Generic Mechanochemical Grafting Strategy toward Organophilic

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A Generic Mechanochemical Grafting Strategy towards Organophilic Carbon Nanotubes Zhijun Yang, Wenyi Kuang, Zhenghai Tang, Baochun Guo, and Liqun Zhang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b00690 • Publication Date (Web): 07 Feb 2017 Downloaded from http://pubs.acs.org on February 8, 2017

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ACS Applied Materials & Interfaces

A Generic Mechanochemical Grafting Strategy towards Organophilic Carbon Nanotubes †

†

†

†

Zhijun Yang, Wenyi Kuang, Zhenghai Tang, Baochun Guo*, and Liqun Zhang*, †

‡

Department of Polymer Materials and Engineering, South China University of Technology,

Guangzhou, 510640, China. ‡

State Key Laboratory of Organic/Inorganic Composites, Beijing University of Chemical

Technology, Beijing, 100029, China KEYWORDS: carbon nanotube, organo-soluble, buckypaper, mechanical properties, flexible conductor

ABSTRACT

Although carbon nanotubes (CNTs) have been produced in industrial scale, their poor dispersibility of in organic solvents still imposes a huge challenge for their practical applications. In the present work, we propose a generic mechanochemical grafting strategy to prepare the organo-soluable CNTs, which is facile, efficient and scalable. Significantly, the solvent spectrum of the CNTs suspension can be simply extended by changing the chemical composition of the grafted elastomer chains. The prospect of the organo-solubale CNTs is demonstrated by the freestanding buckypapers by direct filtration of the CNT colloids. Such buckypapers exhibit great

ACS Paragon Plus Environment

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potential as robust and ultra-flexible conductors due to the combination of high toughness and stable conductivity under cyclic bending and twisting. Furthermore, this facile surface modification strategy of CNTs also enables remarkable improvement in mechanical properties of CNT-based rubber composites. We envision that the present work offers facile yet efficient strategy for scalable production of organosoluable CNTs and other nanoparticles, which is of great scientific and technological interests.

INTRODUCTION

Carbon nanotubes (CNTs) have demonstrated extraordinary mechanical, thermal, and electrical properties,1-3 which lead to a variety of important applications ranging from composite materials to sensors and electronic devices.4-6 However, many of these applications, especially composites processing, have been hindered by the poor dispersibility of CNTs in common organic solvents due to the strong intertube van der Waals interactions. Therefore, the stable and uniform CNT dispersions have been actively pursued and various covalent and non-covalent modification techniques have been attempted for this purpose.7-10 Although covalent functionalization strategy is efficient in stabilizing CNTs, it inevitably disrupts the π−π conjugated structure of CNTs,8 leading to the compromised intrinsic properties, which is detrimental to their electronic applications. As an alternative, non-covalent stabilization realized by physical adsorption of surfactants or polymers onto the CNT surface well preserves the π−π electronic structures of the CNTs.11-15 Nevertheless, this strategy could have limitations. On the one hand, many of these non-covalent functionalized CNTs only exhibit low solubility in selected polar and high-boiling-point sovents (e.g. dimethylformamide and N-methylpyrrolidone). On the other hand, although some specially designed conjugated polymers facilitate the


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dispersion of CNTs in various organic solvents,12-15 the synthesis of these polymers is somewhat sophisticated and involves the use of specialty monomers, which is unfavorable for industrialscale application. Therefore, exploring facile, efficient and scalable approach for dispersing CNTs in various organic solvents, especially nonpolar or weak polar and low-boiling-point solvents, is still highly desirable. Inspired by the facile and efficient mechanochemical modification of carbon materials,16-18 we envisage a novel strategy of non-covalent CNTs modification that first employs an active polymer coating to preserve their structural integrity and then mechanochemical grafting polymer chains onto the polymer coating. Previously, we have revealed that polyrhodanine, a conjugated polymer with pendent thiols which could act as the chain transfer agent, is promising candidate for modification of carbon material.19 Considering that numerous chain radicals are readily generated during two-roll milling of an elastomer (a typical mechanochemistry process),20 the combination of these two process may ideally fulfill the proposed strategy. In this study, for the first time, we propose a generic mechanochemistry strategy for grafting polymer chain onto CNTs. The multi-walled carbon nanotubes (MCNTs) were first wrapped by polyrhodanine

through

π–π

interactions.

Subsequently,

the

elastomer

chains

were

mechanochemically grafted onto the polyrhodanine coating which provides sufficient steric repulsion to prevent nanotube agglomeration. Significantly, the solvent spectrum of the obtained MCNTs suspensions can be simply extended by changing the chemical composition of the elastomer. The efficient preparation process and excellent suspension stability render this method great potential in diverse applications. As a proof of concept, a free-standing buckypaper for robust and ultra-flexible conductors, simply by vacuum filtration of the modified MCNT-toluene dispersion, and CNT-based rubber composites with remarkably improved mechanical properties,


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have been demonstrated.

EXPERIMENTAL SECTION

Materials. MCNTs (purity ≥ 97.5%, 10-15 nm in outer diameter) were supplied by CNano Technology, Ltd., Beijing, China. Single-walled carbon nanotubes (SWCNTs, Trademark: TUBALLTM) were kindly supplied by OCSiAl Ltd., Russia. Rhodanine (99% pure) was purchased from InnoChem Science & Technology Co. Ltd (Beijing, China). Potassium persulfate (KPS) and dicumyl peroxide (DCP) were of analytical grade and used as received. Styrenebutadiene rubber (Trademark: SBR1502) was manufactured by Jilin Chemical Industry Company, Jilin, China. Preparation of organic-soluble MCNTs (GCNTs). GCNTs were synthesized by a two-step surface modification procedure. Firstly, MCNTs (1 g) and rhodanine (0.2 g) were added into preheated water (100 ml, 80 oC). After sonication for 1 h, the mixture were allowed to age for 6h at 50 oC under vigorous stirring, meanwhile KPS solution (about 20 mg/ml, 20 ml) was dropwise added into the mixture in order to initiate the oxidative polymerization of rhodanine. After filtering and washing with ethanol, the MCNT/polyrhodanine core/shell nanotubes (PCNTs) were thus obtained. Then, PCNT and SBR (1:10 by weight) were subjected to shear mixing in a two-roll mill for 15 min, where mechanochemical grafting occured. The resulting mixture was readily dispersed in toluene. After that the suspension was subjected to low-speed centrifugation (10 000 rpm, 10 min) to eliminate the poorly soluble MCNT compound due to the low grafting densities. The supernatant was further centrifuged (14 000 rpm, 45 min) and the sediment, PCNTs grafted by SBR chains (denoted as GCNTs), were obtained. This process was repeated multiple times to ensure the maximum possible removal of the non-grafted SBR chains.


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Synthesis of model compound (SBR-Rh). SBR-Rh was adopted as the model compound to reveal the mechanochemical grafting between SBR chains and polyrhodanine coating. SBR and rhodanine monomer (20:1 by weight) were mixed in a two-roll mill for about 15 min. afterwards, the compound was dissolved in chloroform and the solution was precipitated in ethanol to remove the unreacted rhodanine, after which the precipitated compound was washed thoroughly with ethanol and dried in vacuum oven. This process was repeated three times. Note that, the obtained compound should be the mixture of SBR and rhodanine grafted SBR (SBR-Rh). Preparation of buckypaper. The buckypaper (BP) was prepared by filtering dilute GCNTs toluene suspension (~1 mg/ml, 25 ml) through a 0.22 µm nylon membrane under vacuum assistance. After the solution filtration, the dried buckypaper was immersed into formic acid solution to remove the nylon membrane. And then the free-standing buckypaper was rinsed with deionized water three times and dried in a vacuum oven at 35 oC for 24 h before further analysis. For the crosslinked buckypaper (CBP), DCP (crosslinking agent) solution was permeated through the buckypaper under low vacuum level. After vacuum drying, the complex film was subjected to compression at 160 oC for 30 min and the crosslinked buckypaper was obtained by peeling off from the filter membrane carefully. Preparation of SBR composites. SBR was mixed with pristine MCNTs or PCNT via two-roll milling and then the compounds were subjected to compression at 150 °C for the optimum curing time, which was determined by a vulcameter. The samples are referred to as SBR/CNT-x or SBR/PCNT-x, where x denotes the content of pristine MCNT or PCNT (parts per one hundred parts of rubber, phr) in the composite, respectively. The basic recipe is listed as follows: SBR 100 phr; zinc oxide 5 phr; stearic acid 2 phr; N-isopropyl-N'-phenyl-4-phenylenediamine (4010NA) 1.5 phr; N-cyclohexyl-2-benzothiazole sulfonamide (CBS) 1.5 phr; diphenylguanidine


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1 phr; and sulfur 2 phr. Characterization.

1

HNMR spectrum were recorded by Bruker AVANCE III600 MHz

spectrometer using CDCl3 as the solvent. TEM image and EDX mapping were recorded by a Tecnai G2 F30 S-Twin electron microscope. Atomic force microscopy (AFM) was characterized by Veeco Multimode V operated in a tapping mode. Raman spectra were collected on a LabRAM Aramis Raman spectrometer (HORIBA Jobin Yvon, France) with a He–Ne ion laser (532.0 nm) as excitation source. The morphology and the microstructures of the buckypapers and composites were observed using a FE-SEM (Hitachi S-4800, Japan). Thermal gravimetric analysis (TGA) was performed on a TGA Q500 instrument (USA) under nitrogen purging at a heating rate of 10 oC/min. The mechanical properties of the buckypapers were performed on a DMA Q800 instrument and the electrical conductivity was measured on a Keithley 2365A instrument. Curing characteristics of the SBR compounds were determined at 150 °C by a UCAN UR-2030 vulcameter (Taiwan). Tensile tests of SBR composites were performed on a UCAN UT-2060 instrument (Taiwan) according to ISO standard 37-2005.

RESULTS AND DISCUSSION

Herein, organo-soluble MCNTs were obtained by a two-step strategy, as proposed in Figure 1a. MCNTs were first uniformly wrapped with polyrhodanine via in situ oxidative polymerization

of

rhodanine19,

21-23

(Scheme

S1

and

Figure

S1).

The

formed

MCNT/polyrhodanine core/shell structure nanotubes are denoted as PCNT. Afterwards, PCNT and an elastomer (styrene-butadiene rubber, SBR) were subjected to shear mixing in a two-roll mill, where numerous SBR macromolecular radicals generate due to the chain scission induced by shear force (Scheme S2). Mechanochemical grafting occurs between the macroradicals and


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thiol moieties (–N=C–SH) of polyrhodanine, which are derived from the tautomeric form of – (NH)–(C=S)– moiety24-25 based on radical chain-transfer reaction (Scheme S3). After dissolving and centrifugation, a hybrid (denoted as GCNT) with a polyrhodanine-coated MCNT as the core and a brush-like corona of elastomer chain is obtained. In GCNT, the conjugated polyrhodanine molecules strongly adhere onto the surface of MCNTs through noncovalent π–π interactions without disruption of MCNTs sp2-structure (Figure S2) and hence the intrinsic physical and electrical properties of the MCNTs. In addition, the subsequently grafted elastomer chains endow the GCNTs with versatile solubility in various organic solvents.

Figure 1. a) Schematic diagram of the preparation process for organo-soluble MCNTs. b) 1H NMR spectra of SBR and SBR-Rh complex.


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The mechanochemical grafting of SBR chains onto polyrhodanine coating during shear mixing was confirmed by 1H NMR spectroscopy. Note that, in order to facilitate the analysis, rhodanine, the monomer, having similar functional moiety, was mixed with SBR by two-roll milling and then the compound (SBR-Rh) was subjected to 1H NMR measurement after the removal of unreacted rhodanine. Figure 1b shows the comparison of 1H NMR spectroscopy between SBR-Rh and neat SBR. As can be seen, the absorption peaks in the two spectra are generally similar with slight variation in intensity and can be divided into three main regions. Chemical shifts at δ =7.0-7.3, 4.9-5.8 and 1.0-2.6 ppm are assigned to protons of phenyl ring (peaks a), cis and trans chain end ethylenic protons of butadiene (peaks b) and alkyl chain protons (peaks c), respectively.26 However, by careful inspection of the spectrum of SBR-Rh, two splitting peaks are observed in the chemical shift of about 4.2 ppm (peaks d and e). The resonance at 4.3 ppm can be assigned to –CH proton attached with phenyl ring and rhodanine monomer, while the signal at δ = 4.1 ppm can be ascribed to ethylenic chain-end protons connected with rhodanine. This result verifies that rhodanine has been grafted onto the macromolecular chains of SBR by mechanochemical grafting.


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Figure 2. a) 2D, 3D AFM images and height profile of GCNT. b) 2D AFM image and height profile of pristine MCNT. c) Digital photographs of (1) PCNT, (2) GCNT and (3) SBR/MCNT compound dispersions in toluene and Photographs of GCNT dispersed in various other solvents (1 mg/ml) after settling for one month: (4) benzene, (5) chloroform, (6) n-hexane, and (7) tetrahydrofuran.

Complementary atomic force microscopy (AFM) investigations (Figure 2a and b) allowed a more intuitive analysis of the MCNT before and after surface modification. Within the resolution of AFM, the tube surface of GCNT is vague and blurry. However, the pristine MCNT displays an apparently smooth outer surface and the tube morphology is more homogeneous than those of GCNT. The height profile and zoom-in 3D image reveal that the diameter of GCNT ranges from ca. 20 nm to 30 nm, which is greater than the corresponding value determined for pristine MCNT (~10 − 15 nm). These observations further confirm the well wrapping of polymer chains on MCNTs. When GCNTs are added into the selective “good solvent” for the adopted elastomer, these grafted elastomer chains are swollen and readily dissolved in the solvent which provides sufficient steric repulsion to stabilize the nanotubes. As can be seen in Figure 2c, both PCNT and pristine MCNT/SBR compound cannot stably be suspended in toluene, while GCNT can be well dispersed in toluene and a wide spectrum of solvents including benzene, chloroform, n-hexane and tetrahydrofuran etc. has been demonstrated. Significantly, the selected solvents mentioned above are nonpolar or weak polar solvents with low boiling-point, which is of great interest for solution-processing engineering of CNT-based materials. Further, the solvent spectrum can be further extended by changing the chemical composition of the elastomer. More strikingly, considering that many other nanoparticles such as silica, halloysite, metal oxides, cellulose


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nanocrystals and graphene etc. can also be well-wrapped by polyrhodanine,19,

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22-23, 27-28

this

mechanochemical grafting strategy demonstrated herein could also be applicable to these nanoparticles and enable efficient solubilization in target solvents, which is of great scientific and technological interests. The unique structure and excellent solubility of GCNT in common organic solvents motivate us to study the characteristic of free-standing GCNT membrane which we supposed to differ from those of reported CNT buckypaper.29-31 Four batches of buckypaper with varying polymer contents were fabricated via vacuum filtration of GCNT dispersions. Figure S3 presents photograph of the free standing BPs with satisfying mechanical stability (the thickness of the asprepared buckypapers is about 25±3 µm). It has to be noted that the pristine MCNT and PCNT samples failed to form buckypapers under identical conditions due to the poor dispersibility and weak intertube coupling. The contents of polymer coating in the buckypapers were evaluated by the TGA result (Figure S4) and detailed characteristics of the as-prepared buckypapers are listed in Table S1. Figure 3 shows the morphology of the free standing buckypaper. It can be seen that the BPs exhibit porous structure and are composed of randomly-oriented GCNTs which are predominantly parallel to the buckypaper surface. As the polymer coating increases, the diameters of GCNTs also continuous increase and meanwhile the void regions of the buckypapers decrease gradually, indicating that CNTs are well wrapped with polymer chains. Careful inspection of the buckypapers surface show that some of the neighboring GCNTs are binded together. It is rational to speculate that the chain-entanglement of the grafted elastomer long chains form these connections, serving as flexible junctions between adjacent nanotubes and facilitating the formation of stable free-standing buckypapers. Thus a unique “skeleton/skin”


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architecture with rigid CNTs as the skeleton, grafted elastomer as the skin and connected by flexible joints is developed in the as-prepared BPs.

Figure 3. SEM images of top surfaces of BP-20 (a), BP-10 (b), BP-5 (c) and cross-section of BP-5 (d). The x in BP-x represents the feed weight ratio of MCNT to rhodanine during synthesis of PCNT.

Tensile tests of the as-prepared buckypapers were conducted and the representative stress– strain curves are shown in Figure 4a. With reference to the stress–strain curves, it was observed that the mechanical properties of the buckypapers can be tuned by varying its polymer content. The Young’s modulus and tensile strength of BP-20 were measured to be about 202.9 MPa and 5.1 MPa, respectively. While BP-5 exhibited a modulus of 454.2 MPa and a tensile strength of


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11.0 MPa, which were 1100 and 132-fold higher, respectively, than for the reference neat SBR film (Figure S5). After crosslinking, these mechanical properties can be further improved (CBP5). It has been well established that the mechanical properties of the BPs are largely determined by the nature of intertube junctions.32 Pristine BPs in which CNTs are loosely bonded to each other only by van der Waals forces and feeble entanglement generally exhibit inferior mechanical performances. The improved mechanical properties of buckypaper in the present work should be ascribed to the grafted elastomer chains. The grafted elastomer chains on the one hand endow the GCNTs with favorable dispersibility which is essential for BP fabrication, on the other hand, certain amount of the entangled elastomer chains serves as flexible connections of the tube network (Figure 3) which is beneficial to stress transfer.

Figure 4. a) Representative tensile stress−strain curves of buckypapers and corresponding crosslinked buckypaper. b) Comparison of the as-prepared buckypapers with previously reported


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buckypapers in terms of tensile strength, strain and conductivity. c) Schematic of the deformation of continuous “skeleton/skin” architecture and junction morphology under different strain.

An even more remarkable property of the as-prepared BPs concerns their tensile strains. Typically, free-standing BPs are highly brittle and exhibit tensile strain limits of less than 5%. To overcome this drawback, ductile polymer (polyurethane elastomer) has recently been adopted to infiltrate the BPs.33 Compared with the thermoset resin-infiltrated counterparts,34-35 although largely improvement has been obtained in ductility and toughness of BPs, the failure strain is still less than 40%. Strikingly, the tensile strains of BP-5 can be as high as 95%, which is actually unprecedented. A collection of other reported data concerning the tensile strength, ultimate strain and conductivity of buckapapers is plotted and compared with the present result in Figure 4b (detail data information in Figure 4b is listed in Table S2). By comparison, the results of tensile strength and conductivity of BP-5 in present work are slightly inferior to some of reported BPs, but still of the same order of magnitude. It's worth noting that the electric conductivity of BPs is largely dependent on the type of CNTs used. By adopting SWCNTs, the conductivity of the asprepared SBP-5 can be significantly increased to 104.7 S/cm as shown in the Figure 4b, which is comparable to other reported flexible CNT films

36-37

and this level of conductivity is sufficient

to drive active electronic components, such as organic transistors 38. Specially, when considering the ultimate strain, all of these reported BPs exhibit rather low values (one or two orders of magnitude smaller than present work), suggesting the fragility of these BPs. Such a significant imbalance of the mechanical/electrical properties may greatly limit their practical application. The excellent ductility of the as-prepared BPs should be ascribed to the continuous


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“skeleton/skin” architecture of GCNTs connected by flexible elastomer junctions as schematically shown in Figure 4c. Unlike the elastomer or resin-impregnated BPs, the porous structure is well preserved in the as-prepared BPs, thus certain amount of strain can be accommodated by the free deformation of the nanotube mesh and the breaks of some weak junctions,39 maintaining the structural integrity. Besides, the flexible junctions enable the relative displacement of connected GCNTs, further improving the ductility of the as-prepared BPs. During the initial stretching period (Figure 4c, stage ii), the rigid tube network first undergoes deformation without the break of most flexible junctions, resulting in the alignment of GCNT tubes. Upon further stretching (Figure 4c, stage iii), the sliding of GCNTs only leads to the relative slippage of entangled elastomer chains, rather than immediate fracture, which is the reason for high stretchability of BPs. The as-prepared BP-5 with up to 95% stretchability indicates potential application in ultra-flexible electronics. In view of the fact that BP-5 possesses robust mechanical properties, ultra-high ultimate strain and admirable electronic conductivity, we tested the viability of the as-prepared buckypaper as a flexible conductor by integrating BP-5 strips into blue light emitting diode (LED) circuits. Figure 5ai shows digital photograph of an illuminated LED without applying any strain (the initial length of BP-5 strip is ~ 25mm). Although there is small variation in the brightness, the LED can still work even under 60% strain (Figure 5aii-aiv), illustrating the high stretchability of the buckypaper strips. In addition, the conductor strips were subjected to some other possible deformations, including bending, twisting, folding and knotting as shown in Figure 5b. The LEDs do not show any noticeable brightness fluctuation, implying that there is no significant changes in resistance of BP-5 strips during these deformations.


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Figure 5. Digital photographs of illuminated blue LEDs in a circuit with BP-5 strip under different types of deformation: stretching (ai-aiv), bending, twisting and folding (bii-biv), and knotting (bv). The operating voltage of LEDs are 3 V. c) Dependence of normalized resistance (R/R0) of the BP-5 strips on the number of bending and twisting cycles. The sample shape induced by bending and twisting are shown in the Figure. 5bii and biii, respectively.

Quantitative analysis were conducted to evaluate the flexibility and durability of the asprepared BPs by recording their resistance variation upon deformation. Figure 5c shows the normalized resistance of the BP-5 conductor strips upon cyclic bending and twisting tests for 200 cycles, where R0 is the sample initial resistance without deformation. As can be seen clearly, the electrical property of BP-5 conductor strip exhibits little sensitivity to bending and twisting


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deformations. The resistance of samples remains almost constant with a resistance vibration of only 2% and 5% during 200 bending and twisting cycles, respectively. This slight resistance vibration should arise from the disruption and reconstruction of a small amount of weakly interacting CNT-CNT junctions. Such impressive electrical performances are comparable to those of some CNT-based stretchable conductors,37 which should be attributed to the unique architecture of the free-standing buckypapers as have been depicted above. The rigid carbon nanotube connected by flexible elastomer joints enables a robust, deformable and conductive network throughout the buckypaper. Therefore, the continuous connections between CNTs can effectively retain under various types of deformation, resulting in low resistance variation upon deformation of the as-prepared buckypaper. These results indicate the potential of free-standing buckypapers for flexible electronic applications. To date, several methods have been reported for preparation of CNT-based flexible/stretchable conductors, in which CNT electronic circuits were either built on top of a stretchable substrate or embedded in the stretchable matrix.40 However, these method could have limitations, for example, the exposed CNT films/forests can be easily destroyed by self-delamination or external forces.41 Moreover, the complicated and expensive microfabrication process and the poor mechanical strength of the resulting flexible/stretchable conductors also greatly restrict its practical application.37, 42 Compared with the reported flexible conductors, the as-prepared BPs combine the advantages of the facile fabrication, mechanical robustness, excellent flexibility and durability, which represents a promising alternative approach for the design of flexible conductors. The mechanochemical reactivity between polyrhodanine coating and the elastomer chains make PCNTs an ideal candidate for constructing strong interface between CNTs and elastomer


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matrix, which is beneficial to the CNTs dispersion as well as the stress transfer and hence the ultimate properties of the composites. To evaluate the effect of PCNTs on mechanical properties of SBR composites, both SBR/CNT and SBR/PCNT composites were fabricated by two-roll mill mixing and the stress-strain curves of neat SBR and SBR composites are presented in Figure 6a. Figure 6b shows the increment of tensile strength normalized to the values for neat SBR as a function of filler loadings. Compared with the neat SBR, the strength of the composites are improved by incorporation of both pristine CNTs and PCNTs. And as expected, SBR/PCNT composites exhibit superior tensile strength when compared with the SBR/CNT composites at the same filler content. In particular, the tensile strength of SBR/PCNT-10 is increased by 5.6fold when compared with neat SBR, which is much higher than that of SBR/CNT-10 (3.7-fold). Such a high reinforcing efficiency is also more prominent than other reported CNTs-based rubber composites

43-45

. For example, Endo et al. adopted a multiple process to improve the

dispersion of CNTs in rubber matrix and the incorporation of 9 wt% CNTs only led to an increase of less than 200% in tensile strength. We speculate that this remarkable improvement in tensile strength should be attributed to the combination of largely enhanced interface and improved CNTs dispersion.


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Figure 6. a) Typical stress–strain curves of neat SBR, SBR/CNT-10 and SBR/PCNT-10 composites. b) Incremental stress values for SBR/CNT and SBR/PCNT composites with various filler loadings, normalized to the values of neat SBR. FESEM images of SBR/CNT-10 (c) and SBR/PCNT-10 (d) composites.

In order to investigate the morphology and evaluate the interfacial adhesion of the as-prepared SBR composites, FESEM was performed on the cryogenically fractured surfaces of SBR/CNT10 and SBR/PCNT-10 composites. As is widely known, the pristine CNTs are easily entangled and form aggregated bundles due to the strong van der Waals interactions, which make it difficult to achieve homogeneous dispersion of CNTs in polymer matrix. Obviously, the


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aggregation of pristine CNT into clusters are clearly seen in SBR/CNT-10 composite (Figure 6c, indicated by red circles). Moreover, close inspection indicates that many CNTs are observed to be pulled out of the rubber matrix, indicating weak interfacial interactions between the pristine CNTs and SBR. As for SBR/PCNT-10 composite, the modified CNTs are uniformly distributed throughout the rubber matrix without apparent aggregation and most PCNTs are embedded in the SBR matrix. Based on the mechanochemistry grafting reaction between PCNTs and rubber chains as has been verified above, it is thus believed that the grafted rubber chains on PCNTs can provide sufficient elastic resilience which serve as the driving force for the disentanglement of the CNTs 44. In addition, the grafted rubber chains can also take part in the vulcanization of the composites and thus the strong interfacial adhesion is achieved in SBR/PCNT composites which is responsible for the improvement of mechanical property. All these results demonstrate that the combination of facial modification of CNTs and subsequent mechanochemical grafting during processing can simultaneously promote the dispersion of CNTs and strengthen the interfacial interaction, resulting in a high performance elastomer/CNT composite.

CONCLUSIONS

In conclusion, we have demonstrated a facile yet efficient strategy for scalable production of organo-soluable MCNTs. On the basis of the characterization results, the surface of MCNTs was first well-wrapped by polyrhodanine and the elastomeric chains were then mechanochemically grafted onto the polyrhodanine coating, forming unique “skeleton/skin” architecture GCNTs, resulting excellent dispersity in various organic solvents. Significantly, the solvent spectrum can be simply extended by changing the polarity of the elastomer. This versatile strategy can also be applied to other nanoparticles for respective organo-soluble nanoparticles. In addition, the


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buckypapers obtained by filtration of GCNT toluene solution uniquely combined mechanical robustness, impressive conductivity and ability for large-strain deformation. Furthermore, these buckypapers exhibit stable conductivity upon cyclic bending and twisting, which may guarantee their broad applications in flexible electronics, smart textiles, artificial muscles, and flexible sensors and actuators. Also, this surface modification strategy of CNTs provides a novel and facile route for fabrication of high performance elastomeric composites. ASSOCIATED CONTENT Supporting Information. Polymerization mechanism of rhodanine (Scheme S1), TEM images and EDS elemental mapping of PCNTs (Figure S1), rubber chain scission mechanism (Scheme S2), termination mechanism of rubber macroradicals by polyrhodanine (Scheme S3), Raman spectra (Figure S2), optical image of buckypapers (Figure S3), TGA curves (Figure S4), detailed characteristics of buckypapers (Table S1), stress-strain curve of SBR film(Figure S5) and plot information for Figure 3b (Table S1) are listed in the Supporting Information. This material is available free of charge on the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * B.G. E-mail: [email protected] * L.Z. E-mail: [email protected] ORCID Baochun Guo: 0000-0002-4734-1895


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Liqun Zhang: 0000-0002-5197-2200 Funding Sources The National Basic Research Program of China (2015CB654703) and National Natural Science Foundation of China (51673065, 51473050, 51320105012, 51521062 and U1462116). Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Basic Research Program of China (2015CB654703) and National Natural Science Foundation of China (51673065, 51473050, 51320105012, 51521062 and U1462116). REFERENCES (1) Salvetat, J.-P.; Bonard, J.-M.; Thomson, N. H.; Kulik, A. J.; Forró, L.; Benoit, W.; Zuppiroli, L., Mechanical Properties of Carbon Nanotubes. Appl. Phys. A 1999, 69, 255-260. (2) Berber, S.; Kwon, Y.-K.; Tománek, D., Unusually High Thermal Conductivity of Carbon Nanotubes. Phys. Rev. Lett. 2000, 84, 4613-4616. (3) Odom, T. W.; Huang, J.-L.; Kim, P.; Lieber, C. M., Atomic Structure and Electronic Properties of Single-Walled Carbon Nanotubes. Nature 1998, 391, 62-64. (4) De Volder, M. F. L.; Tawfick, S. H.; Baughman, R. H.; Hart, A. J., Carbon Nanotubes: Present and Future Commercial Applications. Science 2013, 339, 535-539. (5) Zhang, Q.; Huang, J.-Q.; Qian, W.-Z.; Zhang, Y.-Y.; Wei, F., The Road for Nanomaterials Industry: A Review of Carbon Nanotube Production, Post-Treatment, and Bulk Applications for Composites and Energy Storage. Small 2013, 9, 1237-1265.


21


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 22 of 27

(6) Schnorr, J. M.; Swager, T. M., Emerging Applications of Carbon Nanotubes. Chem. Mater. 2011, 23, 646-657. (7) Kim, S. W.; Kim, T.; Kim, Y. S.; Choi, H. S.; Lim, H. J.; Yang, S. J.; Park, C. R., Surface Modifications for the Effective Dispersion of Carbon Nanotubes in Solvents and Polymers. Carbon 2012, 50, 3-33. (8) Hirsch, A., Functionalization of Single-Walled Carbon Nanotubes. Angew. Chem., Int. Ed. 2002, 41, 1853-1859. (9) Zou, J.; Liu, L.; Chen, H.; Khondaker, S. I.; McCullough, R. D.; Huo, Q.; Zhai, L., Dispersion of Pristine Carbon Nanotubes Using Conjugated Block Copolymers. Adv. Mater. 2008, 20, 2055-2060. (10) Sakellariou, G.; Priftis, D.; Baskaran, D., Surface-Initiated Polymerization from Carbon Nanotubes: Strategies and Perspectives. Chem. Soc. Rev. 2013, 42, 677-704. (11) Ji, Y.; Huang, Y. Y.; Tajbakhsh, A. R.; Terentjev, E. M., Polysiloxane Surfactants for the Dispersion of Carbon Nanotubes in Nonpolar Organic Solvents. Langmuir 2009, 25, 1232512331. (12) Lou, X.; Daussin, R.; Cuenot, S.; Duwez, A.-S.; Pagnoulle, C.; Detrembleur, C.; Bailly, C.; Jérôme, R., Synthesis of Pyrene-Containing Polymers and Noncovalent Sidewall Functionalization of Multiwalled Carbon Nanotubes. Chem. Mater. 2004, 16, 4005-4011. (13) Meuer, S.; Braun, L.; Zentel, R., Solubilisation of Multi Walled Carbon Nanotubes by αPyrene Functionalised PMMA and Their Liquid Crystalline Self-Organisation. Chem. Commun. 2008, 3166-3168. (14) Yuan, W. Z.; Mao, Y.; Zhao, H.; Sun, J. Z.; Xu, H. P.; Jin, J. K.; Zheng, Q.; Tang, B. Z., Electronic Interactions and Polymer Effect in the Functionalization and Solvation of Carbon


22

Page 23 of 27

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


Nanotubes by Pyrene- and Ferrocene-Containing Poly(1-Alkyne)s. Macromolecules 2008, 41, 701-707. (15) Vijayakumar, C.; Balan, B.; Kim, M.-J.; Takeuchi, M., Noncovalent Functionalization of Swnts with Azobenzene-Containing Polymers: Solubility, Stability, and Enhancement of Photoresponsive Properties. J. Phys. Chem. C 2011, 115, 4533-4539. (16) Jeon, I.-Y.; Choi, H.-J.; Jung, S.-M.; Seo, J.-M.; Kim, M.-J.; Dai, L.; Baek, J.-B., LargeScale Production of Edge-Selectively Functionalized Graphene Nanoplatelets Via Ball Milling and Their Use as Metal-Free Electrocatalysts for Oxygen Reduction Reaction. J. Am. Chem. Soc. 2013, 135, 1386-1393. (17)

Fan, X.; Chang, D. W.; Chen, X.; Baek, J.-B.; Dai, L., Functionalized Graphene

Nanoplatelets from Ball Milling for Energy Applications. Curr. Opin. Chem. Eng. 2016, 11, 5258. (18) Wu, H.; Zhao, W.; Hu, H.; Chen, G., One-Step in Situ Ball Milling Synthesis of PolymerFunctionalized Graphene Nanocomposites. J. Mater. Chem. 2011, 21, 8626-8632. (19) Yang, Z.; Kuang, W.; Weng, P.; Tang, Z.; Guo, B., Graphene Oxide/Rhodanine Redox Chemistry and Its Application in Designing High-Performance Elastomer/Graphene Composites. RSC Adv. 2015, 5, 84398-84405. (20) Beyer, M. K.; Clausen-Schaumann, H., Mechanochemistry: The Mechanical Activation of Covalent Bonds. Chem. Rev. 2005, 105, 2921-2948. (21)

Kardaş, G.; Solmaz, R., Electrochemical Synthesis and Characterization of a New

Conducting Polymer: Polyrhodanine. Appl. Surf. Sci. 2007, 253, 3402-3407. (22) Kong, H.; Song, J.; Jang, J., One-Step Fabrication of Magnetic γ-Fe2O3/Polyrhodanine Nanoparticles Using in Situ Chemical Oxidation Polymerization and Their Antibacterial


23


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 24 of 27

Properties. Chem. Commun. 2010, 46, 6735-6737. (23) Song, J.; Song, H.; Kong, H.; Hong, J.-Y.; Jang, J., Fabrication of Silica/Polyrhodanine Core/Shell Nanoparticles and Their Antibacterial Properties. J. Mater. Chem. 2011, 21, 1931719323. (24) Enchev, V.; Petkov, I.; Chorbadjiev, S., Tautomerism of Rhodanine. Struct. Chem. 1994, 5, 225-231. (25) Tahmassebi, D., Theoretical Studies of the Tautomerism in Oxazolidine and Thiazolidine Heterocyclic Systems. J. Mol. Struct.: THEOCHEM 2003, 638, 11-20. (26) Liu, X.; Zhao, S.; Zhang, X.; Li, X.; Bai, Y., Preparation, Structure, and Properties of Solution-Polymerized Styrene-Butadiene Rubber with Functionalized End-Groups and Its SilicaFilled Composites. Polymer 2014, 55, 1964-1976. (27) Kuang, W.; Yang, Z.; Tang, Z.; Guo, B., Wrapping of Polyrhodanine onto Tubular Clay and Its Prominent Effects on the Reinforcement of the Clay for Rubber. Composites, Part A 2016, 84, 344-353. (28) Tang, J.; Song, Y.; Tanvir, S.; Anderson, W. A.; Berry, R. M.; Tam, K. C., Polyrhodanine Coated Cellulose Nanocrystals: A Sustainable Antimicrobial Agent. ACS Sustainable Chem. Eng. 2015, 3, 1801-1809. (29) Laird, E. D.; Wang, W.; Cheng, S.; Li, B.; Presser, V.; Dyatkin, B.; Gogotsi, Y.; Li, C. Y., Polymer Single Crystal-Decorated Superhydrophobic Buckypaper with Controlled Wetting and Conductivity. ACS Nano 2012, 6, 1204-1213. (30) Oh, J. Y.; Yang, S. J.; Park, J. Y.; Kim, T.; Lee, K.; Kim, Y. S.; Han, H. N.; Park, C. R., Easy Preparation of Self-Assembled High-Density Buckypaper with Enhanced Mechanical Properties. Nano Lett. 2015, 15, 190-197.


24

Page 25 of 27

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


(31) Jia, L.; Petretic, A.; Molev, G.; Guerin, G.; Manners, I.; Winnik, M. A., Hierarchical Polymer–Carbon Nanotube Hybrid Mesostructures by Crystallization-Driven Self-Assembly. ACS Nano 2015, 9, 10673-10685. (32) Berhan, L.; Yi, Y. B.; Sastry, A. M.; Munoz, E.; Selvidge, M.; Baughman, R., Mechanical Properties of Nanotube Sheets: Alterations in Joint Morphology and Achievable Moduli in Manufacturable Materials. J. Appl. Phys. 2004, 95, 4335-4345. (33)

Han,

J.-H.;

Zhang,

H.;

Chen,

M.-J.;

Wang,

G.-R.;

Zhang,

Z.,

CNT

Buckypaper/Thermoplastic Polyurethane Composites with Enhanced Stiffness, Strength and Toughness. Compos. Sci. Technol. 2014, 103, 63-71. (34) Li, J.; Gao, Y.; Ma, W.; Liu, L.; Zhang, Z.; Niu, Z.; Ren, Y.; Zhang, X.; Zeng, Q.; Dong, H.; Zhao, D.; Cai, L.; Zhou, W.; Xie, S., High Performance, Freestanding and Superthin Carbon Nanotube/Epoxy Nanocomposite Films. Nanoscale 2011, 3, 3731-3736. (35) Trakakis, G.; Tasis, D.; Aggelopoulos, C.; Parthenios, J.; Galiotis, C.; Papagelis, K., Open Structured in Comparison with Dense Multi-Walled Carbon Nanotube Buckypapers and Their Composites. Compos. Sci. Technol. 2013, 77, 52-59. (36)

Ata, S.; Kobashi, K.; Yumura, M.; Hata, K., Mechanically Durable and Highly

Conductive Elastomeric Composites from Long Single-Walled Carbon Nanotubes Mimicking the Chain Structure of Polymers. Nano Lett. 2012, 12, 2710-2716. (37) Shin, M. K.; Oh, J.; Lima, M.; Kozlov, M. E.; Kim, S. J.; Baughman, R. H., Elastomeric Conductive Composites Based on Carbon Nanotube Forests. Adv. Mater. 2010, 22, 2663-2667. (38) Sekitani, T.; Noguchi, Y.; Hata, K.; Fukushima, T.; Aida, T.; Someya, T., A Rubberlike Stretchable Active Matrix Using Elastic Conductors. Science 2008, 321, 1468-1472. (39) Cai, L.; Li, J.; Luan, P.; Dong, H.; Zhao, D.; Zhang, Q.; Zhang, X.; Tu, M.; Zeng, Q.;


25


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 26 of 27

Zhou, W.; Xie, S., Highly Transparent and Conductive Stretchable Conductors Based on Hierarchical Reticulate Single-Walled Carbon Nanotube Architecture. Adv. Funct. Mater. 2012, 22, 5238-5244. (40) Yao, S.; Zhu, Y., Nanomaterial-Enabled Stretchable Conductors: Strategies, Materials and Devices. Adv. Mater. 2015, 27, 1480-1511. (41) Wang, X.; Li, T.; Adams, J.; Yang, J., Transparent, Stretchable, Carbon-Nanotube-Inlaid Conductors Enabled by Standard Replication Technology for Capacitive Pressure, Strain and Touch Sensors. J. Mater. Chem. A 2013, 1, 3580-3586. (42) Niu, Z.; Dong, H.; Zhu, B.; Li, J.; Hng, H. H.; Zhou, W.; Chen, X.; Xie, S., Highly Stretchable, Integrated Supercapacitors Based on Single-Walled Carbon Nanotube Films with Continuous Reticulate Architecture. Adv. Mater. 2013, 25, 1058-1064. (43)

Peddini, S. K.; Bosnyak, C. P.; Henderson, N. M.; Ellison, C. J.; Paul, D. R.,

Nanocomposites from Styrene–Butadiene Rubber (SBR) and Multiwall Carbon Nanotubes (MWCNT) Part 2: Mechanical Properties. Polymer 2015, 56, 443-451. (44) Wu, S.; Lin, T.; Guo, B., Elastic-Resilience-Induced Dispersion of Carbon Nanotubes: A Novel Way of Fabricating High Performance Elastomer. Nanotechnology 2013, 24, 465708. (45) Deng, F.; Ito, M.; Noguchi, T.; Wang, L.; Ueki, H.; Niihara, K.-i.; Kim, Y. A.; Endo, M.; Zheng, Q.-S., Elucidation of the Reinforcing Mechanism in Carbon Nanotube/Rubber Nanocomposites. ACS Nano 2011, 5, 3858-3866.


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Table of Content


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Generic Mechanochemical Grafting Strategy toward Organophilic

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