| Abstract: | Significant modeling and experimental efforts have been carried out to investigate the role of interface on mechanical behavior of polymer nanocomposites (PNCs) based on spherical nanoparticles (NPs) as model systems. However, few studies have focused on structure-property relationships of PNCs based on 2D NPs. This dissertation firstly utilizes a dual epoxide modification of a-zirconium phosphate (ZrP) nanoplatelets, to achieve ZrP exfoliation in epoxy without sacrificing glass transition temperature (Tg). By dual epoxide functionalization of ZrP, it is possible to achieve good dispersion and self-assembly of ZrP at high loadings in epoxy. The dual epoxide functionalization approach involves only simple chemistry with minimal organic fraction to achieve exfoliation in epoxy. This methodology has been demonstrated to be applied for multi-functional applications in a controlled manner. This dissertation also focused on the effect of interface on the dispersion, rheology and mechanical properties of thermoplastics PNCs reinforced by 2D NPs. At second part, epoxide functionalization method coupled with surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET-ATRP), was used to prepare poly(methylmethacrylate) grafted ZrP nanoplatelets (ZrP-g-PMMA) for dispersion in PMMA matrix. The phase behavior of the PMMA nanocomposite with variations in grafting density and grafted PMMA length on ZrP-g-PMMA with a fixed PMMA matrix chain length was investigated using transmission electron microscopy. Various types of polymer brush structures, including mushroom, semi-dilute polymer brush and concentrated polymer brush, were prepared, which correspond to the wetting and dewetting phenomena of ZrP-g-PMMA in the PMMA matrices. Furthermore, the rheological behavior of PMMA/ZrP-g-PMMA which contains 2D nanoplatelets was found to be significantly different from that of the PMMA/silica-g-PMMA which contains spherical nanoparticles. This drastic discrepancy in their rheological behaviors is likely caused by the anisotropy nature of the 2D nanoplatelets in PMMA. Possible underlying physics is proposed to describe the observed unusual phenomena. The polymer grafted nanoplatelets presented in this study can also serve as a model system for preparation of the other polymer nanocomposites for a wide variety of structural and functional applications. |
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