Abstract POSS are interesting new molecules that have unique structural and chemical attributes. ... more Abstract POSS are interesting new molecules that have unique structural and chemical attributes. A POSS molecule is structured to have a POSS core (Si8-O12) and pendent organic groups. The POSS core is a rigid 8‑silicon 3-D cage. The 8‑silicon cage also provides sites for the attachment of different organic groups, which can be reactive, nonreactive, or a mixture of both. Their molecular symmetry, rigidity, and multifunctionality make POSS molecules a good candidate for high-performance dielectric nanocomposites. Low dielectric constant materials, where the dielectric constant K is less than 2, have been demonstrated in multiple POSS polymer nanocomposites. POSS molecules can also lower dielectric loss and improve dielectric breakdown strength. In order to better understand the structure-dielectric property relationship of the POSS nanocomposites, we categorize them into three types based on the type of interaction between the POSS and matrix polymer: nano-POSS polymer nanocomposites, where no covalent bonds exist between POSS molecules and polymers, and POSS presents as a nano-filler; g-POSS polymer nanocomposites, where POSS molecules are grafted to the polymer and become pendent groups on the main chain; and m-POSS (POSS) polymer nanocomposites, where POSS molecules are built into the molecule either as a repeat unit or a crosslinker. The dielectric constant, dissipation factor, and dielectric breakdown strength of various POSS polymer nanocomposites—including polymers of elastomers, plastics, and thermosets—are discussed in this chapter.
Inorganic nanoparticles have the potential of providing functionalities that are difficult to rea... more Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties.
This chapter focuses on the interfaces in nanocomposites of polyurethane (PU). PU nanocomposites ... more This chapter focuses on the interfaces in nanocomposites of polyurethane (PU). PU nanocomposites with various inorganic nanoparticles such as layered silicates, silica, polyhedral oligomeric silsesquioxanes, carbon nanotubes, graphene or graphene oxide nanosheets, silver, and other metal nanoparticles are summarized in individual sections. The interfacial chemistry of the control of particle exfoliation/intercalation and dispersion in the matrix and the creation of interface are discussed, the characterization methods of the interface and the effect of interfacial chemistry on PU morphology are elaborated in detail, and the material properties response with the interface is reported.
The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxa... more The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxane, at a modest temperature (<280℃) was studied with in situ heating Fourier transform infrared spectroscopy (FT-IR) in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2D-COS) analyses. The result revealed detailed structural evolution of these two different gels. When the silica gel was heated, (Si-O)6 rings appeared from the random Si-O-Si network formed after sol gel reaction, followed by condensation of silanol groups. Upon further heating, the existing (Si-O)4 rings were broken down and converted into (Si-O)6 structures, and finally isolated silanols appeared. The transition from (Si-O)4 rings to (Si-O)6 rings was observed by IR and further confirmed with positron annihilation lifetime spectroscopy (PALS). In comparison, during the curing of hybrid silsesquioxane, the condensation of silanols happens immediately upon he...
Abstract POSS are interesting new molecules that have unique structural and chemical attributes. ... more Abstract POSS are interesting new molecules that have unique structural and chemical attributes. A POSS molecule is structured to have a POSS core (Si8-O12) and pendent organic groups. The POSS core is a rigid 8‑silicon 3-D cage. The 8‑silicon cage also provides sites for the attachment of different organic groups, which can be reactive, nonreactive, or a mixture of both. Their molecular symmetry, rigidity, and multifunctionality make POSS molecules a good candidate for high-performance dielectric nanocomposites. Low dielectric constant materials, where the dielectric constant K is less than 2, have been demonstrated in multiple POSS polymer nanocomposites. POSS molecules can also lower dielectric loss and improve dielectric breakdown strength. In order to better understand the structure-dielectric property relationship of the POSS nanocomposites, we categorize them into three types based on the type of interaction between the POSS and matrix polymer: nano-POSS polymer nanocomposites, where no covalent bonds exist between POSS molecules and polymers, and POSS presents as a nano-filler; g-POSS polymer nanocomposites, where POSS molecules are grafted to the polymer and become pendent groups on the main chain; and m-POSS (POSS) polymer nanocomposites, where POSS molecules are built into the molecule either as a repeat unit or a crosslinker. The dielectric constant, dissipation factor, and dielectric breakdown strength of various POSS polymer nanocomposites—including polymers of elastomers, plastics, and thermosets—are discussed in this chapter.
Inorganic nanoparticles have the potential of providing functionalities that are difficult to rea... more Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties.
This chapter focuses on the interfaces in nanocomposites of polyurethane (PU). PU nanocomposites ... more This chapter focuses on the interfaces in nanocomposites of polyurethane (PU). PU nanocomposites with various inorganic nanoparticles such as layered silicates, silica, polyhedral oligomeric silsesquioxanes, carbon nanotubes, graphene or graphene oxide nanosheets, silver, and other metal nanoparticles are summarized in individual sections. The interfacial chemistry of the control of particle exfoliation/intercalation and dispersion in the matrix and the creation of interface are discussed, the characterization methods of the interface and the effect of interfacial chemistry on PU morphology are elaborated in detail, and the material properties response with the interface is reported.
The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxa... more The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxane, at a modest temperature (<280℃) was studied with in situ heating Fourier transform infrared spectroscopy (FT-IR) in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2D-COS) analyses. The result revealed detailed structural evolution of these two different gels. When the silica gel was heated, (Si-O)6 rings appeared from the random Si-O-Si network formed after sol gel reaction, followed by condensation of silanol groups. Upon further heating, the existing (Si-O)4 rings were broken down and converted into (Si-O)6 structures, and finally isolated silanols appeared. The transition from (Si-O)4 rings to (Si-O)6 rings was observed by IR and further confirmed with positron annihilation lifetime spectroscopy (PALS). In comparison, during the curing of hybrid silsesquioxane, the condensation of silanols happens immediately upon he...
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