Preparation And Performance Studies Of Modified Carbon Black/Polymer Nanocomposites With High Refractive Index

In this paper, we report a novel high refractive index (RI) additive-functionalized carbon black (CB), especially to deserve to be mentioned, CB has not been reported to incorporate into polymer matrix to fabricate high RI nanocomposites. The optical properties of CB nanoparticles modified by different experimental methods and their relation with particle structural variations were also studied. The mechanism of high RI CBs and the compatibility between CBs and polymer matrix were investigated. It may be a good inspiration and practical guidance for further study of high RI organic/inorganic composites. The main content as follow:1. The microstructure and electronic structure of modified CB were investigated by Raman spectroscopy, transmission electron microscopy, electron energy loss spectroscopy and ultraviolet spectroscopy. The modified CB samples include oxidised CB (OCB) and ultrasound-treated CB (U-CB) under different modification conditions. Typical parameters, such as graphene layer size, the ratio of sp2/sp3-hybridised carbon atoms, andπ-π* band position, provide information on the microstructure and electronic structure, and these parameters also allow discrimination between different modified CB samples to achieve a desired structure. Oxidation conditions could be carefully chosen to prevent excessive corrosion and form an ordered structure. However, ultrasound has a reverse effect; the graphite layers of the CB samples were exfoliated, and a disordered microstructure was visible. The results indicate that increasing sp2-island size in CB samples increases the order of CBs.2. We study the micromorphology, spectral behavior and electronic structure of modified CBs. The modified CB samples, including OCB, UCB and poly (vinyl alcohol)-encapsulated CB (PVA-CB) are investigated. The aim is to show that the microstructure of the investigated carbon materials correlates with the electronic structure and optical properties in this case with the predominant carbon hybridization. Characterization parameters of optical properties and the extinction behavior are found to be strongly affected by the microstructure and the content of sp2 hybridization of the C atoms. The lower the content of sp2 hybridized carbon, the lower the UV peak position in wavelength and the UV absorption. In addition, PVA-encapsulated-CB particles showed a low absorbance in UV and visible light range. Our results imply that optical properties of CB are significantly altered within its modification methods. Overall, this study is useful to get a better knowledge of the structure-optical properties correlations through the different modification experiments of CB, and also a step toward the possibilities for further optical or high RI application.3. The high RI composite films based on polyimide (PI) and chloride modified CB (CB-COC1) were prepared by conversion of biphenyltetracarboxylic dianhydride and 4,4’-oxydianiline in the presence of CB-COC1, followed by thermal imidization. The presence of chemical bonds between PI and CB-COC1, proved by FTIR spectra of the composites, has a considerable effect on the properties of PI films. The PI/CB-COC1 membranes showed changed morphology compared to reference membranes without CB-COC1. The hybrid films showed an increase in thermal decomposition temperature and a slightly enhanced glass transition temperature. On their mechanical properties, the modulus and ultimate strength of the hybrid films increased and elongation at break decreased with increased CB-COC1 content. The effect of CBs and the interaction between the five-membered imide rings and aromatic rings of CBs on the optical properties of the resulted PI/CB nanocomposites was also discussed. The off-resonant refractive indices of the prepared hybrid films at 633 nm were in the range of 1.711-1.833 as the CB content increased from 0 to 10 wt%. According to the comparison of theory and experimental values, it demonstrates that the increasing of refractive index is mainly from the contribution of the increase in charge transfer interaction between PI and CB. Theoretical equation based on the modified Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values.4. High RI CB particles with low densities would be an optimal candidate for high RI nanocomposite. Nano-CB/polymer composites with high RI were fabricated from poly (vinyl alcohol) (PVA) and covalently functionalized CB (PVA-cs-CB) by simple esterification reaction. Transmission electron microscope showed that a uniform aggregate of PVA-es-CB nanoparticles with a size smaller than 100 nm formed in the nanocomposite films. Ellipsometric measurement indicated that the PVA-es-CB/PVA composite films had a RI in the range 1.52-1.598 linearly increased with the PVA-es-CB volume content. Theoretical equation based on Lorentz-Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The hybrid films also revealed relatively good surface planarity, thermal stability, and optical transparency...