A block copolymer nanotemplate for mechanically tunable polarized emission from a conjugated polymer

A polymer blend system consisting of polystyrene grafted onto poly (p-phenylene ethynylene) (PS-g-PPE) and poly (styrene-block-isoprene-block-styrene) triblock copolymer (SIS) yields highly polarized emission due to the unidirectional alignment of the PPE molecules. During the roll casting, the triblock copolymer microphase separates and creates unidirectionally aligned PS cylindrical microdomains in the rubbery PI matrix. PPE, a fluorescent conjugated polymer, was grafted with polystyrene (PS) side chains that enabled sequestration and alignment of these rigid backbone emitter molecules into the PS microdomains of the SIS triblock copolymer. Deforming the thermoplastic elastomer in a direction perpendicular to the orientation direction of the cylinders causes rotation of the PS cylinders and the PPE emitter molecules and affords tunable polarized emission due to re-orientation of the PPE containing PS cylinders as well as film thinning from Poisson effect.     

Highly ordered microstructures of poly(styrene-b-isoprene) block copolymers induced by solution meniscus

Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3 nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where [111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1 mm². Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation.     

Tuned phase behavior of weakly interacting polystyrene-block-poly(n-pentyl methacrylate) by selective solvent

We investigated, via small angle X-ray scattering, depolarized light scattering, rheometry, and transmission electron microscopy, the phase behavior of the mixture of a symmetric polystyrene-block-poly(n-pentyl methacrylate) copolymer (PS-b-PnPMA) showing the closed-loop phase behavior and excellent baroplasticity, and dodecanol, a PnPMA-selective solvent. We found that the addition of a selective solvent is simple, but very effective to obtain various microdomains including hexagonally packed cylinders and gyroids. Also, with increasing temperature, the mixtures showed multiple ordered-to-ordered transitions (OOTs) in addition to upper ordered-to-disordered transition (UODT). The first observation of gyroid microdomains in PS-b-PnPMA is very important, although they have been widely reported in many block copolymers, for instance, PS-block-polyisoprene copolymer (PS-b-PI) and PS-block-poly(d,l-lactide) copolymer (PS-b-PLA). Since the gyroid microdomains of PS-b-PnPMA show excellent baroplasticity, external pressure instead of temperature could easily change the microdomains.     

Nanostructure and dynamic mechanical properties of silane-functionalized montmorillonite/epoxy nanocomposites

In this work sodium montmorillonite (Na-MMT) was functionalized with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and the corresponding silylated clay was used to modify epoxy matrix cured with triethylenetetramine. The grafting/intercalation of the aminosilane inside the clay galleries were followed by infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and ²⁹Si cross-polarization magic-angle-spinning nuclear magnetic-resonance (CP/MAS NMR) spectroscopy. Epoxy-based nanocomposites were prepared with different amounts of silylated clay or commercial organoclay, Cloisite 30B, whose intercalating agent consists of a methyl, tallow, bis-2-hydroxyethyl quaternary ammonium salt. The degree of intercalation/exfoliation was estimated by X-ray diffraction experiments and confirmed by small angle X-ray scattering. Nanocomposites prepared with silylated clay displayed no peak in both XRD and SAXS curves whereas those prepared with Cloisite 30B exhibited a clear interference peak corresponding to an interlayer spacing d₀₀₁ of 4.1 nm. The former also presented a better dispersion, with a high proportion of tactoids smaller than 2 nm, as estimated by SAXS. From the results of dynamic mechanical analysis it was observed that most of the nanocomposites display higher storage modulus mainly at temperatures above the glass transition temperature. The glass transition temperature is similar or higher than the neat epoxy network for nanocomposites containing 1 wt.% of silylated clay or higher.     

Domain nucleation dictates overall nanostructure in composites of block copolymers and model nanorods

The detailed nanostructure of composites formed from block copolymers and nanoparticles is known to depend sensitively on the preferred morphology of the block copolymer, on the shapes of the particles, and on interactions between the two components. But it can also depend on the kinetics of self-assembly in the polymer, and there are circumstances under which the kinetics of morphologically selective domain nucleation and growth determine the overall nanostructure of the composite. To study the mechanism of morphological seeding in block-copolymer nanocomposites, we have combined cylinder phases of polystyrene-block-polyisoprene diblock (as a solution in dibutylphthalate) and poly(styrene-block-isoprene-block-styrene) triblock (as a blend with homopolystyrene) copolymers with gold nanorods of different diameters and surface treatments. Polarized optical microscopy and transmission electron microscopy on these composites demonstrate that the nanorods selectively nucleate coaxial domains of copolymer cylinders (i.e., domains of cylinders aligned along the same axis as the nanorod). These single nucleation events occur regardless of nanorod diameter and surface character, and determine the order of most of the surrounding polymer. Mesoscale modeling of the nucleation process, performed with nanorods of different diameters and with different polymer-surface interactions, illustrates the mechanism by which copolymer-dispersed nanorods with different sizes and surface chemistry can template the organization of cylindrical copolymer domains.     

Strain‐induced crystallization behavior of phenolic resin crosslinked natural rubber/clay nanocomposites

Nanocomposites of natural rubber (NR) and unmodified clay were prepared by latex compounding method. Phenolic resin (PhOH) was used to crosslink NR. Crosslinked neat NR was also prepared for comparison. The structure–property relationship of uncrosslinked and crosslinked NR/clay nanocomposites was examined to verify the reinforcement mechanism. Microstructure of NR/clay nanocomposites was studied by using transmission electron microscopic (TEM), X‐ray diffraction (XRD), wide angle X‐ray diffraction (WAXD), and small angle X‐ray scattering (SAXS) analyses. The results showed the evidence of intercalated clay together with clay tactoids for the nanocomposite samples. The highest tensile strength was achieved for the crosslinked NR/clay nanocomposite. The onset strain of deformation induced the crystallization of NR for nanocomposites was found at almost the same strain, and furthermore their crystallization was developed at lower strain than that of the crosslinked neat NR because of the clay orientation and alignment. However, at high strain region, the collaborative crystallization process related to the clay dispersion and conventional crosslink points in the NR was responsible to considerably high tensile strength of the crosslinked NR/clay nanocomposite. Based on these analyses, a mechanistic model for the strain‐induced crystallization and orientational evolution of a network structure of PhOH‐crosslinked NR/clay nanocomposite was proposed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42580.     

Exfoliation of organoclay nanocomposites based on polystyrene-block-polyisoprene-block-poly(2-vinylpyridine) copolymer: Solution blending versus melt blending

Exfoliated nanocomposites based on polystyrene-block-polyisoprene-block-poly(2-vinylpyridine) (SI2VP triblock) copolymer were prepared by solution blending and melt blending. Their dispersion characteristics were investigated using transmission electron microscopy, X-ray diffraction, and small-angle X-ray scattering (SAXS). For the study, SI2VP triblock copolymers with varying amounts of poly(2-vinylpyridine) (P2VP) block (3, 5, and 13 wt%) and different molecular weights were synthesized by sequential anionic polymerization. In the preparation of nanocomposites, four different commercial organoclays, treated with a surfactant having quaternary ammonium salt, were employed. It was found from SAXS that the microdomain structure of an SI2VP triblock copolymer having 13 wt% P2VP block (SI2VP-13) transformed from core-shell cylinders into lamellae when it was mixed with an organoclay. It was found further that the solution-blended nanocomposites based on a homogeneous SI2VP triblock copolymer having 5 wt% P2VP block (SI2VP-5) gave rise to an exfoliated morphology, irrespective of the differences in chemical structure of the surfactant residing at the surface of the organoclays, which is attributable to the presence of ion-dipole interactions between the positively charged N⁺ ion in the surfactant residing at the surface of the organoclay and the pyridine rings in the P2VP block of SI2VP-5 and SI2VP-13, respectively. Both solution- and melt-blended nanocomposites based on microphase-separated SI2VP-13 having an order-disorder transition temperature (T_ODT) of approximately 210 °C also gave rise to exfoliated morphology. However, melt-blended nanocomposite based on a high-molecular-weight SI2VP triblock copolymer having a very high T_ODT (estimated to be about 360 °C), which was much higher than the melt blending temperature employed (200 °C), gave rise to very poor dispersion of the aggregates of organoclay. It is concluded that the T_ODT of a block copolymer plays a significant role in determining the dispersion characteristics of organoclay nanocomposites prepared by melt blending.     

Perpendicular oriented cylinders via directional coalescence of spheres embedded in block copolymer films induced by solvent annealing

Polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer with PS volume fraction of 25.2 vol% was synthesized by atom transfer radical polymerization. Non-pretreated silicon wafers were used as the substrates to prepare perpendicular oriented PS cylinders in PMA matrix via solvent annealing which could induce the transformation of spheres to vertically oriented and hexagonally packed cylinders. The spherical microdomains were formed after the evaporation of solvents from the solutions of the block copolymer in selective solvents mixed from methanol, acetone and dichloromethane. The thickness of films could be as thick as 1000 nm, which were much thicker than usual cases and the cylinders came from the directional coalescence of the spheres, thus any pre-treatments of the substrates were not required for perpendicular orientation. The structures were characterized by small angle X-ray scattering (SAXS), transmission electron microscope (TEM), atom force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS).     

Effect of uniaxial drawing on the structure and glass transition behavior of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites

The structure–property relationships of poly(trimethylene 2,6-naphthalate)/layered clay nanocomposites are being investigated under uniaxial drawing by using synchrotron wide angle X-ray diffraction, small angle X-ray scattering, transmission electron microscope and dynamic mechanical analyzer. The cold crystallization at 110 °C of PTN and nanocomposites samples under drawing induced the α-crystal form with the chain axis (c-axis) aligned along the drawing direction as well as parallel to the layered clay surface. However, the broad surfaces of the layered clay are oriented and rotated nearly perpendicular to the sample's surface, forming the house of cards type structure. Such structural formation of layered clay in the PTN matrix influenced the thermomechanical properties depending on the extent of confinement and surface interaction effects. The amorphous and crystallized structures of the nanocomposites showed the analogous tendency in which T_g decreased and increased before and after drawing, respectively, relative to the neat PTN. Despite the evolution of free volume after drawing, the nanocomposites exhibited an unusual positive shifting trend in T_g. The deviation of T_g in the PTN nanocomposites system is ascribed to the interplay of two competing effects; (i) the increase in the local free volume owing to the confining effect of intercalation (enhanced the chain mobility) and (ii) entropic constraint imposed by the stronger interfacial interaction due to the physical jamming of layered clay (retarded the chain mobility).     

Ordering of block copolymer/nanoparticle composite thin films

The ordering behavior of polymer nanocomposites composed of gold nanoparticles confined in the polystyrene (PS) domains of PS based block copolymers was investigated. The results reveal that the self‐assembly of nanoparticles in the PS domains improved the ordering of microdomains. This is attributed to the presence of nanoparticles that reduced the degree of segregation of the system, causing slow phase separation. This facilitates the packing of the cylindrical microdomains, leading to a well‐ordered structure of the composite. When particles were incorporated into the major domains of cylindrically ordered block copolymer, the connectivity of the domains allowed particles to move to the top of the film to gain additional entropy of the system. In contrast, when particles were organized in parallel cylinders in the block copolymer, they were confined in the cylinders which prevented them from diffusing in the depth direction. The aggregation of nanoparticles was amplified when the composite was annealed in air. We believe that the results from this study will enable more understanding of the effects of nanoparticles on the ordering of block copolymer/nanoparticle composite thin films and will provide a tool in the fabrication of composite thin films. Copyright © 2012 Society of Chemical Industry     

Influence of intercalated organoclay on the phase structure and physical properties of PTT–PTMO block copolymers

Poly(trimethylene terephthalate-block-tetramethylene oxide) (PTT–PTMO) copolymer/organoclay nanocomposites were prepared by in situ polymerization. They showed an intercalated silicate structure, as determined by X-ray diffraction and transmission electron microscopy. The influence of intercalated organoclay on the two-phase structure and mechanical properties of PTT–PTMO block copolymer was examined by using DSC and tensile tests. The DSC results imply that the silicate layers (Nanofil 32) in PTT–PTMO act as nucleation agents and accelerate the crystallization of PTT hard phase during the cooling down process from the melt. The introduction of silicate layers does not have great effect on the glass transition temperature of PTMO-rich soft phase, melting temperature of PTT hard phase, and degree of crystallinity of the nanocomposites. As the organoclay loading in the nanocomposites increase, the enhanced tensile modulus and yield stress was observed. The cyclic tensile tests showed that obtained nanocomposites have values of permanent set comparable to the neat PTT–PMO copolymer.     

A combined experimental and theoretical approach to establish the relationship between shear force and clay platelet delamination in melt-processed polypropylene nanocomposites

In this article, a combined experimental and theoretical approach has been proposed to establish a relationship between the required shear force and the degree of delamination of clay tactoids during the melt-processing of polymer nanocomposites. Polypropylene (PP) was selected as a model polymer, and nanocomposites of PP with organically modified clay were prepared by a master batch dilution technique in a twin-screw extruder. The effect of PP throughput during the dilution of the master batch on the dispersion and orientation of clay platelets were studied in detail. Powder X-ray diffraction, small and wide angle X-ray scattering and high resolution transmission electron microscopy were used to study the structure and morphology of the obtained nanocomposites. The results showed that a lower feeding rate led to the orientation of clay platelets almost in the direction of extrusion. The adhesive force and the interaction energy between the clay platelets were theoretically calculated using the Hamaker approach. The analysis showed that the peeling mechanism is a practical explanation for the delamination of clay platelets during melt extrusion and that the dimensions of the clay platelet tactoids play an important role in the peeling due to the shear stress.     

Ion-dipole interactions in the dispersion of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) copolymer

The dispersion characteristics of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) (S2VP diblock) copolymer were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (NMR) spectroscopy. For the investigation, S2VP diblock copolymers having three different compositions were synthesized via sequential anionic polymerization. Each S2VP diblock copolymer was used to prepare nanocomposites by solution blending with natural clay (montmorillonite, MMT) or commercial organoclays (Cloisite 30B, Cloisite 10A, Cloisite 15A, and Cloisite 25A from Southern Clay Products). All four organoclays employed were treated with a surfactant having quaternary ammonium salt with N⁺ ion. It was found, via TEM and XRD, that the nanocomposites with MMT show very poor dispersion characteristics regardless of block copolymer composition. However, the block copolymer composition was found to have a profound influence on the dispersion characteristics of the nanocomposites with an organoclay. Specifically, the nanocomposites based on S2VP-5 having 5 wt% poly(2-vinylpyridine) (P2VP) block gave rise to a very high degree of dispersion, irrespective of the chemical structure of the surfactant residing at the surface of the organoclay employed, whereas the dispersion characteristics of the nanocomposites became progressively poorer as the amount of P2VP block in an S2VP diblock copolymer increased from 5 to 25 wt% and to 56 wt%. The observed dispersion characteristics were explained by hypothesizing the presence of ion-dipole interactions between the positively charged N⁺ ions in the surfactant residing at the surface of the organoclay nanoparticles and the dipoles in the P2VP block of S2VP diblock copolymers. The validity of this hypothesis was confirmed using solid-state NMR spectroscopy, by determining the dependence of the composition of S2VP diblock copolymer on the extent of ion-dipole interactions and thus on the dispersion characteristics of the nanocomposites prepared.     

Synthesis and characterization of (star polystyrene)-block-(polyisoprene)-block-(star polystyrene) copolymers

A (star polystyrene)-block-(linear polyisoprene)-block-(star polystyrene) copolymer, (S)_nI(S)_n, was prepared. The star polystyrene was produced via anionic polymerization of polystyrene macromonomers each containing an unsaturated double bond (vinyl) at the chain end. This vinyl-terminated polystyrene macromonomer (SSTM) was obtained beforehand via the synthesis of a living polystyrene using alkyllithium and the termination with p-chloromethylstyrene (PCMS). The living site in the core of the star polystyrene enabled the construction of the succeeding polyisoprene block resulting in the living (star polystyrene)-block-(linear polyisoprene) copolymer, (S)_nI. This living diblock copolymer was then coupled with 1,2-dibromoethane (DBE) to form the well-defined (S)_nI(S)_n. Compared to a linear polystyrene-block-polyisoprene-block-polystyrene, SIS, with the same molecular weight, (S)_nI(S)_n had a higher T_g and exhibited a lamellae-forming phase separation in conjunction with many dislocation defects. The thermal stability appeared independent of the molecular structure, and the radius of gyration and viscosity of (S)_nI(S)_n were much smaller than SIS.     

Effects of sample preparation and flow geometry on the rheological behaviour and morphology of microphase-separated block copolymers: comparison of cone-and-plate and capillary data

The steady shear viscosities of two microphase-separated triblock copolymers, a polystyrene-block-polybutadiene-block-polystyrene copolymer (Kraton 1102) and a polystyrene-block-polyisoprene-block-polystyrene copolymer (Kraton 1107), were measured at various temperatures, using a cone-and-plate rheometer at low shear rates (ca. 0.01–10s⁻¹) and a capillary rheometer at high shear rates (ca. 5–5000 s⁻¹). In order to investigate the effect of sample preparation on the viscosity, specimens of Kraton 1102 were prepared using two different methods: (a) solvent film casting and (b) compression moulding. Samples of Kraton 1107 were prepared only by compression moulding. In the present study we found that (a) for compression-moulded specimens the shear viscosities obtained using a cone-and-plate rheometer did not overlap those obtained using a capillary rheometer, while for solvent-cast specimens there was a reasonably good agreement between the two, and (b) the viscosities of solvent-cast specimens were much lower than those of compression-moulded specimens. This observation was explained with the aid of transmission electron micrographs, which were taken of ultrathin sections cut parallel and perpendicular to the direction of shear. We found from transmission electron micrographs that the application of steady shear flow affected greatly the morphology of Kraton 1102 having cylindrical microdomains of polystyrene phase, whereas it affected little the morphology of Kraton 1107 having spherical microdomains of polystyrene phase. Also measured were the complex shear viscosities of the two block copolymers at various temperatures. We have shown that neither time-temperature superposition nor the Cox-Merz rule is applicable to microphase-separated block copolymers.     

Surfactant assisted selective confinement of carbon nanotubes functionalized with octadecylamine in a poly(styrene-b-isoprene-b-styrene) block copolymer matrix

We report how dodecanethiol (DT) surfactant can be used as a good dispersant to solubilize octadecylamine functionalized single-walled carbon nanotubes (ODA-SWCNTs) in order to confine them in the polystyrene phase of the polystyrene-b-polyisoprene-b-polystyrene (SIS) block copolymer matrix. It has been also demonstrated how the block copolymer matrix is not able to self-assemble in ordered morphology when the ODA-SWCNTs are not modified with the surfactant. DT assisted confinement of carbon nanotubes into the PS phase causes not only the nanostructuration of the host polymer matrix but also switches the self-assembled nanostructure from ordered cylinders in the case of neat SIS to a self-assembled lamellar nanostructure.     

The pillaring effect of the 1,2-dimethyl-3(benzyl ethyl iso-butyl POSS) imidazolium cation in polymer/montmorillonite nanocomposites

A polyhedral oligomeric silsesquioxane (POSS) tethered imidazolium surfactant was used to exchange montmorillonite for the preparation of polymer nanocomposites in polystyrene, poly(ethylene-co-vinyl acetate), and polyamide-6 using a melt blending technique. Simultaneous temperature resolved small angle X-ray scattering and wide angle X-ray diffraction was used to monitor the surfactant stability and phase behavior of the polyamide-6 nanocomposites. Good thermal stability of the surfactant was in agreement with thermogravimetric analysis. Transmission electron microscopy revealed a mixed intercalated/exfoliated structure, with the presence of small tactoids exhibiting gallery spacings greater than 3.8 nm in all three polymers. Fluorescently tagged organically exchanged montomorillonite was used to assess the quality of nanoparticle dispersion. Exchanging the montmorillonite with lower loadings of the POSS surfactant slightly increased the size of clay tactoids, but did not significantly alter the gallery spacing or overall dispersion. The results suggest that the bulky and rigid structure of POSS, as well as its tendency to aggregate into ordered crystals, form a bilayer structure in the clay galleries and prevent montmorillonite from completely exfoliating, even in polyamide-6.     

Quantification of organoclay dispersion and lamellar morphology in poly(propylene)-clay nanocomposites with small angle X-ray scattering

Intensity profiles of small angle X-ray scattering (SAXS) curves were analyzed to simultaneously gain quantitative information on nanoclay dispersion as well as lamellar ordering in polypropylene-clay nanocomposites. Different types of PP nanocomposites prepared with PP homopolymer (HPP), random propylene-ethylene copolymer (RCP) and a high impact polypropylene-ethylene propylene rubber (ICP) were analyzed. Various one-dimensional models for stacked structures were applied on Lorentz corrected SAXS spectra to derive long period, thicknesses of alternating high and low electron density layers and their distributions, and the number of stacks for both nanoclay and PP lamellae. We applied a mixed thickness distribution model comprising combined Gaussian and exponential for a simple stack of finite thickness, which was found to explain the experimental data better for both nanoclay tactoids and lamellar stacks, compared to simple Gaussian and exponential thickness distributions. Long period X and number of stacks N were derived as important parameters signifying changes in levels of nanoclay exfoliation in PP. Among the three types of polypropylenes studied, better nanoclay exfoliation was obtained for the high impact ICP grade compared to HPP and RCP. Complete exfoliation of nanoclay was achieved in ICP matrix, employing a masterbatch processing route. Moreover, role of nanoclay as a γ nucleating agent was evident from small and wide angle X-ray analyses, and was seen strongly in RCP. Changes in lamellar structure of PP as a result of nanoclay incorporation, double population consisting of both α and γ polytypes in the nanocomposites from that of a primarily α population in neat polymer matrices, were also analyzed in detail with the mixed thickness distribution model, thereby demonstrating its usefulness.     

Effect of clay orientation on the tensile modulus of polypropylene-nanoclay composites

We present an experimental investigation of the effect of clay orientation, as produced by melt extrusion, on the tensile modulus of compatibilized and uncompatibilized syndiotactic polypropylene nanoclay composites. The orientation of the clay tactoids in extruded tape samples was quantified using 2D X-ray diffraction data. It was found that in the case of the tapes made from compatibilized nanocomposites the orientation of the clay tactoids increased with extrusion shear rate, while in the case of tapes extruded from uncompatibilized hybrids the clay orientation was independent of the shear rate. Tensile modulus of the extruded tapes along the flow direction was measured and was found to correlate well with the average orientation of the clay tactoids. In the case of the compatibilized hybrids the modulus increased with the extrusion shear rate until a saturation value, whereas for the uncompatibilized hybrids the modulus was nearly independent of the shear rate. Semi-quantitative predictions of the effect of clay orientation on the tensile modulus of the compatibilized tape samples were obtained using a micromechanical model.     

Improvement of toughness in polypropylene nanocomposite with the addition of organoclay/silicone copolymer masterbatch

Polypropylene nanocomposites were prepared with organic‐modified montmorillonite, by blending the polymer and the organoclay (direct addition), or by blending the polymer with an organoclay/silicone copolymer masterbatch. The effect of the organoclay/silicone copolymer masterbatch on the morphology and properties of polypropylene was compared with that nanocomposite obtained with the direct organoclay addition. The results showed that the morphology of both polypropylene nanocomposites is constituted by clay tactoids together with some few individual platelets and clay aggregates. Smaller tactoids were observed for the nanocomposite prepared with the masterbatch, in which the silicone copolymer remained intercalated in the clay or adjacent to tactoids. The introduction of the organoclay in the polymer matrix resulted only in an increase in the Young's modulus (28%), while yielding stress, elongation at break and Izod impact strength remained practically unchanged. On the other hand, the incorporation of organoclay by using the masterbatch resulted in a marked improvement (111%) in the elongation at break and in Izod impact strength (85%). The improvement in the elongation at break came with the reduction of the modulus and the yielding stress, by 25 and 15%, respectively. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers