Islamic University of Gaza SYNTHESIS AND APPLICATION OF SOME POLYSILOXANE IMMOBILIZED LIGAND SYSTEM Prepared by : Mysaa’a. S. Al-Batnegy Suhad. S. El-Tana Noha M. Motawe’a Chemistry Department Islamic University of Gaza Supervised by : Dr. Nizam M. El-Ashgar May /2007

Synthesis Of Immobilized Ligand Systems These immobilized ligand systems have been made by two different routes: silica gel route: Silica is the most common substance on earth. It occurs in nature as: Crystalline phase (quartz, rice and barely). Amorphous forms (silica glass).

Synthesis of silica gel Formation of a wet gel. Drying of the wet gel. Ex:

Modification method of surface silica By chemical reaction of silica as shown:

The sol gel route: It is a one spot reaction in which the tetraalkoxy silane Si(OR)4 and the silane coupling agent (RO)3Si(CH2)3X mix together in an alcoholic solution in the presence of an acid or base catalysis, where hydrolysis and condensation occurred simultaneously.

The two strategies of preparation of the immobilized polysiloxane ligand system To prepare the silane with complexing group and then to immobilized the complexing ligand by hydrolytic condensation reaction with tetra ethoxy silane. Ex: R = Me or Et R’ = Organofunctionalized ligand The post treatment of the polysiloxane with the complexing ligand.

Features of polysiloxane Insoluble cross-linked organosilicon polymers with a controllable porous structure. They are intermediates in composition between the pure inorganic silica and organic polymers such as polystyrene. Although the chain is entirely inorganic, with alternating Si and O atoms, organic side groups are attached to the silicon atoms. Has an extraordinary flexibility of the siloxane backbone. Si-O bond is significantly longer than the C-C bond. Si-O-Si bond angle of 143 > tetrahedral angle.

Important application It is includes high performance elastomers, membranes, electrical insulators, water repellent sealants, adhesives, protective coatings, hydraulic, heat transfer, dielectric fluids, biomaterials, catalyst supports, chromatography, extraction and uptake of metal ions from aqueous solutions and encapsulation of organic compounds.

The first strategy (sol gel process) Hydrolytic polycondensation of a mixture of tetraethyl orthosilicate (TEOS) and the appropriate silane coupling agent in a definite mole ratio using acid or base catalysts. The process steps: 1- Hydrolysis By mixing low molecular weight tri or/and tetra alkoxysilanes with water in present of a homogenization agent. The hydrolysis catalyzed by acid or base. SiOR + H2O SiOH + ROH 2- Polycondensation Through silanol-silanol condensation SiOH + SiOH Si-O-Si + H2O Silanol-ester condensation. SiOR + SiOH Si-O-Si + ROH Where: R = CH3 or C2H5.

Further polycondensation to form SiO2 net work

Gelation, Drying and Aging Interconnection between particles of the sol increases forcing the sol to become more viscous (gel-point) so lose its fluidity. Drying Evaporation of water and organic solvent from the pores of the glassy material. Shrinking of solid gradually (In some cases, the final volume of the xerogel is  10% of the initial volume of the gel). Large internal pressure gradients in the wet pores. This process causes cracking and fracture in large monoliths. Addition of surfactants, such as Triton-X, were suggested to prevent these fractures Drying the wet gel under monitored conditions also, give free cracks monolith.

SiOH + SiOH SiOSi + H2 Aging The polycondensation reaction, formation of new bonds, water and alcohol still occur as a function of time. Additional cross-linking and spontaneous shrinking occur. So structure and properties of the gel continue changing with time. The gel is aged to complete reaction. The strength of the gel increase with aging. SiOR + H2O SiOH + ROH SiOH + SiOH SiOSi + H2

What do you know about coupling agent ? It have the general formula X3SiR. (Where X is a hydrolyzable group and R represents an organofunctional group). It combine the organic chemistry of organofunctional groups with inorganic chemistry of silicates. It have been used widely to modify surfaces for chemical applications, to immobilize chelating functional groups on silica gel and to prepare organofunctionalized polysiloxanes.

Advantages of Polysiloxane Immobilized Ligand Systems The physical rigidity of their structures. High abrasion resistively. Negligible swelling in both aqueous and organic solutions. Chemical inertness (low interaction with analytes). Slower poisoning by irreversible side reactions. High biodegradation, photochemical and thermal stability. High capacity of functionalized groups. Uniform distributions of ligand sites within the polymer particles. Readily modified by a variety of functional groups to be immobilized either before or after polymerization.

Drawbacks of Polysiloxanes Hydrolysis at high pH ( 12). Leaching of the functional groups from the support surface into the solution. Application of Polysiloxane Immobilized Ligand Systems The extraction and isolation of metal ions. Metal ion separation in columns chromatography. As catalysts in a variety of reactions. Encapsulation of organic and biochemical compounds.

Preparation of polysiloxane immobilized ligand system Preparation of 3-Iodipolysiloxane (P-I) . Preparation of the silane agent by the reaction of 3-chlorotrimethoxysilane with an excess amount of sodium iodide using dry acetone as a solvent . Hydrolytic polycondensation of the 3-iodotrimethoxysilane agent with tetraethylorthosilicate (TEOS), in the ratio 1:2 respectively .

Preparation of polysiloxane-immobilized Triamine ligand system (P-TA). By the reaction of 3-iodopropylpolysiloxane with an excess of diethylenertiamine in the presence of triethylamine .

Preparation of polysiloxane Iminodiacetic Acid ligand system (P-IDA). By the reaction of 3-iodopolysiloxane with diethyliminodiacetate (DEIDA) in the presence of triethyl amine . The product then hydrolysis using HCl .

Preparation of polysiloxane 2-Aminothiophenol ligand system (P-ATP). By the reaction of 3-iodopolysiloxane with 2-aminothiophenol in ethanol at 60 C for 48 hours .

5. Preparation of polysiloxane phenylene diamine ligand system (P-PDA). By dissolving phenylenediamine in ethanol and adding it to 3-iodo propyltrimethoxysilane then adding the product dropwise to TEOS.

Characterization of Functionalized Polysiloxanes Elemental Analysis : 3-Iodipolysiloxane (P-I) . C/X I% Cl% H% C% Element 3 37.2 1.8 10.5 Expected 32.3 2.2 9.0 Found

2. Triamine polysiloxane (P-TA) . mmol N/g C/N N% H% C% Element 7.6 2.5 10.7 5.5 22.7 Expected 7.1 9.89 4.9 21.3 found Iminodiacetic acid polysiloxane (P-IDA) mmol N/g C/N N% H% C% Element 1.70 11.0 3.1 4.4 29.1 Expected 1.24 12.7 1.73 4.1 18.8 found

FTIR : For 3-Iodopolysiloxane (P-I) .

2- For triamine polysiloxane (P-TA) .

3. For iminodiacetic acid polysiloxane (P-DIDA) .

4. For iminodiacetic acid polysiloxane (P-IDA)

Application Metal Uptake Capacity : 1. For Triamine polysiloxane (P-TA) . Maximum Uptake Co2+ Ni2+ Cu2+ mg M2+/g Ligand 27 34.2 49 mmol M2+/g Ligand 0.46 0.57 0.77

Effect of pH Uptake of metal ions by P-TA versus pH values, (72 hr shaking time).

Chromatographic study Effect of pH on metal desorption Amount of Cu(II) desorbed as a function of eluent volume at different pH values (flow rate 1.5 mL/min

Relation between total amount of Cu(II) desorbed & adsorbed as a function of pH Amount of Cu(II) desorbed and retained at different pH values (flow rate 1.5 mL/min

Metal Uptake Capacity : For Iminodiacetic acid polysiloxane (P-IDA) . Maximum Uptake Co2+ Ni2+ Cu2+ mg M2+/g Ligand 66.93 72.10 84.85 mmol M2+/g Ligand 1.13 1.21 1.33

Effect of pH Uptake of metal ions by P-IDA versus pH values, (72 hr shaking time).

Chromatographic study Effect of pH on metal desorption Amount of Cu(II) desorbed as a function of eluent volume at different pH values (flow rate 1.5 mL/min).

Relation between total amount of Cu(II) desorbed & adsorbed as a function of pH Amount of Cu(II) desorbed and retained at different pH values (flow rate 1.5 mL/min).

Metal ions Separation Separation of Co(II), Ni(II) and Cu(II) at different pH values (flow rate 1.5 mL/min).

Maximum Uptake Co2+ Ni2+ Cu2+ Metal Uptake Capacity : 2. For 2-Aminothiophenol polysiloxane (P-IDA) . Maximum Uptake Co2+ Ni2+ Cu2+ mg M2+/g Ligand 58.3 66.8 77.3 mmol M2+/g Ligand 0.98 1.12 1.21

Effect of pH Uptake of metal ions by P-TA versus pH values, (72 hr shaking time).

Chromatographic study Effect of pH on metal desorption Amount of Cu(II) desorbed as a function of eluent volume at different pH values (flow rate 1.5 mL/min).

Relation between total amount of Cu(II) desorbed & adsorbed as a function of pH Amount of Cu(II) desorbed and retained at different pH values (flow rate 1.5 mL/min).

Metal ions Separation Separation of Co(II), Ni(II) and Cu(II) at different pH values (flow rate 1.5 mL/min).

Conclusion In this study some insoluble functionalized polysiloxane immobilized ligand systems, have been prepared include: Polysiloxane immobilized triamine ligand system. Polysiloxane immobilized iminodiacetic acid ligand system Polysiloxane immobilized phenylnediamine ligand system Polysiloxane immobilized aminothiophenol ligand system The preparation methods were mainly based on the sol-gel process, which summarized in hydrolytic polycondensation of TEOS and an appropriate silane coupling agent. These polysiloxane immobilized ligand systems were well characterized by some of physical techniques.

FTIR provided strong qualitative evidences about the functional groups of the immobilized ligands. Elemental analysis provided the exact content of the functionalized ligand groups that attached to the immobilized ligand systems. These immobilized ligand systems exhibit high potential for preconcentration of divalent metal ions (Co2+, Ni2+ and Cu2+) from aqueous solutions. The optimum experimental conditions that studied showed that maximum uptake could be attained at pH 5.5 for 48 hours. These immobilized ligand systems were used as chromatographic stationary phases for separation of metal ions in aqueous solution by pH control.

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