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Mohammed  A Sharaf

Mohammed A Sharaf
Istanbul University-Cerrahpasa · Faculty of Enginering

Ph.D.

About

33
Publications
11,050
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477
Citations
Citations since 2017
0 Research Items
74 Citations
201720182019202020212022202305101520
201720182019202020212022202305101520
201720182019202020212022202305101520
201720182019202020212022202305101520
Introduction
Nanocatalysis for Environmental Remediation, Nanocomposites, Biomaterials and Tissue Engineering, Mechanical properties of Polymers, Laser Interaction with polymers.

Publications

Publications (33)
Article
Full-text available
Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs as compared with liquid formulations. However, the respirable particles must have a diameter of 1–5 μm in order to deposit in the lungs. Controlled agglomeration of the nanoparticles increases their geometric particle size so they can deposit easily in the lungs.
Data
Full-text available
Hard implants undergo detachment from the host tissues due to inadequate biocompatibility, poor adhesion and subsequent cell integration. Thereby, surface engineering seems to offer solutions for improved functionality and biocompatibility of material implants inside the biological environment. Polycaprolactone (PCL) thin film has been fabricated v...
Article
Full-text available
Morphology and mechanical properties of scaffolds seeded with osteoblastes cells used for bone and cartilage repair are the critical factors in bone tissue engineering. In this work, adding CMC and controlling temperature for nano-hydroxyapatite (HA)-b-tricalcium phosphate (b-TCP) scaffold using Polymeric sponge method provide suitable properties....
Article
Full-text available
Tissue engineering is a new field that made rapid advances. Tissue engineering eliminates re-operations by using biological substitutes that allow native cells to grow. Scaffolds and its properties play important role for success of this technique. Porous calcium phosphate ceramics (mainly hydroxyapatite (HA) and tricalcium phosphate (TCP)) with in...
Article
Full-text available
Porous scaffolds are promising materials for tissue engineering. It offers a temporary carrier for cells and is considered the key for success of this strategy. Pore size, porosity and interconnection between pores are important factors. Interconnected pores permit tissue and bone ingrowths. Characteristics of porous structure are essential to dete...
Article
Full-text available
The diameter of silica nanoparticles is affected by the relative contribution from nucleation and growth processes. Therefore, it is affected b y T E O S and NH 3 concentrations. Herein, we have studied the effect of TEOS and NH 3 concentrations on particle size of silica nanoparticles. The size of silica particles increases with increasing TEOS an...
Article
Two new chelating polymeric hydrogels, crosslinked polyacrylamide/triethylenetetraamine/CS(2)Na (hydrogel I) and crosslinked polyacrylamide/diethylenetriamine/CS(2)Na (hydrogel II), were prepared by the transamidation and dithiocarbamylation of crosslinked polyacrylamide. The products were characterized with elemental analysis and IR spectroscopy....
Article
Positron annihilation lifetime spectroscopy (PALS) has been employed to measure the variation of free volume hole parameters in poly(carbonate) (PC) after plastic deformation below the glass transition temperature (T<sub align="right">g</sub>). Changes in nano-scale free volume holes (V<sub align="right">h</sub>) and in their fraction (%f<sub align...
Conference Paper
Natural polymers continue to provide effective biocompatible scaffolds for use in tissue engineering applications. In some respects, their chemical structure closely mimics that of the extracelluar matrix of biological tissues. Eventhough a wide variety of biopolymers can be used for these applications, no single polymer has been yet found to fulfi...
Conference Paper
Full-text available
The modification of cross-linked polyacrylamide (CPAAm) and incorporation of methyl thiourea (MeTU) or phenyl thiourea (PhTU) group were utilized in the preparation of two new chelating resins CPAAm-EDA-MeTU (resin I) and CPAAM-EDA-PhTU (resin II), [EDA=ethylenediamine]. The prepared resins were characterized by elemental analysis and IR spectrosco...
Article
A cationic ring‐opening polymerization was used to prepare hydroxyl‐terminated polytetrahydrofuran (PTHF) [–(CH2)4O–] having a number‐average molecular weight of 20,700 g mol, and a relatively narrow molecular weight distribution. Elastomeric tetrafunctional networks were prepared by hydrolysis–condensation reactions on this polymer and on two othe...
Article
Preoriented poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (Nodax™) films were obtained via the drawing of films to prestretching ratios ranging from 200 to 1000%. As expected, preorientation resulted in substantial improvements in the mechanical properties of the films from the corresponding increases in the amount and nature of the crystallinity p...
Article
Gamma radiation and high-energy electrons were used to crosslink two types of polybutadiene (PBD), the first having random cis-trans-vinyl contents and the second consisting primarily of blocks of cis units and blocks of trans. The resulting elastomers were studied in elongation in the unswollen stale, generally at 5°C, and in swelling equilibrium...
Article
Poly(methyl methacrylate) (PMMA) networks having different degrees of cross linking have been synthesized. The networks thus prepared were characterized by swelling and stress-strain measurements. Molecular orientation of the polymer chains (long chains) and the cross linker (short chains) has been investigated by Fourier-transform infrared (FTIR)...
Article
Although the filler particles typically used to reinforce elastomers are at least approximately spherical, prolate (needle-shaped) or oblate (disc-shaped) particles have been used in some cases. The fact that anisotropic structures and properties can be obtained in these cases has encouraged a number of experimental and theoretical investigations....
Article
Particulate fillers used to reinforce polymers need not be spherical; some experiments have in fact been carried out on prolate ellipsoidal particles. These experimental results encouraged Monte Carlo simulations on prolate particles in amorphous polyethylene described in the present report. The particles were placed on a cubic lattice, and were or...
Article
Monte Carlo computer simulations were carried out on filled networks of poly(dimethylsiloxane) (PDMS), which were modeled as composites of crosslinked chains and randomly arranged spherical filler particles. The primary concern of the investigation was the effect of the excluded volume of these particles on the elastomeric properties of the polymer...
Article
Full-text available
This investigation focused on the study of dynamic mechanical losses in silica-filled networks of poly(dimethylsiloxane) (PDMS). Some of the samples were filled using a novel method, specifically the in situ precipitation of particulate silica either after or during network formation. Others were filled using the customary method of mechanically bl...
Article
Several groups have now prepared poly(dimethylsiloxane) networks of high cross-link functionality by end-linking vinyl-terminated chains by means of SiH groups in siloxane oligomers (CH3)3SiO[SiHCH3O]xSi(CH3)3. The elongation moduli of these networks were generally found to be considerably larger than the values predicted from the functionality and...
Article
Small-strain moduli reported in the literature for polydimethylsiloxane (PDMS) model networks have been critically re-examined, with account being taken of recent studies which have demonstrated the occurrence of significant side reactions in hydrosilylations. When the effects of such side reactions on network structure parameters are properly take...
Article
Monte Carlo computer simulations have been carried out on filled networks of (amorphous) polyethylene and poly(dimethylsiloxane) using a method based on the authors' general theoretical approach for filled elastomeric materials [Kloczkowski , Comput. Polym. Sci.3 (1993) 39–45]. This approach enables estimation of the effect of the excluded volume o...
Article
This study reanalyzes some elastomeric properties in elongation reported for poly(dimethylsiloxane) (PDMS) networks of high cross-link functionality which had been prepared by using multifunctional siloxane oligomers to end link vinyl-terminated PDMS chains. The extent of reaction of the vinyl end groupsPvi spanned the range of 0.40 to 0.95. These...
Article
The ultimate properties of stereoregular and stereoirregular 1,4-polybutadiene (PB) networks covering a range in micro-chemical structure (cis-trans-vinyl) have been investigated The dependence of the ultimate PrOperties, namely the ultimate strength and the maximum extensibility, on sterochemical structure, has been demonstrated at different tempe...
Article
Poly(dimethylsiloxane) networks of high crosslink functionality have been prepared by endlinking polydisperse vinyl-terminated chains with multifunctional oligomeric methylhydrosiloxane chains. The vinyl-terminated short-chain components covered a wide range in molecular masses, thus resulting in various polydisperse chain-length distributions. The...
Article
In several published studies, randomly crosslinked networks were prepared from poly(dimethylziloxane) by the selective crosslinking of vinyl side chains with a silicon-hydride crosslinking agent. Stress-strain measurements on these elastomers gave values of the elongation modulus in the limits of small and large deformations which exceeded those pr...
Article
There have now been a number of experimental studies on the preparation and elastomeric properties of random bimodal networks of polydimethylsiloxane. The mole per cent of the short chains and their molecular masses covered a wide range, thus resulting in various polydisperse chain-length distributions. The networks were studied with regard to thei...
Article
Regular bimodal tetrafunctional networks of polydimethylsiloxane have been synthesized. The regularity achieved pertains to the specification that each junction in the network be connected to a constant number ϕs of short chains and ϕ1 of long chains thus giving a value of the network functionality ϕo = ϕs + ϕ1. The short chains covered a wide rang...
Article
Poly(dimethylsiloxane) networks of high cross-link functionality have been prepared by end linking vinyl-terminated chains with multifunctional poly(methylhydrosiloxane) chains. They covered a wide range in the extent of reaction, Pvi, of the vinyl end groups. At small strains, these networks had elongation moduli that significantly exceeded the va...
Chapter
Full-text available
It has frequently been observed that some elastomeric networks show an abrupt increase in the nominal stress, and consequently the modulus [f*], at high elongations.1 Molecular interpretation of this upturn has generally been attributed to strain-induced crystallization.
Article
Silicone networks of high junction functionality can be prepared by end linking vinyl-terminating groups on α, ω-divinylpolydimethylsiloxane (α, ω-divinyl PDMS) with Si-H groups in the junction precursor molecule polymethylhydrosiloxane (PMHS). The present study deals with high-functionality networks formed so as to have low extents of reaction of...
Article
Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (98.5 mol percent) and from other samples having relatively high trans contents (72 to 80 mol percent). The cross-linking techniques employed were gamma irradiation, ultraviolet irradiation, and peroxide thermolysis. The resulting elastomers were studied...
Article
Elastomeric networks were prepared by end-linking vinyl-terminated polydimethylsiloxane (PDMS) chains having number-average molecular weights of 11.3 × 103 g mol−1. The tetra-functional end-linking agent, Si[OSi(CH3)2H]4, was used in varying amounts smaller than that corresponding to a stoichiometric balance between its active hydrogen atoms and th...
Article
This paper is concerned with the glass transition temperature T//g of an elastomer which is of great importance with regard to its utilization since at this temperature and below, the material can no longer exhibit rubberlike behavior. In the present study, networks were prepared from atactic poly(vinyl acetate) and poly(isobutyl methacrylate), bot...

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