Open Access Opinion Article

Properties of Materials and their Molecular Bases. New Approaches towards Understanding Liquid Crystals and Polymers

Sosale Chandrasekhar

Journal of Materials Science Research and Reviews, Page 31-46

The fundamental bases of liquid crystals and polymers–both widely employed in, and critically important to, modern society–apparently remain poorly understood. Hence, the need to explore alternative explanations to current paradigms.

Thus, liquid crystals are viewed as partially molten solids that retain a semblance of the order of their crystalline precursors. However, this seems unviable as the long-range order in the resulting mesophase cannot survive at temperatures higher than the melting point of the crystal itself.

In polymers, the non-covalent intermolecular forces are believed to be additively amplified along the length of the macromolecule. However, this ignores the fact that the said forces remain minuscule at the sub-unit level, so a collection of macromolecules would be continually associating and dissociating at each contact point. It is doubtful that this can explain the observed mechanical strength of polymers (leading to the “polythene enigma”). 

It is argued herein that liquid crystals arise via the entanglement of long chains and U-shaped moieties in the incipient crystalline melt, a process essentially facilitated by proximity effects in the crystal. Thus, the entanglements are not easily reversed once the proximity effects are lost in the mesophase, which is likely a nanoparticle aggregate possibly composed of quasi-rotaxane and quasi-catenane species. Furthermore, liquid crystals–even those derived from achiral molecules–display optical activity, which is critical to their application in display devices. Although this symmetry breaking remains enigmatic, a chiral mechanochemical effect or even parity violation are possible explanations.

In the case of macromolecular association, it is argued that the van der Waals force is inherently strong in enthalpy terms, but is stymied by entropic effects which dominate in the weak forces (generally). However, the entropic effects are possibly “damped” in the macromolecule (although in a subtle manner), so association is much greater than currently estimated. These lead to interesting theoretical insights into enthalpy-entropy relationships in atomic and molecular interactions, a sigmoid relationship possibly being indicated.

Open Access Original Research Article

Experimental Determination of the Thermal Conductivity of New Compressed Clay Formulations Stabilized with Gum Arabic, Measurement and Impact on Summer Comfort

Jean Louis Tanguier, Abakar Ali, Abdallah Dadi Mahamat, André Donnot, Jean Michel Drouet

Journal of Materials Science Research and Reviews, Page 1-14

Our work expressed that compressed and stabilized clay with arabic gum is a suitable building material in regards to the mechanical properties. This paper presents an experimental study of the determination of thermal conductivity in a steady state cylindrical geometry configuration  approach. 

The results obtained give a thermal conductivity in the order of 1 W.m-1. K-1, quite similar to other building materials. On the other hand, because of its inertia, the material dampens the temperature variations between the inside and the outside.

Open Access Original Research Article

Optimising Medicinal Plants Values Grown in Nigeria for Prevention, Controlling and Treatment of Infectious Diseases, Determinant Factors of Infant Mortality Using Mathematical Modelling Protégé

Oludare Temitope. Osuntokun, Adeyemi O. Binuyo

Journal of Materials Science Research and Reviews, Page 15-30

Infant mortality is a challenge for third-world countries like Nigeria where there is little next to non-availability of conventional drugs, and if available, it is costly and out of the reach of the common populace. It is a fact that medicinal plant is a gift from Mother Nature, but its uses and efficacy have been overlooked over the century because of the over super-imposed of conventional drugs but its medicinal plants efficacy is still intact. The objectives of this work are to optimise medicinal plants values being grown in Nigeria, West Africa, in the prevention, control and treatment of infectious diseases which is a determinant factors of infant mortality using mathematical model protégés. the research/review scientific point of view. The x-rays features of this paper is to formulate and analyse a mathematical model that extends and complements the ones in the literatures by incorporating medicinal plant class denoted by M(t). Mathematical models are widely used to examine, explain and predict the dynamics of infectious diseases transmission. Models have played important roles in developing public health strategies for control and prevention of infectious diseases. The mathematical model is a system of first-order non-linear ordinary differential equations which are partitioned into five different compartments. Two equilibria states exist, the disease-free equilibrium and endemic equilibrium which are locally asymptotically stable if the basic reproductive number is less than one and unstable if the basic reproductive number is greater than one. Numerical simulations were performed using hypothetical values for the parameters used in the model. The model shows that an increase in the medicinal plants grown or found in the country leads to low disease prevalence among the susceptible infant population considered in this work. Therefore, our medicinal plants become a very alternative for the prevention, control, and treatment of infectious diseases to reduce or prevent infant mortality among infants, especially in rural areas. Also, this will elevate the knowledge from African trado-medical practice and rejuvenate our ethno-botanical properties and characteristics for future uses.

Open Access Original Research Article

The Stress Field of a Rectangular Dislocation Loop in an Infinite Medium: Analytical Solution with Verification

Luo Li, Tariq A. Khraishi

Journal of Materials Science Research and Reviews, Page 47-59

The stress field of a rectangular dislocation loop in an isotropic solid, which is in an infinite medium, is obtained here for a Volterra-type dislocation which has three non-zero Burgers vector components. Explicitly, the stress field of the dislocation loop in an infinite isotropic material is developed by integrating the Peach-Koehler equation over a finite rectangular dislocation loop. In this work, analytical/numerical verification of the stress field is demonstrated. To be specific, the verification is carried out to ensure that both the Equilibrium Equations and the Strain Compatibility Equations are satisfied. Moreover, a comparison with the stress field of a rectangular loop summed as four dislocation segments, using the DeVincre formula, is performed. Due to analytical verification, no error was detected in the presented solution. Also, comparing with the DeVincre formula presented identical results, qualitatively and quantitatively.

Open Access Original Research Article

Simulation and Performance of Natural Sensitizer Dye from Lagerstroemia speciosa Flowers and Leaves

C. O. Ogabi, B. A. Idowu, A. O. Boyo, S. O. Oseni, R. O. Kesinro

Journal of Materials Science Research and Reviews, Page 60-65

Dye-Sensitized Solar Cells (DSSCs) are solar cell devices that work using electrochemical principles in which sensitive dyes are absorbed in the titanium dioxide (TiO2) photo-electrode layer. One of the key components of dye sensitized solar cells for developing high performance devices is the dye, which acts as the photosensitizer. However, using natural dyes from plant sources has produced low power conversion efficiency (PCE) compared to organic synthetic dyes. In this study, the performance of locally extracted dye from Lagerstroemia speciosa leaves and flowers has been determined by simulation using MATLAB based on TiO2 by modifying the internal parameters such as the absorption coefficient and diffusion coefficient, external, and previous DSSC research data. The simulation produced a high-power conversion efficiency and current density of 1.82% and 14.32 mA/cm-2 respectively. The results obtained from the simulation shows that this plant can be used as photosensitizers in DSSCs in the future.