Novel nanocomposites based on reactive organoclay of l-tyrosine and amine end-capped poly(amide–imide): Synthesis and characterization

In the present study, a series of nanocomposite materials were successfully prepared using a poly(amide–imide) (PAI) matrix and novel reactive organoclay as a reinforcing agent. The organoclay was synthesized from Cloisite Na⁺ and protonated form of l-tyrosine amino acid via ion-exchange reaction. It was confirmed by Fourier transform infrared spectroscopy, X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetry analysis techniques. An optically active PAI was synthesized via solution polycondensation reaction of N,N′-(pyromellitoyl)-bis-phenylalanine diacid chloride and 4,4′-diaminodiphenylether. Then it was end-capped with amine end groups near the completion of the reaction to interact chemically with organoclay. Organoclay/PAI nanocomposite films containing different amounts of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. The nanostructures and properties of the organoclay/PAI hybrids were investigated using different techniques. Thermogravimetry analysis results indicated that the addition of organoclay into the PAI matrix increased the thermal decomposition temperatures of the resulting hybrid materials. The presence of amino acids as a biodegradable segment in both novel organoclay and optically active PAI, made the resulting nanostructure materials susceptible for biodegradation.     

Insertion of novel optically active poly(amide-imide) chains containing pyromellitoyl-bis-l-phenylalanine linkages into the nanolayered silicates modified with l-tyrosine through solution intercalation

In the present investigation, for the first time, functional optically active poly(amide-imide) (PAI)/organonanosilica bionanocomposite films were successfully fabricated through solution intercalation technique. At the start, Cloisite Na⁺ and protonated form of l-tyrosine amino acid were used for the preparation of the novel chiral organoclay via ion-exchange reaction. Then, PAI containing phenylalanine amino acid was synthesized via solution polycondensation of N,N’-(pyromellitoyl)-bis-phenylalanine diacid chloride (5) with 4,4′-diaminodiphenylsulfone (6). This polymer was end-capped with amine end groups near the completion of the reaction to interact chemically with organoclay. Finally, PAI/organ-nanosilica bionanocomposites films containing 5, 10 and 15% of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. The nanostructures and properties of the PAI/organoclay hybrids were investigated using Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis (TGA) techniques. XRD, FE-SEM and TEM results revealed the formation of exfoliated and intercalated organoclay platelets in the PAI matrix. TGA results indicated that the addition of organoclay into the PAI matrix increases in the thermal decomposition temperatures of the resulted bionanocomposites. The transparency of the nanocomposite films decreased gradually by the addition of organoclay, and the films became semitransparent as well as brittle at high loading of organoclay. Mechanical data indicated improvement in the tensile strength and modulus with organoclay loading. The film containing a 10 wt.%. of organoclay had a tensile strength of the order of 85.24 MPa relative to the 67.52 MPa of the pure PAI.     

Production and evaluation of the surface properties of chiral poly(amide-imide)/TiO2 nanocomposites containing L-phenylalanine units

This study concerted on the immobilization of nano-titanium dioxide particles (TiO₂, 30–50 nm particle size) into or onto an optically active poly(amide-imide) (PAI). The matrix PAI consisted of the chiral units in the main and hydroxybenzamide functional groups in the side chains. The macromolecule structure has been fabricated from the reaction of 3,5-diamino-N-(4-hydroxyphenyl) benzamide and N,N′-(pyromellitoyl)-bis-L-phenylalanine diacid chloride at low temperature. The hydroxyl groups on the side chains of the PAI could provide better compatibility and bonding, which cause to suitable homogenous dispersion of nanoparticles (NPs) in the obtained nanocomposites (NCs). Also due to prevention of aggregation, the surface of TiO₂ NPs was functionalized by 3-aminopropyltri-ethoxysilane as a coupling agent to introduce amine groups on the NPs surfaces. Atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy and contact angle measurements were used for investigation of the surface properties of obtained NCs. These results confirmed the well-dispersion of nanoTiO₂ in the PAI matrix.     

Poly(amide‐imide)/organoclay nanocomposites using glycine as a natural amino acid: study on fire and thermal behavior

In the present study, new functional poly(amide‐imide)/organoclay nanocomposite films were successfully fabricated through the solution intercalation technique. New poly(amide‐imide) (PAI) containing glycine was synthesized via solution polycondensation of 1,1',3,3'‐tetraoxo(5,5'‐biisoindoline‐2,2'‐diyl)diacetic acid with 4,4′‐diaminodiphenylsulfone. The synthesized PAI was characterized by ¹H NMR, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography, elemental analysis and inherent viscosity. Then, PAI/organoclay nanocomposite films containing 4 and 8 wt% of organoclay were prepared via solution intercalation through blending of organoclay 30B with the PAI solution. The nanostructures and properties of the PAI/organoclay were investigated using FTIR spectroscopy, XRD, transmission electron microscopy (TEM), TGA, DSC and microscale combustion calorimetry. XRD and TEM revealed the good dispersion of organoclay in the polymer matrix. TGA indicated that the addition of organoclay into the PAI matrix increases the thermal decomposition temperatures and char yields of the nanocomposites. Organoclay shows a positive effect in improving the flame retardancy of the PAI, reflecting the decrease in heat release rate, the total heat release and the heat release capacity of the PAI nanocomposites, while the thermal stability of the PAI nanocomposites only increased slightly compared with the neat polymer. © 2013 Society of Chemical Industry     

Preparation of new polymer nanocomposites based on chiral poly(amide-imide)/surface-modified ZnO nanoparticles containing 4,4′-methylene bis(3-chloro-2,6-diethylaniline) linkages via ultrasonication-assisted process

In the present investigation, a novel chiral poly(amide-imide) (PAI) was synthesized via direct polycondensation reaction of chiral diacid monomer with 4,4′-methylene bis(3-chloro-2,6-diethylaniline) in molten tetrabutylammonium bromide as a green solvent. Then PAI-based bionanocomposites (BNC)s have been successfully prepared via ultrasonic irradiation method using zinc oxide (ZnO) nanoparticles functionalized by γ-aminopropyltriethoxysilane as a coupling agent to decrease aggregation of nanoparticles in polymer matrix. The physicochemical and morphology properties of the neat PAI and BNCs were studied using ¹H-NMR, FT-IR spectroscopy, specific rotation, elemental analysis, X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR and TEM depicted that the ZnO nanoparticles function as a physical cross-linking agent with PAI through hydrogen bonding between the OH on the ZnO nanoparticles and the C=O of the amide and imide groups. Also, TEM and FE-SEM images revealed that ZnO nanoparticles were dispersed in PAI matrix with particle size between 15 and 25 nm. Thermogravimetric analysis data showed an improvement of thermal stability of new BNCs in comparison with the pure PAI.     

Determination of the glass transition temperature of polymer/layered silicate nanocomposites from positron annihilation lifetime measurements

The glass transitions of acrylonitrile-butadiene rubber (NBR)/organoclay nanocomposites with various silicate contents were investigated using positron annihilation lifetime spectroscopy (PALS). The nanocomposites were prepared through melt intercalation of NBR with various concentrations of organoclay (OC30B) modified with the organic modifier, methyl tallow bis(2-hydroxyethyl) quaternary ammonium (MT2EtOH), i.e., Cloisite^® 30B. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the NBR/OC30B nanocomposites showed that the NBR chains were intercalated between the silicate layers, thereby increasing the gallery heights of the organosilicates. The glass transition temperature of NBR was determined using differential scanning calorimetry (DSC). However, it seemed to be very difficult to clearly resolve the very small differences in T_gs caused from various loading of nanosized silicate in NBR/OC30B nanocomposites. Hence, we performed positron annihilation lifetime spectroscopy (PALS) on NBR/OC30B nanocomposites containing various amounts of OC30B (1-10 wt%). Significant changes in the temperature dependencies of free volume parameters (i.e., lifetimes and intensities) were observed at the transition temperature, T_g,PALS, and the T_g,PALS values were found to increase with increasing organoclay content in the samples. These observations are consistent with PALS having a higher sensitivity in the detection of very small changes in free volume properties. The present findings thus highlight the usefulness of PALS for studying phase transition phenomena in polymeric materials with nanoscale structural variations.     

Design and Characterization of Chiral and Thermally Stable Nanostructure Poly(amide-imide)s Containing Different Trimellitylimido-Amino Acid-Based Diacids and 4,4′-Methylenebis(3-chloro-2,6-diethylaniline) Units

In this study new chiral nanostructure poly(amide-imide)s (PAI)s were synthesized via direct polycondensation of different trimellitylimido-amino acid-based diacids and 4,4′-methylenebis(3-chloro-2,6-diethylaniline), using tetra-n-butylammonium bromide and triphenyl phosphite as a green media. The formation of these nanostructure PAIs was confirmed by ¹H-NMR, Fourier transform infrared spectroscopy, specific rotation, elemental analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and thermo gravimetric analysis techniques. The FE-SEM micrographs and XRD patterns showed that, the obtained PAIs are nanostructured with different shapes and noncrystalline polymers.     

Preparation and Properties of Nanocomposites Derived from Aromatic Polyamide and Surface Functionalized Nanoclay

Nanocomposites were synthesized from polyamide and aminosilane functionalized montmorillonite through solution intercalation method. Polyamide resin was prepared by reacting a mixture of p-phenylenediamine and 4,4′-oxydianiline with isophthaloyl chloride (IPC) in N,N′-dimethyl acetamide (DMAc) under anhydrous conditions. The resulting chains were end capped with carbonyl chloride using slight excess of IPC near the end of reaction. 3-Aminopropyltriethoxysilane (APTS) was used for the surface modification of clay. Triethoxysilane groups of APTS promoted the reaction between silane and hydroxyl groups on the surface of clay. The compatibility between the two disparate phases was achieved through interaction of free amine groups of modified clay with carbonyl chloride of the matrix. Thin films obtained by evaporating the solvent were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), and tensile measurements. XRD and TEM results revealed the formation of partially delaminated and intercalated clay platelets in the matrix. Mechanical data showed improvement in the tensile strength and moduli of the nanocomposites with clay loading up to 6 wt.%. The glass transition temperature increased up to 134°C for the nanocomposites containing 6 wt.% clay content and also the thermal stability augmented with increasing clay loading.     

Preparation and characterization of novel optically active poly(amide‐imide)/α‐Fe2O3 nanocomposites containing l‐alanine moieties

An optically active poly(amide‐imide) (PAI) was synthesized from the polymerization reaction of N,N′‐(Pyromellitoyl)‐bis‐l ‐alanine diacid chloride with 2,5‐diaminotoluene. The obtained inorganic metal oxide nanocomposites composed of PAI/nanostructured hematite (α‐Fe₂O₃) were synthesized through ultrasonic irradiation. The resulting nanocomposites were characterized by Fourier transform infrared spectroscopy, powder X‐ray diffraction, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The TEM results indicated that the nanoparticles were dispersed homogeneously in PAI matrix on nanoscale. TGA confirmed that the heat stability of the nanocomposites was improved in the presence of α‐Fe₂O₃ nanoparticles. POLYM. COMPOS., 37:1805–1811, 2016. © 2014 Society of Plastics Engineers     

Using Mg‐Al‐layered double hydroxide intercalated with chiral dicarboxylic acid for the reinforcement of isoleucine amino acid containing poly(amide‐imide)

A series of bionanocomposite (BNC) materials based on isoleucine containing poly(amide‐imide) (PAI) and modified MgAl‐layered double hydroxide (LDH) were prepared by solution intercalation method for the first time. An optically active PAI was synthesized by direct polycondensation reaction of N,N'‐(pyromellitoyl)‐bis‐isoleucine with 3,5‐diamino‐N‐(thiazol‐2‐yl)benzamide under green conditions. Organically modified LDH was prepared via ion exchange reaction of MgAl‐LDH in a solution of N,N'‐(pyromellitoyl)‐bis‐l‐ isoleucine in distilled water. X‐ray diffraction (XRD) results of modified LDH show an increase in interlayer distance as compared to the unmodified one. The obtained polymer and modified LDH were used to prepare chiral and high‐performance hybrid materials. Fourier transform infrared spectroscopy, XRD, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis (TGA) techniques were used to study the morphology and thermal properties of the obtained hybrid materials. TGA data indicated an increase in thermal stability of the BNCs as compared to the pure polymer. POLYM. COMPOS., 37:3288–3295, 2016. © 2015 Society of Plastics Engineers     

Production and characterization of nanocomposites based on poly(amide-imide) containing 4,4′-methylenebis(3-chloro-2,6-diethylaniline) using nano-TiO2 surface-coupled by 3-aminopropyltriethoxysilane

In this work, the poly(amide-imide) (PAI) was synthesized from the polymerization reaction of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) under green condition using molten tetra-n-butylammonium bromide and triphenylphosphite. Ultrasonic technique was used for preparation of PAI/TiO₂ nanocomposites (PAI/TiO₂ NCs). For the improvement of TiO₂ nanoparticles (NPs) dispersion and enhancing interactions between NPs and polymeric matrix the surface of TiO₂ was successfully modified by silane coupling agent (3-aminopropyltriethoxysilane). The resulting NCs were characterized by FT-IR, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The TGA of the obtained NCs proves the enhancement in the thermal stability with an increase in the percentage of titania NPs. TEM and FE-SEM images showed that the NPs were uniformly dispersed in the polymer matrix. The shielding effect of nano TiO₂ under UV radiation was examined by UV–vis.     

The preparation of cation-functionalized multi-wall carbon nanotube/sulfonated polyurethane composites

Covalent functionalization of multi-wall carbon nanotubes (MWCNTs) with minimal alteration to the MWCNT surface is important to achieve homogenously dispersed carbon nanotubes while maintaining their unique mechanical and electrical properties. Carboxylic acid derivatized MWCNTs (MWCNT-COOH) were covalently functionalized with 3,3′-iminobis(N,N-dimethylpropylamine) (DMPA). Upon subsequent quaternization of DMPA, dendritic ammonium cation-functionalized MWCNTs (MWCNT-DMPA⁺) were formed, where two ammonium cations were incorporated per amide site. Thermogravimetric analysis and X-ray photoelectron spectroscopy demonstrated successful covalent functionalization and formation of the surface-bound ammonium salt. Raman spectroscopy and atomic force microscopy indicated the absence of an appreciable decrease in the MWCNT aspect ratio. Compared with pristine MWCNTs and MWCNT-COOH, MWCNT-DMPA⁺ exhibited enhanced dispersibility in N,N-dimethylformamide (DMF) as observed with UV–Visible spectroscopy and transmission electron microscopy (TEM). In addition, blending the cation-bound MWCNT-DMPA⁺ with anion-bound sulfonated polyurethane in DMF generated novel composites with a nanotube content ranging from 0.5 to 5 wt.%. Characterization of the composite films using both field emission scanning electron microscopy and TEM revealed that MWCNT-DMPA⁺ exhibited uniform dispersion in sulfonated polyurethane matrices even at 5 wt.%. Tensile analysis showed that the modulus of the sulfonated polyurethane matrix linearly increased with MWCNT-DMPA⁺ content.     

Thermal and morphology characterization study of bio‐active poly(amide‐imide)‐based nanocomposites reinforced with modified SiO2 nanoparticle with poly(vinyl alcohol)

Among the nanoparticles (NPs), the amorphous SiO₂ NPs are very useable, because of their important characteristics for different applications, such as mechanical performance, thermal properties, and biodegradability effects. For this manifest features SiO₂ NPs were used as filler in this study. Firstly, these NPs were modified with poly(vinyl alcohol) (PVA). Then, the poly(amide‐imide) (PAI) was synthesized from reaction between N‐trimellitylimido‐l ‐methionine and 4,4′‐diaminodiphenylether in the presence of ionic liquid and triphenyl phosphite. Next, the modified SiO₂ NPs with PVA (SiO₂‐PVA) were incorporated into the PAI matrix for the preparation of PAI‐SiO₂‐PVA nanocomposites (PSiPNs). Finally, the resulting SiO₂‐PVA and PSiPNs were characterized by different analyses like field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and thermogravimetric analysis (TGA). TGA showed high thermal stability of the obtained PSiPNs compared to the pure PAI. POLYM. COMPOS. 37:1231–1237, 2016. © 2014 Society of Plastics Engineers     

A facile and green method for the production of novel and potentially biocompatible poly(amide-imide)/ZrO2–poly(vinyl alcohol) nanocomposites containing trimellitylimido-l-leucine linkages

We have reported the synthesis of nanocomposites (NCs) based on chiral poly(amide-imide) (PAI) and modified zirconium nanoparticles (ZrO₂ NPs) with poly(vinyl alcohol) (PVA). The optically active PAI was prepared under the green condition via the direct polycondensation of biocompatible trimellitylimido-l-leucine diacid and 4,4′-diaminediphenylsulfone in the presence of tetrabutylammonium bromide and triphenyl phosphite as the green solvent and the activating agents. NPs, due to a high surface to volume ratio, have a great tendency to agglomerate in the polymer matrix. So, at first, the surface of ZrO₂ NPs was modified with the PVA as the biodegradable and biocompatible polymer. Afterward, the modified NPs were added into the PAI matrix in the ethanol solution under ultrasonic irradiations. The obtained PAI/ZrO₂–PVA NCs (PZ–PNC)s were characterized by various techniques. The Fourier transform infrared proved the formation of PZ–PNCs. Field emission-scanning electron microscopy exhibited that ZrO₂ NPs had good dispersion in the PAI matrix, and transmission electron microscopy indicated that ZrO₂ NPs were coated by a nanometer-thick layer of PVA that was about 10 nm. X-ray diffraction analysis showed that the ZrO₂ NPs retained their crystalline structure after they were added in the PAI matrix. Thermogravimetric analysis illustrated that the prepared PZ–PNCs had a better thermal stability than the neat PAI.     

Novel electrically conductive and ferromagnetic composites of poly(aniline‐co‐aminonaphthalenesulfonic acid) with iron oxide nanoparticles: Synthesis and characterization

Nanocomposites of iron oxide (Fe₃O₄) with a sulfonated polyaniline, poly(aniline‐co‐aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5‐amino‐2‐naphthalenesulfonic acid/1‐amino‐5‐naphthalenesulfonic acid in the presence of Fe₃O₄ nanoparticles. The nanocomposites [Fe₃O₄/SPAN(ANSA)‐NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe₃O₄ particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe₃O₄ particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (～ 0.5 S cm^?1) is higher than that of pristine PANI (～ 10^?3 S cm^?1). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi‐1D variable range hopping (quasi‐1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g^?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Novel amino acid-based polymers for pharmaceutical applications

Summary Entirely amino acid-based polymers were prepared by side-chain attachment to polysuccinimide derived from the thermal polycondensation of aspartic acid. Following deprotonation of various amino acid ester hydrochlorides by a secondary amine, the restored primary amino groups initiated the ring-opening of succinimide to form amide bonds. ¹H and ¹³C NMR measurements revealed that the mole fraction of the introduced amino acid side chains could be controlled by the reaction time, while no hydrolysis of methyl ester groups was observed. The synthesized polymers contain exclusively amino acids, which makes them promising candidates as base materials of controlled drug delivery systems.     

N-Propargyl-substituted aromatic polyamides: preparation and thermal crosslinking

A series of high molecular weight aromatic polyamide copolymers derived from 4,4′-bis(methylamino)-diphenylmethane, 4,4′-bis(propargylamino)diphenylmethane and isophthaloyl dichloride was prepared as potential candidates for use as matrix resins in Kevlar^(R) fibre composites. These polyamides, which contain pendant propargyl groups, underwent facile crosslinking at 280°C as evidenced by dramatic increases in their glass transition temperatures (T_g) and accompanying loss of solubility. Other attempts to effect crosslinking by exposure to ultraviolet light, electron beam or gamma radiation were unsuccessful.     

A facile route for the preparation of novel optically active poly(amide–imide)/functionalized zinc oxide nanocomposites containing pyromellitoyl-bis-l-phenylalanine moieties

In the present investigation, at first, the surface of zinc oxide (ZnO) nanoparticles was treated with a silane coupling agent of γ-methacryloxypropyltrimethoxy silane (KH570), which introduces organic functional groups on the surface of ZnO nanoparticles. Secondly, optically active poly(amide–imide) (PAI) was synthesized via solution polycondensation of N,N′-(pyromellitoyl)-bis-phenylalanine diacid chloride 1 (M-1) with 4,4′-diaminodiphenylsulfone 2 (M-2). The polycondensation of diacid chloride with aromatic diamine was carried out with N,N-dimethylacetamide/triethylamine systems. Finally PAI/ZnO nanocomposites (NCs) containing 4, 8, and 12% of nanoparticles were successfully fabricated through ultrasonic irradiation technique. The obtained NCs were characterized by Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV–Vis spectroscopy, scanning electron microscopy (SEM), field emission-scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The FT-IR spectroscopy indicated that the silane coupling agent was anchored on the surface of ZnO nanoparticles. SEM, FE-SEM, and TEM images were showed ZnO nanoparticles were dispersed homogeneously in PAI matrix.     

Introduction of quaternary amines onto a film surface by graft polymerization

Quaternary amines were introduced onto a poly(ethylene terephthalate) (PET) film surface by two different methods using UV-induced graft polymerization. The first involves a two-step reaction: graft polymerization of N,N′-(dimethylamino)ethyl methacrylate (DMAEMA) onto the PET film, followed by quaternization of the tertiary N,N′-dimethylamino groups of grafted chains using alkyl bromides (R_nBr). The second is direct graft polymerization of DMAEMA having pendant quaternary amines onto the PET film. The alkyl bromides used for quaternization of the monomers and graft chains include: n-propyl, n-butyl, n-octyl, n-lauryl, and n-cetyl bromide. The two-step method could quaternarize 90% of the pendant N,N′-dimethylamino groups of the graft chains when R₃Br was used. The extent of quaternization decreased with the increasing carbon number of alkyl bromide. The direct one-step method gave a graft amine density of 8 nmol/cm² when the monomer quaternized with R₃Br was used for the graft polymerization in the presence of 1 X 10^-3M sodium metaperiodate. The carbon number of alkyl chains in the quaternary amines estimated from XPS spectra was in good agreement with that of R_nBr used for quaternization. © 1996 John Wiley & Sons, Inc.     

Dual-stimuli sensitive composites based on multi-walled carbon nanotubes and poly(N,N-diethylacrylamide-co-acrylic acid) hydrogels

A strategy to prepare dual-stimuli sensitive poly(N,N-diethylacrylamide-co-acrylic acid) composite hydrogels has been demonstrated. Multi-walled carbon nanotubes (MWCNTs) functionalized with vinyl groups were copolymerized with N,N-diethylacrylamide (DEA), acrylic acid (AA) and N,N′-methylenebisacrylamide (NNMBA) to obtain the composites (NCG). As expected, the compression properties of the NCG were greatly improved without noticeably reducing the response rates to temperature changes. Field emission scanning electron microscopy showed that the surface of the NCG was denser, which affords the NCG better compression properties, while there was obvious MWCNTs aggregation on the surface of the hybrid gel sample by physical mixing of the MWCNTs (HYG).