Nanoparticles In Polymer Nanocomposites Research Articles

A review on synthesis, characterization and applications of nanoparticles in polymer nanocomposites

The smallest particles known as nanoparticles have sizes between 1 and 100 nm, which in contrast to their bulk counterparts, possess special properties, including increased surface area, quantum confinement effects and optical, magnetic, catalytic features that are size-dependent. Several different materials possibly used to create nanoparticles, involving metals, ceramics, polymers, and metal oxides. Different biological, chemical, and physical characteristics are displayed by nanoparticles which make them appealing to numerous applications in industries like healthcare, electronic devices, energy and environmental remediation. In medicine, drug delivery with specificity is accomplished by nanoparticles, which improves treatment effectiveness while reducing side effects. This abstract investigates the characteristics and applications that contain nanoparticles, including their synthesis methods, characterization techniques and synergistic impact of hybrid nanoparticles on material characteristics. In order to ensure the safe and sustainable use of nanomaterials, responsible development and regulation of these substances are also discussed, along with challenges and opportunities within the discipline of nanotechnology.

Influence of nanoparticle size on the mechanical and tribological characteristics of TiO2 reinforced epoxy composites

Photosensitive resins (PSR) were exposed to challenging operational conditions in different technological domains. It is desirable to enhance the mechanical durability of PSR for its usage in real-world applications. We use TiO2 to improve the mechanical strength and durability of PSR and comprehend nanoparticles' impact on PSR's durability. Herein, we compare the mechanical properties of photosensitive resins (PSR) and TiO2-based polymer nanocomposites (T@PNCs) with varying nanoparticle sizes [1 μm and 20 nm]. Firstly, the ultrasonic dual mixing (UDM) technique is employed, which involves the simultaneous use of ultrasonic mixing and stirring to produce nanocomposites of T@PNCs slurry. Before printing, the initial designs were created using solidworks software, and 3D-Printing was performed using a 3D Moon Ray Printer. Rod and flat specimens were printed, and their structural and mechanical strength were analyzed. The experimental results suggest that larger nanoparticles, measuring 1 μm, decrease the mechanical durability of T@PNCs. However, reducing the size of nanoparticles in polymer nanocomposites (PNCs) to 20 nm increases mechanical resilience, leading to improved flexural and tensile strength. Our experimental results demonstrate that the nanoparticles' size strongly influences PSR's mechanical properties.

Using Focused Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry to Depth Profile Nanoparticles in Polymer Nanocomposites.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a versatile surface-sensitive technique for characterizing both hard and soft matter. Its chemical and molecular specificity, high spatial resolution, and superior sensitivity make it an ideal method for depth profiling polymeric systems, including those comprised of both inorganic and organic constituents (i.e., polymer nanocomposites, PNCs). To best utilize ToF-SIMS for characterizing PNCs, experimental conditions must be optimized to minimize challenges such as the matrix effect and charge accumulation. Toward that end, we have successfully used ToF-SIMS with a Xe+ focused ion beam to depth profile silica nanoparticles grafted with poly(methyl methacrylate) (PMMA-NP) in a poly(styrene-ran-acrylonitrile) matrix film by selecting conditions that address charge compensation and the primary incident beam angles. By tracking the sputtered Si+ species and fitting the resultant concentration profile, the diffusion coefficient of PMMA-NP was determined to be D = 2.4 × 10-14 cm2/s. This value of D lies between that measured using Rutherford backscattering spectrometry (6.4 × 10-14 cm2/s) and the value predicted by the Stokes-Einstein model (2.5 × 10-15 cm2/s). With carefully tuned experimental parameters, ToF-SIMS holds great potential for quantitatively characterizing the nanoparticles at the surfaces and interfaces within PNC materials as well as soft matter in general.

Comparison of nanocomposite dispersion and distribution for several melt mixers

Breakup (dispersion) and distribution of nanoparticles are the chief hurdles towards taking advantage of nanoparticles in polymer nanocomposites for reinforcement, flame retardancy, conductivity, chromaticity, and other properties. Microscopy is often used to quantify mixing, but it has a limited field of view, does not average over bulk samples, and fails to address nano-particle hierarchical structures. Ultra-small-angle X-ray scattering (USAXS) can provide a macroscopic statistical average of nanoscale dispersion (breakup) and emergent hierarchical structure, as well as the distribution on the nanoscale. This work compares several common mixer geometries for carbon black-polystyrene nanocomposites. Two twin-screw extruder geometries, typical for industrial processing of melt blends, are compared with a laboratory-scale single screw extruder and a Banbury mixer. It is found that for a given mixer, nanoscale distribution increases following a van der Waals function using accumulated strain as an analogue for temperature while macroscopic distribution/dispersion, using microscopy, does not follow this dependency. Breakup and aggregation in dispersive mixing follow expected behavior on the nanoscale. Across these drastically different mixing geometries an unexpected dependency is observed for nanoscale distributive mixing (both nano and macroscopic) as a function of accumulated strain that may reflect a transition from distributive turbulent to dispersive laminar mixing as the mixing gap is reduced.

The effect of dynamically heterogeneous interphases on the particle dynamics of polymer nanocomposites.

The entanglements of dynamically asymmetric polymer layers influence relaxations of nanoparticles in polymer nanocomposites. In this work, the dynamics of polymer-adsorbed and polymer-grafted nanoparticles in a poly(methyl acrylate) matrix polymer was investigated using X-ray photon correlation spectroscopy (XPCS) to understand the role of chain rigidity and chemical heterogeneities in particle dynamics. Locations of dynamic heterogeneities close to nanoparticles and away from particle surfaces were examined with the comparison of adsorbed and grafted nanoparticles. Our results show that the chemical heterogeneities around dispersed nanoparticles transitioned the particle dynamics from Brownian diffusion into hyperdiffusion, and moreover, the high rigidity of chains in the chemically heterogeneous interfacial layers slowed down the particle dynamics. The hyperdiffusion measured both in grafted particles and adsorbed particles was attributed to the dense interfacial mixing of dynamically heterogeneous chains.

Nonlinear optical properties of LLDPE composites with titanium dioxide anatase phase

In this research work, the linear and nonlinear optical properties of linear low-density polyethylene (LLDPE) composites with anatase phase of titanium dioxide nanoparticles in different weight percentages are investigated. Solvent casting method have been used to synthesize the thin film of LLDPE/anatase nanocomposites. Thin films are characterized via XRD technique and field emission scanning electron microscope (FESEM). Wrinkles formed on the surface of thin films by adding the titanium dioxide. Linear optical and electrical parameters such as linear absorption coefficient, extinction coefficient, refractive indices, optical conductivity, and dielectric constants at various wavelengths from 190 nm to 2700 nm are determined for different weight percentages of nanoparticles in polymer nanocomposites. Z-scan technique has been employed to explore the nonlinear optical properties using CW laser at 532 nm wavelength. The nonlinearity is examined at various irradiance of laser to study the effect of irradiance on nonlinear optical properties. Pure LLDPE has saturable absorption (SA) at low laser irradiance. As the laser irradiance increases, the nonlinearity behavior turns from SA to reverse saturable absorption (RSA). The results show the suitability of the thin films for the applications in optical devices that involve the use of optical limiting properties of materials.

Obtention of higher refractive index and transparent polymeric nanocomposite systems with small amounts of fillers for lenses application

The development of new materials for obtaining ophthalmic lenses is a subject of great interest due to the great necessity of corrective lenses uses. The application of the lenses based on polymeric material that guarantees greater lightness and less risk of breakage, ensuring greater comfort to users of glasses. The use of nanoparticles in polymer nanocomposites can generate different properties in the final material, mainly when used in hybrid systems in which synergistic effects can be produced. Thus, the present work aimed to evaluate the optical properties of systems with poly(methyl methacrylate) and oxide nanoparticles (silica, zinc, zirconium, and titanium). The systems were characterized in terms of their optical behaviors (refractive index, transmittance, and color change) and mechanical behaviors (nanoindentation, and tensile strength). The results showed that silica-based systems tended to have greater transparency but generate lower refractive indexes. Systems containing zirconia, titanium, and zinc have a higher refractive index and smaller transparency than systems containing silica. Besides, the use of zirconia and titanium increases the nano-hardness and elastic modulus. The results showed that the use of these nanoparticles in binary systems leads to obtaining materials with higher refractive index, greater transparency, and best mechanical behavior. The combination of the nanoparticles also led to a better dispersion, reducing the impact on the color system and improve transparency. In this way, the materials developed using small amounts of fillers and present highly promising for the development of thinner, more resistant to scratching due to high hardness and higher transparent lenses.

Tuning the Electrically Conductive Network of Grafted Nanoparticles in Polymer Nanocomposites by the Shear Field

Controlling the formation of the conductive network in the polymer nanocomposites (PNCs) is very meaningful to enhance their electrical property. In this work, we investigated the effect of grafted nanoparticles (NPs) on the conductive probability of PNCs in the quiescent state as well as under the shear field via a coarse-grained molecular dynamics simulation. It is found that the smallest percolation threshold is realized at the moderate grafting density, the moderate length of grafted chains or the moderate interaction between grafted chains and free chains. Corresponding to it, the dispersion state of NPs varies from the contact aggregation to the uniform dispersion. By analyzing the connection mode among NPs, the probability of NPs which connect three other ones reaches the maximum value at their moderate dispersion state which is responsible for the optimal conductive probability. In addition, the main cluster size is characterized to better understand the conductive network which is consistent with the percolation threshold. It is interesting to find that the percolation threshold is smaller under the shear field than under the quiescent state. The shear field induces more NPs which connect three other ones. This benefits the formation of the new conductive network. Meanwhile, the anisotropy of the conductive probability is reduced with increasing the grafting density. In summary, this work provides a clear picture on how the conductive network of grafted NPs evolves under the shear field.

Strong Reduction in Amplitude of the Interfacial Segmental Dynamics in Polymer Nanocomposites

Despite the wide use of polymer nanocomposites (PNCs) in various applications, our understanding of the microscopic parameters controlling their macroscopic properties remains limited. In this study, we examine the dielectric strength of segmental dynamics, ΔeIL(T) in the interfacial polymer layer surrounding the nanoparticles in PNCs. The presented analysis reveals a significant drop in ΔeIL(T) and its anomalous temperature dependence in the polymer layer adsorbed to nanoparticles. The drop in ΔeIL(T) was observed in all samples regardless of whether segmental relaxation time in the interfacial layer was slower or faster than in the bulk polymer, excluding interpretation of the “dead” layer. We ascribe the observed decrease in the dielectric strength to the restricted amplitude of segmental relaxation in the interfacial/adsorbed layer. Our results provide a new perspective on discussion of dynamics in the interfacial layer in PNCs and thin polymer films, demonstrating that not only segmental relaxation time but also its amplitude can be strongly affected by the interface.

The interfacial zone in thin polymer films and around nanoparticles in polymer nanocomposites.

We perform coarse-grained simulations of model unentangled polymer materials to quantify the range over which interfaces alter the structure and dynamics in the vicinity of the interface. We study the interfacial zone around nanoparticles (NPs) in model polymer-NP composites with variable NP diameter, as well as the interfacial zone at the solid substrate and free surface of thin supported polymer films. These interfaces alter both the segmental packing and mobility in an interfacial zone. Variable NP size allows us to gain insight into the effect of boundary curvature, where the film is the limit of zero curvature. We find that the scale for perturbations of the density is relatively small and decreases on cooling for all cases. In other words, the interfaces become more sharply defined on cooling, as naively expected. In contrast, the interfacial mobility scale ξ for both NPs and supported films increases on cooling and is on the order of a few nanometers, regardless of the polymer-interfacial interaction strength. Additionally, the dynamical interfacial scale of the film substrate is consistent with a limiting value for polymer-NP composites as the NP size grows. These findings are based on a simple quantitative model to describe the distance dependence of relaxation that should be applicable to many interfacial polymer materials.

A quantum dot model for nanoparticles in polymer nanocomposites

Nanoparticles in polymer nanocomposites can be dielectric quantum dots (DQDs). A quantum dot model is proposed for nanoparticles imbedded in polymers based on both this new concept and the multicore model proposed in 2005. QDs should be as small as de Broglie's wavelength and the exciton Bohr diameter, and accommodate a countable number of charge carriers. DQDs are a little bit larger than metal and semiconductor QDs. Some of dielectric performances such as permittivity, charge transport, space charge and treeing can be explained in terms of nonlinear multi-functional traps derived from the DQD model. It was verified that different combination of polymers and nanoparticles lead to different characteristics.

Diffusion of Nanoparticles in Polymer Systems

The state-of-the-art in research of the mobility of nanoparticles in polymer melts is presented. It is important to determine the mechanisms of diffusion processes in these systems and factors affecting the diffusion of nanoparticles of different sizes when developing methods for controlling the distribution of nanoparticles in polymer nanocomposites that play an increasingly important role in various industries. The modern theoretical concepts of the diffusion of small particles in solutions and polymer melts, as well as results of computer simulation and experimental studies, are discussed. It is shown that the key factor determining the nature of the motion of nanoparticles is the ratio of the particle size to the characteristic dimensions of the polymer, which explains the strong relationship between the mobility of nanoparticles and the local structure of polymer molecules.

Novel non-destructive evaluation technique for the detection of poor dispersion of carbon nanotubes in nanocomposites

A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference in the thermal response to heat transfer transients. Thus, the thermal response of a nanocomposite allows one to identify consistently good levels of dispersion with respect to lower levels of dispersion. A reference product, which has the expected dispersion level and achieves the desired design performance, can be used to test the thermal behaviour of other products coming out of the production process and those with poor dispersion can be identified. The physical phenomena that can explain the effects of multi-walled carbon nanotubes (MWCNTs) dispersion on the thermal response of the nanocomposites to the heat transfer transients were also identified.

Evaluation and Development of Expanded Equations Based on Takayanagi Model for Tensile Modulus of Polymer Nanocomposites Assuming the Formation of Percolating Networks

In this study, the tensile modulus of polymer nanocomposites is analyzed by the development of expanded Takayanagi models considering the fractions of networked and dispersed nanoparticles above the percolation threshold. The tensile moduli of networked and dispersed phases are calculated by suitable models. This study focuses on “polymer-carbon nanotubes” nanocomposites, but the developed model can be applied for samples reinforcing with long fillers such as clay and graphene. The expanded Takayanagi model suggests two different forms which are evaluated by the experimental results of “polymer-carbon nanotubes” nanocomposites. Only one form shows the best results compared to the experimental data, whereas another form underestimates the modulus. The developed model (correct form) shows that the fraction of filler network meaningfully changes the reinforcement of nanocomposites. The network level and other correlated parameters with the percolation threshold can be calculated by comparing the experimental data with the developed model. The logical outputs confirm the correct development of Takayanagi model assuming the network and dispersion of nanoparticles in polymer nanocomposites.

Polymeric nanocomposites: account for the effect of size distribution of nanoparticles

The essence of the work lies in the theoretical analysis of the influence of size distribution of nanoparticles in polymer nanocomposites on the glass transition temperature Tg and coefficient of thermal expansion CTE. Both of these characteristics are important for building materials containing polymers. If the values of these characteristics exceed the allowable value, the material will soften and you should not alter its size.Methods: used the Poisson distribution applied to the radius of the nanoparticles. The analysis is performed at the expected mean values of 5 and 10 nm. As object of research used in the cured epoxy resin filled with nanoparticles of SiO2. The surface modified nanoparticles grafted polar groups possessing a dipole-dipole interaction and hydrogen bonds. The analysis is based on previously obtained relationships connecting the Tg and CTE with a set of atomic physical constants. This set depends on the chemical structure of the repeating unit of the polymer or molecular fragment of a polymer network. Among these constants, Van-der-Waals volume and the energy of the dispersion interaction of each atom, as well as energy dipole-dipole interaction or hydrogen bonds to polar groups.The results of the study: they consist in the fact that the dependencies of Tg and CTE on the expected mean radius of nanoparticles are obtained. Considered part of the epoxy resin will be cured with usual methylhydrophthalic anhydride and another part of the epoxy resin will be cured with anhydride-modifier. The formulas for quantitative assessment of the values of Tg and CTE for such copolymer structures are obtained. The greatest increase in Tg of 430 to 465 K was observed when reducing the radius of the nanoparticles from 8 to 3 nm at the mean expected value of 5 nm. This is true when chemical interaction between the epoxy resin and anhydride-modifier takes place. The magnitude of the CTE increases from 1.95×10-4 up to 2.05×10-4 by increasing mean radius of nanoparticles from 3 to 7 nm.Conclusions: The expression for the theoretical estimation of Tg value of nanocomposites was modified in order to account for the polydispersity of nanoparticles. The theoretical estimation shows that the influence of the size distribution of the silica nanoparticles on the both of Tg and CTE values of the epoxy/silica nanocomposite can be quite considerable. The most significant effect will be achieved at the conditions, when nanoparticles play the role of multifunctional curing agent.

Rapid quantitative mapping of multi-walled carbon nanotube concentration in nanocomposites

Inhomogeneous distributions of nanoparticles in polymer nanocomposites have a strong influence on final material properties. Quantitative methods to characterise particle dispersion are rarely applied but are critical for advancing understanding of material behaviour, developing accurate computer models, and optimizing processing. Two complementary quantitative methods were developed to map local concentration, based on Raman spectroscopy and simple optical absorbance, respectively. The approaches are demonstrated for a model multi-walled carbon nanotube (MWNT) epoxy nanocomposite, but should be widely applicable. Maps of absolute concentration can be produced with submicron resolution, allowing analysis of the uniformity of MWNT concentration distribution via the coefficient of variation. The two approaches correlate closely, providing validation of both methods. However, the optical absorbance approach is likely to be more practical, in most cases, as it uses a standard laboratory microscope to analyse large areas rapidly.

Self-Assembly of Block Copolymer Chains To Promote the Dispersion of Nanoparticles in Polymer Nanocomposites.

In this paper we adopt molecular dynamics simulations to study the amphiphilic AB block copolymer (BCP) mediated nanoparticle (NP) dispersion in polymer nanocomposites (PNCs), with the A-block being compatible with the NPs and the B-block being miscible with the polymer matrix. The effects of the number and components of BCP, as well as the interaction strength between A-block and NPs on the spatial organization of NPs, are explored. We find that the increase of the fraction of the A-block brings different dispersion effect to NPs than that of B-block. We also find that the best dispersion state of the NPs occurs in the case of a moderate interaction strength between the A-block and the NPs. Meanwhile, the stress–strain behavior is probed. Our simulation results verify that adopting BCP is an effective way to adjust the dispersion of NPs in the polymer matrix, further to manipulate the mechanical properties.

Diffusion dynamics of nanoparticle and its coupling with polymers in polymer nanocomposites

Diffusion dynamics of nanoparticles in polymer nanocomposites is investigated by coarse-grained molecular dynamics simulations. We report a strong polymer chain length dependent non-Gaussian diffusion of nanoparticles (NPs) in entangled polymer melt. By analyzing the NP motion and the polymer relaxation at different length and time scales, we find that the non-Gaussian diffusion of NPs originates from a dynamic coupling at a specific length scale with the melt polymer chain segments that possess similar size with NP. Our results provide a microscopic understanding of the complex particle environment interactions and a detailed mechanism for nanoparticle diffusion in entangled polymer melt.

The reinforcing and characteristics of interphase as the polymer chains adsorbed on the nanoparticles in polymer nanocomposites

In this study, the adsorbed polymer chains on the nanoparticle surface are assumed as an interphase layer, which increases the reinforcing efficiency of nanoparticles in polymer nanocomposites. The interphase is taken into account to enhance the effective volume fraction of nanoparticles, which is determined by the Maxwell model for Young’s modulus of composites. Also, the modulus and strength of interphase are calculated by proper models. The interphase properties are estimated and discussed for various samples containing different nanoparticles. The present methodology gives fine agreement between the experimental results of mechanical properties and the calculations. Also, the acceptable results for interphase properties are obtained which confirm the validity of the presented models. The small nanoparticles and thick interphase significantly increase the nanocomposite reinforcement. Additionally, Young’s modulus of nanoparticles causes negligible effect on the modulus of nanocomposites in spite of the interphase properties such as thickness and interfacial area.

Analyzing the Interfacial Layer Properties in Polymer Nanocomposites by Broadband Dielectric Spectroscopy

Probing the properties of the interfacial layer between the polymer matrix and nanoparticles in polymer nanocomposites (PNCs) remains a challenging task. Here, we apply three methods—a single Havriliak–Negami (HN) function fit, a two HN functions fit, and the heterogeneous model analysis (HMA)—to analyze the dielectric spectra of model poly(vinyl acetate)/SiO2 nanocomposites for the thickness and the average slowing down in dynamics of the interfacial layer. We find the HMA presents the most accurate analysis on both the thickness and dynamics of the interfacial layer, in comparison to the other two methods that have been actively applied in the field. In addition, the dielectric spectra at low temperatures reveal unexpectedly nonmonotonous changes in the secondary relaxation of the polymer with nanoparticle loadings. These results clearly demonstrate that dielectric spectroscopy is an easy and robust method to study a wide range of dynamic properties of the interfacial layer in PNCs.