Poly(ethylene terephthalate) and polyhedral oligomeric silsesquioxane nanohybrids and their physical characteristics

Excerpt

Poly(ethylene terephthalate) (PET) is a semicrystalline thermoplastic polyester with a variety of applications such as fiber, bottles, films, and engineering plastics in automobiles and electronics because of its low cost and high performance [1, 2], whereas polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals, with their organic–inorganic hybrid nature, well-defined three-dimensional nanoscopic architecture, and monodisperse particle size, are the subject of intense research interest. Silsesquioxane is the term used for all structures with the formula (RSiO_1.5) _n , where R is hydrogen or any alkyl, alkylene, aryl, arylene, or organofunctional derivative or alkyl, alkylene, aryl, or arylene group [3]. Silsesquioxanes may form ladder, cage, partial cage, and polymer structures [4, 5]. Among the various types of silsesquioxanes, the POSS cage consists of 8, 10, or 12 Si atoms, with an Si:O ratio of 2:3, Si–Si diameter of 0.54 nm and Si–C bond length in the range of 1.83–2.03 Å [3]. The cage can be functionalized with a wide range of organic substituents [6‐8]. If the polymerizable R groups are selected properly [9‐11], the organic components can be varied to control the cross-linking density about the cube, the segment distances between the cross-links, the packing of individual cubes with respect to one another, and the stability of the cube-organic bond. Over the past decade, much of the research effort into POSS molecules has centered on the synthesis of homo- and block-copolymers with POSS as an integral part of the polymer chain [12‐14], with fewer studies of POSS/melt blended nanocomposites being conducted [15, 16]. They reported that the incorporation of POSS could lead to substantial improvements in the polymer properties including increases in the operation temperature, oxidation resistance, surface hardening, and mechanical properties, as well as reductions in the flammability, heat evolution, and viscosity during processing [12‐18]. Especially, Yoon et al. [17] reported that the tensile strength and modulus of the PET nanohybrids containing epoxy-functionalized POSS showed slightly higher values than PET despite the relatively small amounts (1 wt%) of POSS used. In addition, Kim et al. [18] studied the rheological behavior of PET/POSS nanohybrids prepared by the in situ polymerization. They reported that the observation of a plateau region of nanohybrids containing 1 wt% of POSS in the plot of G′ versus log G″ indicates strong interfacial interactions between PET and POSS. …