Mustapha Raihane
Université Cadi Ayyad, Chemistry, Faculty Member
Poly(hydroxyurethanes) (PHUs) have been suggested as isocyanate-free, low-toxicity alternatives to polyurethanes (PUs). However, PHUs present low mechanical properties due to the presence of side reactions that limit the production of... more
Poly(hydroxyurethanes) (PHUs) have been suggested as isocyanate-free, low-toxicity alternatives to polyurethanes (PUs). However, PHUs present low mechanical properties due to the presence of side reactions that limit the production of high-molar mass polymers. Here, we present the synthesis under mild conditions and atmospheric pressure of bi-cyclic carbonate monomer for the production of PHU nanocomposites with good physical properties. The kinetics of the bi-cyclic carbonate synthesis and its complete conversion to urethane were followed by FTIR. The addition of functionalized boron nitrate (f-BN) with sucrose crystals improved the thermal degradation temperature as well as the glass transition by approximately 20 °C and 10 °C, respectively. The storage modulus of PHU films gradually increases with the concentration of f-BN in the composite.
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In this work, the electrical properties of green nanocomposites based on natural rubber (NR) had been explored. Nanocellulose was extracted from the rachis of date palm tree and used as nanofillers in two forms: nanofibrillated cellulose... more
In this work, the electrical properties of green nanocomposites based on natural rubber (NR) had been explored. Nanocellulose was extracted from the rachis of date palm tree and used as nanofillers in two forms: nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNCs). The resulting samples were characterized by dielectric spectroscopy in a board temperature range (20 °C–200 °C) and in the frequency range of 0.1 Hz to 1 MHz. The temperature and frequency dependencies of conductivity give evidence for ion transport mechanism via the occurred agreement of experimental results with the employed hopping model (Random Free-Energy Barrier model). Conductivity was found to increase highly for filled nanocomposite, especially at high CNC content. Favorable interactions between NFC and NR were evidenced and assumed to be partially responsible for the lower conductivity of NFC-filled nanocomposites. The NR–CNC green nanocomposite films had a high potential to be used for electrical a...
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Polystyrene (PS) is an important commercially polymer with good light transmittance. The favorable physical properties of PS coupled with ease of processing make it useful as optical device materials [1]. However, high losses in the... more
Polystyrene (PS) is an important commercially polymer with good light transmittance. The favorable physical properties of PS coupled with ease of processing make it useful as optical device materials [1]. However, high losses in the visible and near infrared region are dominated by the combinations of stretch and deformation vibrations of C-H bonds [2].When heavier atoms such as deuterium or fluorine replace the hydrogen atoms in C-H bond, the band vibration energy is decreased and thus the absorption band is minimized. Thus, fluorine containing polystyrene such as poly(2,3,4,5,6-pentafluorostyrene)and poly(4-trifluoromethyl 2,3,5,6-tetrafluorostyrene) were synthesized [3]. They are thermally stable and transparent, but their glass transition temperatures (Tg) were about 110 °C. However, some applications such as in automobile and airplane require optical polymers with higher Tg (>120 °C) [4]. Bomer and Hagemann [5] reported that when CF 3 group substituted on the ortho position ...
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Market for biodegradable polymers is growing every year. Polymer blends and composites of starch (plasticizer or granular) and aliphatic (for example Poly(-Caprolactone) PCL), are of great interest as new biodegradable polymer materials.... more
Market for biodegradable polymers is growing every year. Polymer blends and composites of starch (plasticizer or granular) and aliphatic (for example Poly(-Caprolactone) PCL), are of great interest as new biodegradable polymer materials. However, conventional melt-processing usually provides starch-based composites with very poor mechanical properties, mainly due to thermal starch decomposition, strong water absorption and poor interfacial adhesion. In order to overcome these drawbacks, physical (hydrophobic coating, cross-linking, addition of external plasticizers) and chemical (grafting reactions and substitution of the hydroxyl with functional group like esters, ethers, isocyanates, anhydride), we have performed modifications of starch. Range of strach-graft-poly(-caprolactone) was synthesized from industrial grade corn starch. Grafting was carried out in two different polymerization methods: (i) “Grafting from” using -CL monomer (ii) “Grafting onto” using end-reactive PCL pol...
Fluorinated polymers are very interesting materials because of their high thermal and chemical stability, dielectric behavior, and unique surface (oil and water repellency) and optical properties [1-4]. Within this class of polymers,... more
Fluorinated polymers are very interesting materials because of their high thermal and chemical stability, dielectric behavior, and unique surface (oil and water repellency) and optical properties [1-4]. Within this class of polymers, those in which the presence of fluorine atoms or side chain fluoroalkyl moieties is associated with that of other highly polar main chain substituents, such as the nitrile group, are of interest for the development of advanced materials for electrical [5] and coating [6] applications. Due to their strong electron withdrawing effect, these substituents can significantly affect the reactivity of the respective monomers, allowing obtaining more or less regularly alternating copolymer structures when copolymerized with more nucleophilic monomers. Furthermore, they generally induce a strong influence on the chemical (thermal, hydrolytic, photochemical) stability of the resulting polymers, and are capable of inducing large dipole moments that may result in un...
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... 17 Da Roz, AL, Carvalho, AJF, Gandini, A., Curvelo, AAS, The effect of plasticizers on thermoplastic starch compositions obtained by melt processing. Carbohydr. Polym. 2006, 63, 417 424. ... 37 Hussain, MA, Liebert, T., Heinze, T.,... more
... 17 Da Roz, AL, Carvalho, AJF, Gandini, A., Curvelo, AAS, The effect of plasticizers on thermoplastic starch compositions obtained by melt processing. Carbohydr. Polym. 2006, 63, 417 424. ... 37 Hussain, MA, Liebert, T., Heinze, T., Acylation of cellulose with N,N ...
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ABSTRACT Copolymerization of fluorine ring-substituted 2-phenyl-1,1-dicyanoethenes, RC 6 H 3 CH C(CN) 2 (R is 2,3-F,F, 2,4-F,F, 2,5-F,F, 2,6-F,F, and 4-CF 3) with 4-fluorostyrene were prepared in the presence of a radical initiator (ABCN)... more
ABSTRACT Copolymerization of fluorine ring-substituted 2-phenyl-1,1-dicyanoethenes, RC 6 H 3 CH C(CN) 2 (R is 2,3-F,F, 2,4-F,F, 2,5-F,F, 2,6-F,F, and 4-CF 3) with 4-fluorostyrene were prepared in the presence of a radical initiator (ABCN) at 70 • C. The composition of the copolymers was calculated from nitrogen analysis, and the copolymers were characterized by IR, 1 H and 13 C-NMR, GPC, DSC, and TGA. The monomer reactivity ratios for 4-fluorostyrene (M 1), r 1 = 0.6 and 2-(2,4-difluorophenyl)-1,1-dicyanoethene (M 2), r 2 = 0 were determined from Fineman-Ross plot. The order of relative reactivity (1/r 1) for difluoro-substituted monomers is 2,4-F,F (0.31) > 2,3-F,F (0.25) > 2,5-F,F (0.22) > 2,6-F,F (0.10). DSC curves showed that the copolymers were amorphous with high T g in comparison with that poly(4-fluorostyrene) indicating a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer units. From the thermogravimetric analysis, the copolymers began to degrade in the range 214–260 • C. The copolymer of 4-fluorostyrene and 2-(2,4-difluorophenyl)-1,1-dicyanoethene and poly(4-fluorostyrene) were dielectrically characterized in the range 25–200 • C. The dominating relaxation process detected in both materials was the α-relaxation, associated with the dynamic glass transition. The relationship polarity-permittivity was discussed.
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Novel copolymers of trisubstituted ethylene monomers, fluorine ring-substituted 2-phenyl-1, 1-dicyanoethenes, RC6H4CH [dbnd] C (CN) 2 (where R is 2-F, 3-F, and 4-F) and 4-fluorostyrene were prepared at equimolar monomer feed composition... more
Novel copolymers of trisubstituted ethylene monomers, fluorine ring-substituted 2-phenyl-1, 1-dicyanoethenes, RC6H4CH [dbnd] C (CN) 2 (where R is 2-F, 3-F, and 4-F) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution ...