Sage Journals: Discover world-class research

Abstract

The chiral poly(amide-imide) (PAI) was synthesized by the direct polycondensation reaction of imide-dicarboxylic acid, N-trimellitylimido-l-phenylalanine with diamine and 1,5-naphthalenediamine. Multiwalled carbon nanotubes (MWCNTs)/polymer composite films were prepared via dispersing of acid-functionalized MWCNTs (MWCNT-COOH) as reinforcement at MWCNT loadings of 5, 10, and 15 wt%. The PAI/MWCNT composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy (TEM). The TEM results confirmed that the carboxylated MWCNTs were well dispersed in the polymer matrix. The thermogravimetric analysis data showed an improvement of thermal stability of composites containing the MWCNT as compared to the pure polymer. In this research, PAI/MWCNT composite 15 wt% was used as a novel and efficient adsorbent for removal of malachite green dye from aqueous solution.

Keywords

Carbon nanotube poly(amide-imide)composites malachite green

Introduction

Ijima first discovered carbon nanotubes (CNTs) in 1991.¹ Since then, attention to this class of one-dimensional nanomaterials has been growing in various disciplines because of their unique electrical, mechanical, and thermal properties.^2,3 It is well known that CNTs have found in a wide range of applications such as electronic devices,⁴ biosensors,⁵ field emission displays,⁶ hydrogen storage,⁷ and composites.⁸ Furthermore, CNTs are exciting ultra-high-strength reinforcements in polymer matrix composites.^9

–12 CNTs with higher flexibility and lower density can enhance the mechanical, thermal, and conductive properties of the polymers as compared to metal nanofillers. Nanotube–polymer composites have applications in ultrafast all-optical switches,¹³ electromagnetic interference shielding,¹⁴ photovoltaic devices,¹⁵ gas sensors,¹⁶ and biocatalytic films.¹⁷

Aromatic polyimides are well known as a class of high-performance polymers because of their excellent thermal, mechanical, chemical, and physical properties.^18,19 However, their poor processability has been major problems as a result of high melting or glass transition temperatures and limited solubility in most organic solvents. To overcome such a difficulty, different copolyimides have been developed. Therefore, poly(amide-imide)s (PAI)s have been developed as one of the most successful classes of high-performance polymers that offer a concession between the superior mechanical properties associated with amide units and the high thermal stability gritty by imide structures.^20
–22

The design and development of synthetic optically active polymers have received considerable attention due to their sophisticated functions related to their structures. Synthetic chiral polymers are applied in various uses, for instance, the separation of racemic compounds,²³ electrodes for enantioselective recognition for performing bioelectro synthesis,²⁴ microwave absorbents,²⁵ liquid crystals,²⁶ nonlinear optics,²⁷ and the catalysis of asymmetric syntheses.²⁸ Amino acid–based chiral polymers are likely to possess crystallinity with the ability to form higher ordered structures that show enhanced solubility characteristics.²⁹

In this study, we report the fabrication and characterization of composite films by the dispersion of acid-functionalized multiwalled carbon nanotubes (MWCNTs) in a chiral PAI containing amino acid, l-phenylalanine. The resulting composites were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). This study also reports on the feasibility of applying PAI/MWCNTs composite as an efficient adsorbent for malachite green (MG) removal from aqueous solution.

Experimental

Materials

All chemicals were purchased from Fluka Chemical Co. (Buchs, Switzerland), Aldrich Chemical Co. (Milwaukee, WI, USA), Riedel-deHaen AG (Seelze, Germany), and Merck Chemical Co (Darmstadt, Germany). 1,2,4-Benzene tricarboxylic anhydride, l-phenylalanine, and 1,5-naphthalenediamine were utilized as obtained without additional purification. MWCNT (diameter 10–20 nm, length approximately 30 μm, and purity >95 wt%) was purchased from Neutrino Co. (Tehran, Iran). N-Methyl-2-pyrrolidinone (NMP) was dried over barium oxide, followed by fractional distillation. The MG, (C.I. Basic Green 4 C.I.) with classification number of 42000, chemical formula of C₅₂H₅₄N₄O₁₂ (M _w = 927.00), and λ _max of 617 nm was supplied by Sigma-Aldrich (M) Sdn Bhd, Malaysia, and used as received.

Techniques

Proton nuclear magnetic resonance (¹H NMR) spectra were recorded on Bruker Avance 400 MHz spectrometer (Rheinstetten, Germany) in dimethyl sulfoxide-d ₆ (DMSO-d ₆). Inherent viscosity was measured by a standard procedure using a Cannon-Fenske routine viscometer (Mainz, Germany) at the concentration of 0.5 g/dL at 25°C. FTIR spectra were recorded with a Jasco-680 spectrometer (Tokyo, Japan) in the range of 400–4000 cm⁻¹. Vibration bands were reported as wave number (cm⁻¹). FTIR spectra of all samples were collected by making their pellets in KBr as a medium. The XRD pattern of prepared materials was recorded in the reflection mode using a Bruker, D8 Advance diffractometer (Rheinstetten, Germany). Nickel-filtered CuKα radiation (radiation wavelength, λ = 0.154 nm) was produced at an operating voltage of 45 kV and a current of 100 mA. The redox behavior was investigated with cyclic voltammetry (CV) on a potentiostat (EG&G Co., PARSTAT 2273, Tennessee, USA) instrument. It was conducted for the dipped polymer film on the working electrode in dry acetonitrile containing tetrabutylammonium hexafluorophosphate (0.1 M) as an electrolyte. The morphology and dispersity analysis were performed on TEM analyzer on Philips CM 120 (Eindhoven, The Netherlands) operating at 100 kV. The reaction was carried out on a Misonix ultrasonic liquid processor (Eindhoven, The Netherlands), XL-2000 Series (Eindhoven, The Netherlands). Ultrasound was a wave of frequency 2.25 × 10⁴ Hz and power 100 W. TGA is performed with a STA503 (Eindhoven, The Netherlands) win TA at a heating rate of 10°C/min from 25°C to 800°C under a nitrogen atmosphere.

Monomer synthesis

N-Trimellitylimido-l-phenylalanine (1) as an imide-dicarboxylic acid monomer was prepared according to the reported procedure (Figure 1).³⁰

Figure 1.

Synthesis of imide-dicarboxylic acid monomer 1.

Polymer synthesis

A mixture of 0.10 g (2.95 × 10⁻⁴ mol) of imide-dicarboxylic acid 1, 0.0466 g (2.95 × 10⁻⁴ mol) of diamine, 1,5-naphthalenediamine (2), 0.06 g of calcium chloride, 0.31 mL (1.18 × 10⁻³ mol) of triphenyl phosphite (TPP), 0.15 mL of pyridine, and 0.4 mL of NMP was refluxed for 3 h. After cooling, the reaction mixture was poured into 30 mL of methanol with constant stirring, and the precipitate was washed thoroughly with methanol and hot water, collected on a filter, and dried under vacuum to give 0.114 g (78%) of PAI.

PAI: FTIR (KBr, cm⁻¹): υ = 3276 (m), 3027 (m), 2927 (m), 1776 (m), 1718 (s), 1675 (s), 1617 (s), 1600 (s), 1485 (m), 1380 (m), 1327 (m). ¹H NMR (DMSO-d ₆, ppm): δ = 10.87 (d, 1H, N–H), 10.29 (d, 1H, N–H), 8.56–7.10 (m, Ar), 5.40 (m, 1H, CH), 3.64 (m, 2H).

Functionalization of MWCNT

The chemical treatment on MWCNTs was done as suggested by Esumi et al.³¹ The required sample of MWCNTs was suspended in the mixture of concentrated nitric acid (65%) and sulfuric acid (98%) by the volume ratio of 1:3 and refluxed at 140°C for 30 min. After washing the MWCNTs with deionized water until the supernatant attained a pH around 7, the samples were dried at 100°C. Thus, the chemically treated sample was obtained.

Preparation of the PAI/MWCNT-COOH composite films

PAI/MWCNT-COOH composite films were prepared with different weight percentages of MWCNT-COOH (5, 10, and 15 wt%) as follows:

First, PAI was dissolved and MWCNT-COOH was separately dispersed in DMAc with stirring at 40°C for 1 day. Then, two stock solutions were mixed to achieve the desired weight percentages of MWCNT-COOH (5, 10, and 15 wt%). The PAI/MWCNT-COOH mixture was stirred at 40°C for 1 day and then ultrasonicated in a water bath for 2 h. The PAI/MWCNT-COOH mixture was spread on a glass plate, and the solvent was removed at 60°C for 1 day; then, the semidried film was further dried in vacuum at 160°C for 8 h in order to remove the residue solvent and a solid film was formed.

PAI/MWCNT-COOH 10 wt%: FTIR (KBr, cm⁻¹): υ = 3434 (m), 2923 (m), 1778 (m), 1716 (m), 1639 (m), 1378 (m).

Results and discussion

Polymer synthesis

The PAI was prepared via the direct polycondensation of optically active imide-dicarboxylic acid 1 with aromatic diamine 2 through Yamazaki phosphorylation reaction, using TPP/Py/NMP/CaCl₂ as a condensing agent (Figure 2). The polymerization in NMP proceeded homogeneously, indicating that the polymer showed good solubility in the polymerization media. The PAI was obtained almost in good yield (78%) and had inherent viscosity value 0.41 dL g⁻¹. The structure of PAI was confirmed by FTIR and ¹H NMR spectroscopic analyses. FTIR spectrum of PAI (Figure 3(a)) revealed the characteristic absorptions of imide groups occurred at 1776, 1718, and 1380 cm⁻¹, and those of the amide group occurred around 3276 and 1675 cm⁻¹. The assignments of the ¹H NMR spectrum of PAI agree well with the proposed polymer structure (Figure 4).

Figure 2.

Preparation of PAI. PAI: poly(amide-imide).

Figure 3.

FTIR spectra of PAI and the PAI/MWCNT composites: (a) PAI, (b) MWCNT/PAI 5 wt%, (c) MWCNT/PAI 10 wt%, (d) MWCNT/PAI 15 wt%, (e) acid-functionalized MWCNT. PAI: poly(amide-imide); MWCNT: multiwalled carbon nanotube.

Figure 4.

¹H NMR spectrum of PAI in DMSO-d ₆ solution.

Preparation of PAI/MWCNT-COOH composite films

The effective utilization of nanotubes in composites depends on the ability to disperse CNTs homogeneously throughout the matrix without destroying their integrity. Also, prior to the mixing of CNTs with a matrix, it is required to perform a chemical treatment on CNTs, since a better interfacial bonding between CNT and polymer and also the enhancement of load transfer are believed to occur. So, for better dispersion of MWCNTs into the polymer matrix, carboxylated MWCNTs were applied in this work. PAI/MWCNT-COOH composite films were prepared by dispersion of the different amounts of acid-functionalized MWCNT (5, 10, and 15 wt%) solutions of PAI in DMAc via a vigorous stirring for 1 day, using a homogenizer, followed by utrasonication for 2 h.

Characterization of the composites

The acid-functionalized MWCNTs were characterized by FTIR. The FTIR spectrum of carboxylated MWCNTs (Figure 3(e)) shows a broad absorption band centered at 3424 cm⁻¹, which is attributed to the O–H stretching bands of carboxylic acid moieties from the surface of MWCNTs. The peak around 2923 cm⁻¹ is ascribed to aliphatic sp³ C–H of defects.³² The presence of MWCNTs in the polymer matrix showed very little changes in the FTIR spectrum, probably due to the low MWCNT composition and the weak vibration signals of MWCNTs. The FTIR spectra of PAI/MWCNT-COOH composites with different contents of MWCNT-COOH are shown in Figure 3(b) to (d). From these data, it is clear that with increasing the amount of MWCNT-COOH, the intensity of absorption related to aliphatic sp³ C–H bonds was enhanced.

XRD patterns of PAI (a), PAI/MWCNT-COOH composite 10 wt% (b), and MWCNT-COOH (c) are given in Figure 5. The diffraction pattern for the pure PAI shown in Figure 5(a) demonstrates that the PAI is completely amorphous. For the MWCNTs, two peaks appear at 2θ =26° and 43° which correspond to the interlayer spacing d ₍₀₀₂₎ and d ₍₁₀₀₎ reflection of the CNTs (Figure 5(b)).³³

Figure 5.

XRD patterns for (a) neat PAI, (b) MWCNT/PAI composite containing 10 wt% MWCNT, and (c) MWCNT-COOH.

TEM analysis was performed for PAI/MWCNT-COOH composite 10 wt% to identify the distribution of MWCNT within polymer matrix. Figure 6 shows the TEM image of the composite 10 wt%. As can be seen, the MWCNTs were well dispersed in the polymer matrix.

Figure 6.

TEM image of PAI/MWCNT composite containing 10 wt% MWCNT. PAI: poly(amide-imide); MWCNT: multiwalled carbon nanotube.

The ultraviolet–visible (UV–vis) spectra of the PAI and composites were recorded in DMF. It is apparent that the wavelength of maximum absorption is related to the π → π* transition resulting from the conjugation between the aromatic rings and nitrogen atoms in the aforementioned compounds. All of these compounds show almost similar UV–vis spectra pattern. The PAI showed maximum absorption at 304 nm, while the composite films exhibited maximum absorption around 298 nm in DMF solution. In UV–vis spectra of the composite films with different MWCNT contents with the increasing CNT, the absorption band moves toward shorter wavelength.

Charge transport in organic materials is believed to be governed by the hopping process involving redox reaction of charge transport molecules. CV is a preliminary characterization method to determine the redox properties of polymeric materials. Figure 7 shows the representative cyclic voltammogram of PAI/MWCNT-COOH composite 15 wt% in acetonitrile with 0.1 M Bu₄NPF₆. One pair of redox waves was observed in these composites. As shown in this figure, composite showed an oxidation wave of which a peak top is at 1.7 V (versus Ag/AgCl).

Figure 7.

Cyclic voltammogram of PAI/MWCNT-COOH composite containing 10 wt% MWCNT in acetonitrile with 0.1 M Bu₄NPF₆.

The thermal properties of pure PAI and PAI/MWCNT-COOH composites 5 and 15 wt% were studied using TGA at a heating rate of 10°C min⁻¹, under a nitrogen atmosphere. The TGA curves of pure PAI and PAI/MWCNT-COOH composites 5 and 15 wt% are shown in Figures 8 to 10. The thermoanalysis data of these samples are summarized in Table 1. These studies show that the composites are thermally stable up to 450°C. The 10% weight loss temperatures of the pure PAI and composites were recorded in 498, 523, and 537°C for PAI and PAI/MWCNT-COOH composites 5 and 15 wt%, respectively. The amount of residue (char yield (CR)) of these composites was more than 12% at 800°C. As shown in Figures 9 and 10, the thermal stability of composites is higher than pure PAI that is due to the good compatibility of carboxylated MWCNTs with polymer matrix. CNTs have high thermal stability due to their larger surface area, so the incorporation of MWCNTs can improve the thermal resistance of composites.

Figure 8.

TGA thermogram of neat PAI. PAI: poly(amide-imide); TGA: thermogravimetric analysis.

Figure 9.

TGA thermogram of PAI/MWCNT composite containing 5 wt% MWCNT. PAI: poly(amide-imide); TGA: thermogravimetric analysis; MWCNT: multiwalled carbon nanotube.

Figure 10.

TGA thermogram of PAI/MWCNT composite containing 15 wt% MWCNT. PAI: poly(amide-imide); TGA: thermogravimetric; MWCNT: multiwalled carbon nanotube.

Table 1.

Thermal properties of the pure PAI and PAI/MWCNT composite films 5 and 15 wt%.

Polymer	Decomposition temperature (°C)		Char yield^c (%)	LOI
Polymer	T ₅ ^a	T ₁₀ ^b	Char yield^c (%)	LOI
PAI	465	498	9	17.9
PAI/MWCNT 5 wt%	500	523	12	22.3
PAI/MWCNT 15 wt%	512	537	22	26.3

LOI: limiting oxygen index; PAI: poly(amide-imide); TGA: thermogravimetric analysis; MWCNT: multiwalled carbon nanotube.

^aTemperature at which 5% weight loss was recorded by TGA at a heating rate of 10°C/min under nitrogen atmosphere.

^bTemperature at which 10% weight loss was recorded by TGA at a heating rate of 10°C/min under nitrogen atmosphere.

^cPercentage weight of material left undecomposed after TGA analysis at maximum temperature 800°C under nitrogen atmosphere.

CR can be applied as decisive factor for estimating limiting oxygen index (LOI) of the polymers based on Van Krevelen and Hoftyzer equation³⁴:

LOI = 17.5 + 0.4CR .

The composites had LOI values calculated derived from their CR was higher than 22. On the basis of LOI values, such composites can be classified as self-extinguishing materials.

Removal of MG from aqueous solution by PAI/MWCNT-COOH composite 15 wt% adsorbent

PAI/MWCNT 15 wt% was used as a novel and effective adsorbent for ultrasonic-assisted removal of MG dye from aqueous solution. The sonochemical adsorption experiment was carried out in a batch method as follows: 0.02 g of adsorbent was thoroughly dispersed in 50 mL of MG solution (5 mg L⁻¹) at pH 6, and Erlenmeyer flask was immersed in an ultrasonic bath for 30, 45, and 60 min at room temperature. In later stage, the sample was immediately centrifuged for 5 min at 3500–4000 r min⁻¹ and MG final concentration was quantified by UV–vis spectrophotometer. Figure 11 shows the UV–vis absorption spectra obtained at different times of ultrasonication exposed to reaction mixture. The quantitative amount of MG removed by PAI/MWCNT-COOH composite 15 wt% was obtained higher than 62%.

Figure 11.

The change in UV–Vis spectra after the addition of 0.02 g PAI/MWCNT composite containing 15 wt% MWCNT to 5 mg L⁻¹ MG at pH 6) at different times (0–45 min.)

Conclusions

Novel optically active amino acid–based PAI/MWCNT-COOH composite films were successfully prepared and characterized by different methods. For prevention of aggregation, the carboxyl-modified MWCNTs were used. TEM image confirmed nanoscale and homogeneous dispersion of MWCNTs in the PAI matrix. The TGA results indicate that the resulting PAI/MWCNT-COOH composite films are thermally stable. The use of PAI/MWCNT-COOH composite film as eco-friendly adsorbent was investigated as an ideal alternative material for toxic adsorbents to remove MG from wastewater.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflict of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors wish to express gratitude to the Yasouj University for financial assistance.

ORCID iD

Zahra Rafiee

References

Iijima

. Helical microtubules of graphitic carbon. Nature 1991; 354: 56–58.

Lourie

Dyer

. Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load. Science 2000; 287: 637–640.

Wilder

Venema

Rinzler

. Electronic structure of atomically resolved carbon nanotubes. Nature 1998; 391: 59–62.

Timmermans

Estrada

Nasibulin

. Effect of carbon nanotube network morphology on thin film transistor performance. Nano Res 2012; 5: 307–319.

Wang

. Carbon-nanotube based electrochemical biosensors: a review. Electroanal 2005; 17: 7–14.

Alvi

Al-Ghamdi

Husain

. Field emission study of MWCNT/conducting polymer nanocomposite. Physica B: Condensed Mater 2014; 454: 31–34.

Liu

Chen

. Hydrogen storage in carbon nanotubes revisited. Carbon 2010; 48: 452–455.

Khare

Bose

. Carbon nanotube based composites-A review. J Miner Mater Charact Eng 2005; 4: 31–46.

Spitalsky

Tasis

Papagelis

. Carbon nanotube-polymer composites: chemistry, processing, mechanical and electrical properties. Prog Polym Sci 2010; 35: 357–401.

10.

Liu

Kumar

. Polymer/carbon nanotube nanocomposite fibers—a review. ACS Appl Mater Interfaces 2014; 6: 6069–6087.

11.

Velasco-Santos

Martinez-Hernandez

Castano

. Carbon nanotube-polymer nanocomposites: the role of interfaces. Compos Interface 2005; 11: 567–586.

12.

Al-Shabanat

. Electrical studies of nanocomposites consisting of MWNTs and polystyrene. J Polym Res 2012; 19: 9795–9802.

13.

Son

Ryu

Park

. A nonvolatile memory device made of a ferroelectric polymer gate nanodot and a single-walled carbon nanotube. ACS NANO 2010; 4: 7315–7320.

14.

Zhang

Shi

. Preparation and microwave absorbing characteristics of multi-walled carbon nanotube/chiral-polyaniline composites. J Polym Chem 2014; 4: 62–72.

15.

Yun

Feng

. Controllable functionalization of single-wall carbon nanotubes by in situ polymerization method for organic photovoltaic devices. Synth Met 2008; 158: 977–983.

16.

Sharma

Hussain

Singh

. MWCNT-conducting polymer composite based ammonia gas sensors: a new approach for complete recovery process. Sens Actuators B: Chem 2014; 194: 213–219.

17.

Rege

Raravikar

Kim

. Enzyme-polymer-single walled carbon nanotube composites as biocatalytic films. Nano Lett 2004; 3: 829–832.

18.

Ghosh

Mittal

. Polyimides: Fundamentals and applications. New York: Marcel Decker, 1996.

19.

Bauer

Farris

. Stresses in polyimide films. In: Feger

Khojasteh

McGrath

(eds) Polyimides: Materials, chemistry and characterization. Amsterdam: Elsevier, 1989, pp. 549–562.

20.

Zhang

. Synthesis and properties of polyamide-imides containing fluorenyl cardo structure. J Appl Polym Sci 2007; 106: 2494–2501.

21.

Liaw

. Synthesis and characterization of new polyamide-imides containing pendent adamantyl groups. Polymer 2001; 42: 839–845.

22.

Mallakpour

Shahmohammadi

. Synthesis of new optically active poly(amide-imide)s derived from N, N′-(pyromellitoyl)-bis-S-valine diacid chloride and aromatic diamines under microwave irradiation and classical heating. Iranian Polym J 2005; 14: 473–483.

23.

Nakano

. Optically active synthetic polymers as chiral stationary phases in HPLC. J Chromatogr A 2001; 906: 205–225.

24.

Chen

Takei

Deore

. Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate. Analyst 2000; 125: 2249–2254.

25.

Petrov

Gagulin

. Microwave absorbing materials. Inorg Mater 2001; 37: 93–98.

26.

Shibaev

Bobrovsky

Boiko

. Photoactive liquid crystalline polymer systems with light-controllable structure and optical properties. Prog Polym Sci 2003; 28: 729–836.

27.

Singer

Petschek

Ostroverkhov

. Non-polar second-order nonlinear and electro-optic materials: axially ordered chiral polymers and liquid crystals. J Polym Sci Part B: Polym Phys 2003; 41: 2744–2754.

28.

Hodge

Synthesis of peptides and polynucleotides. In: Epton

(ed) Innovation and perspectives in solid phase synthesis. Birmingham, England: SPCC (UK) Ltd., 1990, p. 273.

29.

Baughman

Wagener

. Recent advances in ADMET polymerization, metathesis polymerization. Adv Polym Sci 2005; 176: 1–42.

30.

Mallakpour

Hajipour

Habibi

. Synthesis of new poly(amide-imide)s derived from trimellitylimido-L-phenylalanine. Polym Int 2001; 50: 331–337.

31.

Esumi

Ishigami

Nakajima

. Chemical treatment of carbon nanotubes. Carbon 1996; 34: 279–281.

32.

Lee

Choi

. In situ synthesis of poly(ethylene terephthalate) (PET) in ethylene glycol containing terephthalic acid and functionalized multiwalled carbon nanotubes (MWNTs) as an approach to MWNT/PET nanocomposites. Chem Mater 2005; 17: 5057–5064.

33.

Perez-Cabero

Rodriguez-Ramos

Guerrero-Ruiz

. Characterization of carbon nanotubes and carbon nanofibers prepared by catalytic decomposition of acetylene in a fluidized bed reactor. J Catal 2003; 215: 305–316.

34.

Van Krevelen

Hoftyzer

. Properties of polymers, 3rd ed. Amsterdam: Elsevier, 1976.

Synthesis and characterization of chiral poly(amide-imide) composite thin films containing functionalized multiwalled carbon nanotubes

Abstract

Keywords

Introduction

Experimental

Materials

Techniques

Monomer synthesis

Polymer synthesis

Functionalization of MWCNT

Preparation of the PAI/MWCNT-COOH composite films

Results and discussion

Polymer synthesis

Preparation of PAI/MWCNT-COOH composite films

Characterization of the composites

Removal of MG from aqueous solution by PAI/MWCNT-COOH composite 15 wt% adsorbent

Conclusions

Footnotes

Declaration of Conflicting Interests

Funding

ORCID iD

References