Vesna Volovšek - Academia.edu (original) (raw)

Papers by Vesna Volovšek

Aminopropylsilanetriol (APST) is one of the most frequently used organofunctional silane coupling... more Aminopropylsilanetriol (APST) is one of the most frequently used organofunctional silane coupling agents. This molecule also emerges through the hydrolysis of other alkoxysilanes as a product of hydrolysis. Because of its two functional groups located at the opposite molecular sites, it can react with organic polymers as well as with inorganic substrates and fillers. Conformational stability and vibrations of APST has been investigated using DFT calculations, but the vibrational spectra were recorded only for water solution and condensed, polymerized structure. In this work we present Raman spectrum of APST in vapor phase. In order to get Raman spectra of vaporized APST the following procedure was used: 25% water solution of APST was filled in glass capillary and frozen in liquid nitrogen bath. The capillary was then connected to the vacuum pump in order to evacuate all the air above the sample. After evacuation the capillary was sealed and left at room temperature. Raman spectra of...

Spectrochimica Acta Part A: Molecular Spectroscopy, 1993

IR and Raman spectra of benzophenone and several of its isotopomers (d,-, dID', 13C_ and 13Cd5,be... more IR and Raman spectra of benzophenone and several of its isotopomers (d,-, dID', 13C_ and 13Cd5,benzophenone) are the experimental basis for the normal coordinate analysis. The possibility of determining the conformation of the benzophenone molecule in solution from its vibrational spectrum is considered carefully. The dihedral angle between the central part of the molecule and the phenyl ring has been determined by fitting the calculated to the observed spectra. The final force field for the molecule was obtained for the dihedral angle of 35°. 2071 'IIS2 962 963 127,u '1120 962 964 128 11 '1153 948 948 49T+23IJ+18Jl '1'21 925 928 118 11 V.14 917 918 104,u '1'22 855 855 112,u 'IISS 852 854 112,u '1123 766 772 51,u + 31z + 24M 'IIS6 741 110,u + 34z + 17M '1124

The Journal of Physical Chemistry, 1989

The Journal of Physical Chemistry, 1993

ABSTRACT

e-Polymers, 2004

Poly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechan... more Poly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechanical mixing of untreated CaCO

e-Polymers, 2004

In this work we have investigated the effects of CaCO

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014

Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperatur... more Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperature in macro chamber utilizing two-mirror technique over the sample tube. Unlike predominantly trans molecular conformation in condensed phase, the spectra of vapor show that the molecules are solely in gauche conformation with intramolecular hydrogen bond N···HO which reduces the molecular energy in respect to trans conformation by 0.152 eV. The assignment of the molecular spectra based on the DFT calculation is presented. The strong vibrational bands at 354 cm(-1), 588 cm(-1) and 3022 cm(-1) are proposed for verifying the existence of the ring like, hydrogen bonded structure. Special attention was devoted to the high frequency region, where hydrogen bond vibrations are coupled to stretchings of amino and silanol groups.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2006

Density functional theory (DFT), using the B3-LYP/6-31G(d,p) method have been used to investigate... more Density functional theory (DFT), using the B3-LYP/6-31G(d,p) method have been used to investigate the conformation and vibrational spectra of aminopropylsilanetriol (APST) NH2CH2CH2CH2Si(OH)3. The potential function for CCCSi torsion gives rise to two distinct conformers trans and gauche. The predicted energy of the more stable trans conformer is 337 cm-1 less than the energy of gauche conformer. The calculated barriers to the conformation interchange are: 1095, 2845 and 438 cm-1 for the trans to gauche, gauche to gauche and gauche to trans conformers, respectively. For the trans conformer the potential energy curve for the Si(OH)3 groups torsion in APST has been calculated changing the HOSiC dihedral angle. The barrier for the internal rotation of 3065 cm-1 has been obtained. The optimized molecular structure of APST dimer calculated for trans conformer has a SiOSi angle of 143.2 degrees, and a SiOSi bond length of 0.164 nm. A complete vibrational assignment for both conformers as well as for trans-dimer is supported by the normal coordinate analysis, calculated IR intensities as well as Raman activities. On the basis of the results, the vibrational spectra of APST aqueous solution and APST polymer have been analyzed. The average error between the observed and calculated frequencies is 14 cm-1.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009

Molecular structure and vibrational frequencies of 3-glycidoxypropyltrimethoxysilane (GPTMS) have... more Molecular structure and vibrational frequencies of 3-glycidoxypropyltrimethoxysilane (GPTMS) have been investigated by density functional theory (DFT) calculations using Becke's three-parameter exchange functional combined with Lee-Young-Parr correlation functional (B3-LYP) and standard basis set 6-311++G(d,p). In order to reveal some possible conformations of GPTMS, potential energy scan has been performed in three dihedral angles SiCCC, CCCO and OCCO. The calculations predict the existence of seven different conformations. Raman and IR spectra of liquid samples were recorded and complete assignment of the observed vibrational bands of GPTMS molecule has been proposed. Temperature dependence of Raman spectra between 203K and 293K was examined and vibrational modes characteristic for different conformers were detached.

Molecular Physics, 2001

Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeutera... more Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeuterated isotopomer, Dwortho-tephenyl, have been recorded. Optimized geometries and vibrational frequencies were calculated by the semiempirical RHF/AMl method and by DFT using the B3L YP functional and 6-31 G(d) basis set. In both cases the lowest energy conformation is of Cj syrnrnetry. With the scaled AMI and B3LYP/6-31 G(d) force fields the average error in reproducing the experimental molecular vibrational frequencies is 13 cm-I and 5 cm-I, respectively. The AM I potential energy surface for phenyl torsions was mapped on a l S" grid. The barrier to concerted internal rotation is estimated to lie between 3 kJ mol-I and 6 kJ mol-I. The calculations of the lattice dynamics at k = O in the low temperature fully ordered crystal phase of parent and deuterated ortho-terphenyl were performed with inclusion of six low lying intramolecular vibrations. The conformational change of the ortho-terphenyl molecule induced by crystal packing forces was taken into account by redefining the unperturbed molecular vibrational state. Although an accurate assignment of lattice vibrations was not possible, the calculated spectra give quite a reasonable picture of the low frequency dynamics in crystalline ortho-terphenyl. The relevance of the resuIts obtained to the glass forming property of ortho-terphenyl is discussed.

Macromolecular Symposia, 2014

ABSTRACT In this work 3-glycidoxypropyltrimethoxysilane polymer with inorganic SiOSi bonds was pr... more ABSTRACT In this work 3-glycidoxypropyltrimethoxysilane polymer with inorganic SiOSi bonds was prepared by a sol-gel process. The structure of polymer was characterized by vibrational spectroscopy (Raman and IR). The interpretation of vibrational spectra is supported by the normal coordinate analysis based on density functional theory (DFT) calculations. A conformational and vibrational analysis of lowest energy dimer structure has been carried out by DFT calculations using Becke's three-parameter exchange functional in combination with the Lee-Young-Parr correlation functional (B3-LYP) and standard 6–311 + G(d,p) basis set.The comparison of theoretical spectra with the experimental data enabled us to extract the characteristic vibrational bands of polymer structure. The inorganic polymerization gives rise to siloxane network with SiOSi stretchings at 1030 and 1134 cm−1 suggesting the ladder-type structure of GPTMS polymer.

Macromolecular Symposia, 2008

ABSTRACT The Raman spectra of aminopropylsiloxane (APS) polymerized on PVC substrate in DC electr... more ABSTRACT The Raman spectra of aminopropylsiloxane (APS) polymerized on PVC substrate in DC electric field were measured to study the structure of deposited films. The modelling of low wavenumber Raman spectra was achieved using contribution of acoustic phonons, intramolecular vibrations as well as optical phonons related to librational motions of ladders. Results suggest that electric field influences the orientations of ladders increasing thus the degree of order in microdomains.

Macromolecular Symposia, 2008

ABSTRACT Micro Raman spectroscopy was used to investigate the structures formed at the surface of... more ABSTRACT Micro Raman spectroscopy was used to investigate the structures formed at the surface of amorphous pirogenic silica Aerosil 200. Nanoparticles were treated with 25% water solution of aminopropylsilanetriol and dried in laboratory atmosphere and under vacuum of about 5 mbar. Spectra of pure silica nanoparticles and treated nanoparticles were recorded in the frequency range 20–1700 cm−1 and 2500–3800 cm−1. Comparative analysis reveals the existance of different structures formed at the surface of silica nanoparticles depending on drying conditions.

Journal of Raman Spectroscopy, 1984

ABSTRACT

Journal of Raman Spectroscopy, 1983

ABSTRACT

Aminopropylsilanetriol (APST) is one of the most frequently used organofunctional silane coupling... more Aminopropylsilanetriol (APST) is one of the most frequently used organofunctional silane coupling agents. This molecule also emerges through the hydrolysis of other alkoxysilanes as a product of hydrolysis. Because of its two functional groups located at the opposite molecular sites, it can react with organic polymers as well as with inorganic substrates and fillers. Conformational stability and vibrations of APST has been investigated using DFT calculations, but the vibrational spectra were recorded only for water solution and condensed, polymerized structure. In this work we present Raman spectrum of APST in vapor phase. In order to get Raman spectra of vaporized APST the following procedure was used: 25% water solution of APST was filled in glass capillary and frozen in liquid nitrogen bath. The capillary was then connected to the vacuum pump in order to evacuate all the air above the sample. After evacuation the capillary was sealed and left at room temperature. Raman spectra of...

Spectrochimica Acta Part A: Molecular Spectroscopy, 1993

IR and Raman spectra of benzophenone and several of its isotopomers (d,-, dID', 13C_ and 13Cd5,be... more IR and Raman spectra of benzophenone and several of its isotopomers (d,-, dID', 13C_ and 13Cd5,benzophenone) are the experimental basis for the normal coordinate analysis. The possibility of determining the conformation of the benzophenone molecule in solution from its vibrational spectrum is considered carefully. The dihedral angle between the central part of the molecule and the phenyl ring has been determined by fitting the calculated to the observed spectra. The final force field for the molecule was obtained for the dihedral angle of 35°. 2071 'IIS2 962 963 127,u '1120 962 964 128 11 '1153 948 948 49T+23IJ+18Jl '1'21 925 928 118 11 V.14 917 918 104,u '1'22 855 855 112,u 'IISS 852 854 112,u '1123 766 772 51,u + 31z + 24M 'IIS6 741 110,u + 34z + 17M '1124

The Journal of Physical Chemistry, 1989

The Journal of Physical Chemistry, 1993

ABSTRACT

e-Polymers, 2004

Poly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechan... more Poly(vinyl acetate) (PVAc) composites were prepared by different approaches, namely (i) by mechanical mixing of untreated CaCO

e-Polymers, 2004

In this work we have investigated the effects of CaCO

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014

Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperatur... more Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperature in macro chamber utilizing two-mirror technique over the sample tube. Unlike predominantly trans molecular conformation in condensed phase, the spectra of vapor show that the molecules are solely in gauche conformation with intramolecular hydrogen bond N···HO which reduces the molecular energy in respect to trans conformation by 0.152 eV. The assignment of the molecular spectra based on the DFT calculation is presented. The strong vibrational bands at 354 cm(-1), 588 cm(-1) and 3022 cm(-1) are proposed for verifying the existence of the ring like, hydrogen bonded structure. Special attention was devoted to the high frequency region, where hydrogen bond vibrations are coupled to stretchings of amino and silanol groups.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2006

Density functional theory (DFT), using the B3-LYP/6-31G(d,p) method have been used to investigate... more Density functional theory (DFT), using the B3-LYP/6-31G(d,p) method have been used to investigate the conformation and vibrational spectra of aminopropylsilanetriol (APST) NH2CH2CH2CH2Si(OH)3. The potential function for CCCSi torsion gives rise to two distinct conformers trans and gauche. The predicted energy of the more stable trans conformer is 337 cm-1 less than the energy of gauche conformer. The calculated barriers to the conformation interchange are: 1095, 2845 and 438 cm-1 for the trans to gauche, gauche to gauche and gauche to trans conformers, respectively. For the trans conformer the potential energy curve for the Si(OH)3 groups torsion in APST has been calculated changing the HOSiC dihedral angle. The barrier for the internal rotation of 3065 cm-1 has been obtained. The optimized molecular structure of APST dimer calculated for trans conformer has a SiOSi angle of 143.2 degrees, and a SiOSi bond length of 0.164 nm. A complete vibrational assignment for both conformers as well as for trans-dimer is supported by the normal coordinate analysis, calculated IR intensities as well as Raman activities. On the basis of the results, the vibrational spectra of APST aqueous solution and APST polymer have been analyzed. The average error between the observed and calculated frequencies is 14 cm-1.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009

Molecular structure and vibrational frequencies of 3-glycidoxypropyltrimethoxysilane (GPTMS) have... more Molecular structure and vibrational frequencies of 3-glycidoxypropyltrimethoxysilane (GPTMS) have been investigated by density functional theory (DFT) calculations using Becke's three-parameter exchange functional combined with Lee-Young-Parr correlation functional (B3-LYP) and standard basis set 6-311++G(d,p). In order to reveal some possible conformations of GPTMS, potential energy scan has been performed in three dihedral angles SiCCC, CCCO and OCCO. The calculations predict the existence of seven different conformations. Raman and IR spectra of liquid samples were recorded and complete assignment of the observed vibrational bands of GPTMS molecule has been proposed. Temperature dependence of Raman spectra between 203K and 293K was examined and vibrational modes characteristic for different conformers were detached.

Molecular Physics, 2001

Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeutera... more Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeuterated isotopomer, Dwortho-tephenyl, have been recorded. Optimized geometries and vibrational frequencies were calculated by the semiempirical RHF/AMl method and by DFT using the B3L YP functional and 6-31 G(d) basis set. In both cases the lowest energy conformation is of Cj syrnrnetry. With the scaled AMI and B3LYP/6-31 G(d) force fields the average error in reproducing the experimental molecular vibrational frequencies is 13 cm-I and 5 cm-I, respectively. The AM I potential energy surface for phenyl torsions was mapped on a l S" grid. The barrier to concerted internal rotation is estimated to lie between 3 kJ mol-I and 6 kJ mol-I. The calculations of the lattice dynamics at k = O in the low temperature fully ordered crystal phase of parent and deuterated ortho-terphenyl were performed with inclusion of six low lying intramolecular vibrations. The conformational change of the ortho-terphenyl molecule induced by crystal packing forces was taken into account by redefining the unperturbed molecular vibrational state. Although an accurate assignment of lattice vibrations was not possible, the calculated spectra give quite a reasonable picture of the low frequency dynamics in crystalline ortho-terphenyl. The relevance of the resuIts obtained to the glass forming property of ortho-terphenyl is discussed.

Macromolecular Symposia, 2014

ABSTRACT In this work 3-glycidoxypropyltrimethoxysilane polymer with inorganic SiOSi bonds was pr... more ABSTRACT In this work 3-glycidoxypropyltrimethoxysilane polymer with inorganic SiOSi bonds was prepared by a sol-gel process. The structure of polymer was characterized by vibrational spectroscopy (Raman and IR). The interpretation of vibrational spectra is supported by the normal coordinate analysis based on density functional theory (DFT) calculations. A conformational and vibrational analysis of lowest energy dimer structure has been carried out by DFT calculations using Becke's three-parameter exchange functional in combination with the Lee-Young-Parr correlation functional (B3-LYP) and standard 6–311 + G(d,p) basis set.The comparison of theoretical spectra with the experimental data enabled us to extract the characteristic vibrational bands of polymer structure. The inorganic polymerization gives rise to siloxane network with SiOSi stretchings at 1030 and 1134 cm−1 suggesting the ladder-type structure of GPTMS polymer.

Macromolecular Symposia, 2008

ABSTRACT The Raman spectra of aminopropylsiloxane (APS) polymerized on PVC substrate in DC electr... more ABSTRACT The Raman spectra of aminopropylsiloxane (APS) polymerized on PVC substrate in DC electric field were measured to study the structure of deposited films. The modelling of low wavenumber Raman spectra was achieved using contribution of acoustic phonons, intramolecular vibrations as well as optical phonons related to librational motions of ladders. Results suggest that electric field influences the orientations of ladders increasing thus the degree of order in microdomains.

Macromolecular Symposia, 2008

ABSTRACT Micro Raman spectroscopy was used to investigate the structures formed at the surface of... more ABSTRACT Micro Raman spectroscopy was used to investigate the structures formed at the surface of amorphous pirogenic silica Aerosil 200. Nanoparticles were treated with 25% water solution of aminopropylsilanetriol and dried in laboratory atmosphere and under vacuum of about 5 mbar. Spectra of pure silica nanoparticles and treated nanoparticles were recorded in the frequency range 20–1700 cm−1 and 2500–3800 cm−1. Comparative analysis reveals the existance of different structures formed at the surface of silica nanoparticles depending on drying conditions.

Journal of Raman Spectroscopy, 1984

ABSTRACT

Journal of Raman Spectroscopy, 1983

ABSTRACT