Добірка наукової літератури з теми "Nanoparticle-polymer Blend Films"

Application of shear stress has been shown to unidirectionally orient the microstructures of block copolymers and polymer blends. In the present work, we study the phase separation of a novel nanoparticle (NP)–polymer blend thin film system under shear using a soft-shear dynamic zone annealing (DZA-SS) method. The nanoparticles are densely grafted with polymer chains of chemically dissimilar composition from the matrix polymer, which induces phase separation upon thermal annealing into concentrated nanoparticle domains. We systematically examine the influence of DZA-SS translation speed and thus the effective shear rate on nanoparticle domain elongation and compare this with the counterpart binary polymer blend behavior. Unidirectionally aligned nanoparticle string-domains are fabricated in the presence of soft-shear in confined thin film geometry. We expect this DZA-SS method to be applicable to various NP–polymer blends towards unidirectionally aligned nanoparticle structures, which are important to functional nanoparticle structure fabrication.

Polyvinyl pyrrolidone (PVP)-polyvinyl alcohol (PVA) (1:1) polymer mixture films were developed using the solution-casting technique. Physical properties engineering of as grown chemical casting films were achieved through the Tb–NiO nanoparticles mixing in a polymer blend with different content of 0.0, 0.037, 0.37, 1.85, and 3.7 wt%. The variation of physical properties of nanocomposites thin layer was examined from X-ray diffractometer, atomic force microscope (AFM), FTIR spectroscopy, and Uv-visible spectroscopy. Optical band gaps of polymer nanocomposites films were calculated to study the influence of Tb–NiO nanoparticle doping are decreased after addition of Tb–NiO nanostructures in the composites. AFM images of films reveal successful adsorption of Tb–NiO nanoparticles in polymer blend. In addition, FTIR spectra showed successful loading of Tb–NiO nanoparticles in PVP/PVA blend matrix. The extinction coefficients, refractive index, optical dielectric constant and optical conductivity were also investigated in correlation with different wt% Tb–NiO doping concentrations. In addition, the values of oscillator, dispersion energies Eo, Ed and static refractive indices no were calculated. The optical limiting behavior of films showed that the polymer nanocomposite films are suitable for flexible optoelectronics devices.

The n-type semiconductor SnO2 nanoparticles were synthesised using standard route and the effect of this nanoparticle doping on structural, morphological and thermal properties of PVA-PVP polymer blend has been investigated. Pure and PVA-PVP/SnO2 Nanocomposite films were prepared using solution casting technique. The powder X-ray diffraction result shows that the crystalline nature of the blend increases with doping level. FESEM study shows that the surface morphology of the polymer nanocomposite varies with doping level. AFM study reveals that in the nanocomposite films, the average roughness changes with dopant concentration. The DSC studies on the samples were performed from 40°C to 400°C under nitrogen atmosphere and it shows that the thermal properties of the blend changes with doping concentration.

Chitosan (CH) / Poly (1-vinylpyrrolidone-co-vinyl acetate) (PVP-co-VAc) blend (1:1) and nanocomposites reinforced with CaCO3 nanoparticles were prepared by solution casting method. FTIR analysis, tensile strength, Elongation, Young modulus, Thermal conductivity, water absorption and Antibacterial properties were studied for blend and nanocomposites. The tensile results show that the tensile strength and Young’s modulus of the nanocomposites were enhanced compared with polymer blend [CH/(PVP-co-VAc)] film. The mechanical properties of the polymer blend were improved by the addition of CaCO3 with significant increases in Young’s modulus (from 1787 MPa to ~7238 MPa) and tensile strength (from 47.87 MPa to 79.75 MPa). Strong interfacial bonding between the CaCO3 nanoparticles and the [CH/(PVP-co-VAc)), homogenous distribution of the nanoparticles in the polymer blend, are assistance of noticeably raised mechanical durability. The thermal conductivity of the polymer blend and CaCO3 nanocomposite films show that it decreased in the adding of nanoparticle CaCO3. The solvability measurements display that the nanocomposite has promoted water resistance. The weight gain lowered with the increase of nano CaCO3. Blending chitosan CH with (PVP-co-VAc) enhanced strength and young modules of the nanocomposites and increased the absorption of water because hydrophilic of the blended polymers films. The effect of two types of positive S.aurous and negative E. coli was studied. The results showed that the nanocomposites were effective for both types, where the activity value ranged from (12 ~ 21). The best results were found for S.aurous bacteria.

Ternary blend film of conjugated polymer, fullerene and inorganic nanoparticles has intensively studied as active material for high power conversion efficiency (PCE) of hybrid organic-inorganic solar cells. The incorporation of two electron acceptor materials of organic fullerene and inorganic nanoparticles into hybrid with electron donor conjugated polymer is strongly believed can improve the PCE of solar cells by increasing exciton dissociation efficiency due to an increase of interface area between donor and acceptor materials where the positive and negative charges dissociated. We studied optical, structural and morphological properties of ternary thin film containing blend of conjugated polymer poly(3-hexylthiophene (P3HT):fullerene derivative PCBM:Zinc oxide nanoparticles (ZnO-NP) by measuring its optical absorption, crystal structure and film surface morphology. Zinc oxide nanoparticle was prepared by sol-gel method. It has optical absorption below 370 nm and average particle size 40 nm as shown by TEM picture. Ternary thin blend films of P3HT:PCBM:ZnO-NP were prepared by use of spin-coating method. The UV-Vis spectrum of thin film contains absorption peaks originated from contribution of P3HT at wavelengths 520 nm, 550 nm and 600 nm, from contribution of PCBM at 260 nm and 330 nm and from ZnO-NP at wavelengths below 370 nm which confirms that these three materials were well mixed in the films. Its XRD pattern also contains the peaks from each of these three-materials. In this report, we compare surface morphology of thin films of pure P3HT, pure ZnO-NP, blend of P3HT:PCBM, blend of P3HT:ZnO-NP and ternary blend of P3HT:PCBM:ZnO-NP.

Advances in food processing and food packaging play a major role in keeping food safe, increasing the shelf life, and maintaining the food supply chain. Good packaging materials that enable the safe travel of food are often non-degradable and tend to persist in the environment, thereby posing a hazard. One alternative is to synthesize biodegradable polymers with an antimicrobial property while maintaining their mechanical and thermal properties. In the present study, biodegradable composites of PVA–starch–glycerol (PSG) incorporated with CuO and ZnO nanoparticles (NPs) were prepared as PSG, PSG–Cu, PSG–Zn, and PSG–CuZn films. Scanning electron microscopy, energy dispersive x-ray analysis, and thermogravimetric analysis were performed to study and characterize these films. The water barrier properties of the films improved significantly as the hydrophobicity of the PSG–CuZn film increased by 32.9% while the water absorptivity and solubility decreased by 51.49% and 60% compared to the PSG film. The Young’s modulus of the films incorporated with CuO and ZnO nanoparticles was lower than that reported for PVA, suggesting that the film possessed higher flexibility. The thermogravimetric analysis demonstrated high thermal stability for films. Biosynthesized CuO and ZnO nanoparticles exhibited antifungal activity against vegetable and fruit spoilage fungi, and hence the fabricated polymers incorporated with nanoparticles were anticipated to demonstrate an antifungal activity. The nanoparticle incorporated films exhibited fungicidal and bactericidal activity, suggesting their role in extending the shelf life of packaged food. The result of ICP-OES studies demonstrated the steady release of ions from the polymer films, however, EDX analysis demonstrated no leaching of CuO and ZnO nanoparticles from the films, thus ruling out the possibility of nanoparticles entering the packaged food. The strawberries wrapped with the fabricated films incorporated with nanoparticles demonstrated improved shelf life and retained the nutritional quality of the fruit. Among the four films, PSG–CuZn was the most promising for food wrapping since it exhibited better water-resistance, antimicrobial, thermal, and mechanical properties.

Polycarbonate is an important thermoplastic polymer. Due to its high performance, polycarbonate has a range of engineering applications in construction, automotive, aircraft, data storage, electrical, and telecommunication hardware. However, polycarbonate’s use is limited in advanced applications due to limitations, such as strong hydrophobicity, relatively limited chemical functionality, high melt viscosity, notch sensitivity of mechanical properties, and relative softness. Blending with other thermoplastic polymers improves its physical characteristics. The present review outlines up-to-date developments concerning the design and application of polycarbonate blends. A particular emphasis has been given to establish polycarbonate blends such as: • polycarbonate/polyethylene • polycarbonate/poly(methyl methacrylate) • polycarbonate/poly(vinylchloride) • polycarbonate/ polystyrene • polycarbonate/polyurethane • polycarbonate/polyester • polycarbonate/poly(ɛ-caprolactone). To improve the polycarbonate blend properties, fillers including organic and inorganic reinforcement materials (carbon nanotube, montmorillonite nanoclay, and metal nanoparticle) have also been employed. Polycarbonate blend applications in biomedical, flame retardant, and membrane materials have also been reviewed. To fully exploit the future potential for polycarbonate-based engineering materials, the structure–property relationship and compatibilization mechanisms need to be further explored.

In this thesis, atomic force microscopy (AFM), transmission electron microscopy (TEM) and optical microscopy techniques were used to investigate systematically the self-assembled nanostructure behaviour of two different types of spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9- dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated polymer blends. In the particular case of the polymer blend thin films, the morphology of their composites with cadmium selenide (CdSe) quantum dot (QD) nanoparticles was also investigated. For the diblock copolymer thin films, the behaviour of the nanostructures formed and the wetting behaviour on mica, varying the volume fraction of the PEO block (fPEO) and the average film thickness was explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per weight), spin-coating parameters and solution concentration on the phase-separated nanodomains was investigated. The influence of the quantum dots on the phase separation when these were embedded in the F8BT:TFB thin films was also examined. It was found that in the case of PI-b-PEO copolymer thin films, robust nanostructures, which remained unchanged after heating/annealing and/or ageing, were obtained immediately after spin coating on hydrophilic mica substrates from aqueous solutions. The competition and coupling of the PEO crystallisation and the phase separation between the PEO and PI blocks determined the ultimate morphology of the thin films. Due to the great biocompatible properties of the PEO block (protein resistance), robust PEO-based nanostructures find important applications in the development of micro/nano patterns for biological and biomedical applications. It was also found that sub-micrometre length-scale phase-separated domains were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of F8BT-rich and TFB-rich areas were close to one order of magnitude smaller (in the lateral direction) than those reported in the literature. When the quantum dot nanoparticles were added to the blend thin films, it was found that the QDs prefer to lie in the F8BT areas alone. Furthermore, adding quantum dots to the system, purer F8BT and TFB nano-phase separated domains were obtained. Conjugated polymer blend thin films are excellent candidates for alternatives to the inorganic semiconductor materials for use in applications such as light emitting diodes and photovoltaic cells, mainly due to the ease of processing, low-cost fabrication and mechanical flexibility. The rather limited optoelectronic efficiency of the organic thin films can be significantly improved by adding inorganic semiconducting nanoparticles.

Thin film bilayers and blends composed of polymers and nanoparticles are increasingly important for technological applications that range from space survivable coatings to novel drug delivery systems. Dewetting or spontaneous hole formation in amorphous polymer films and phase separation in multicomponent polymer films can hinder the stability of these systems at elevated temperatures. Hence, fundamental understanding of dewetting and phase separation in polymer/nanoparticle bilayer and blend films is crucial for controlling transport and thermomechanical properties and surface morphologies of these systems. This dissertation provides studies on morphological evolution driven by phase separation and/or dewetting in model polymer/nanoparticle thin film bilayers and blends at elevated temperatures. Morphological evolution in dewetting bilayers of poly(t-butyl acrylate) (PtBA) or polystyrene (PS) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP) is explored at elevated temperatures. The results demonstrate unique dewetting morphologies in both PtBA/TPP and PS/TPP bilayers that are significantly different from those typically observed in dewetting polymer/polymer bilayers. Upon annealing the PtBA/TPP bilayers at 95°C, a two-step dewetting process is observed. PtBA immediately diffuses into the upper TPP layer leading to hole formation and subsequently the holes merge to form interconnected rim structures in the upper TPP layer. Dewetting of both the TPP and PtBA layers at longer annealing times leads to the evolution of scattered holes containing TPP-rich, fractal aggregates. The fractal dimensions of the TPP-rich, fractal aggregates are ~2.2 suggesting fractal pattern formation via cluster-cluster aggregation. Dewetting in PS/TPP bilayers also proceeds via a two-step process; however, the observed dewetting morphologies are dramatically different from those observed in PtBA/TPP bilayers. Cracks immediately form in the upper TPP layer during annealing of PS/TPP bilayers at 200°C. With increasing annealing times, the cracks in the TPP layer act as nucleation sites for dewetting and aggregation of the TPP layer and subsequent dewetting of the underlying PS layer. Complete dewetting of both the TPP and PS layers results in the formation of TPP encapsulated PS droplets. Phase separation in PtBA/TPP thin film blends is investigated as functions of annealing temperature and time. The PtBA/TPP thin film blend system exhibits an upper critical solution temperature (LCST) phase diagram with a critical composition and temperature of 60 wt% PtBA and ~70°C, respectively. Spinodal decomposition (SD) is observed for 60 wt% PtBA blend films and off-critical SD is seen for 58 and 62 wt% PtBA blend films. The temporal evolution of SD in 60 wt% PtBA blend films is also explored. Power law scaling for the characteristic wavevector with time (q ~ t^n with n = -1/4 to -1/3) during the early stages of phase separation yields to domain pinning at the later stages for films annealed at 75, 85, and 95°C. In contrast, domain growth is instantly pinned for films annealed at 105°C. Our work provides an important first step towards understanding how nanoparticles affect polymer thin film stability and this knowledge may be utilized to fabricate surfaces with tunable morphologies via controlled dewetting and/or phase separation.
Ph. D.

We studied dispersion state and dynamics of polymer grafted nanoparticle in photopolymer matrix nanoparticle-polymer blend- and their thermal and rheological properties. While thinking about a nanoparticle-polymer blend, the first question comes in is the dispersion state of nanoparticle in polymer. Especially in case of a blend film, dispersion of nanoparticle is very crucial in deciding its properties. It is still a challenging problem to get the dispersed blend even after 30 years of its invention. So, we started our work with the investigation of nanoparticle dispersion in polymer melt film and its evolution with time at high temperature. Eventually we studied the dynamics of nanoparticle in polymer melts at high temperature and the rheological and thermal properties of these blends. In chapter 1, I have provided the introductory discussion about polymer’s conformation, dynamics etc. Polymer grafted nanoparticle dispersion and its dynamical behaviour in polymer matrix has been discussed in this chapter briefly. The experimental techniques used for this work have been explained in chapter 2. It is well known that preparation process of a blend film has a significant contribution to the final dispersion state of nanoparticle. A good practice to prepare such blend films is to anneal the film after it spincoated on a hard substrate. The purpose is to remove the trapped solvent as well as removing the unstable/meta-stable state achieved by sudden freezing of the polymers during spincoating. It was observed that the dispersion state of nanoparticle is improved after annealing. We study this evolution of dispersion at annealing temperature using in-situ X-ray scattering measurement and presented in chapter 3. We found super-diffusive in-plane and very slow out of plane motion of polystyrene grafted gold nanoparticle (PGNP) in polystyrene (PS) matrix at high temperature (T>Tg). The PGNP dispersion becomes homogeneous throughout the film which is otherwise a segregated film. After cooling down to room temperature, even though a partial reversal of the segregation occurs, the final dispersion state is better than that before annealing. We have shown a method of capturing the well dispersed state (the high temperature dispersion state) of PGNP at room temperature. In chapter 4 we presented the study of PGNP dynamics in the polymer melt film at high temperature where the particles are expected to be almost homogeneously dispersed as we found in the previous observations. Anomalous relaxation dynamics is observed leading to an unusual temperature dependence of effective viscosity of the film and the anomaly increases under confinement. The observed anomalous behaviour could be explained in terms of the hydrodynamic slip experienced by the PGNP while the system has a dewetting PGNP-polymer interface. We estimated approximate slip length at the PGNP-polymer interface as a function of temperature and thickness. The slip length diverges at low temperature. Thickness dependent study reveals an increase of slip length under confinement resulting in a stronger anomaly for thinner films. Slip length at a polymer melt-polymer grafted wall interface (flat interface) as well as polymer melt-polymer grafted spherical particle interface (spherical interface) has been calculated by varying temperature and miscibility parameter, f (f=ratio of grafted and matrix chain molecular weight) using molecular dynamics simulations. A good agreement established between the simulation and the observed experimental results. In associated with the interface slip, the PGNP-polymer interface layer seems to have an effective interface viscosity which is different from bulk polymer viscosity. A strong wave vector dependent hydrodynamic interaction between PGNPs was indicated by the observed temperature and wave vector dependent short time diffusion coefficient. This phenomenon could be explained in terms of the full slip boundary condition at the PGNP-polymer interface. It is not surprising that the properties, e.g. thermal, rheological properties would get affected by the dispersion of PGNP as well as their dynamics. In chapter 5 we explored rheological propertis of nanoparticle-polymer blend film such as viscosity using force-distance spectroscopy for different miscibility parameters, f and temperature. A reduction in the viscosity of the blend film was observed with respect to its pristine polymer film for a smaller f value. The deviation of blend film viscosity from pristine polymer film viscosity reduces with increase in f. The extent of the viscosity reduction for smaller f increases towards lower temperature. Further, we have studied demixing temperature of a two component polymer blend system (Polystyrene (PS)/Poly (vinyl methyl ether) (PVME) blend) getting influenced by the presence of PGNP dispersed in it. When the grafted chain length is much higher than the matrix PS chain, the demixing temperature gets increased, while the grafted chain length is much smallerthan matrix PS leads almost no change. The PGNPs are observed to be present inthe PVME phase while the grafted PS chains are too short compared to the matrix PS chains and in opposite case while grafted chain is larger compared to matrix PSchains, the PGNPs are located at the PS matrix Rheological property of the PGNP suspensions in presence of linear PS chains hasbeen studied using diffusing wave spectroscopy and presented in chapter 6. A change in frequency dependence of viscous modulus was observed in a case where the linear PS chain is much longer than the grafted PS chains with increasing concentrations of PS linear chains indicating a shear thickening behaviour at higher linear PS concentrations. Presence of shorter linear chains do not show any such change in frequency dependence. To investigate about the observed shear thickening, dynamic light scattering measurement were performed on these samples. A large shrinkage of nanoparticlecorona in presence of large linear chains was observed which could lead to the observed shear thickening behaviour. The shorter linear chains inter-penetrate into the grafted chains resulting in a swelling of nanoparticle grafts. Comparatively lower resultant viscosity observed for shorter chains possibly due to the faster mobility of shorter chains penetrating into the grafts. Finally in chapter 7, I summarize my thesis work and express my future work plan.