helpful to induce the naked chains being destroyed by phytic acid to self-aggregate sufficiently in parallel manner. Then, these nanofibers aligned along the drawing direction are incorporated into filaments during the plasticized stretching in hot water (60 oC) to form nanocomposite filaments consisted of ordered nanofibers and NFC. Besides, the carboxyl groups on NFC form new hydrogen bond with hydroxyl groups of the regenerated cellulose molecules in regeneration,29 which has a positive influence on crystallization, enhancing the mechanical properties of the composite filaments. Namely, NFC is helpful for nanofibers parallel arrangement and inducing crystallization, to make up for the defects, resulting in nanofibrils structure and high orientation.



Figure 7. Schematic diagram to describe the formation of the CFs’：(a) the formation of fiber only containing nanofibers regenerated in 15 wt% phytic acid with 5 wt% phytic acid lithium at 5 oC; (b) the formation of all-cellulose composite filaments containing nanofibers and NFC regenerated in 15 wt% phytic acid with 5 wt% phytic acid lithium at 5 oC;

Physical and mechanical Properties of CFs. The mechanical properties of CFs are presented in Figure 8. Obviously, the incorporation of NFC into the cellulose matrix results in the reinforcing of the materials, from 2.86 cN/dT for CF-0 to 3.92 cN/dT for CF-3, thanks to nanofibers structure and the strong interactions between the cellulose matrix and NFC through hydrogen bonds. Besides, during the drawing process in wet spinning, NFC orients uniaxially along the fiber axial direction firstly, leading to the naked cellulose parallel arrangement and crystallization. However, CF-5 and CF-7 exhibit a slight decrease in strength compared to CF-3. It is noted that some agglomeration


Page 18 of 31

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

Biomacromolecules

problems in NFC cause a lower improvement of mechanical properties of filaments.55, 56 Therefore, the optimal amount of NFC in the nanocomposite filaments should be 3−5 wt %, where the original defects of filaments can be effectively improved, resulting in a marked enhancement in the mechanics strength and Young’s modulus (E) (Figure 8 a−b). In addition, silk luster and excellent flexibility of CF-3 can be observed from Figure 8c. Noteworthy, compared to Figure 8e, the SEM images of the pulled section of CF-0 is relatively neat (Figure 8d), whenas there are some pulled out fibrils. As presented in Figure 8g, the longish NFCs are pulled out from the matrix requiring more displacement,57 which provides a good explanation that the addition of NFC leads to the increase in elongation at break of the composite filaments. Moreover, a larger area under the CF-3 stress−strain curve used as a measurement of the polymer toughness, indicates its better toughness than others. In addition, as shown in Figure 8f, when soaked in 1mg/mL−1 congo red solution for 5 min at ambient temperature, followed by washing and drying, the original white multifilaments (left) are stained to red (right), suggesting the as-prepared composite filaments are easily dyed, which demonstrates their potential application in the textile industry.



Figure 8. (a) Typical stress-strain curves of CFs; (b) Modulus of CFs ; (c) Photograph of a tube of CF-3; (d) SEM images of the pulled section of CF-0 and (e) CF-3; (f) CF-3 can be easily dyed into red after soaking in cogong red solution (1 mg mL−1) for 5 min at room temperature; (g) Diagram of fracture mechanism for CF-0 (left) and CF-3 (right), respectively.


Page 20 of 31

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

Biomacromolecules

The TGA curves of the composite filaments are exhibited in Figure 9. Figure 9a illustrates all the samples have good hygroscopicity, ensuring their good dyeing properties, which can be corroborated from the Figure 8f. Notably, with the increase of NFC, the microstructure changes leading to various bibulous rate of composite filaments, but the hygroscopicity still can satisfy the requirement of textile industry. Figure 9b shows the decomposition temperature of the sample, as expected, all composite filaments show good thermal stability because of the well heat resistance of NFC (Figure S3). In detail, the thermal stability for the filaments slightly increases with the introduction of NFC and heralds that CFs can be used for a long time under 200−250 oC. However, a decreased thermal stability is observed in the CF with high NFC concentration. This is relative to the phase separation as a consequence of the NFC agglomeration.43

Figure 9. The weight change of CFs dependeing on temperature: (a) the loss of water and (b) decomposition.

Conclusions The

all-cellulose

nanocomposite

multifilaments

can

be

fabricated

by

blending

the

TEMPO-oxidized nanofibrillated cellulose (NFC) and cellulose dissolved in 4.6% LiOH/15% urea aqueous system precooled to -12 °C. NFC is stable in the alkaline solution at room temperature and



benefits to enhance the stability of spinning dope. During the wet spinning process, NFC is embedded in cellulose matrix and maintains its original nanofiber structure. The NFC (cellulose crystal I) and cellulose solution containing nanofibers are regenerated in 15 wt% phytic acid/5 wt% phytic acid lithium to form filaments, namely all-cellulose nanocomposite multi-filaments. Small amount of NFC can effectively make up for the defects and form perfect filaments structure due to the nanofibril-induced orientation as well as crystallization. CF-3 with 3 wt % NFC possesses excellent mechanical properties as a result of the nano-reinforcement mechanism and strong interaction between the two components. The tensile strength and breaking elongation reach to 3.92 cN/dtex and 14.6% for CF-3, respectively. However, excess NFC will unite due to the huge aspect ratio as well as the force of strong hydrogen bonding, leading to more pores in CFs (CF-7). Therefore, the well-dispersed NFC occupies a critical position in the improvement of the properties of composite filaments. The work provides a positive guidance for the preparation of super strong cellulose multi-filaments from alkali/urea solution.

Supporting information Additional photos including FT-IR spectra, TGA date, and XRD patterns of the samples.

Corresponding Authors E-mail: [email protected] (Q. Fu) E-mail: [email protected] (F. Chen) E-mail: [email protected] (L. Zhang)


Page 22 of 31

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

Biomacromolecules

Notes There are no competing financial interest to declare.

Acknowledgements Strong financial support was supplied by the National Natural Science Foundation of China (Grant No. 51721091 and 51573102) in this work.

References (1) Zhu, H.; Luo, W.; Ciesielski, P. N.; Fang, Z.; Zhu, J. Y.; Henriksson, G.; Himmel, M. E.; Hu, L. Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications. Chem. Rev. 2016, 116 (16), 9305-9374. (2) Xu, D.; Xiao, X.; Cai, J.; Zhou, J.; Zhang, L., Highly rate and cycling stable electrode materials constructed from polyaniline/cellulose nanoporous microspheres. J. Mater. Chem. A 2015, 3 (32), 16424-16429. (3) Klemm, D.; Heublein, B.; Fink, H. P.; Bohn, A. Cellulose: fascinating biopolymer and sustainable raw material. Angew. Chem.,Int. Ed. 2005, 44 (22), 3358-3393. (4) Huang, J.; Zhong, Y.; Zhang, L.; Cai, J. Extremely Strong and Transparent Chitin Films: A High ‐Efficiency, Energy‐Saving, and “Green” Route Using an Aqueous KOH/Urea Solution. Adv. Funct. Mater. 2017, 27 (26) 1701100. (5) Cai, J.; Zhang, L.; Zhou, J.; Li, H.; Chen, H.; Jin, H. Novel fibers prepared from cellulose in NaOH/urea aqueous solution. Macromol. Rapid Commun. 2004, 25 (17), 1558-1562. (6) 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 (6), 821-825. (7) Chen, X.; Burger, C.; Wan, F.; Zhang, J.; Rong, L.; Hsiao, B. S.; Chu, B.; Cai, J.; Zhang, L. Structure study of cellulose fibers wet-spun from environmentally friendly NaOH/urea aqueous solutions. Biomacromolecules 2007, 8 (6), 1918-1926. (8) Wegner, T. H.; Jones, P. E. Advancing cellulose-based nanotechnology. Cellulose 2006, 13 (2), 115-118. (9) Yao, J.; Chen, S.; Chen, Y.; Wang, B.; Pei, Q.; Wang, H. Macrofibers with High Mechanical Performance Based on Aligned Bacterial Cellulose Nanofibers. ACS Appl. Mater. Interfaces 2017, 9 (24), 20330-20339. (10) Sha, W.; Feng, J.; Xu, X.; Yudi, K.; Kun, F.; Emily, H.; Liangbing, H. Super‐Strong, Super‐ Stiff Macrofibers with Aligned, Long Bacterial Cellulose Nanofibers. Adv. Mater. 2017, 29 (35), 1702498. (11) Moon, R. J.; Martini, A.; Nairn, J.; Simonsen, J.; Youngblood, J. Cellulose nanomaterials review: structure, properties and nanocomposites. Chem. Soc. Rev. 2011, 40 (7), 3941-3994. (12) Iwamoto, S.; Kai, W.; Isogai, A.; Iwata, T. Elastic Modulus of Single Cellulose Microfibrils from Tunicate Measured by Atomic Force Microscopy. Biomacromolecules 2009, 10 (9), 2571-2576. (13) Mittal, N.; Jansson, R.; Widhe, M.; Benselfelt, T.; Håkansson, K. M.; Lundell, F.; Hedhammar, M.; Söderberg, L. D. Ultrastrong and Bioactive Nanostructured Bio-Based Composites. ACS nano 2017, 11 (5), 5148-5159. (14) Song, J.; Chen, C.; Yang, Z.; Kuang, Y.; Li, T.; Li, Y.; Huang, H.; Kierzewski, I.; Liu, B.; He, S.; Gao, T.; Yuruker, S. U.; Gong, A.; Yang, B.; Hu, L. Highly Compressible, Anisotropic Aerogel with


Page 24 of 31

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

Biomacromolecules

Aligned Cellulose Nanofibers. ACS Nano 2018, 12 (1), 140-147. (15) Habibi, Y.; Lucia, L. A.; Rojas, O. J. Cellulose Nanocrystals: Chemistry, Self-Assembly, and Applications. Chem. Rev. 2010, 110 (6), 3479-3500. (16) Qi, H.; Schulz, B. r.; Vad, T.; Liu, J.; Mäder, E.; Seide, G.; Gries, T. Novel carbon nanotube/cellulose composite fibers as multifunctional materials. ACS Appl. Mater. Interfaces 2015, 7 (40), 22404-22412. (17) Duan, B.; Chang, C.; Ding, B.; Cai, J.; Xu, M.; Feng, S.; Ren, J.; Shi, X.; Du, Y.; Zhang, L., High strength films with gas-barrier fabricated from chitin solution dissolved at low temperature. J. Mater. Chem. A 2013, 1 (5), 1867-1874. (18) Iwamoto, S.; Isogai, A.; Iwata, T. Structure and Mechanical Properties of Wet-Spun Fibers Made from Natural Cellulose Nanofibers. Biomacromolecules 2011, 12 (3), 831-836. (19) Torres-Rendon, J. G.; Schacher, F. H.; Ifuku, S.; Walther, A. Mechanical Performance of Macrofibers of Cellulose and Chitin Nanofibrils Aligned by Wet-Stretching: A Critical Comparison. Biomacromolecules 2014, 15 (7), 2709-2717. (20) Yu, L.; Lin, J.; Tian, F.; Li, X.; Bian, F.; Wang, J., Cellulose nanofibrils generated from jute fibers with tunable polymorphs and crystallinity. Journal of Materials Chemistry A 2014, 2 (18), 6402-6411. (21) Cai, J.; Zhang, L.; Chang, C.; Cheng, G.; Chen, X.; Chu, B. Hydrogen‐Bond‐Induced Inclusion Complex in Aqueous Cellulose/LiOH/Urea Solution at Low Temperature. ChemPhysChem 2007, 8 (10), 1572-1579. (22) Cai, J.; Liu, Y.; Zhang, L. Dilute solution properties of cellulose in LiOH/urea aqueous system. J. Polym. Sci. Pt. B-Polym. Phys. 2006, 44 (21), 3093-3101.



(23) 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 via Inducing Formation of Nanofibers. ACS Sustainable Chem. Eng. 2018, 6 (4), 5314-5321. (24) 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 (3), 4056-4067. (25) Hauru, L. K.; Hummel, M.; Michud, A.; Sixta, H. Dry jet-wet spinning of strong cellulose filaments from ionic liquid solution. Cellulose 2014, 21 (6), 4471-4481. (26) Müller, B.; Gebert-Germ, M.; Russler, A. Viscont HT—the future of high performance viscose filaments and their textile applications. Lenzinger Ber 2012, 90, 64-71. (27) Wu, K.; Fang, J.; Ma, J.; Huang, R.; Chai, S.; Chen, F.; Fu, Q. Achieving a Collapsible, Strong, and Highly Thermally Conductive Film Based on Oriented Functionalized Boron Nitride Nanosheets and Cellulose Nanofiber. ACS Appl. Mater. Interfaces 2017, 9 (35), 30035-30045. (28) Li, Y.; Zhu, H.; Shen, F.; Wan, J.; Lacey, S.; Fang, Z.; Dai, H.; Hu, L. Nanocellulose as green dispersant for two-dimensional energy materials. Nano Energy 2015, 13, 346-354. (29) Yang, Q.; Saito, T.; Berglund, L. A.; Isogai, A. Cellulose nanofibrils improve the properties of all-cellulose composites by the nano-reinforcement mechanism and nanofibril-induced crystallization. Nanoscale 2015, 7 (42), 17957-17963. (30) Siró, I.; Plackett, D. Microfibrillated cellulose and new nanocomposite materials: a review. Cellulose 2010, 17 (3), 459-494. (31) Wang, M.; Anoshkin, I. V.; Nasibulin, A. G.; Korhonen, J. T.; Seitsonen, J.; Pere, J.; Kauppinen,


Page 26 of 31

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

Biomacromolecules

E. I.; Ras, R. H.; Ikkala, O. Modifying native nanocellulose aerogels with carbon nanotubes for mechanoresponsive conductivity and pressure sensing. Adv. Mater. 2013, 25 (17), 2428-2432. (32) Saito, T.; Kimura, S.; Nishiyama, Y.; Isogai, A. Cellulose nanofibers prepared by TEMPO-mediated oxidation of native cellulose. Biomacromolecules 2007, 8 (8), 2485-2491. (33) Chinga-Carrasco, G.; Syverud, K., Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels. J. Biomater. Appl. 2014, 29(3), 423-432. (34) Cai, J.; Zhang, L. Rapid dissolution of cellulose in LiOH/urea and NaOH/urea aqueous solutions. Macromol. Biosci. 2005, 5 (6), 539-548. (35) Shinoda, R.; Saito, T.; Okita, Y.; Isogai, A. Relationship between length and degree of polymerization of TEMPO-oxidized cellulose nanofibrils. Biomacromolecules 2012, 13 (3), 842-849. (36) Saito, T.; Isogai, A. TEMPO-mediated oxidation of native cellulose. The effect of oxidation conditions on chemical and crystal structures of the water-insoluble fractions. Biomacromolecules 2004, 5 (5), 1983-1989. (37) Jiang, Z.; Fang, Y.; Ma, Y.; Liu, M.; Liu, R.; Guo, H.; Lu, A.; Zhang, L. Dissolution and Metastable Solution of Cellulose in NaOH/Thiourea at 8 °C for Construction of Nanofibers. J. Phys. Chem. B 2017, 121 (8), 1793-1801. (38) Jiang, Z.; Fang, Y.; Xiang, J.; Ma, Y.; Lu, A.; Kang, H.; Huang, Y.; Guo, H.; Liu, R.; Zhang, L. Intermolecular Interactions and 3D Structure in Cellulose–NaOH–Urea Aqueous System. J. Phys. Chem. B 2014, 118 (34), 10250-10257. (39) 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 (4), 1410-1417.



(40) Wang, S.; Lu, A.; Zhang, L. Recent advances in regenerated cellulose materials. Prog. Polym. Sci. 2016, 53, 169-206. (41) Cai, J.; Zhang, L. Unique gelation behavior of cellulose in NaOH/urea aqueous solution. Biomacromolecules 2006, 7 (1), 183. (42) Papthanasiou, T.; Guell, D. C. Flow-induced alignment in composite materials. Polymer 1979, 20, 1284-1288. (43) Qi, H.; Cai, J.; Zhang, L.; Kuga, S. Properties of films composed of cellulose nanowhiskers and a cellulose matrix regenerated from alkali/urea solution. Biomacromolecules 2009, 10 (6), 1597-1602. (44) Fu, F.; Guo, Y.; Wang, Y.; Tan, Q.; Zhou, J.; Zhang, L. Structure and properties of the regenerated cellulose membranes prepared from cellulose carbamate in NaOH/ZnO aqueous solution. Cellulose 2014, 21 (4), 2819-2830. (45) Dobb, M.; Johnson, D.; Majeed, A.; Saville, B. Microvoids in aramid-type fibrous polymers. Polymer 1979, 20 (10), 1284-1288. (46) Saijo, K.; Arimoto, O.; Hashimoto, T.; Fukuda, M.; Kawai, H. Moisture sorption mechanism of aromatic polyamide fibres: diffusion of moisture into regular Kevlar as observed by time-resolved small-angle X-ray scattering technique. Polymer 1994, 35 (3), 496-503. (47) Zhu, C.; Liu, X.; Guo, J.; Zhao, N.; Li, C.; Wang, J.; Liu, J.; Xu, J. Relationship between performance and microvoids of aramid fibers revealed by two-dimensional small-angle X-ray scattering. J. Appl. Crystallogr. 2013, 46 (4), 1178-1186. (48) Yin, C.; Dong, J.; Tan, W.; Lin, J.; Chen, D.; Zhang, Q. Strain-induced crystallization of polyimide fibers containing 2-(4-aminophenyl)-5-aminobenzimidazole moiety. Polymer 2015, 75,


Page 28 of 31

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

Biomacromolecules

178-186. (49) Luo, L.; Wang, Y.; Zhang, J.; Huang, J.; Feng, Y.; Peng, C.; Wang, X.; Liu, X. The Effect of Asymmetric Heterocyclic Units on the Microstructure and the Improvement of Mechanical Properties of Three Rigid‐Rod co‐PI Fibers. Macromol. Mater. Eng. 2016, 301 (7), 853-863. (50) Ruan D, Zhang L, Lue A, et al. A rapid process for producing cellulose multi‐filament fibers from a NaOH/thiourea solvent system. Macromol. Rapid Commun. 2006, 27 (17), 1495-1500. (51) Chen, X.; Burger, C.; Fang, D.; Dong, R.; Zhang, L.; Hsiao, B. S.; Chu, B. X-ray studies of regenerated cellulose fibers wet spun from cotton linter pulp in NaOH/thiourea aqueous solutions. Polymer 2006, 47 (8), 2839-2848. (52) Hu, X.; Xu, C.; Gao, J.; Yang, G.; Geng, C.; Chen, F.; Fu, Q. Toward environment-friendly composites of poly(propylene carbonate) reinforced with cellulose nanocrystals. Compos. Sci. Technol. 2013, 78, 63-68. (53) Nan, F.; Nagarajan, S.; Chen, Y.; Liu, P.; Duan, Y.; Men, Y.; Zhang, J. Enhanced Toughness and Thermal Stability of Cellulose Nanocrystal Iridescent Films by Alkali Treatment. ACS Sustainable Chem. Eng. 2017, 5 (10), 8951-8958. (54) Fu, F.; Zhou, J.; Zhou, X.; Zhang, L.; Li, D.; Kondo, T. Green Method for Production of Cellulose Multifilament from Cellulose Carbamate on a Pilot Scale. ACS Sustainable Chem. Eng. 2014, 2 (10), 2363-2370. (55) Wang, Y.; Zhang, J.; Qiu, C.; Li, J.; Cao, Z.; Ma, C.; Zheng, J.; Huang, G. Self-recovery magnetic hydrogel with high strength and toughness using nanofibrillated cellulose as a dispersing agent and filler. Carbohydr. Polym. 2018, 196, 82-91. (56) Campano, C.; Merayo, N.; Balea, A.; Tarrés, Q.; Delgado-Aguilar, M.; Mutjé, P.; Negro, C.;



Blanco, Á. Mechanical and chemical dispersion of nanocelluloses to improve their reinforcing effect on recycled paper. Cellulose 2018, 25 (1), 269-280. (57) Yao, X.; Qi, X.; He, Y.; Tan, D.; Chen, F.; Fu, Q. Simultaneous reinforcing and toughening of polyurethane via grafting on the surface of microfibrillated cellulose. ACS Appl. Mater. Interfaces 2014, 6 (4), 2497-2507.


Page 30 of 31

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

Biomacromolecules

For Table of Contents Use Only

Super Strong all-cellulose nanocomposite multifilaments by adding nanofibrillated cellulose is demonstrated via wet spinning.


Super Strong All-Cellulose Composite Filaments by Combination of

Recommend Documents