13 research outputs found
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The Electronic Structure and Spectroscopy of Diarylidene-Cycloalkanones and Their Protonated Cations
A series of 2,5-diarylidene-cyclopentanones (ndbcp), their protonated cations (ndbcp-H+), and a substituted compound, 2,5-bis-[3-(4-dimethylamino-phenyl)-allylidene-cyclopentanone (2dbma) have been synthesized. Their electronic absorption and fluorescence spectra have been measured. The absorption spectra have been assigned with the aid of INDO/S calculations. Molecular structures used for the INDO/S calculations were computed with the PM3 Hamiltonian. Polarized excitation spectra have been measured for 2dbcp and 3dbcp at 77 K in ethanol/methanol glass and used as an aid for the assignments of electronic transitions. Absorption and fluorescence spectra have been measured in solvents of varying polarity for all compounds synthesized. The influence of hydrogen bonding on the excitation spectra of compounds has been investigated. Solvent induced shifts in the absorption and fluorescence spectra of 3dbcp and 2dbma in combination with the PM3 calculated ground state dipole moment have been used to determine the excited state dipole moment of these compounds. Fluorescence quantum yields have been obtained to analyze the changes in the nonradiative rate of decay from S1. The protonated cations have been prepared in acids of different strength. The influence of acid strength on the excitation and emission spectra has been analyzed by gradually diluting acid solution. Evidence for excited state proton transfer in weak acids has been obtained for 2dbcp and 3dbcp.
Brief photochemical studies of 1dbcp and 1dbcp-H+ have been carried out and analyzed by HPLC
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications
Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications
Herein, the development of new nanocomposite systems
is reported
based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral
oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets
(GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS
was effectively synthesized via a two-step synthesis protocol, including
ultrasonication-assisted reaction and precipitation, and carefully
characterized with respect to its chemical and crystalline structure,
morphology, and thermal stability. FTIR and XPS spectroscopy analyses
revealed that POSS interacts with the residual oxygen moieties of
the GNPs through both covalent and noncovalent bonding. The X-ray
diffraction pattern of GNP-POSS further revealed that the crystallinity
of the GNPs was not altered after their functionalization with POSS.
GNP-POSS was successfully incorporated in PU at contents of 1, 3,
5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR
analysis of these films confirmed the presence of strong interfacial
interactions between the urea groups of PU and the GNP-POSS functionalities.
Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal
stability and mechanical properties compared to those of the neat
PU film. The quasi-static tensile testing of the PU/GNP-POSS samples
revealed remarkable enhancements in the tensile strength (from 7.9
for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young’s modulus
(238–617 MPa), while elongation at break and toughness also
showed 14 and 125% improvements, respectively. Finally, the effects
of GNP-POSS content on the morphological, quasistatic tensile, and
high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite
films were also investigated. Overall, the tests performed using a
split-Hopkinson pressure bar setup revealed a large increase in the
film strength (from 147.6 for the neat PU film to 199 MPa for the
PU/GNP-POSS film) and a marginal increase in the energy density of
the film (38.1–40.8 kJ/m3). These findings support
the suitability of the PU/GNP-POSS nanocomposite films for force protection
applications