Nanocomposites Based on Chitosan-Graft-Poly(N-Vinyl-2-Pyrrolidone): Synthesis,Characterization, and Biological Activity

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na⁺-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer.     

New heat resistant nanocomposites reinforced silicate nanolayers containing triazine rings based on polyamide: Synthesis,characterization, and flame retardancy study

N¹,N¹′‐(6‐methoxy‐1,3,5‐triazine‐2,4‐diyl)dibenzene‐1,4‐diamine (MTDA) containing triazine ring structure was synthesized and characterized. A new, montmorillonite (Mt) modified by MTDA (MTDA‐Mt), was prepared by ion‐exchange of sodium montmorillonite (Na⁺‐Mt) with protonated form of MTDA. It was confirmed by Fourier transform infrared spectroscopy and X‐ray powder diffraction (XRD) techniques. The results of XRD indicated that MTDA had intercalated with Na⁺‐Mt. A new polyamide (PA) containing triazine ring was synthesized by direct polycondensation reaction of 4,4′‐(6‐methoxy‐1,3,5‐triazine‐2,4‐diyl)bis(azanediyl)dibenzoic acid and 4,4′‐diaminodiphenylether and characterized. PA/MTDA‐Mt nanocomposites containing 4 and 8 mass% of MTDA‐Mt were prepared via blending of MTDA‐Mt with the PA by solution intercalation technique in N‐methyl‐2‐pyrrolidone. The nanostructures and properties of the PA/MTDA‐Mt nanocomposites were investigated using different techniques. Transmission electron microscopy and XRD results revealed the good dispersion nano silicate layers in the polymer matrix. Thermal properties and flame retardancy of the resulting PA/MTDA‐Mt nanocomposites were investigated by thermal gravimetry analyses and microscale combustion calorimetry techniques. The results showed that the addition of MTDA‐Mt enhanced the flame retardancy of PA, reflecting the decrease in heat release rate from 111 W/g for PA to 91 and 77 W g⁻¹ for PA/MTDA‐Mt nanocomposites. POLYM. COMPOS., 188–198, 2016. © 2014 Society of Plastics Engineers     

Fabrication and in vitro investigation of nanohydroxyapatite,chitosan, poly(L‐lactic acid) ternary biocomposite

The nanohydroxyapatite/chitosan/poly(L ‐lactic acid) (HA/CS/PLLA) ternary biocomposites were prepared by blending the hydroxyapatite/chitosan (HA/CS) nanocomposites with poly(L ‐lactic acid) (PLLA) solution. Surface modification by grafting D ‐, L ‐lactic acid onto the HA/CS nanocomposites was designed to improve the bonding with PLLA. The FTIR and ¹³C‐NMR spectrum confirmed that the oligo(lactic acid) was successfully grafted onto the HA/CS nanocomposites, and the time‐dependent phase monitoring showed that the grafted copolymers were stable. The TEM morphology of the HA/CS/PLLA ternary nanocomposites showed that nano‐HA fibers were distributed homogeneously, compacted closely and wrapped tightly by the CS and PLLA matrix. The ternary biocomposites with the HA content of 60 and 67 wt % exhibited high compressive strength of about 160 MPa and suitable hydrophilicity. The in vitro tests exhibited that the ternary biocomposites have good biodegradability and bioactivity when immersed in SBF solutions. All the results suggested that the n‐HA/CS/PLLA ternary biocomposites are appropriate to application as bone substitute in bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and Characterization of Temperature-Sensitive Poly(N-isopropylacryamide-co-acrylamide)/Montmorillonite Nanocomposite Hydrogels

This paper reports a temperature-sensitive poly(N-isopropylacryamide-co-acrylamide)/montmorillonite (P(NIPAAm-co-Am)/MMT) nanocomposite hydrogel with enhanced mechanical properties and thermodynamic stability based on chitosan and nanoparticle MMT. With biodegradable N-maleyl chitosan crosslinker, the temperature-sensitive nanocomposite hydrogel was prepared by free radical polymerization in aqueous solution, using N-isopropylacryamide (NIPAAm), acrylamide (Am), and montmorillonite (MMT) as materials. The clay content varied from 0 to 7 wt% (based on the monomer). The temperature-sensitive behavior, mechanical property, thermodynamic stability, and enzymatic degradation of the nanocomposite hydrogels were investigated in detail.     

Preparation and Characterization of Polyvinylpyrrolidone/L-leucine Amino Acid–Modified Montmorillonite/Chiral Diacid–Functionalized Mg-Substituted Fluorapatite Nanocomposites by Ultrasonic-Assisted Rapid Process

In this work, the surface of synthetic nanosized Mg-substituted fluorapatite particles was modified with biodegradable diacid N-trimellitylimido-L-leucine as a coupling agent in methanol. Furthermore, different contents of N-trimellitylimido-L-leucine-modified Mg-substituted fluorapatite were doped into polyvinylpyrrolidone/L-leucine-modified montmorillonite material to prepare novel ternary polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite nanocomposites by an efficient sonication process. Nanocomposite containing 5?wt% modified montmorillonite and 3, 5, and 7?wt% N-trimellitylimido-L-leucine-modified Mg-substituted fluorapatite contents were prepared and labeled as polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 3, polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 5, and polyvinylpyrrolidone/modified montmorillonite/N-trimellitylimido-L-leucine-Mg-substituted fluorapatite 7, respectively. The structure and morphology of the aforesaid products were characterized by different analytical apparatuses.     

Preparation and characterization of anionically polymerized butadiene‐isoprene copolymer/clay nanocomposites

Butadiene‐isoprene copolymer/montmorillonite (BIR/MMT) nanocomposites were synthesized successfully via in situ anionic polymerization. The results of transmission electron microscopy and X‐ray diffractometer showed that the clay layers were exfoliated and high reaction temperature benefited the exfoliation of layers in BIR/MMT. The polymerization still exhibited “living” characteristics with the addition of organophilic montmorillonite (OMMT). However, the contents of 1,2‐polybutadiene and 3,4‐polyisoprene of the copolymer decreased with the addition of OMMT, because of its absorption effect on N,N,N′,N′‐tetramethylethanediamine as revealed by ¹H NMR. Moreover, it was observed that the glass‐transition temperature of the BIR/MMT nanocomposites also decreased when compared with the BIR copolymers. The thermal stability of the nanocomposites was improved, because of the barrier property of exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 1167–1172, 2006     

Mechanical,Morphological and Thermal Properties of Polycarbonate/SEBS-G-MA/Montmorillonite Nanocomposites

Nanocomposites based on polycarbonate (PC) containing sodium montmorillonite (NaMMT) and maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MA) were prepared by melt compounding method followed by injection molding. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed the formation of intercalated nanocomposites. Incorporation of SEBS-g-MA into the PC/MMT nanocomposites enhanced ductility and impact strength but slightly reduced tensile strength and stiffness. The glass transition temperature (T _g – detected from DMTA) and onset temperature (T _onset – detected from TGA) of the PC nanocomposites was increased in the presence of SEBS-g-MA. For this PC/NaMMT system, SEBS-g-MA could act as an effective toughening agent.     

Preparation of syndiotactic polystyrene/montmorillonite nanocomposites via in situ intercalative polymerization of styrene with monotitanocene catalyst

Syndiotactic polystyrene (sPS)/montmorillonite nanocomposites were prepared via in situ intercalative coordination polymerization using mono‐(η⁵‐pentamethylcyclopenta‐ dienyl) tribenzyloxy titanium [Cp*Ti(OBz)₃] complex activated by methylaluminoxanes (MAO) and triisobutylaluminum (TIBA). The influences of polymerization conditions, such as the weight ratio of montmorillonite and styrene, temperature, and monomer concentration, on the preparation of sPS/montmorillonite nanocomposites was investigated. The intercalation spacing in the nanocomposites, as well as the exfoliation of the montmorillonite interlayers, was characterized with wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). The dispersibility of the nanoscale elements depended on the polymerization conditions and the surfactant treatment. The crystallizability and thermal properties of these nanocomposites were determined by differential scanning calorimetry (DSC) analysis and thermogravimetric analysis (TGA). Experimental results indicated that the degree of crystallinity of the sPS nanocomposite increased with increasing montmorillonite content and with higher T_g and thermal decomposition temperature than pure sPS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1412–1417, 2005     

Polypropylene‐organoclay nanocomposite: Preparation,microstructure, and mechanical properties

A series of polypropylene (PP) nanocomposites containing 2, 4, and 6 wt % of an organophilic montmorillonite clay was prepared via direct melt mixing in the presence of maleic anhydride grafted polypropylene (PP‐g‐MAH) as compatibilizing agent. Microstructure characterization was performed by X‐ray diffraction analysis. Nanocomposites exhibited a 15 and 22% enhancement in tensile modulus and impact strength, respectively. The heat deflection temperature of PP nanocomposites was 36°C greater than for pure PP. Thermal and mechanical properties of nanocomposites were compared to properties of traditional PP‐talc and PP‐glass fiber composites. The results showed that the properties of nanocomposites improved compared to ordinary polypropylene composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Copolymerization of styrene with N‐phenyl maleimide in the presence of montmorillonite

The copolymerization of styrene with N‐phenyl maleimide in the presence of organomodified montmorillonite or Na⁺ montmorillonite was investigated. The conversion of the monomer was determined dilatometrically or gravimetrically. The copolymerization rate was accelerated and the polymerization activation energy in bulk and solution copolymerization decreased in the presence of montmorillonite. The tendency of alter‐copolymerization was enhanced for bulk and solution polymerization, but not affected for emulsion polymerization, by the addition of organomodified montmorillonite or Na⁺ montmorillonite. X‐ray diffraction studies showed that the methods of emulsion and bulk intercalative polymerization were more appropriate techniques for preparing nanocomposites with good dispersibility of clay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1932–1937, 2005     

Poly lactic acid nanocomposites containing modified nanoclay with synergistic barrier to water vapor for coated paper

The binary nanocomposites of poly lactic acid (PLA) with the montmorillonite modified with trisilanol polyhedral oligomeric silsesquioxanes (Trisilanolisooctyl POSS^®) were prepared via a solution‐blending process and coated on paper by bar coating and compress hot melt coating methods. The resulting components were characterized with Fourier transform infrared spectroscopy, and X‐ray diffraction (XRD) techniques. Moreover, the water vapor transmission rates (WVTR) for the coated writing paper were determined using an IGA‐003. The results indicated that the modified clay PLA nanocomposites enhanced the water vapor barrier properties of coated paper significantly. The permeability of PLA nanocomposites to water vapor decreased by 74% [26.0 g/(m² day)], respectively, as compared to those of the paper coated with pure PLA. The dispersion and phase behavior of the modified montmorillonite in PLA matrix was revealed by Transmission electron microscope. The intercalation of montmorillonite with PLA was further demonstrated using XRD. WVTR results indicated that the compress hot melt coating of the nanocomposites is an effective method to improve the water vapor resistance of coated paper. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40952.     

New aramid‐based nanocomposites: Synthesis and characterization

New type of nanocomposites containing various proportions of montmorillonite in aromatic polyamide was prepared via solution intercalation method. Aramid chains were synthesized by reacting 4,4′‐oxydianiline with isophthaloyl chloride in N,N′‐dimethyl acetamide. Dodecylamine was used as swelling agent to change the hydrophilic nature of montmorillonite into organophilic. Appropriate amounts of organoclay were mixed in the polymer solution using high‐speed mixer for complete dispersion of the clay. Thin films cast from these materials after evaporating the solvent were characterized by XRD, TEM, mechanical, thermal, and water absorption measurements. The structure and morphology of the nanocomposites determined by XRD and TEM revealed the formation of exfoliated and intercalated clay platelets in the aramid matrix. Mechanical data indicated improvement in the tensile strength and modulus of the nanocomposites with clay loading up to 6 wt%. The glass transition temperature increased up to 12 wt% clay content and thermal stability amplified with increasing clay loading. The water absorption reduced gradually as a function of organoclay and approached to zero with 20 wt% organoclay in the aramid. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Synthesis of hyperbranched organo‐montmorillonite and its application into high‐temperature vulcanizated silicone rubber systems

N,N‐Di(2‐hydroxyethyl)‐N‐dodecyl‐N‐methyl ammonium chloride was used as intercalation agent to treat Na⁺‐montmorillonite and form a type of organic montmorillonite (OMMT). Hyperbranched OMMT (HOMMT) was prepared by condensation reaction between OMMT and the monomer we synthesized. It was then used in the preparation of high‐temperature vulcanizated silicone rubber (HTV‐SR)/HOMMT nanocomposite. Different types of HTV‐SR/HOMMT nanocomposites were prepared with different amounts of HOMMT and compared with the composites directly incorporated with OMMT. Tensile properties such as tensile strength, elongation at break, permanent distortion, and shore A hardness were researched and compared. A combination of Fourier transform infrared spectroscopy, wide angle X‐ray diffraction, and transmission electron microscopy studies showed that HTV‐SR/HOMMT composites were on the nanometer scale, and the structure of HTV‐SR was not interfered by the presence of HOMMT. Results showed that the tensile properties of HTV‐SR/HOMMT systems were better than that of the HTV‐SR/HOMMT and HTV‐SR. This was probably due to the surface effect of the exfoliated silicate layers and anchor effect of HOMMT in the SR matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

DNA adsorption on poly(N,N‐dimethylacrylamide)‐grafted chitosan hydrogels

In this study, poly(N,N‐dimethylacrylamide) grafted chitosan (PDMAAm‐g‐CT) hydrogels were prepared for deoxyribonucleic acid (DNA) adsorption. Instead of directly grafting the N,N‐dimethylacrylamide (DMAAm) monomer onto the chitosan (CT) chains, poly(N,N‐dimethylacrylamide) with carboxylic acid end group (PDMAAm‐COOH) was firstly synthesized by free‐radical polymerization using mercaptoacetic acid (MAAc) as the chain‐transfer agent and then grafted onto the CT having amino groups. The synthesis of PDMAAm‐COOH and its grafting onto the CT chains were confirmed by attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy. From gel permeation chromatography measurements, the number‐average molecular weight (M _n) and polydispersity index of PDMAAm‐COOH were found as 2400 g/mol and 2.3, respectively. The PDMAAm‐g‐CT hydrogels were utilized as the adsorbents in DNA adsorption experiments conducted at +4°C in a trisEDTA solution of pH 7.4. The hydrogels produced with higher PDMAAm‐COOH content exhibited higher DNA adsorption capacity. The DNA adsorption capacity up to 4620 μg DNA/g dry gel could be achieved with the PDMAAm‐g‐CT hydrogels prepared in 80.0 wt % PDMAAm‐COOH feed concentration. This value is approximately seven times higher than that of CT alone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dynamic mechanical,thermal, and morphological properties of silane‐treated montmorillonite reinforced polycarbonate nanocomposites

Three different loading of 3‐aminopropyltriethoxysilane (APS) was used to modify the Na‐montmorillonite via cation exchange technique. The Na‐MMT and silane‐treated montmorillonite (STMMT) were melt‐compounded with polycarbonate (PC) by using Haake Minilab machine. The PC nanocomposite samples were prepared by using Haake Minijet injection molding technique. The intercalation and exfoliation of the PC/MMT nanocomposites were characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal properties of the PC nanocomposites were investigated by using dynamic mechanical analyzer and thermogravimetry analyzer. XRD and TEM results revealed partial intercalation and exfoliation of STMMT in PC matrix. Increase of APS concentration significantly enhanced the storage modulus (E′) and improved the thermal stability of PC nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanocomposite materials based on isosorbide methacrylate/Cloisite 20A

This paper reports experiments on grafting of a new polymerizable monomer onto organophilic montmorillonite. The monomer, 5‐methacryloyloxy‐1,4:36‐D ‐anhydrosorbitol (MAS), was synthesized by reacting methacryloyl chloride and isosorbide in the presence of Et₃N as base. Then, Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogen carbonate to prevent the exchange of quaternary alkylammonium cations with H⁺ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. After the reaction, the product maintained the same basal spacing as the precursor. The radical polymerization of the product with MAS as a vinyl monomer led to chemical grafting of the polymer onto the montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed using infrared spectroscopy. The prepared nanocomposite materials and the grafted nanoparticles were studied using X‐ray diffraction and scanning and transmission electron microscopy. Exfoliated nanocomposite was obtained for 1 wt% clay loadings. The nanocomposites were studied using thermogravimetric and dynamic mechanical analyses. Improved thermal properties were observed for nanocomposites with 1–5 wt% clay content. © 2012 Society of Chemical Industry     

Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Impact,thermal, and morphological properties of functionalized rubber toughened‐poly(ethylene terephthalate) nanocomposites

In this study, poly(ethylene terephthalate)/organo‐montmorillonite (PET/OMMT) nanocomposites were melt‐compounded using twin screw extruder followed by injection molding. Maleic anhydride grafted styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) was used to improve the impact properties of the PET/OMMT nanocomposites. The notched and un‐notched impact strength of PET/OMMT nanocomposites increased at about 2.5 times and 5.5 times by the addition of 5 wt % of SEBS‐g‐MAH. Atomic force microscopy (AFM) scans were taken from the polished surface of both PET/OMMT and SEBS‐g‐MAH toughened PET/OMMT nanocomposites. The addition of SEBS‐g‐MAH altered the phase structure and clay dispersion in PET matrix. It was found that some of the OMMT silicate layers were encapsulated by SEBS‐g‐MAH. Further, the addition of SEBS‐g‐MAH decreased the degree of crystallinity of the PET/OMMT nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Chitosan intercalated montmorillonite: Preparation, characterization and cationic dye adsorption

Chitosan intercalated montmorillonite (Chi-MMT) was prepared by dispersing sodium montmorillonite (Na⁺-MMT) into chitosan solution at 60 °C for 24 h. The Chi-MMT was characterized by XRD, XRF and FT-IR. The intercalation was accomplished via the ion-exchange of Na⁺ ions with –NH₃⁺ of chitosan, resulting in the expansion of d₀₀₁ from 1.42 nm of Na⁺-MMT to 2.21 nm of Chi-MMT. The chitosan content in the Chi-MMT measured by TGA was about 17 mass%. The adsorption capacity of Chi-MMT was investigated in comparison with the starting Na⁺-MMT and chitosan using three different cationic dyes, i.e. basic blue 9 (BB9), basic blue 66 (BB66) and basic yellow 1 (BY1). The Chi-MMT showed the highest adsorption capacity in the range of 46–49 mg/g when the initial dye concentration was 500 mg/L, being equivalent to 92–99 wt.% of dye removal. The adsorption capacities of Chi-MMT for all basic dyes increased with an increase of initial dye concentration. An increase of adsorption capability of Chi-MMT was attributed to the existence of intercalate-chitosan. It could enlarge the pore structure of Chi-MMT, facilitating the penetration of macromolecular dyes, and also electrostatically interact with the applied dyes. These results indicated the competency of Chi-MMT adsorbent for basic dye adsorption.