Self-assembled amphiphilic polyhedral oligosilsesquioxane (POSS) grafted poly(vinyl alcohol) (PVA) nanoparticles

Sheikh, F.A.,Barakat, N.A.M.,Kim, B.S.,Aryal, S.,Khil, M.S.,Kim, H.Y. Elsevier 2009 Materials Science and Engineering C Vol.29 No.3

In the present study, spherical nanoparticles (NPs) containing polyhedral oligosilsesquioxane (POSS) as an inner hydrophobic core and poly(vinyl alcohol) PVA as a hydrophilic outer shell were prepared by dialysis approach. Preparation of amphiphilic POSS-grafted-PVA co-polymer was characterized by <SUP>1</SUP>H NMR and FT-IR. The results indicated urethane linkage between monoisocyanate group of POSS macromer and the hydroxyl groups of PVA. The dynamic light scattering (DLS) and electrophoretic light scattering (ELS) of the NPs revealed that they have an average hydrodynamic diameter and negative zeta (ζ)-potential of 215 nm and -161 mV, respectively. Atomic force microscopy (AFM) and bio-transmission electron microscope (BIO-TEM) have shown unagglomerated NPs within a diameter range of 60-90 nm. The prepared NPs were investigated to improve the control release of anticancer drug; paclitaxel as a model drug. Due to drug loading, the hydrodynamic diameter and negative zeta (ζ)-potential have changed to 325 nm and -14 mV, respectively. In addition, in-vitro drug release experiments were conducted; the obtained results explicated continuous release for over 40 days. However, in case of using pure drug only, the drug completely released within 1 h.

A compressible finite element model for hyperelastic members under different modes of deformation

Manna, M.C.,Sheikh, A.H.,Bhattacharyya, R. Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.2

The performance of a three dimensional non-linear finite element model for hyperelastic material considering the effect of compressibility is studied by analyzing rubber blocks under different modes of deformation. It includes simple tension, pure shear, simple shear, pure bending and a mixed mode combining compression, shear and bending. The compressibility of the hyperelastic material is represented in the strain energy function. The nonlinear formulation is based on updated Lagrangian (UL) technique. The displacement model is implemented with a twenty node brick element having u, ${\nu}$ and w as the degrees of freedom at each node. The results obtained by the present numerical model are compared with the analytical solutions available for the basic modes of deformation where the agreement between the results is found to be satisfactory. In this context some new results are generated for future references since the number of available results on the present problem is not sufficient enough.

A super hydrophilic modification of poly(vinylidene fluoride) (PVDF) nanofibers: By in situ hydrothermal approach

Sheikh, Faheem A.,Zargar, Mohammad Afzal,Tamboli, Ashif H.,Kim, Hern Elsevier 2016 APPLIED SURFACE SCIENCE - Vol.385 No.-

<P><B>Abstract</B></P> <P>Nanofibers fabricated from Poly(vinylidene fluoride) (PVDF) possesses potential applications in the field of filtrations, because of their excellent resistance towards harsh chemicals. However, the hydrophobicity restricts its further application. In this work, we focus on optimal parameters for post-electrospun tethering of Poly(vinyl alcohol) (PVA) as superhydrophilic domain onto each individual PVDF nanofibers by exploiting the in situ hydrothermal approach. The results indicated an increase in nanofiber diameters due to coating of PVA and improved surface wettability of PVDF nanofibers. The tensile tests of nanofibers indicated that mechanical properties of PVDF nanofibers could be sharply tuned from rigid to ductile. Furthermore, the studies strongly suggest that in situ hydrothermal treatment of post-electrospun nanofibers can improve the water contact angle and these nanofibers can be used in varied applications (e.g., in water purification systems).</P> <P><B>Highlights</B></P> <P> <UL> <LI> PVA coated PVDF nanofibers can be easily prepared by hydrothermal treatment. </LI> <LI> The inherent hydrophobicity of PVDF nanofibers can be changed to hydrophilic. </LI> <LI> The hydrogen bonding interaction can induce the crystalline conformation of PVDF. </LI> <LI> Resultant nanofibers have significant improvement in the tensile strength. </LI> <LI> Prepared membranes promise to aid in filtration due to involvement of PVA coating. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Glycerol functionalized imidazolium tri-cationic room temperature ionic liquids: Synthesis, properties and catalytic performance for 2-azidoalcohol synthesis from epoxide

Chaugule, A.A.,Tamboli, A.H.,Sheikh, F.A.,Chung, W.J.,Kim, H. Elsevier 2015 Journal of molecular liquids Vol.208 No.-

Imidazolium based tri-cationic room temperature ionic liquid (RTILs) were synthesized and characterized, and their physicochemical properties such as thermal stability, viscosities and solubility were investigated. These ionic liquids exhibited excellent catalytic activity for 2-azidoalcohol synthesis from epoxide and sodium azide. The present tri-cationic RTILs/water catalytic systems showed better catalytic performance than their mono-cationic counterparts. Among all prepared ionic liquids, [GLY(mim)<SUB>3</SUB>][OMs] gave best results with up to 96% yield of 2-azidoalcohol. The reusability test of glycerol-tri (3-methylimidazolium) trimesylate [GLY(mim)<SUB>3</SUB>][OMs]<SUB>3</SUB> were studied for five consecutive cycles presenting the highest yield without loss in their catalytic activity. Hence, the experimental results demonstrated that structural variation of synthesized tri-cationic RTILs can dictate their physicochemical and catalytic activities.

Static analysis of rubber components with piezoelectric patches using nonlinear finite element

M. C. Manna,A. H. Sheikh,R. Bhattacharyya 국제구조공학회 2009 Smart Structures and Systems, An International Jou Vol.5 No.1

In order to reduce vibration or to control shape of structures made of metal or composites, piezoelectric materials have been extensively used since their discovery in 1880’s. A recent trend is also seen to apply piezoelectric materials to flexible structures made of rubber-like materials. In this paper a non-linear finite element model using updated Lagrangian (UL) approach has been developed for static analysis of rubber-elastic material with surface-bonded piezoelectric patches. A compressible stain energy function has been used for modeling the rubber as hyperelastic material. For formulation of the nonlinear finite element model a twenty-node brick element is used. Four degrees of freedom u, v and w and electrical potential ϕ per node are considered as the field variables. PVDF (polyvinylidene fluoride) patches are applied as sensors/actuators or sensors and actuators. The present model has been applied to bimorph PVDF cantilever beam to validate the formulation. It is then applied to study the smart rubber components under different boundary and loading conditions. The results predicted by the present formulation are compared with the analytical solutions as well as the available published results. Some results are given as new ones as no published solutions available in the literatures to the best of the authors’ knowledge.

Static analysis of rubber components with piezoelectric patches using nonlinear finite element

Manna, M.C.,Sheikh, A.H.,Bhattacharyya, R. Techno-Press 2009 Smart Structures and Systems, An International Jou Vol.5 No.1

In order to reduce vibration or to control shape of structures made of metal or composites, piezoelectric materials have been extensively used since their discovery in 1880's. A recent trend is also seen to apply piezoelectric materials to flexible structures made of rubber-like materials. In this paper a non-linear finite element model using updated Lagrangian (UL) approach has been developed for static analysis of rubber-elastic material with surface-bonded piezoelectric patches. A compressible stain energy function has been used for modeling the rubber as hyperelastic material. For formulation of the nonlinear finite element model a twenty-node brick element is used. Four degrees of freedom u, v and w and electrical potential ${\varphi}$ per node are considered as the field variables. PVDF (polyvinylidene fluoride) patches are applied as sensors/actuators or sensors and actuators. The present model has been applied to bimorph PVDF cantilever beam to validate the formulation. It is then applied to study the smart rubber components under different boundary and loading conditions. The results predicted by the present formulation are compared with the analytical solutions as well as the available published results. Some results are given as new ones as no published solutions available in the literatures to the best of the authors' knowledge.

Buckling and vibration analysis of stiffened plate subjected to in-plane concentrated load

Srivastava, A.K.L.,Datta, P.K.,Sheikh, A.H. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.15 No.6

The buckling and vibration characteristics of stiffened plates subjected to in-plane concentrated edge loading are studied using finite element method. The problem involves the effects of non-uniform stress distribution over the plate. Buckling loads and vibration frequencies are determined for different plate aspect ratios, boundary edge conditions and load positions. The non-uniform stresses may also be caused due to the supports on the edges. The analysis presented determines the initial stresses all over the region considering the pre-buckling stress state for different kinds of loading and edge conditions. In the structural modeling, the plate and the stiffeners are treated as separate elements where the compatibility between these two types of elements is maintained. The vibration characteristics are discussed and the results are compared with those available in the literature and some interesting new results are obtained.

Treatment of industrial wastewater containing copper and cobalt ions using modified chitosan

Nabel A. Negma,Ragaa El Sheikh,Ahmed. F. El-Farargy,Hassan H.H. Hefni,Mahmoud Bekhit 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Chitosan was extracted and characterized using several analyses. The produced chitosan was reacted byglycine and chloroacetic acid. Chemical structures of biosorbents were confirmed. Adsorptionefficiencies of the two biosorbents in neutral and alkaline medium at 25 8C were determined usingatomic absorption spectroscopic analysis. Adsorption capacity ofmodified biosorbents toward Cu(II) andCo(II) ions was determined and compared to virgin chitosan. The biosorbents showed lower adsorptionefficiency toward copper and cobalt ions compared to virgin biosorbent. Furthermore, adsorptioncapacity of glycine–chitosan was higher than chloroacetic acid–chitosan biosorbents, which attributedto chelating of amino groups than chloro-substituted polymer. Thermodynamic studies showed thespontaneous behavior of the adsorption process of metal ions under the studied conditions. Entropychanges indicate that the adsorption of the metal ions are endothermic process, and lower values of DS8indicate the affinity toward metal ions by the biosorbents at different degrees depending on theirchemical structures.

Oscillation and nonoscillation of nonlinear second order difference equations}

M. M. A. EL-Sheikh,M. H. Abd Alla,E. M. EL-Maghrabi 한국전산응용수학회 2006 Journal of applied mathematics & informatics Vol.21 No.1-2

Buckling and vibration analysis of stiffened plate subjected to in - plane concentrated load

P.K.Datta,A.K.L.Srivastava,A.H.Sheikh 국제구조공학회 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.15 No.6