Modifications of EHPDB Physical Properties through Doping with Fe2O3 Nanoparticles (Part II)

The aim of our study was to analyze the influence of various concentrations of γ-Fe2O3 nanoparticles on the physical properties of the liquid crystalline ferroelectric SmC* phase, as well as to check the effect of introducing nanoparticles in the LC matrix on their properties in the prepared five nanocomposites. UV-vis spectroscopy showed that the admixture reduced the absorption of nanocomposites in the UV range, additional absorption bands appeared, and all nanocomposites were transparent in the range of 500–850 nm. The molecular dynamics in particular phases of the nanocomposites were investigated by the dielectric spectroscopy method, and it was found that nanoparticles caused a significant increase in the dielectric constant at low frequencies, a strong modification of the dielectric processes in the SmC* phase, and the emergence of new relaxation processes for the highest dopant concentrations. SQUID magnetometry allowed us to determine the magnetic nature of the nanoparticles used, and to show that the blocked state of nanoparticles was preserved in nanocomposites (hysteresis loops were also registered in the ferroelectric SmC* phase). The dependence of the coercive field on the admixture concentration and the widening of the hysteresis loop in nanocomposites in relation to pure nanoparticles were also found. In turn, the FT-MIR spectroscopy method was used to check the influence of the impurity concentration on the formation/disappearance or modification of the absorption bands, and the modification of both the FWHM and the maximum positions for the four selected vibrations in the MIR range, as well as the discontinuous behavior of these parameters at the phase transitions, were found.

Download Full-text

Investigation of Dielectric Properties, Electric Modulus and Conductivity of the Au/Zn-Doped PVA/n-4H-SiC (MPS) Structure Using Impedance Spectroscopy Method

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2017-1091 ◽

2020 ◽

Vol 234 (3) ◽

pp. 505-516 ◽

Cited By ~ 1

Author(s):

Havva Elif Lapa ◽

Ali Kökce ◽

Ahmet Faruk Özdemir ◽

Şemsettin Altındal

Keyword(s):

Impedance Spectroscopy ◽

Electric Modulus ◽

Forward Bias ◽

Spectroscopy Method ◽

Complex Dielectric Constant ◽

Relaxation Processes ◽

Low Frequencies ◽

High Frequencies ◽

The Real ◽

Wide Range

AbstractThe 50 nm thickness Zn-doped polyvinyl alcohol (PVA) was deposited on n-4H-SiC semiconductor as interlayer by electro-spinning method and so Au/Zn-doped PVA/n-4H-SiC metal-polymer-semiconductor (MPS) structure were fabricated. The real and imaginary parts of the complex dielectric constant (ε′, ε′′), loss-tangent (tan δ), the real and imaginary parts of the complex electric modulus (M′, M′′) and ac electrical conductivity (σac) behavior of this structure were examined using impedance spectroscopy method in a wide range of frequency (1 kHz–400 kHz) and voltage (−1 V)–(+6 V) at room temperature. The values of ε′, ε′′, tan δ, M′, M′′ and σac are determined sensitive to the frequency and voltage in depletion and accumulation regions. The values of ε′ and ε′′ decrease with increasing frequency while the values of M′ and σac increase. The peak behavior in the tan δ and M′′ vs. frequency curves was attributed to the dielectric relaxation processes and surface states (Nss). The plots of ln (σac) vs. ln (f) at enough high forward bias voltage (+6 V) have three linear regions with different slopes which correspond to low, intermediate and high frequencies, respectively. The dc conductivity is effective at low frequencies whereas the ac conductivity effective at high frequencies. According to experimental results, the surface/dipole polarizations can occur more easily occur at low frequencies and the majority of Nss between Zn-doped PVA and n-4H-SiC contributes to the deviation of dielectric behavior of this structure.

Download Full-text

Influence of Calcination Temperature on Crystal Growth and Optical Characteristics of Eu3+ Doped ZnO/Zn2SiO4 Composites Fabricated via Simple Thermal Treatment Method

Crystals ◽

10.3390/cryst11020115 ◽

2021 ◽

Vol 11 (2) ◽

pp. 115

Author(s):

Suhail Huzaifa Jaafar ◽

Mohd Hafiz Mohd Zaid ◽

Khamirul Amin Matori ◽

Sidek Hj. Ab Aziz ◽

Halimah Mohamed Kamari ◽

...

Keyword(s):

Thermal Treatment ◽

Band Gap ◽

Calcination Temperature ◽

Emission Intensity ◽

Emission Spectra ◽

Treatment Method ◽

Absorption Bands ◽

Vis Spectroscopy ◽

Doped Zno ◽

Zno Crystal

This research paper proposes the usage of a simple thermal treatment method to synthesis the pure and Eu3+ doped ZnO/Zn2SiO4 based composites which undergo calcination process at different temperatures. The effect of calcination temperatures on the structural, morphological, and optical properties of ZnO/Zn2SiO4 based composites have been studied. The XRD analysis shows the existence of two major phases which are ZnO and Zn2SiO4 crystals and supported by the finding in the FT-IR. The FESEM micrograph further confirms the existence of both ZnO and Zn2SiO4 crystal phases, with progress in the calcination temperature around 700–800 °C which affects the existence of the necking-like shape particle. Absorption humps discovered through UV-Vis spectroscopy revealed that at the higher calcination temperature effects for higher absorption intensity while absorption bands can be seen at below 400 nm with dropping of absorption bands at 370–375 nm. Two types of band gap can be seen from the energy band gap analysis which occurs from ZnO crystal and Zn2SiO4 crystal progress. It is also discovered that for Eu3+ doped ZnO/Zn2SiO4 composites, the Zn2SiO4 crystal (5.11–4.71 eV) has a higher band gap compared to the ZnO crystal (3.271–4.07 eV). While, for the photoluminescence study, excited at 400 nm, the emission spectra of Eu3+ doped ZnO/Zn2SiO4 revealed higher emission intensity compared to pure ZnO/Zn2SiO4 with higher calcination temperature exhibit higher emission intensity at 615 nm with 700 °C being the optimum temperature. The emission spectra also show that the calcination temperature contributed to enhancing the emission intensity.

Download Full-text

Synthesis and characterization of liquid crystalline epoxy resins to study the effect of mesogenic length on the physical properties

Journal of Polymer Research ◽

10.1007/s10965-020-02370-4 ◽

2021 ◽

Vol 28 (2) ◽

Author(s):

Yi-Sheng Lin ◽

Steve Lien-Chung Hsu ◽

Tsung-Han Ho ◽

Li-Cheng Jheng ◽

Yu-Hsiang Hsiao

Keyword(s):

Physical Properties ◽

Epoxy Resins ◽

Liquid Crystalline ◽

Synthesis And Characterization ◽

Liquid Crystalline Epoxy

Download Full-text

Synthesis and Properties of Biodegradable Liquid Crystalline Poly(ester-Urethane)s Based on Poly(L-Lactic Acid)

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.459 ◽

2013 ◽

Vol 652-654 ◽

pp. 459-462

Author(s):

Ya Tong Guo ◽

Zhu Zheng ◽

Zhen Qi Hou ◽

Jie Du

Keyword(s):

Phase Transition ◽

Thermal Stability ◽

Lactic Acid ◽

Physical Properties ◽

Liquid Crystalline ◽

Degradation Rate ◽

Hydrolytic Degradation ◽

Hexamethylene Diisocyanate ◽

Solution Polymerization ◽

Phase Transition Temperatures

A series of biodegradable segmented liquid crystalline poly(ester-urethane)s were prepared by solution polymerization of poly(L-lactic acid) (PLLA), mesogenic diol prepolymer poly(butylene terephthaloyldioxy dibenzoates) (MD), and hexamethylene diisocyanate (HDI). The MD content was varied from 0 to 40 mol% so that the effects of the mesogen content on the thermal and physical properties, and hydrolytic degradation were examined respectively. It was found that introducing mesogens units could increase the thermal stability and the elastic properties, while reduced the phase transition temperatures and the hydrolytic degradation rate.

Download Full-text

Comparison of the Dielectric Properties of Ecoflex® with L,D-Poly(Lactic Acid) or Polycaprolactone in the Presence of SWCN or 5CB

Materials ◽

10.3390/ma14071719 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1719

Author(s):

Patryk Fryń ◽

Sebastian Lalik ◽

Natalia Górska ◽

Agnieszka Iwan ◽

Monika Marzec

Keyword(s):

Oleic Acid ◽

Dielectric Properties ◽

Polymer Matrix ◽

Liquid Crystalline ◽

Weight Ratio ◽

Poly Lactic Acid ◽

Relaxation Processes ◽

The Matrix ◽

Walled Carbon Nanotubes ◽

Hybrid Layers

The main goal of this paper was to study the dielectric properties of hybrid binary and ternary composites based on biodegradable polymer Ecoflex®, single walled carbon nanotubes (SWCN), and liquid crystalline 4′-pentyl-4-biphenylcarbonitrile (5CB) compound. The obtained results were compared with other created analogically to Ecoflex®, hybrid layers based on biodegradable polymers such as L,D-polylactide (L,D-PLA) and polycaprolactone (PCL). Frequency domain dielectric spectroscopy (FDDS) results were analyzed taking into consideration the amount of SWCN, frequency, and temperature. For pure Ecoflex®, two relaxation processes (α and β) were identified. It was shown that the SWCN admixture (in the weight ratio 10:0.01) did not change the properties of the Ecoflex® layer, while in the case of PCL and L,D-PLA, the layers became conductive. The dielectric constant increased with an increase in the content of SWCN in the Ecoflex® matrix and the conductive behavior was not visible, even for the greatest concentration (10:0.06 weight ratio). In the case of the Ecoflex® polymer matrix, the conduction relaxation process at a frequency ca. several kilohertz appeared and became stronger with an increase in the SWCN admixture in the matrix. Addition of oleic acid to the polymer matrix had a smaller effect on the increase in the dielectric response than the addition of liquid crystal 5CB. Fourier transform infrared (FTIR) results revealed that the molecular structure and chemical character of the Ecoflex® and PCL matrixes remained unchanged upon the addition of SWCN or 5CB in a weight ratio of 10:0.01 and 10:1, respectively, while molecular interactions appeared between L,D-PLA and 5CB. Moreover, adding oleic acid to pure Ecoflex® as well as the binary and ternary hybrid layers with SWCN and/or 5CB in a weight ratio of Ecoflex®:oleic acid equal to 10:0.3 did not have an influence on the chemical bonding of these materials.

Download Full-text

Controlling the Kinetics of an Enzymatic Reaction through Enzyme or Substrate Confinement into Lipid Mesophases with Tunable Structural Parameters

International Journal of Molecular Sciences ◽

10.3390/ijms21145116 ◽

2020 ◽

Vol 21 (14) ◽

pp. 5116

Author(s):

Marco Mendozza ◽

Arianna Balestri ◽

Costanza Montis ◽

Debora Berti

Keyword(s):

Reaction Kinetics ◽

Self Assembly ◽

Liquid Crystalline ◽

Structural Parameters ◽

Enzymatic Reaction ◽

X Ray Scattering ◽

Nitrophenyl Phosphate ◽

Vis Spectroscopy ◽

Kinetics Of ◽

Enzyme Alkaline Phosphatase

Lipid liquid crystalline mesophases, resulting from the self-assembly of polymorphic lipids in water, have been widely explored as biocompatible drug delivery systems. In this respect, non-lamellar structures are particularly attractive: they are characterized by complex 3D architectures, with the coexistence of hydrophobic and hydrophilic regions that can conveniently host drugs of different polarities. The fine tunability of the structural parameters is nontrivial, but of paramount relevance, in order to control the diffusive properties of encapsulated active principles and, ultimately, their pharmacokinetics and release. In this work, we investigate the reaction kinetics of p-nitrophenyl phosphate conversion into p-nitrophenol, catalysed by the enzyme Alkaline Phosphatase, upon alternative confinement of the substrate and of the enzyme into liquid crystalline mesophases of phytantriol/H2O containing variable amounts of an additive, sucrose stearate, able to swell the mesophase. A structural investigation through Small-Angle X-ray Scattering, revealed the possibility to finely control the structure/size of the mesophases with the amount of the included additive. A UV–vis spectroscopy study highlighted that the enzymatic reaction kinetics could be controlled by tuning the structural parameters of the mesophase, opening new perspectives for the exploitation of non-lamellar mesophases for confinement and controlled release of therapeutics.

Download Full-text