Structure Of Polymer Nanocomposites Research Articles

Predicting mechanical heterogeneity in glassy polymer nanocomposites via an inverse computational approach based on atomistic molecular simulations and homogenization methods

Probing the mechanical behavior of the region formed between a nanoparticle reinforcement and a polymer matrix in a polymer nanocomposite structure, denoted as the “interphase”, is a main challenge as such regions are difficult to investigate by experimental methods. Here, we accurately characterize the heterogeneous mechanical behavior of polymer nanocomposites, focusing on polymer/nanofiller interphases via a combination of nanomechanical simulations and numerical homogenization techniques. Initially, the global mechanical performance of a glassy poly(ethylene oxide) polymer nanocomposite reinforced with silica nanoparticles is studied using detailed atomistic molecular dynamics simulations for 1.9% and 12.7% silica volume fractions. Next, the polymer/silica interphase thickness is identified by probing the polymer atom-based density distribution profile in the vicinity of the nanofiller at equilibrium. On the basis of this thickness, the interphase is subdivided to check the position-dependent change in mechanical properties. Then, using continuum mechanics and atomistic simulations, we proceed to compute the effective Young’s modulus and Poisson’s ratio of the polymer/nanoparticle interphase as function of the distance from the nanoparticle. In the last step, an inverse numerical homogenization model is proposed to predict the mechanical properties of the interphase on the basis of a comparison criteria with the data from MD. The results were found to be acceptable, raising the possibility of accurately and efficiently predicting interfacial properties in nanostructured materials.

Nanocomposite Material Based on Polyvinyl Alcohol Modified with Carbon Nanotubes: Mechanism of Formation and Electronic Energy Structure

The physical chemistry of surface phenomena in polymers is an important issue when studying the interaction of polymers with solid surfaces. This is due to the fact that most of the modern polymer materials are heterogeneous systems with highly developed phase separation surfaces. An example of such materials can be reinforced plastic, filled thermoplastics, reinforced rubber, paint coatings, etc. Polymer adsorption at the boundary of the phase separation process in solids plays an important role in the reinforcing effect of fillers, adhesion, gluing and obtaining composite materials with high strength properties. Compositions based on polyvinyl alcohol (PVA) modified with carbon nanotubes (CNTs) can be used as an interesting and informative system for studying the structure and properties of polymer nanocomposites, especially in a highly oriented state. PVA has one of the simplest chemical structure among the polymers, containing a functional (hydroxyl) group capable of participating in interphase interactions. In turn, carbon nanotubes with unique strength properties are currently products of industrial production, which makes it possible to control and modify their properties. To prove the possibility of creating new composite materials with improved strength characteristics, the mechanisms of interaction between PVA and CNTs are studied by modeling the adsorption processes of a polymer fragment on the outer surface of single-layer carbon nanotubes of different chirality, performed within the framework of the modern DFT calculation method. The main adsorption characteristics of the process and the features of the electron energy structure of the resulting composite systems are determined.

An effective route to the additive manufacturing of a mechanically gradient supramolecular polymer nanocomposite structure

3D Printing techniques are additive methods of fabricating parts directly from computer-aided designs. Whilst the clearest benefit is the realisation of geometrical freedom, multi-material printing allows the introduction of compositional variation and highly tailored product functionality. The paper reports a proof-of-concept additive manufacturing study to deposit a supramolecular polymer and a complementary organic filler to form composites with gradient composition to enable spatial distribution of mechanical properties and functionality by tuning the number of supramolecular interactions. We use a dual-feed extrusion 3D printing process, with feed stocks based on the supramolecular polymer and its organic composite, delivered at ratios predetermined. This allows for production of a graded specimen with varying filler concentration that dictates the mechanical properties. The printed specimen was inspected under dynamic load in a tensile test using digital image correlation to produce full-field deformation maps, which showed clear differences in deformation in regions with varying compositions, corresponding to the designed-in variations. This approach affords a novel method for printing material with graded mechanical properties which are not currently commercially available or easily accessible, however, the method can potentially be directly translated to the generation of biomaterial-based composites featuring gradients of mechanical properties.

The Influence of Aging on the Structure and Properties of Composite Materials Based on Polyurethane and Silver Nanoparticles

The aging processes and their influence on structure, thermophysical and antimicrobial properties of polymer nanocomposites based on segmented polyurethane and silver nanoparticles were studied. It was established that an increase in the intensity of intermolecular interactions of polyurethane occurred regardless of the concentration of silver in the silver nanoparticles due to a change in the packing of macromolecules. It was shown that in the process of aging of composites, the effective size of crystallites of polymer matrix decreases and varies in the range of 1.35–1.50 nm. The most pronounced effect of aging is manifested on the melting temperatures of the crystalline phase of polyurethane and the degree of crystallinity. It was found that polyurethane–silver nanoparticle composites exhibit a very high inhibitory capacity against Staphylococcus aureus, Escherichia coli, and Candida albicans. It is shown that aging processes do not affect the antimicrobial characteristics of the studied materials, which indicates their stability. Due to their unique characteristics, synthesized nanocomposite films can be promising for use as antimicrobial coatings in various applications.

Influence of Structure and Composition of Polymer Nanocomposites with Carbon and Hybrid Fillers on the Efficiency of Electromagnetic Shielding

AbstractThe shielding efficiency (absorption SEA, reflection SER, and total SET) and conductivity of composites based on organic–inorganic polymer matrix (OIM) and polyethylene (UHMWPE) containing mixtures (hybrid fillers) of carbon black (CB), carbon nanotubes (CNT), and iron oxide (Fe2O3) are studied. The best shielding results (SET = 23.1 dB, SEA = 17.7 dB) show a composite based on UHMWPE with a segregated structure of the hybrid filler CNT+CB with a total content of 10 vol%, due to the high electrical conductivity of the composite. It is found a close correlation between the conductivity of the composite and the absorption efficiency SEA which sharply increases when the value of conductivity becomes above 10−3 S cm−1. In composites based on OIM with hybrid filler CNT+Fe2O3, the moderate shielding characteristics are achieved (SET = 12.3–12.7 dB, SEA = 8.8–9.2 dB), but they have the conductivity more than two orders of magnitude lower than the composites with carbon fillers. This effect arises due to the additional contribution to the absorption efficiency of the interaction of ferromagnetic non‐conductive oxide with the magnetic component of electromagnetic wave. Such composites have the potential to achieve high shielding performance at determining the optimal composition of the hybrid filler.

How Tuning Interfaces Impacts the Dynamics and Structure of Polymer Nanocomposites Simultaneously

Fundamental understanding of the macroscopic properties of polymer nanocomposites (PNCs) remains difficult due to the complex interplay of microscopic dynamics and structure, namely interfacial layer relaxations and three-dimensional nanoparticle (NP) arrangements. The effect of surface modification by alkyl methoxysilanes at different grafting densities has been studied in PNCs made of poly(2-vinylpyridine) and spherical 20 nm silica NPs. The segmental dynamics has been probed by broadband dielectric spectroscopy and the filler structure by small-angle X-ray scattering and reverse Monte Carlo simulations. By combining the particle configurations with the interfacial layer properties, it is shown how surface modification tunes the attractive polymer-particle interactions: bare NPs slow down the polymer interfacial layer dynamics over a thickness of ca. 5 nm, while grafting screens these interactions. Our analysis of interparticle spacings and segmental dynamics provides unprecedented insights into the effect of surface modification on the main characteristics of PNCs: particle interactions and polymer interfacial layers.

The effect of silver nanoparticles on the structure and functional properties of antimicrobial polymer nanocomposites based on polyethylene oxide

The presence of antibacterial materials in biomedicine and related fields of science and technology has become essential. Excellent antibacterial activity and low cytotoxic potential of silver nanoparticles generally depend not only on their size, but also on the distribution in matrix media. The development of stabilized polymer-silver nanocomposites containing nanoparticles is considered to be one of the most promising solutions. We developed a new approach to the synthesis of silver nanoparticles. The structure and properties of antimicrobial nanocomposite materials based on polyethylene oxide and synthesized silver particles were studied using the methods of electron microscopy, differential scanning calorimetry, impedance spectroscopy and disk-diffusion microbiological method. As a result, silver nanoparticles with an average size of about 8-10 nm were obtained. It was established that stabilized silver nanoparticles significantly affect the thermophysical and electrical properties of the polymer matrix at relatively low concentrations of the nanofiller (1-2%). The total electrical conductivity of the systems increases by two orders of magnitude when 2% filler is added. Nanocomposite material containing 2% of silver nanoparticles shows significant activity against Staphylococcus aureus (inhibition zone 22 mm). The novel aproach for synthesis of stabilized silver nanoparticles open a new window of possibilities in the development of new antimicrobial materials, based on various polymer matrix: from thermoplastic to elastic. The developed materials with improved functional characteristics in the future can be used as antimicrobial coatings, antimicrobial films and creams, as well as construction products with the necessary functional characteristics and antimicrobial function.

Publisher Correction: Effect of initial solvent concentration on the structure and property of polymer nanocomposites

Publisher Correction: Effect of initial solvent concentration on the structure and property of polymer nanocomposites

Using a carbon fiber sizing to tailor the interface-interphase of a carbon nanotube-polymer system

The primary goal of this work is to integrate a critical step (sizing application to fiber) of conventional carbon fiber-reinforced composite (CFRPs) manufacturing to carbon nanotube composite fabrication. A polyimide-based (Hydrosize HP 1632) sizing agent was used in studying the effect of sizing on interface-interphase properties of the CNT-BMI composite system. The effect of CNT and degree of functionalization and defects (DOFD) of CNTs in the cure kinetics and reaction of polyimide-based sizing was investigated via DSC and XPS analysis. The DSC results showed that the presence of CNTs changes the cure kinetics of the sizing agent, and functionalized CNTs have the most prominent effect compared to unfunctionalized CNTs as it changes the endothermic curing of pristine sizing to exothermic curing by addition of 25 wt% functionalized CNTs. Then the effect of sizing in CNT on the CNT/BMI composite interface-interphase was investigated by studying the cure kinetics of the high strength BMI matrix. Thermomechanical properties, molecular heterogeneity, and molecular hierarchy of the nanocomposite were studied and presented. The outcome of this study demonstrates the CNTs with sizing can significantly alter the cure reactions of the resin as well as the structure and thermo-mechanical properties of the CNT polymer nanocomposites.

Effect of initial solvent concentration on the structure and property of polymer nanocomposites

Effect of initial solvent concentration on the structure and property of polymer nanocomposites

Recent scattering approaches to structure and dynamics of polymer nanocomposites

The characterization of polymer nanocomposites on molecular length scales and timescales is a challenging task, which is also indispensable for the understanding of macroscopic material's properties. Neutron scattering is one of the techniques which are very well-suited for studying the structure and molecular motion in such soft matter systems. X-rays can also be used for the same purpose, however, with higher energy and thus a different focus on dynamics, where they are better suited for nanoparticle motion. In this mini-review, we aim at highlighting recent results in the field of polymer nanocomposites, including nanoparticle structure in various experimental systems, from model to industrial, and polymer and particle dynamics. This allows establishing the link between microscopic and macroscopic properties, in particular rheology.

Progressive Intercalation and Exfoliation of Clay in Polyaniline–Montmorillonite Clay Nanocomposites and Implication to Nanocomposite Impedance

Conducting polymers, such as polyaniline (PANi) and polypyrrole (PPy), and their nanocomposites, are desired in a wide range of applications, including supercapacitors, lithium ion battery, chemical sensors, biosensors, barrier thin films, and coatings, because of their interesting electrical and electrochemical properties. It is well known that the properties of polymer nanocomposites depend on their chemical structure, as well as their microstructure, yet scientists and engineers have not fully understood how to properly control the structure of polymer nanocomposites. In this study, it is shown that the structure of polyaniline–montmorillonite clay nanocomposites (PACN) can be controlled by varying the ammonium persulfate (APS, oxidant) concentration. The structure of polyaniline and Cloisite 20A clay are, therefore, profoundly affected during the synthesis of PACN nanocomposites. The thickness of polyaniline crystal decreased with increasing oxidant concentration. Fourier transform infrared spectroscopy (FTIR) was used to determine the oxidation state of PANi. The structure of the nanocomposites was studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), wide-angle X-ray scattering (WAXS), and small-angle X-ray scattering (SAXS). Electrochemical impedance spectroscopy (EIS) analysis of polyimide nanocomposite coatings containing PACN with varying levels of intercalation and exfoliation indicate that the coating impedance decreased with exposure time for some coating systems. It is shown that polyimide–PACN nanocomposite coating containing highly intercalated clay was more durable and maintained constant impedance after 20 weeks of exposure in a corrosive medium.

Production of different metal oxide nanoparticle embedded polymer matrix composite structures by the additive manufacturing technology and investigation of their properties

AbstractMetal oxide nano additives are widely used as a second phase modifier as they improve the properties of the matrix materials. Nano additives also supply various advantages for polymers which can be employed in additive manufacturing methods. Among the additive manufacturing methods, stereolithography is one of the most remarkable to produce nano‐modified polymers because of the easy nano modification of the photocurable resins. In the present study, we mixed the metal oxide particles; Fe2O3, ZnO, NiO, Al2O3, TiO2, and MgO with the photocurable epoxy and used the mixtures to print the specimens. We investigated the structural morphology, thermal and mechanical properties of the printed specimens with an optical microscope, scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimeter, differential thermogravimetric analysis, and microhardness, respectively. Findings proved the dilute agglomeration of the nano additives. Besides, nano additives can improve the thermal stability of the photo‐cured polymer. The microhardness of the Fe2O3 added polymers reached 27.63 HV levels while it was measured as 16.16 HV for the pristine samples (~70% raise was experienced). The maximum degradation temperatures of the polymer nanocomposite structures were measured in the range of 396–420 °C.

Nanoparticle layer via UV-induced directional migration of iron-doped titania nanoparticles in polyvinyl butyral films and superior UV-stability

The migration of nanoparticles in polymer matrix is significant for the structure and performance of polymer nanocomposites after the initial formation. However, the understanding and controlling of migration of nanoparticles in polymer matrix remains a challenge. Herein, we report using ultraviolet (UV) light to perform the directional migration of inorganic nanoparticles in polymer film, generating an ultrathin (100–200 nm) nanoparticle layer on the light exposure surface of the film. The prepared iron-doped titania nanoparticles (Fe–TiO 2 ) are initially uniformly dispersed into polyvinyl butyral (PVB) film, and homogeneous distribution remains unchanged even after thermal treatment. However, the UV irradiation induces the directional migration of nanoparticles towards the illuminated surface. The mechanism indicates that the directional migration of nanoparticles is related with the increase of interfacial energy and conformational entropic effect between Fe–TiO 2 and PVB upon UV irradiation. The formed nanoparticle layer endowed the PVB/Fe–TiO 2 film with superior UV-stability. Our work extends the study of controlling migration of nanoparticles in polymer matrix by applying external stimuli, and provides a novel strategy for the functionalization of polymer nanocomposite materials. • Iron-doped TiO 2 nanoparticles with low photocatalytic activity is prepared. • UV-induced unidirectional migration of iron-doped TiO 2 nanoparticles in polyvinyl butyral is firstly reported. • The mechanism of UV-induced migration of nanoparticles is investigated in detail. • A nanoparticle layer formed on the exposed surface by UV-induced unidirectional migration of nanoparticles. • Nanoparticle layer imparted superior UV-stability to polymer nanocomposite film.

Exploration of spectroscopic, surface morphological, structural, electrical, optical and mechanical properties of biocompatible PVA-GO PNCs

The studies carried out in this paper are directed towards preparation of nanocomposite films of PVA (polyvinyl alcohol)-GO (graphene oxide) with variable wt% of GO by simple solution mixing technique and exploration of spectroscopic, surface morphological, structural, optical, electrical, and mechanical properties. In this article, the detailed molecular structure of PVA-GO polymer nanocomposites (PNCs) was optimized by using the Gaussian code (B.01 version). Experimentally, the structural information was gathered by using the X-ray diffractometer and determined the crystalline size (varying from 12. 82 nm to 24.62 nm for 1–5 wt% of GO in PVA/GO PNCs) and micro-strain (varying between 7.21 × 10−3 and 42.12 × 10−3) produced in the samples through Williamson-hall plot. The existence of the functional groups with their role in the nanocomposites was also examined with the help of FTIR technique. In order to identify the Raman bands (availability of D and G bands at ~1340 and 1595 cm−1, respectively, while the 2D band at ~2910 cm−1) and corresponding structural changes were studied by Raman spectrometer (with the usage of 532 nm laser). The study of surface morphology was performed by utilizing the AFM and FESEM (with EDAX) techniques and effect of GO on the surface roughness of the nanocomposite film was studied. The r.m.s. roughness of the films were set up to be 90.375 nm, 96.449 nm, 98.120 nm, 99.006 nm and 99.891 nm for GO of 1–5 wt%, respectively. The optical properties were determined using UV–Vis-NIR spectrophotometer and tuning of optical bandgap (varied from 3.56 eV to 2.45 eV with 1–4 GO wt%) was investigated. The resulting variation due to GO concentration was also confirmed with structural information. The electrical characteristics (capacitance, dissipation factor and electrical conductivity) were also investigated. The DMA analysis of the nanocomposites was performed to measure the mechanical property (Young's Modulus varying from 2 GPa to 16 GPa for 1–5 GO wt%) and found that the nanofillers (GO) plays an important role to enhance the various abovementioned properties.

Structure and thermal properties of copper-polypropylene based nanocomposites

Polymer nanocomposites based on PP/Cu were obtained by the combining of ex-situ casting solution and hot pressing methods. The structure of polymer nanocomposites was characterized by XRD, SEM, EDS, AFM and FT-IR spectroscopy analysis. The thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the addition of copper nanoparticles to the PP polymer matrix increases the thermal stability of the polymer, and this thermal stability reaches its maximum value at 3% content of copper nanoparticles in the polymer. The reason for the increase in the thermal properties of nanocomposites is associated with the formation of a more perfect, dense and ordered structure of PP-based composites and the fact that nanoparticles play the role of a nucleus of crystallization for polymer matrices.

Experiments on the Molecular Mechanism and Interface Structure of Pure and Doped Polymer Nanocomposites Used in Microelectronics

Experiments on the Molecular Mechanism and Interface Structure of Pure and Doped Polymer Nanocomposites Used in Microelectronics

Phase diagram of bare particles in polymer nanocomposites: Uniting solution and melt blending

Nanoparticle (NP) spatial arrangement in polymer matrix is a widely investigated scientific issue of great practical importance. The structure of polymer nanocomposites (PNCs) with bare non-grafted NPs are usually evaluated separately for blending in polymer melt and in polymer solution. To the best of our knowledge, no theory of PNC structure has successfully integrated all aspects of solution blending yet, let alone brought a direct comparison of PNC structures prepared by melt and solution blending. In the current study, we for the first time implement the role of solvent into the existing PRISM theory for nanoparticle ordering in polymer melts, compare the theoretical prediction to experimentally prepared structures, and present a united phase diagram for both melt and solution blended PNCs with bare non-grafted NPs.

Structure, optical and photoluminescent properties of hybrid polymer nanocomposites on the base PP+CdS/ZnS

In this work, PP+CdS/ZnS transparent hybrid polymer nanocomposites were synthesized and studied. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive (EDS), and UV-spectroscopy analysis. It was found that the bandgap of PP+1%CdS/ZnS; PP+3%CdS/ZnS, and PP+5%CdS/ZnS; PP+10%CdS/ZnS nanocomposites is 5.2 eV, 5.1 eV, 4.6 eV, respectively. SEM analysis showed that the ZnS and CdS nanoparticles are evenly distributed in the polymer matrix. Furthermore, the average size of nanoparticles in the PP+3%CdS/ZnS, PP+5%CdS/ZnS nanocomposite is 40-54 nm, 29-56 nm, respectively. Photoluminescence properties of hybrid PP+CdS/ZnS nanocomposites were also investigated. It was established that introduction of ZnS and CdS semiconductor nanoparticles into the polypropylene matrix leads to expanding the region of the spectral sensitivity of hybrid nanocomposites. The photosensitivity of PP+CdS/ZnS nanocomposite films was also investigated.

The structure of carbon nanotubes in a polymer matrix

We carried out an analytical structural analysis of interfacial effects and differences in the reinforcing ability of carbon nanotubes for polydicyclopentadiene/carbon nanotube nanocomposites with elastomeric and glassy matrices. In general, it showed that the reinforcing (strengthening) element of the structure of polymer nanocomposites is a combination of the nanofiller and interfacial regions. In the polymer matrix of the nanocomposite, carbon nanotubes form ring-like structures. Their radius depends heavily on the volume content of the nanofiller. Therefore, the structural reinforcing element of polymer/carbon nanotube nanocomposites can be considered as ring-like formations of carbon nanotubes coated with an interfacial layer. Their structure and properties differ from the characteristics of the bulk polymer matrix.According to this definition, the effective radius of the ring-like formations increases by the thickness of the interfacial layer. In turn, the level of interfacial adhesion between the polymer matrix and the nanofiller is uniquely determined by the radius of the specified carbon nanotube formations. For the considered nanocomposites, the elastomeric matrix has a higher degree of reinforcement compared to the glassy matrix, due to the thicker interfacial layer. It was shown that the ring-like nanotube formations could be successfully modelled as a structural analogue of macromolecular coils of branched polymers. This makes it possible to assess the effective (true) level of anisotropy of this nanofiller in the polymer matrixof the nanocomposite. When the nanofiller content is constant, this level, characterised by the aspect ratio of the nanotubes, uniquely determines the degree of reinforcement of the nanocomposites