scholarly journals Fluctuation In the Phase Transition Temperature of Poly (NIPAAm-co-HEMA-co-DMAMVA)-Post-guanine Affected by Hydrophilic/hydrophobic Interaction: Fabrication and Characterizations

2021 ◽  
Author(s):  
Momen Abdelaty
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Polymer Solution ◽  
Phase Transition Temperature ◽  
Click Reaction ◽  
Aldehyde Group ◽  
Solution Temperature ◽  
Hydroxyethyl Methacrylate ◽  
Dual Responsive ◽  
Vis Spectroscopy

Abstract The phase separation and transition temperature of poly (N-isopropylacrylamide) have been developed by the terpolymerization with new pH-responsive monomer and highly hydrophilic 2-Hydroxyethyl methacrylate. The new monomer based on vanillin is called 2-((dimethylamino)methyl)-4-formyl-6-methoxyphenyl acrylate (DMAMVA), and is investigated by chemical methods (1H, 13C NMR, FTIR, and mass spectroscopy). Terpolymers of dual-responsive thermo-pH with functional groups were fabricated via free radical polymerization of N-isopropylacrylamide (NIPAAm), 10 mol% 2-Hydroxyethyl methacrylate (HEMA), and 5, 10, and 20 mol% DMAMVA. A selected terpolymer was used for post-polymerization with guanine via click reaction and the formation of an imine between the aldehyde group of DMAMVA and the amine group of guanine. All terpolymer and post-terpolymer are chemically evaluated. The physical properties have been implemented by GPC (molecular weight and dispersity), DSC (glass transition temperature Tg), TGA (steps of degradation), and SEM (morphological features). The fluctuations in phase transition temperature Tc or the lower critical solution temperature LCST of the polymer solution in different pH solutions have been performed by two methods, first, the turbidity test by UV-Vis-spectroscopy, second, by micro-DSC for aqueous polymer solution. This work will be extended for more applications in bio-separation technology.

scholarly journals Tuning Anatase-Rutile Phase Transition Temperature: TiO2/SiO2 Nanoparticles Applied in Dye-Sensitized Solar Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Billy N. Cardoso ◽  
Emerson C. Kohlrausch ◽  
Marina T. Laranjo ◽  
Edilson V. Benvenutti ◽  
Naira M. Balzaretti ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Surface Area ◽  
Phase Transition Temperature ◽  
Dye Sensitized Solar Cells ◽  
Rutile Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Molar Percent

TiO2/SiO2 nanoparticles with 3, 5, and 10 molar percent of silica, were synthesized by hydrothermal method and characterized by SEM, TEM, N2 adsorption-desorption isotherms, X-ray diffraction, and Raman and UV-Vis spectroscopy. While pristine TiO2 thermally treated at 500°C presents a surface area of 36 m2 g-1 (±10 m2 g-1), TiO2/SiO2 containing 3, 5, and 10 molar percent of silica present surface areas of 93, 124, and 150 m2 g-1 (±10 m2 g-1), respectively. SiO2 is found to form very small amorphous domains well dispersed in the TiO2 matrix. X-ray diffraction and Raman spectroscopy data show that anatase-to-rutile phase transition temperature is delayed by the presence of SiO2, enabling single-anatase phase photoanodes for DSSCs. According to the I×V measurements, photoanodes with 3% of SiO2 result in improved efficiency, which is mainly related to increased surface area and dye loading. In addition, the results suggest a gain in photocurrent related to the passivation of defects by SiO2.

Synthesis of Nanogels of Poly Methyacrylic Acid Using Methyl Cellulose as a Template

2014 ◽  
Vol 787 ◽  
pp. 401-406
Author(s):  
Jun Li Zhang ◽  
Peng Wang ◽  
Dong An ◽  
Xue Ting Li ◽  
Qian Wu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Methacrylic Acid ◽  
Aqueous Media ◽  
Polymer System ◽  
Methyl Cellulose ◽  
Solution Temperature ◽  
Lower Phase ◽  
Lower Temperature

In recent decades, thermo sensitive polymer system has been intensively studied due to significant importance in fundamental studies and various applications. Methyl cellulose (MC) is a thermo sensitive natural polymer, having a phase transition temperature or a lower critical solution temperature of about 65 °C. When methacrylic acid (MAA) was added to the MC solution, the phase transition of MC occurred at a lower temperature less than 65°C, and a higher concentration of MAA leds to a lower phase transition temperature of MC. Based on the phase transition of MC solution triggered by MAA, the surfactant-free poly (methacrylic acid) nanogels were synthesized by using methyl cellulose as a template in an aqueous media. The resulting PMAA nanogels characterized by using dynamic light scattering (DLS) and Fourier Transform Infrared Spectroscopy (FTIR). The nanogels of poly methyacrylic acid (PMAA) were affected by the concentration of both MC and MAA. A higher concentration of MAA led to a higher polymerization rate, and the higher concentration of MC resulted in the formation of the samller size of PMAA nanogels.

scholarly journals Poly(N-isopropylacrylamide-co-2-((diethylamino)methyl)-4-formyl-6-methoxyphenyl acrylate) Environmental Functional Copolymers: Synthesis, Characterizations, and Grafting with Amino Acids

Biomolecules ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 138 ◽  
Author(s):  
Momen Abdelaty
Keyword(s):  
Aldehyde Group ◽  
Size Exclusion ◽  
Solution Temperature ◽  
Grafted Polymer ◽  
Molar Ratios ◽  
Chemical Structures ◽  
Dual Responsive ◽  
Imine Group ◽  
13C Nuclear Magnetic Resonance ◽  
Vis Spectroscopy

Vanillin was used to synthesize a new derivative with an active aldehyde group and response to pH. It is named 2-((diethylamino) methyl)-4-formyl-6-methoxyphenyl acrylate, abbreviated to DEAMVA. The chemical structures were evaluated by 1H, 13C nuclear magnetic resonance (NMR), infrared (IR), and UV-Vis-spectroscopy, and all results demonstrated good statement. In order to achieve the dual responsive behavior thermo-pH with functionality, free radical polymerization of N-isopropylacrylamide with DEAMVA in different molar ratios (5, 10, 15 mol%) has been used, with azobisisobutyronitrile (AIBN) as the initiator. The chemical structure of the polymers was investigated by 1H NMR and IR. The dual responsive functional copolymer was exposed to a grafted process with tryptophan and tyrosine, both of which were also evaluated by 1HNMR and IR. Copolymers before and after grafting were physically investigated by size exclusion chromatography (SEC) for estimation of the molecular weight, the glass transition temperature by differential scanning calorimeter (DSC) and scanning electron microscope (SEM) for the surface morphology. The phase separation or lower critical solution temperature (LCST) (Tc) of the polymer solution was determined not only by a turbidity method using the change in the transmittance with temperature, but also by micro-DSC. The conversion to an amino acid-grafted polymer was detected through Beer’s law for the absorption of the –CH=N- imine group by UV-Vis-Spectroscopy.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

scholarly journals Study of physical properties of a ferrimagnetic spinel Cu1.5Mn1.5O4: spin dynamics, magnetocaloric effect and critical behavior

RSC Advances ◽  
2021 ◽  
Vol 11 (41) ◽  
pp. 25664-25676
Author(s):  
Abir Hadded ◽  
Jalel Massoudi ◽  
Sirine Gharbi ◽  
Essebti Dhahri ◽  
A. Tozri ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Physical Properties ◽  
Magnetocaloric Effect ◽  
Phase Transition Temperature ◽  
Magnetic Phase Transition ◽  
Critical Behavior ◽  
Magnetic Phase ◽  
Spin Dynamics ◽  
Critical Behaviour

The present work reports a detailed study of the spin dynamics, magnetocaloric effect and critical behaviour near the magnetic phase transition temperature, of a ferrimagnetic spinel Cu1.5Mn1.5O4.

scholarly journals Modulating the phase transition temperature of giant magnetocaloric thin films by ion irradiation

2017 ◽  
Vol 1 (6) ◽  
Author(s):  
S. Cervera ◽  
M. Trassinelli ◽  
M. Marangolo ◽  
C. Carrétéro ◽  
V. Garcia ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Ion Irradiation
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