A study on the melting and crystallization of polyoxymethylene‐copolymer/hydroxyapatite nanocomposites

In this work, isothermal crystallization kinetics of polyoxymethylene copolymer (POM) in POM/hydroxyapatite (HAp) nanocomposites has been investigated. Melting behavior and crystalline structure formation were studied using TOPEM DSC, positron lifetime spectroscopy (PALS), atomic force microscopy (AFM) and ¹³C and ³¹P solid‐state NMR. The highest degree of crystallinity was found for POM/0.5% HAp nanocomposite and the lowest for POM/2.5% HAp. Isothermal crystallization analysis showed that an introduction of HAp nanoparticles led to effective heterogeneous nucleation and formation of crystals with higher Avrami exponent. Besides, changes in overall crystallization rate were observed – the highest overall crystallization rate was found for POM/0.5% HAp sample, while the lowest for POM/2.5% HAp was observed. Generally, for POM in POM/HAp nanocomposites, a significant decrease in nucleation activation energy (K_g), and the fold surface free energy (σ_e) was found. For nanocomposite containing 2.5% HAp, heterogeneous nucleation takes place as well, but too high concentration of nanoparticles hinders POM crystallization and enhances formation of more defected crystals as confirmed by AFM data. The presence of HAp nanoparticles in the POM matrix was confirmed by ³¹P MAS‐NMR, but their influence on the crystallization process was not observed in the ¹³C CP‐MAS‐NMR spectra. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation and characterization of nano‐platelet‐like hydroxyapatite/gelatin nanocomposites

Nature has succeeded in creating numerous bionanocomposites such as bones and teeth consisting of nano‐platelets and biopolymers. Understanding of the mechanisms of formation and of the relation between structure and properties is vital for development of new materials for biomedical and engineering applications. In this work, varying contents of nano‐platelet‐like hydroxyapatite (HAp) has been used to reinforce gelatin (Gel) to produce nanocomposites. The prepared HAp/Gel nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG/DTG) analyses. XRD, TEM, and FTIR results confirm the synthesis of intercalated and exfoliated nanostructures depending on the amount of gelatin. TG results reveal that the intercalated HAp/gelatin nanocomposites show improved thermal properties as compared to pristine gelatin. The results reported here can be expanded to other HAp–polymer systems, thus paving a new way of designing and fabricating biomemitic nanocomposites for future engineering and particularly for biomedical applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Biodegradable poly(p‐dioxanone) reinforced and toughened by organo‐modified vermiculite

Poly(p‐dioxanone) (PPDO)/vermiculite (VMT) nanocomposites with exfoliated structure were prepared successfully by in situ intercalative polymerization of p‐dioxanone (PDO) in the presence of organo‐modified vermiculite (OVMT) with the aid of ultrasonic action. The nano‐structure of the nanocomposites was established using X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations. The investigation of crystallization behavior by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) proved that exfoliated OVMT platelets acted as a template for spherulite growth. The thermal stability of nanocomposites was enhanced than that of pure PPDO. Dynamic mechanical analysis (DMA) indicated nanoscale OVMT platelets restricted the motion of PPDO segments, which benefitted the increase of storage and loss modulus. The tensile properties showed that nanocomposites were reinforced and toughened significantly by the addition of nanoscale OVMT platelets. Copyright © 2009 John Wiley & Sons, Ltd.     

Polypropylene/montmorillonite nanocomposites toughened with SEBS‐g‐MA: Structure–property relationship

Polypropylene (PP)/organo‐montmorillonite (Org‐MMT) nanocomposites toughened with maleated styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) were prepared via melt compounding. The structure, mechanical properties, and dynamic mechanical properties of PP/SEBS‐g‐MA blends and their nanocomposites were investigated by X‐ray diffraction (XRD), polarizing optical microscopy (POM), tensile, and impact tests. XRD traces showed that Org‐MMT promoted the formation of β‐phase PP. The degree of crystallinity of PP/SEBS‐g‐MA blends and their nanocomposites were determined from the wide angle X‐ray diffraction via profile fitting method. POM experiments revealed that Org‐MMT particles served as nucleating sites, resulting in a decrease of the spherulite size. The essential work of fracture approach was used to evaluate the tensile fracture toughness of the nanocomposites toughened with elastomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3112–3126, 2005     

Poly(L‐lactide)/layered double hydroxides nanocomposites: Preparation and crystallization behavior

Novel nanocomposites from poly(L ‐lactide) (PLLA) and an organically modified layered double hydroxide (LDH) were prepared using the melt‐mixing technique. The structure and crystallization behavior of these nanocomposites were investigated by means of wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). WAXD results indicate that the layer distance of dodecyl sulfate‐modified LDH (LDH‐DS) is increased in the PLLA/LDH composites, compared with the organically modified LDH. TEM analysis suggests that the most LDH‐DS layers disperse homogenously in the PLLA matrix in the nanometer scale with the intercalated or exfoliated structures. It was found that the incorporation of LDH‐DS has little or no discernable effect on the crystalline structure as well as the melting behavior of PLLA. However, the crystallization rate of PLLA increases with the addition of LDH‐DS. With the incorporation of 2.5 wt % LDH‐DS, the PLLA crystallization can be finished during the cooling process at 5 °C/min. With the addition of 5 wt % LDH‐DS, the half‐times of isothermal melt‐crystallization of PLLA at 100 and 120 °C reduce to 44.4% and 57.0% of those of the neat PLLA, respectively. POM observation shows that the nucleation density increases and the spherulite size of PLLA reduces distinctly with the presence of LDH‐DS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2222–2233, 2008     

Effect of processing method on the structure and properties of HDPE/EAA/LDHs nanocomposites

High-density polyethylene/ethylene–acrylic acid copolymer/layered double hydroxides (LDHs) nanocomposites were prepared by the methods of one-step extrusion and twice extrusion in this paper. The structure and properties of the nanocomposites were also studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry (TG), and the cone calorimeter. The results of XRD, SEM, and TEM analyses demonstrated that the method of twice extrusion gave the LDHs a higher level of exfoliation within the matrix compared with the method of one-step extrusion. The DSC and TG analysis revealed that the crystalline property and the thermal stability of the nanocomposites could be improved by the method of secondary extrusion. The cone calorimeter test showed that the method of secondary extrusion could improve the flame retardant property of the nanocomposites to some degree.     

Novel polymer nanocomposites based on polystyrene and Ti‐functionalized polyhedral silsesquioxanes

Ti‐based polyhedral silsesquioxanes (Ti‐POSSs) have been prepared and dispersed in polystyrene (PS), by in situ polymerization, and the resulting materials have been characterized by several experimental techniques including both scanning (SEM) and transmission (TEM) electron microscopy, wide angle X‐ray diffraction (WAXD), X‐ray photospectroscopy (XPS), and thermogravimetric analysis (TGA/DTG). TEM and SEM analyses proved that PS nanocomposites of the samples based on heptaisobutyl‐Ti‐POSS (HEI‐Ti‐POSS) are formed, where HEI‐Ti‐POSS cages are directly linked to the macromolecules via Ti‐C bonds. The presence of HEI‐Ti‐POSS enhances the thermo‐oxidative stability of PS‐based nanocomposites and does not significantly affect the polymer molecular mass. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystallization behavior and morphology of poly(ethylene‐co‐trimethylene terephthalate)s

The melt crystallization behaviors and crystalline structures of poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate), and poly(ethylene‐co‐trimethylene terephthalate) (PETT) were investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction at various crystallization temperatures (T_cs). The PETT copolymers were synthesized via the polycondensation of terephthalate with ethylene glycol and trimethylene glycol (TG) in various compositions. The copolymers with 69.0 mol % or more TG or 31.0 mol % or less TG were crystallizable, but the other copolymers containing 34–56 mol % TG were amorphous. The DSC isothermal results revealed that the addition of a small amount of flexible TG (up to 21 mol %) to the PET structure slightly reduced the formation of three‐dimensional spherulites. A greater TG concentration (91–100%) in the copolyesters changed the crystal growth from two‐dimensional to three‐dimensional. The DSC heating scans after the completion of isothermal crystallization at various T_cs showed three melting endotherms for PET, PETT‐88, PETT‐84, and PETT‐79 and four melting endotherms for PETT‐9 and PETT. The presence of an additional melting endotherm could be attributed to the melting of thinner and imperfect copolyester crystallites. Analyses of the Lauritzen–Hoffman equation demonstrated that PETT‐88 had the highest values of the product of the lateral and folding surface free energies, and this suggested that the addition of small amounts of flexible trimethylene terephthalate segments to PET disturbed chain regularity, thus increasing molecular chain mobility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4255–4271, 2004     

Preparation and characterization of vinylidene chloride‐co‐vinyl chloride copolymer/fluorinated synthetic mica nanocomposites I thermal and mechanical properties studies

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified fluorinated synthetic mica (MEE) (VDC‐VC/MEE) nanocomposites were prepared by melt blending of VDC‐VC copolymer with MEE, in the presence of dioctyl phthalate (DOP) which acted as a plasticizer and a cointercalating agent. The nanostructure, thermal, and dynamic mechanical properties of the VDC‐VC/MEE nanocomposites were studied by wide angle X‐ray diffractometer (WAXD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). It was found that partially intercalated and partially exfoliated structures coexisted in VDC‐VC/MEE nanocomposities. Below 8 wt % MEE content, the intercalation effect of nanocomposites decreased with increasing the MEE content. Under a nitrogen atmosphere, VDC‐VC/MEE nanocomposites exhibited a single step thermal degradation behavior. The nanostructure of VDC‐VC/MEE can effectively prevent volatile gases from being released, and thus enhances its thermal stability. The thermal stability of VDC‐VC/MEE nanocomposites is strongly related to the morphology of nanocomposites and the degraded composites structure. DMA revealed a significant improvement in the storage modulus within the testing temperature range. The increase in storage modulus depends on the MEE content, which is attributed to the dispersed phase morphology. The glass transition temperature of VDC‐VC/MEE nanocomposites is affected by the chain mobility in the nanocomposites rather than the aggregative morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1214–1225, 2008     

Functional copolymer/organo‐MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA‐alt‐1‐octadecene)‐g‐PLA layered silicate nanocomposites with nanoporous core–shell morphology

Novel bioengineering functional copolymer‐g‐biopolymer‐based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L‐lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1‐octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo‐MMT clay (reactive ODA‐MMT and non‐reactive DMDA‐MMT) complexes as nanofillers and tin(oct)₂ as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT‐IR spectroscopy, X‐ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA‐DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro‐ and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H‐bonding and self‐organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride‐containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer‐g‐biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Gold Nanorod‐Assembled PEGylated Graphene‐Oxide Nanocomposites for Photothermal Cancer Therapy

Gold nanorod‐attached PEGylated graphene‐oxide (AuNR‐PEG‐GO) nanocomposites were tested for a photothermal platform both in vitro and in vivo. Cytotoxicity of AuNR was reduced after encapsulation with PEG‐GO along with the removal of cetyltrimethylammonium bromide (CTAB) from AuNR by HCl treatment. Cellular internalization of the CTAB‐eliminated AuNR‐PEG‐GO nanocomposites was examined using dark‐field microscopy (DFM), confocal Raman microscopy and transmission electron microscopy (TEM). To determine the photothermal effect of the AuNR‐PEG‐GO nanocomposites, A431 epidermoid carcinoma cells were irradiated with Xe‐lamp light (60 W cm^?2) for 5 min after treatment with the AuNR‐PEG‐GO nanocomposites for 24 h. Cell viability significantly decreased by ~40% when the AuNR‐PEG‐GO‐encapsulated nanocomposites were irradiated with light as compared with the cells treated with only the AuNR‐PEG‐GO nanocomposites without any illumination. In vivo tumor experiments also indicated that HCl‐treated AuNR‐PEG‐GO nanocomposites might efficiently reduce tumor volumes via photothermal processes. Our graphene and AuNR nanocomposites will be useful for an effective photothermal therapy.     

Bio‐based hyperbranched polyurethane/clay nanocomposites: adhesive,mechanical, and thermal properties

The unison of vegetable oil‐based hyperbranched polymers with nanotechnology can unhook myriad of avant‐garde applications of such materials. Thus Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/clay nanocomposites and their performance, with special reference to adhesive strength, are reported for the first time. The nanocomposites of the hyperbranched polyurethane with organically modified nanoclay were obtained by ex situ solution technique and cured by bisphenol‐A‐based epoxy with poly(amido amine) hardener system. The partially exfoliated and well‐distributed structure of nanoclay was confirmed by XRD, SEM, and TEM studies. FTIR spectra indicate the presence of H‐bonding between nanoclay and the polymer matrix. Two times improvement in the adhesive strength and scratch hardness, 10 MPa increments in the tensile strength and 112°C more thermo‐stability have been observed without much affecting the impact resistance, bending, and elongation at break of the nanocomposites compared to the pristine epoxy modified HBPU system. Thus, the resulted nanocomposites are promising materials for different advanced applications including adhesive. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of benzoyl‐hydrazide‐derivatized poly(lactic acid) and γ‐cyclodextrin inclusion complex and its effect on the performance of poly(lactic acid)

A nucleating agent, benzyl‐hydrazide‐derivatized poly(lactic acid) (PLA) and γ‐cyclodextrin inclusion complex (PLA‐IC‐BH), was synthesized through a series of reactions. Poly(lactic acid) and γ‐cyclodextrin inclusion complex (PLA‐IC) was first obtained by ultrasonic co‐precipitation, which was then subjected to carboxylation, acylation, and amidation using benzoyl hydrazine and thionyl chloride. The composition and structure of PLA‐IC‐BH was confirmed by ¹H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. PLA/PLA‐IC‐BH composites were prepared by melt blending and a hot‐press forming process. Mechanical properties, thermal stabilities, and crystallization behaviors of PLA/PLA‐IC‐BH samples were investigated by thermogravimetric analysis, differential scanning calorimetry (DSC), polarized optical microscopy (POM), rheological analysis, and so on. Mechanical testing and thermogravimetric analysis showed that the tensile strengths, impact properties, and thermal stabilities of PLA/PLA‐IC‐BH composites were improved significantly compared to pure PLA and PLA/PLA‐IC. DSC results showed that crystallinity of PLA was increased from 5.17% to 38.93% after introduction of PLA‐IC‐BH. POM results showed that PLA‐IC‐BH acted as a nucleating agent for PLA and enhanced its crystallization rate. Rotational rheological behaviors of PLA/PLA‐IC‐BH demonstrated that incorporation of PLA‐IC‐BH increased the rigidity of the network structure of the PLA matrix. Compared to those of PLA, the maximum torque and apparent viscosity of PLA/PLA‐IC‐BH composites were increased by 55.56% and 25.59%, respectively. Copyright © 2017 John Wiley & Sons, Ltd.     

Isothermal crystallization behavior of exfoliated‐PP/IMMT nanocomposites via in situ polymerization

Highly exfoliated isotactic‐polypropylene/alkyl‐imidazolium modified montmorillonite (PP/IMMT) nanocomposites have been prepared via in situ intercalative polymerization. TEM and XRD results indicated that the obtained composites were highly exfoliated PP/IMMT nanocomposites and the average thickness of IMMT in PP matrix was less than 10 nm, and the distance between adjacent IMMT particles was in the range of 20–200 nm. The isothermal crystallization kinetics of highly exfoliated PP/IMMT nanocomposites were investigated by using differential scanning calorimeter(DSC) and polarized optical microscope (POM). The crystallization half‐time t_1/2, crystallization peak time t_max, and the Avrami crystallization rate constant K_n showed that the nanosilicate layers accelerate the overall crystallization rate greatly due to the nucleation effect, and the crystallization rate was increased with the increase in MMT content. Meanwhile, the crystallinity of PP in nanocomposites decreased with the increase in clay content which indicated the PP chains were confined by the nanosilicate layers during the crystallization process. Although the well‐dispersed silicate layers did not have much influence on spherulites growth rate, the nucleation rate and the nuclei density increased significantly. Accordingly, the spherulite size decreased with the increase in MMT content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2215–2225, 2009     

Mechanical properties and structural characteristics of PP/PP‐g‐SBR nanocomposites prepared by dynamical photografting

Poly(propylene) (PP)/PP grafted styrene‐butadiene rubber (PP‐g‐SBR) nanocomposite was prepared by blending PP with PP‐g‐SBR using dynamical photografting. The crystal morphological structure, thermal behavior, and mechanical properties of PP/PP‐g‐SBR nanocomposites have been studied by photoacoustic Fourier transform infrared spectroscopy (PAS‐FT‐IR), wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and mechanical measurements. The data obtained from the mechanical measurements show that the PP‐g‐SBR as a modifier can considerably improve the mechanical properties of PP/PP‐g‐SBR nanocomposites, especially for the notched Izod impact strength (NIIS). The NIIS of the nanocomposite containing 2 wt% PP‐g‐SBR measured at 20°C is about 2.6 times that of the control sample. The results obtained from PAS‐FTIR, WAXD, SEM, and DSC measurements revealed the enhanced mechanism of impact strength of PP/PP‐g‐SBR nanocomposites as follows: (i) the β‐type crystal of PP formed and its content increased with increasing the photografting degree of PP‐g‐SBR; (ii) the size of PP‐g‐SBR phase in the PP/PP‐g‐SBR nanocomposites obviously reduced and thus the corresponding number of PP‐g‐SBR phase increased with increasing the photografting degree of PP‐g‐SBR. All the earlier changes on the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP at low temperature. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermomechanical properties and crystallization behavior of layered double hydroxide/poly(ethylene terephthalate) nanocomposites prepared by in‐situ polymerization

Thermomechanical properties and crystallization behavior of poly(ethylene terephthalate) (PET) nanocomposites containing layered double hydroxide (LDH) were investigated. To enhance the compatibility between PET matrix and LDH, dimethyl 5‐sulfoisophthalate (DMSI) anion intercalated LDH (LDH‐DMSI) was synthesized by coprecipitation method, and its structure was confirmed by Fourier transform infrared (FTIR) spectrometer and X‐ray diffraction (XRD) measurements. Then, PET nanocomposites with LDH‐DMSI content of 0, 0.5, 1.0, and 2.0 wt% were prepared by in‐situ polymerization. The dispersion morphologies were observed by transmission electron microscopy (TEM) and XRD, showing that LDH‐DMSI was exfoliated in PET matrix. Thermal and mechanical properties, such as thermal stability, tensile modulus, and tensile yield strength of nanocomposites, were enhanced by exfoliated LDH‐DMSI nanolayers. However, elongation at break was drastically decreased with LDH loading owing to the increased stiffness and microvoids. The effect of exfoliated nanolayers, which acted as a nucleating agent confirmed by differential scanning calorimeter (DSC), on the microstructural parameters during isothermal crystallization, was analyzed by synchrotron small‐angle X‐ray scattering (SAXS). It is believed that nanocomposites could be crystallized more easily owing to the increased nucleation sites, which lead to the decrease of average amorphous region size and the long period with the increase of LDH‐DMSI content. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 28–40, 2007     

High‐density polyethylene/expanded graphite nanocomposites produced by polymerization‐filling technique using an industrial heterogeneous catalyst

High‐density polyethylene nanocomposites with different expanded graphite (EG) contents (0.34–1.80 wt %) were prepared by polymerization‐filling technique using an industrial heterogeneous catalyst ( cat K ), and characterized using a range techniques: melting flow index (MFI), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The MFI data showed that EG acts as a plasticizer decreasing melt viscosity in comparison to neat HDPE produced exclusively by cat K . DSC results showed that EG nucleated the HDPE crystallization as established by the increased crystallization temperature, and the degree of crystallinity. HDPE/EG nanocomposites displayed a significant improvement in the flexural (increased from 1458 to 1831 MPa), and storage modulus (increased from 122 to 1627 MPa) at only 1.80 wt % EG content. TEM images confirmed a homogeneous distribution of EG into the polymer matrix with the presence of dispersed, intercalated and aggregated EG nanofillers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1260–1267     

Novel biomimetic composite based on collagen and poly(γ‐benzyl L‐glutamate)‐co‐poly(glutamic acid)

Novel biomimetic composite was prepared by the reaction of collagen and poly(γ‐benzyl L ‐glutamate)‐co‐poly(glutamic acid) (PBLG‐co‐PGA), which were crosslinked by non‐toxic crosslinking reagents 1‐ethyl‐(dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The composite was characterized by FTIR and DSC. FTIR results confirmed that the collagen in the composite was successfully crosslinked with PBLG‐co‐PGA. DSC results showed that the composites possessed higher shrinkage temperature and higher thermal stability than the collagen. The water absorption test showed that the water absorbency of the composites increased with the increase in PBLG‐co‐PGA content in the composite. The studies of collagenase degradation and the tensile strength showed that the biostability and the tensile strength of the composites were significantly improved in comparison with that of the collagen. According to the investigations of cell adherent ratio and cell proliferation in vitro, the composite possessed good biocompatibility. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and applications of novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite nanocomposites

Novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Brominated poly(isobutylene‐co‐para‐methylstyrene) (BIMS)‐clay nanocomposites: Synthesis and characterization

In this work, preparation and properties of different nanoclays modified by organic amines (octadecyl amine, a primary amine, and hexadecyltrimethylammonium bromide, a tertiary amine) and brominated polyisobutylene‐co‐paramethylstyrene (BIMS)‐clay nanocomposites are reported. The clays and the rubber nanocomposites have been characterized with the help of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The X‐ray diffraction peaks observed in the range of 3 °–10 ° for the modified clays disappear in the rubber nanocomposites. TEM photographs show predominantly exfoliation of the clays in the range of 12 ± 4 nm in the BIMS. In the FTIR spectra of the nanocomposites, there are common peaks of virgin rubber as well as those of the clays. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed on incorporation of the nanoclays in the BIMS. Structure‐property correlation in the above nanocomposites is attempted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4489–4502, 2004