Arabian Journal of Chemistry (2017) 10, S651–S656

King Saud University

Arabian Journal of Chemistry

www.ksu.edu.sawww.sciencedirect.com

ORIGINAL ARTICLE

New poly(ether-amide-imide) reinforced layersilicate nanocomposite: Synthesis and properties

* Corresponding author. Mobile: +98 9188630427; fax: +98 861

2774031.

E-mail address: k-faghihi@araku.ac.ir (K. Faghihi).

Peer review under responsibility of King Saud University.

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http://dx.doi.org/10.1016/j.arabjc.2012.10.027

1878-5352 ª 2012 Production and hosting by Elsevier B.V. on behalf of King Saud University.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Khalil Faghihi a,*, Saed Aibod a, Meisam Shabanian b

a Polymer Research Laboratory, Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iranb Department of Chemistry, Farahan Branch, Islamic Azad University, Farahan, Iran

Received 18 September 2011; accepted 27 October 2012Available online 16 November 2012

KEYWORDS

Poly(ether-amide-imide);

Nanocomposite;

Organoclay;

Morphology

Abstract A new series of poly(ether-amide-imide)/organoclay were generated through solution

intercalation technique. Cloisite� 20A was used as a Modified montmorillonite for ample compat-

ibilization with the PEAI matrix. The poly(ether-amide-imide) (PEAI) 3 chains were synthesized by

the direct polycondensation reaction of N,N0-(4,40-diphenylether)bistrimellitimide 1 with 4,40-dia-

mino diphenyl ether two in the presence of triphenyl phosphite (TPP), CaCl2, pyridine and N-

methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PEAI-nanocomposite

films 3a–3b with (5–10 wt%) silicate particles were characterized by FTIR spectroscopy, X-ray dif-

fraction (XRD) and scanning electron microscopy (SEM). The effect of clay dispersion and the

interaction between clay and polymeric chains on the properties of nanocomposite films were inves-

tigated by using UV–Vis spectroscopy, thermogravimetric analysis (TGA) and water uptake mea-

surements.ª 2012 Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access

article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

1. Introduction

Polymer-clay nanocomposites have received significant atten-tion, since the first report of polyamide-6-clay nanocompositesby Toyota’s research group in 1990 (Lai et al., 2008). Subse-

quent studies have discovered that physical and chemical prop-erties of organic polymers, such as thermal stability, (Lan

et al., 1994) mechanical strength, (Tyan et al., 1999) solvent

resistance, (Burnside and Giannelis, 1995) flame retardation,(Gilman et al., 2000) ionic conductivity, (Vaia et al., 1995)corrosion resistance, (Yu et al., 2004) gas barrier properties,

(Messersmith and Giannelis, 1995), and dielectric properties(Koo et al., 2003) are substantially improved by the introduc-tion of small portions of inorganic clay. Unique properties ofthe nanocomposites are usually observed when the ultra fine

silicate layers are homogenously dispersed throughout thepolymer matrix at nanoscale. The uniform dispersion ofsilicate layers is usually desirable for maximum reinforcement

of the materials. Due to the incompatibility of hydrophiliclayered silicates and hydrophobic polymer matrix, theindividual nanolayers are not easily separated and dispersed

in many polymers. For this purpose, silicate layers are usuallymodified with an intercalating agent to obtain organically

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S652 K. Faghihi et al.

modified clay prior to use in nanocomposite formation(Wilson et al., 1990).

High-performance polymeric materials are currently receiv-

ing considerable attention for their potential applications in ad-vanced technology demands. Aromatic polyimides are wellknown high-performance polymers that show excellent thermal,

mechanical and electrical properties (Cassidy, 1980; Saxenaet al., 2003). However, applications may be rather limited dueto their high softening or melting temperatures and their insol-

uble nature in most organic solvents (Liaw et al., 2001).Modification of high performance materials by increasing

the solubility and lowering the transition temperatures whilemaintaining thermal stability is of particular interest. Copoly-

condensation is one of the possible ways for modification ofpolymer properties. Thus, for the processing of polyimidesmany copolyimides, such as poly(amide-imide)s, poly(ester-imi-

de)s, and other copolymers have been prepared (Mallakpourand Kowsari, 2006; Hajibeygi et al., 2011; Faghihi et al., 2010,2011, 2009a,b; Hale et al., 1967; Johnson et al., 1967).

Aromatic polymers that contain aryl ether linkages gener-ally have lower glass transition temperatures, greater chainflexibility and tractability in comparison to their correspond-

ing polymers of these groups in the chain (Bottino et al.,2001; Gutch et al., 2003; Faghihi et al., 2009a,b).

The lower glass transition temperatures and also improvedsolubility are attributed to the flexible linkages that provide a

polymer chain with a lower energy of internal rotation (Fag-hihi et al., 2009a,b).

In this article, two new PEAI-nanocomposite (PEAIN) films

with 5% and 10% silicate particles were prepared by using aconvenient solution intercalation technique. Poly(ether-amide-imide) was prepared by reacting 4,4-diamino diphenyl

ether two with N,N0-(4,40-diphenylether)bistrimellitimide onein N-methyl-2-pyrrolidone (NMP). Structure and morphologyof the PEAIN were determined by FT-IR, UV–Vis, XRD and

SEM, TGA and water absorption measurements. The newnanocomposites containing ether group have good solubilitywith high thermal stability.

2. Experimental section

2.1. Materials

Trimellitic anhydride, 4,40-diamino diphenyl ether, acetic acid,triphenyl phosphite (TPP), CaCl2, pyridine and N-methyl-2-

pyrrolidone (NMP) were purchased from Merck Chemical

Table 1 Organic modifiers and interlayer distance of the

clays.

Type of clay Organic modifier Concentration of

organic modifier

(meq/100 g clay)

Interlayer

distance g/cc

Cloisite� 20A

N+ HT

HT

CH3

CH395 1.77

HT=Hydrogenated Tallow (�65% C18; �30% C16; �5% C14).

Company and used without further purification. The organi-cally modified Cloisite� 20A supplied by Southern ClayProducts (TX), was used as polymer nano reinforcement.

The organic modifier and the interlayer distance of the claysare shown in Table 1 to account for the structuralmodifications of the functionalizations.

2.2. Monomer synthesis

2.2.1. Synthesis of N,N0-(4,40-diphenylether)bistrimellitimide 1

This compound was prepared according to our previous work(Faghihi and Hajibeygi, 2004).

2.3. Polymer synthesis

A mixture of 1.1 g (2 mmol) of N,N’-(4,40-diphenylether)bistri-mellitimide, 0.4 g (2 mmol) of 4,40-diamino diphenyl ether 2,

0.2 g of CaCl2, 0.6 mL of Pyridine, 2 mL of TPP, and 2 mLof NMP were heated while being stirred at 120 �C for 5 h.The viscosity of the reaction solutions increased after 30 min,

and additional NMP was added to the reaction mixture. Atthe end of the reaction, the obtained polymer solution wastrickled into stirred methanol. The yellow, stringy polymer

was washed thoroughly with hot water and methanol, collectedby filtration, and dried at 100 �C under reduced pressure. Theresulting polymer 3 was dried under vacuum to leave 0.13 g(97%) of solid polymer. The inherent viscosity of this soluble

PEAI 3 was 0.42 dL/g. IR (KBr): 3235 (m), 3064 (m), 1776(w), 1726 (s), 1672 (s), 1605 (m), 1508 (m), 1421 (m), 1380(m), 1302 (s), 1220 (m), 1141 (m), 794 (w), 756 (w), 725(w).

2.4. PEAI-nanocomposite synthesis of 3a and 3b

PEAI-nanocomposites 3a and 3b were produced by the solu-

tion intercalation method, two different amounts of organo-clay particles (5 and 10 wt.%) were mixed with appropriateamounts of PEAI solution in N-methyl-2-pyrrolidone (NMP)

to yield particular nanocomposite concentrations. To controlthe dispersibility of organoclay in poly(amide-imide) matrix,constant stirring was applied at 25 �C for 24 h. Nanocompositefilms were cast by pouring the solutions of each concentration

into Petri dishes placed on a leveled surface followed by theevaporation of solvent at 70 �C for 12 h. Films were dried at

Scheme 1 Synthetic route of N,N0-(4,40-diphenylether)

bistrimellitimide.

New poly(ether-amide-imide) reinforced layer silicate nanocomposite: Synthesis and properties S653

80 �C under vacuum to a constant weight. Scheme 1 shows theflow sheet diagram and the synthetic scheme for PEAI-nano-composite films 3a and 3b.

2.5. Measurements

IR spectra were recorded on a Galaxy series FTIR 5000

spectrophotometer (England). Band intensities are assignedas weak (w), medium (m), strong (s) and band shapes asshoulder (sh), sharp (s) and broad (br). UV–Vis absorptions

were recorded at 25 �C in the 190–700 nm spectral regionswith a Perkin-Elmer Lambda 15 spectrophotometer onNMP solutions by using cell path lengths of 1 cm. Inherent

viscosity was measured by a standard procedure using aTechnico� viscometer. Thermogravimetric analysis (TGA)data were taken on a Mettler TA4000 System under N2atmosphere at a rate of 10 �C/min. The morphology of nano-composite film was investigated on a Cambridge S260 scan-ning electron microscope (SEM).

3. Results and discussion

3.1. Monomer synthesis

Diacid 1 was synthesized by the condensation reaction of twoequimolars of trimellitic anhydride with one equimolar of 4,40-

diamino diphenyl ether in acetic acid solution (Scheme 1).The chemical structure of diacid 3 was confirmed by FT-IR

and 1H-NMR spectroscopy.

Scheme 2 Flow sheet diagram for the synthes

3.2. PEAI-nanocomposite films

PEAI-Nanocomposites were prepared by the appropriateamounts of Cloisite� 20A and PEAI in NMP (Scheme 2).PEAI-nanocomposite films were transparent and yellowish

brown in color. The incorporation of organoclay changedthe color of films to dark yellowish brown. Moreover, a de-crease in the transparency was observed at higher clay con-tents. Scheme 2 shows the flow-sheet diagram and the

synthetic scheme for PEAI-nanocomposite films 3a and 3b.

3.3. FT-IR spectroscopy analysis

FT-IR data of PEAI-nanocomposite films 3b and 3b showedthe characteristic absorption bands of the Si-O and Mg-O moi-eties at 1019 and 1018 cm�1 respectively. The incorporation of

organic groups in PEAI-nanocomposite films was confirmedby the presence of peaks around 1776, 1726, 1380, 725 (imiderings) and 1650 (amide carbonyl group) (Fig. 1).

3.4. X-ray diffraction analysis

The XRD is most useful for the measurement of interlayerspacing of the organoclay upon the formation of the nanocom-

posites. It supplies information on the change of d-spacing ofordered immiscible and ordered intercalated nanocomposites.Fig. 2 shows the XRD patterns of PEAI-nanocomposite films

3a and 3b containing 5 and 10 wt.% of silicate particles. TheCloisite� Na gives a distinct peak around 2h equal to 8.93,

is of PEAI-nanocomposite films 3a and 3b.

Figure 1 FT-IR spectra of PEAI, nanocomposites 3a and 3b.

Figure 2 X-ray diffraction patterns of organoclay, PEAI-nano-

composites 3a and 3b.

S654 K. Faghihi et al.

which corresponds to a basal spacing of around 1.00 nm. Theorganically modified Cloisite� 20A employed for the prepara-tion of nanocomposites has a typical peak at 2h equal to 6.56increased d-spacing, when the amount of organoclay increased(5–10 wt.%) in the nanocomposites. These results indicated a

significant expansion of the silicate layer after the insertionof PEAI chains. The shift in the diffraction peaks of PEAI-Nanocomposite films confirms that intercalation has taken

place. This is direct evidence that PEAI-Nanocomposites havebeen formed as the nature of intercalating agent also affectsthe organoclay dispersion in the polymer matrix. Usually thereare two types of nanocomposites depending upon the disper-

sion of clay particles. The first type is an intercalated polymerclay nanocomposite, which consists of well ordered multi lay-ers of polymer chain and silicate layers a few nanometers thick.

The second type is an exfoliated polymer–clay nanocomposite,in which there is a loss of ordered structures due to the exten-sive penetration of polymer chain into the layer of silicate.

Such part would not produce distinct peaks in the XRD pat-tern (Krishnan et al., 2007).

3.5. Scanning electron microscopy

In order to investigate the morphology, fractured surfacesof PEAI-nanocomposite films were studied using SEM.

The micrographs of the nanocomposites containing 5 and10 wt.% silica in the matrix are shown in Fig. 3. The resultsshow a fine dispersion of silica particles in the matrix when

the concentration of inorganic phase is increased. Nanocom-posite films have a homogeneous distribution with no pref-erential accumulation of silica in any region across the

films. The micrographs also indicate the presence of inter-connected silica domains in the continuous polyamidephase, which demonstrates better compatibility betweensmaller silica nanoparticles and the PEAI in the nanocom-

posite films.

3.6. Optical clarity of PEAI-nanocomposite films

Optical clarity of PEAI-nanocomposite films containing 5–10 wt.% clay platelets and neat PEAI was compared byUV–Vis spectroscopy in the region of 260–800 nm. Fig. 4

shows the UV–Vis transmission spectra of pure PEAI andPEAI-nanocomposite films containing 5 and 10 wt.% clayplatelets. These spectra show that the UV–Visible region(250–800 nm) is affected by the presence of clay particles

and exhibiting low transparency reflected to the primarilyintercalated composites. Results show that pure PEAI andPEAI-nanocomposite films with various amounts of silica

are transparent. The maximum transmittance was found forthe PEAI. The transparency of these naocomposites dependsupon the size and spatial distribution of silica particles in the

PEAI matrix. Nanocomposite films were transparent becausethe average size of ceramic particles is smaller than the wave-length of light, and the distribution of particles is relatively

uniform. Ultimately the tendency for the agglomeration ofsmall particles into larger ones may increase, which decreasesthe homogeneity of the system. As particle size becomes lar-ger, the transmittance values decrease.

3.7. Thermal properties

The thermal properties of PEAI-nanocomposite films contain-

ing 5 and 10 wt.% clay platelets and neat PEAI were investi-gated by TGA in a nitrogen atmosphere at a heating rate of10 �C/min (Fig. 5). Initial decomposition temperature, 5%and 10% weight loss temperatures (T5, T10) and char yieldsare summarized in Table 2. These samples exhibited goodresistance to thermal decomposition. T5 for neat PEAI and

PEAI-nanocomposite films containing 5 and 10 wt.% clayplatelets ranged from 270 to 337 �C and T10 for them rangedfrom 388 to 418 �C, and residual weights at 800 �C rangedfrom 38% to 44.5% in nitrogen respectively. Incorporation

of organoclay into the PEAI matrix also enhanced the thermalstability of the nanocomposites. Thus, we can speculate thatinteracting PEAI chains between the clay layers serve to im-

prove the thermal stability of nanocomposites. The additionof organoclay in polymeric matrix can significantly improvethe thermal stability of PEAI.

Figure 3 SEM micrographs of the PEAI-nanocomposites with various silica contents (wt%): 5 and 10.

Figure 4 UV–Vis spectra of PEAI 5, PEAI-nanocomposite films

3a–3b.

Figure 5 TGA–DTG curve for (a) PEAI, (b) PEAI-nanocom-

posite 3a, and (c) PEAI-nanocomposite 3b.

Table 2 Thermal behaviors and water uptake of neat PEAI 3

and PEAI-nanocomposite films 3a and 3b.

Polyimide T5 (�C) a T10 (�C)b Char Yield c Water uptake (%)

3 270 388 38 16.01

3a 337 400 40 13.85

3b 327 418 44.5 11.55

a,b Temperature at which 5% or 10% weight loss was recorded by

TGA at a heating rate of 10 �C/min in N2.c Weight percentage of material left after TGA analysis at a

maximum temperature of 800 �C in N2.

New poly(ether-amide-imide) reinforced layer silicate nanocomposite: Synthesis and properties S655

3.8. Water absorption measurements

The water absorption of PEAI-nanocomposite films was car-ried out using a procedure under ASTM D570-81 (Zulfiqarand Sarwar, 2008). The results showed a monotonic maxi-

mum water uptake for the pure polyamide (16.01%) butan asymptotic decrease thereafter (Table 2). The exposureof polar groups to the surface of polymer where water mol-

ecules develop secondary bond forces with these groups. Theclay platelets obviously restrict the access of water to thehydrogen-bonding sites on the polymer chains. The weight

gain by the films gradually decreased as the clay contentwas increased. It is apparently due to the mutual interactionbetween the organic and inorganic phases. This interaction

resulted in the lesser availability of polar groups to interactwith water. Secondly, the impermeable clay layers mandatea tortuous pathway for a permeant to transverse the nano-composite. The enhanced barrier characteristics, chemical

resistance and reduced solvent uptake of PEAI-nanocompos-ites all benefit from the hindered diffusion pathways throughthe nanocomposite.

S656 K. Faghihi et al.

4. Conclusions

The PEAI-nanocomposites were successfully prepared usingthe solution intercalation method. The structure and the uni-

form dispersion of organoclay throughout the PEAI matrixwere confirmed by FTIR, XRD and SEM analyses. The opti-cal clarity and water absorption property of PEAI-nanocom-

posites were decreased significantly with increasingorganoclay contents in the PEAI matrix. On the contrary thethermal stability of PEAI-nanocomposites was increasedsignificantly with increasing the organoclay contents in the

PEAI matrix. The enhancements in the thermal stability ofthe nanocomposite films 3a and 3b caused by introducingorganoclay may be due to the strong interactions between

polymeric matrix and organoclay generating well intercalationand dispersion of clay platelets in the PEAI matrix. Thermaland organosoluble properties can make these nanocomposites

attractive for practical applications such as processable high-performance engineering plastics.

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New poly(ether-amide-imide) reinforced layer silicate nanocomposite: Synthesis and properties1 Introduction2 Experimental section2.1 Materials2.2 Monomer synthesis2.2.1 Synthesis of N,N'-(4,4'-diphenylether)bist

2.3 Polymer synthesis2.4 PEAI-nanocomposite synthesis of 3a and 3b2.5 Measurements

3 Results and discussion3.1 Monomer synthesis3.2 PEAI-nanocomposite films3.3 FT-IR spectroscopy analysis3.4 X-ray diffraction analysis3.5 Scanning electron microscopy3.6 Optical clarity of PEAI-nanocomposite films3.7 Thermal properties3.8 Water absorption measurements

4 ConclusionsReferences