A study on the kinetics and thermal properties of polystyrene/diatomite nanocomposites prepared via in situ ATRP

2018 ◽  
Vol 33 (2) ◽  
pp. 180-197 ◽  
Author(s):  
Khezrollah Khezri ◽  
Yousef Fazli
Keyword(s):  
Molecular Weight ◽  
In Situ Polymerization ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Linear Increase ◽  
Size Exclusion ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Exclusion Chromatography

Pristine mesoporous diatomite was employed to prepare polystyrene/diatomite composites. Diatomite platelets were used for in situ polymerization of styrene by atom transfer radical polymerization to synthesize tailor-made polystyrene nanocomposites. X-Ray fluorescence spectrometer analysis and thermogravimetric analysis (TGA) were employed for evaluating some inherent properties of pristine diatomite platelets. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the diatomite platelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Linear increase of ln ( M0/M) with time for all the samples shows that polymerization proceeds in a living manner. Addition of 3 wt% pristine mesoporous diatomite leads to an increase of conversion from 72% to 89%. Molecular weight of polystyrene chains increases from 11,326 g mol−1 to 14134 g mol−1 with the addition of 3 wt% pristine mesoporous diatomite; however, polydispersity index values increases from 1.13 to 1.38. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 81.9°C to 87.1°C by adding 3 wt% of mesoporous diatomite platelets.

Effect of Mesoporous Diatomite Particles on the Kinetics of SR&NI ATRP of Styrene and Butyl Acrylate

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Khezrollah Khezri ◽  
Moosa Ghasemi ◽  
Yousef Fazli
Keyword(s):  
Molecular Weight ◽  
Butyl Acrylate ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Size Exclusion ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Exclusion Chromatography ◽  
Adsorption Desorption ◽  
Mesoporous Diatomite Nanoplatelets

Abstract Mesoporous diatomite particles were employed to prepare different poly(styrene-co-butyl acrylate)/diatomite nanocomposites. Diatomite nanoplatelets were used for in situ copolymerization of styrene and butyl acrylate by SR&NI ATRP to synthesize well-defined poly(styrene-co-butyl acrylate) nanocomposites. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the diatomite nanoplatelets. Evaluation of pore size distribution and morphological studies were also performed by SEM and TEM. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of 3 wt% pristine mesoporous diatomite nanoplatelets leads to increase of conversion from 73 to 89%. Molecular weight of poly(styrene-co-butyl acrylate) chains increases from 17,115 to 20,343 g·mol−1 by addition of 3 wt% pristine mesoporous diatomite; however, polydispersity index values increases from 1.14 to 1.37. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 35.26 to 39.61°C by adding 3 wt% of mesoporous diatomite nanoplatelets.

INTRODUCTION OF A DOUBLE BOND CONTAINING MODIFIER ON THE SURFACE OF MCM-41 NANOPARTICLES: APPLICATION FOR SR&NI ATRP OF STYRENE

NANO ◽  
2014 ◽  
Vol 09 (02) ◽  
pp. 1450023 ◽  
Author(s):  
KHEZROLLAH KHEZRI ◽  
VAHID HADDADI-ASL ◽  
HOSSEIN ROGHANI-MAMAQANI
Keyword(s):  
Molecular Weight ◽  
Double Bond ◽  
Mesoporous Silica Nanoparticles ◽  
Nitrogen Adsorption ◽  
Size Exclusion ◽  
Proton Nuclear Magnetic Resonance ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Exclusion Chromatography ◽  
Mcm 41

Mesoporous silica nanoparticles (MCM-41) surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant double bond containing nanoparticles were used in grafting through simultaneous reverse and normal initiation technique for atom transfer radical polymerization (SR&NI ATRP) of styrene to synthesize well-defined polystyrene nanocomposites with twofold chains. Nitrogen adsorption/desorption isotherm and X-ray diffraction analysis were used to evaluate characteristics of spherical MCM-41 nanoparticles. Morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of MCM-41 nanoparticles by 3 wt.% results in a decrease of conversion from 93% to 82%. Molecular weight of the free and attached polystyrene chains decreases by adding 3 wt.% MCM-41 nanoparticles; however, PDI values increases from 1.27 to 1.78 for free chains and 1.87 to 2.48 for attached chains. A peak around 4.1 ppm which originates from hydrogen atom of terminal units of polystyrene chains in proton nuclear magnetic resonance spectra in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. Increasing thermal stability of the nanocomposites is demonstrated by Thermogravimetric analysis. Differential scanning calorimetry also shows a decrease in glass transition temperature by increasing MCM-41 nanoparticles.

Investigation of the effect of mesoporous diatomaceous earth particles on RATRP of styrene and butyl acrylate

2018 ◽  
Vol 32 (2) ◽  
pp. 248-266 ◽  
Author(s):  
Khezrollah Khezri ◽  
Hassan Alijani ◽  
Yousef Fazli ◽  
Zahra Shariatinia
Keyword(s):  
Molecular Weight ◽  
Butyl Acrylate ◽  
Nitrogen Adsorption ◽  
Size Exclusion ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Transmission Electron ◽  
Exclusion Chromatography ◽  
Adsorption Desorption ◽  
Mesoporous Diatomite Nanoplatelets

Mesoporous diatomite nanoplatelets were employed to prepare various poly (styrene-co-butyl acrylate)/diatomite nanocomposites by in situ reverse atom transfer radical polymerization of styrene and butyl acrylate. Fourier-transform infrared spectroscopy, thermogravimetric analysis (TGA), and nitrogen adsorption/desorption isotherm were employed for evaluating some properties of the pristine diatomite nanoplatelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Addition of 3 wt% pristine mesoporous diatomite nanoplatelets leads to an increase in conversion from 77% to 92%. Molecular weight of poly (styrene-co-butyl acrylate) chains increases from 17,348 g mol−1 to 21,346 g mol−1 with the addition of 3 wt% pristine mesoporous diatomite nanoplatelets; however, polydispersity index values increases from 1.38 to 1.65. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 35.5°C to 39.4°C with the addition of 3 wt% mesoporous diatomite nanoplatelets.

Investigating the Effect of Silica Aerogel Nanoparticles on the Kinetics of AGET ATRP of Methyl Methacrylate

2019 ◽  
Vol 233 (3) ◽  
pp. 393-411 ◽  
Author(s):  
Maryam Karimi ◽  
Soroush Davoudizadeh ◽  
Saeed Bahadorikhalili ◽  
Khezrollah Khezri
Keyword(s):  
Molecular Weight ◽  
Methyl Methacrylate ◽  
Silica Aerogel ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Linear Increase ◽  
Modified Silica ◽  
Aget Atrp ◽  
Morphological Studies ◽  
Living Nature

Abstract Hexamethyldisilazane-modified silica aerogel nanoparticles were used for in situ polymerization of methyl methacrylate by activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) to synthesize tailor-made PMMA nanocomposites. Appropriate dispersion of silica aerogel nanoparticles in the monomer solution and improvement in interfacial interaction between the PMMA matrix and nanoparticles are two main reasons for application of HMDS-modified silica aerogel nanoparticles. Nitrogen adsorption/desorption isotherm was employed to examine surface area and structural characteristics of the HMDS-modified silica aerogel nanoparticles. Evaluation of size distribution and morphological studies were also performed by SEM and TEM. Conversion and molecular weight determinations were carried out using GC and SEC, respectively. Addition of 3 wt% HMDS-modified silica aerogel nanoparticles leads to decrement of conversion from 85 to 64%. Molecular weight of PMMA chains also decreases from 13,912 to 10,810 g⋅mol−1 by addition of only 3 wt% HMDS-modified silica aerogel nanoparticles; however, polydispersity index values increases from 1.18 to 1.51. Linear increase of ln(M0/M) with time for all the samples shows that polymerization proceeds in a living manner. In addition, suitable agreement between theoretical and experimental molecular weight in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. TGA results indicate that by increasing HMDS-modified silica aerogel nanoparticles content, slight improvements in thermal stability of the nanocomposites were obtained. DSC results show a decrease in Tg from 86.9 to 80.1°C by addition of 3 wt% HMDS-modified silica aerogel nanoparticles.

scholarly journals The Use of Epoxy Silanes on Montmorillonite: An Effective Way to Improve Thermal and Rheological Properties of PLA/MMT Nanocomposites Obtained via “In Situ” Polymerization

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Valentina Sabatini ◽  
Hermes Farina ◽  
Luca Basilissi ◽  
Giuseppe Di Silvestro ◽  
Marco A. Ortenzi
Keyword(s):  
Thermal Stability ◽  
Rheological Properties ◽  
In Situ Polymerization ◽  
Rheological Behaviour ◽  
Size Exclusion ◽  
Melt Crystallization ◽  
Scanning Calorimetry ◽  
Molecular Weights ◽  
Exclusion Chromatography

Polylactic acid (PLA) nanocomposites were prepared via “in situ” ring opening polymerization (ROP) of lactide using a montmorillonite, Cloisite 15A, employed after surface treatment with 3-Glycidoxypropyltrimethoxysilane. The dispersion of the nanoparticles was checked using Wide Angle X-Ray Scattering (WAXS) and Transmission Electron Microscopy (TEM); both the effects of different amounts of montmorillonite and silane were measured on molecular weights and on thermal and rheological properties, using Size Exclusion Chromatography (SEC), Differential Scanning Calorimetry (DSC), thermogravimetric analyses (TGA), and rheological analyses. It was found that even very low amounts (0.1% w/w) of nanoparticles greatly affect nanocomposites properties. Unmodified montmorillonite tends to decrease molecular weights, deactivating the catalytic system used for ROP of lactide, but when epoxy silane is present molecular weights increase. Melt crystallization temperatures increase with modified nanoparticles, which enhance crystallization process. TGA analyses show that when pure montmorillonite is present, nanocomposites have lower thermal stability with respect to standard PLA; when silane is used thermal stability can get much higher than standard PLA as silane content increases. The rheological behaviour of nanocomposites shows that melt viscosity is far higher than that of standard PLA at low shear rates and also a marked shear thinning behaviour can be achieved.

Reverse Atom Transfer Radical Polymerization of Styrene in the Presence of Functionalized Silica Aerogel Nanoparticles

2016 ◽  
Vol 230 (10) ◽  
Author(s):  
Khezrollah Khezri ◽  
Hossein Mahdavi
Keyword(s):  
Molecular Weight ◽  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Silica Aerogel ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Size Exclusion ◽  
Atom Transfer ◽  
Functionalized Nanoparticles ◽  
Morphological Studies

AbstractPristine silica aerogel nanoparticles surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant functionalized nanoparticles were used in grafting through polymerization of styrene by reverse initiation technique for atom transfer radical polymerization. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the synthesized nanoparticles. Evaluation of size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of MPS-functionalized nanoparticles by 3 wt % results in a decrease of conversion from 98 to 81%. Molecular weight (

Effect of HMDS-modified silica aerogel nanoparticles on ATRP of styrene and methyl methacrylate: Kinetics and thermal studies

2019 ◽  
pp. 089270571988167
Author(s):  
Khezrollah Khezri ◽  
Yousef Fazli
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Methyl Methacrylate ◽  
Silica Aerogel ◽  
Structural Characteristics ◽  
Thermal Studies ◽  
Size Exclusion ◽  
Gravimetric Analysis ◽  
Modified Silica ◽  
Morphological Studies

Surface of pristine silica aerogel nanoparticles was hydrophobically modified with hexamethyldisilazane (HMDS). Then, the resultant modified nanoparticles were used for in situ atom transfer radical copolymerization of styrene and methyl methacrylate. Surface area and structural characteristics of the HMDS-modified silica aerogel nanoparticles (H-SANs) were examined by nitrogen adsorption/desorption isotherm. Evaluation of size distribution and morphological studies were also performed by scanning electron microscopy and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas chromatography and size exclusion chromatography, respectively. Adding of H-SAN by 3 wt% results in decrement of conversion from 98% to 79%. In addition, molecular weight of copolymer chains decreases from 20,372 g·mol−1 to 16,487 g·mol−1. However, polydispersity index values increases from 1.38 to 1.76. Linear increase of ln( M 0/ M) with time for all the samples shows that polymerization proceeds in a living manner. Increasing thermal stability of the nanocomposites is demonstrated by thermal gravimetric analysis. Differential scanning calorimetry shows a decrease in glass transition temperature from 67.4°C to 59.8°C by the addition of 3 wt% of the H-SAN.

Synthesis and Characterization of Poly (styrene-co-butyl acrylate)/Silica Aerogel Nanocomposites by in situ AGET ATRP: Investigating Thermal Properties

2017 ◽  
Vol 36 (10) ◽  
pp. 955-962 ◽  
Author(s):  
Khezrollah Khezri ◽  
Yousef Fazli
Keyword(s):  
Molecular Weight ◽  
Butyl Acrylate ◽  
Silica Aerogel ◽  
Size Exclusion ◽  
Proton Nuclear Magnetic Resonance ◽  
Molar Ratio ◽  
Resonance Spectroscopy ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Exclusion Chromatography

AbstractHydrophilic silica aerogel nanoparticles surface was modified with hexamethyldisilazane. Then, the resultant modified nanoparticles were used in random copolymerization of styrene and butyl acrylate via activators generated by electron transfer for atom transfer radical polymerization. Conversion and molecular weight determinations were performed using gas and size exclusion chromatography respectively. Addition of modified nanoparticles by 3 wt% results in a decrease of conversion from 68 to 46 %. Molecular weight of copolymer chains decreases from 12,500 to 7,500 g.mol–1 by addition of 3 wt% modified nanoparticles; however, PDI values increase from 1.1 to 1.4. Proton nuclear magnetic resonance spectroscopy results indicate that the molar ratio of each monomer in the copolymer chains is approximately similar to the initial selected mole ratio of them. Increasing thermal stability of the nanocomposites is demonstrated by thermal gravimetric analysis. Differential scanning calorimetry also shows a decrease in glass transition temperature by increasing modified silica aerogel nanoparticles.

scholarly journals Polyethylene-Waste Tire Dust Composites Via In Situ Polymerization

2017 ◽  
Vol 58 (2) ◽  
Author(s):  
Yadira Karina Reyes Acosta ◽  
Rosa Idalia Narro Céspedes ◽  
María Guadalupe Neira Velázquez ◽  
José Díaz Elizondo ◽  
Francisco Enríquez-Medrano ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
In Situ Polymerization ◽  
Metallocene Catalyst ◽  
Size Exclusion ◽  
Molar Ratio ◽  
Scanning Calorimetry ◽  
Co Catalysts ◽  
Waste Tire ◽  
Scanning Transmission

Polyethylene/waste tire dust (WTD) composites were obtained by an <em>in situ</em> polymerization technique. The surface of the WTD was modified with deposition of polyethylene by using plasma polymerization. Ethylene polymerization was carried out using bis(cyclopentadienyl) titanium dichloride (Cp<sub>2</sub>TiCl<sub>2</sub>) as homogeneous metallocene catalyst, while diethylaluminum chloride (DEAC), <em>ethylaluminum sesquichloride</em> (EASC) and methyl aluminoxane (MAO) were used as co-catalysts at two different [Al]/[Ti] molar ratio. The main characteristics of the obtained polyethylenes were determined by size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that by using EASC and MAO the highest catalytic activities were presented at a [Al]/[Ti] molar ratio of 9.17 and 18.33 respectively. Even though it was possible to obtain polyethylene using WTD (modified or unmodified) the catalytic activity was lower than in the case in which no WTD was added in ethylene polymerization. Scanning transmission electronic microscopy images evidenced that the original morphology of the polyethylenes was not modified by the presence of WTD.

Sign in / Sign up

Export Citation Format

Share Document