الفهرس 
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Abstract
Hydrogels are polymeric materials that do not dissolve in water at physiological temperature and pH. Being insoluble in water, these three-dimensional hydrophilic networks can retain a large amount of water that not only contribute to their good compatibility but also maintains a certain degree of structural integrity and elasticity. Ionizing radiation has been recognized as a very suitable tool for the formation of hydrogels. Nanocomposite materials consisting of metallic nanoparticles incorporated in or with polymers have attracted much attention because of their distinct optical, electrical and catalytic properties, which have potential applications in the fields of catalysis, bioengineering, photonics, electronics medical, pharmaceutical, industrial and environmental.
The objective of the present study divided into two parts:
Part 1: Preparing of P (PVA/AAc), P (PVA/AAc)-Fe, P(PVA/AAc)-Ag and P(PVA/AAc)-Fe-Ag nanoparticles hydrogels with different metal contents by gamma radiation for targeting colon drug delivery.
Part 2: Preparing of P(PVA/AAm), P(PVA/AAm)-Fe, P(PVA/AAm)-Ag and P(PVA/AAm)-Fe-Ag nanoparticles hydrogels to used as adsorbents materials for Cu+2 and dyes from aqueous solution.
The appropriate reaction conditions, such as the effect of gamma irradiation dose, monomer composition ratio and comonomer concentrations at which the copolymerization process was carried out successfully were selected. The properties of the prepared polymeric materials such as swelling behavior, thermal stability and surface topography were investigated. The nanometal particle size was measured by transimission electron microscope (TEM) and dynamic light scattering (DLS). Furthermore, the possibility of using P(PVA/AAc) and P(PVA/AAc)-Fe-Ag nanoparticles as drug carrier and the use of P(PVA/AAm) and P(PVA/AAm)-Fe-Ag nanoparticles for wastewater treatment will be estimated.
The obtained results in this work may be summarized as follows:
Part 1:
1- P(PVA/AAc) hydrogels were prepared by using gamma irradiation with a composition (20:80) at irradiation dose 20 kGy. Magnetic iron and silver nanoparticles P(PVA/AAc)-Fe-Ag have been entrapped within hydrogel network. The swollen P(PVA/AAc) hydrogels were immersed in a solution of FeSO4 and AgNO3 at different concentrations then transferred to NH4OH and NaBH4 to be reduced. The effect of the composition and irradiation dose on the hydrogels gelation percent was investigated.
2- The gelation (%) increased with increasing the ratio of AAc in the composition from 20 up to 80. The gelation (%) of P(PVA/AAc) hydrogels was found to be sharply increased with increasing irradiation dose up to 20 kGy then showed a slight decrease in the gelation (%) up to 30 kGy.
3- a) The swelling of P(PVA/AAc) hydrogels nearly tends to increase with increasing AAc concentration in the hydrogel composition. The swelling (%) found to be decrease as the irradiation dose increase up to 40 kGy which may be due to increasing of the cross-linking in the network structure.
b) The swelling behavior at different pHs of P(PVA/AAc) hydrogels results showed that, the P(PVA/AAc) hydrogel has low swelling in acidic medium (pH 3) and extensive swelling in pH 6.8 and pH 10.
c) As fick’s law, the mechanism of the swelling was found to be non-fickian or anomalous diffusion mechanism where 0.5< n <1 which indicate that the diffusion and relaxation rates are comparable for the prepared hydrogels.
d) Swelling properties of the prepared hydrogel nanoparticles results show that the swelling percent of P(PVA/AAc)-Fe-Ag nanoparticles increases by the increasing of pH value from 3 to 6.8 and 10. The swelling capacity value of the pristine hydrogel was less than that of hydrogel-Fe-Ag nanocomposite.
4- To proper the possibility of chemical interaction between P(PVA/AAc) molecules and magnetic iron, silver nanoparticles, FT-IR spectra of the pure hydrogels and the hydrogels stabilized magnetic iron-silver nanoparticles were characterized. The presence of the metal nanoparticles in the hydrogel samples leads to decrease the intensity of all bands represent the interaction between PVA and AAc which may be due to the chemical interaction between hydrogels molecules and metal nanoparticles.
5- The UV-vis spectra of magnetic iron and silver nanoparticles embedded in the hydrogel networks have shown a distinct characteristic absorption peaks around 421 nm. This must be due to the characteristic surface plasmon resonance effect of quantum –size metal nanoparticles present in the hydrogel networks.
6- The surface morphology of P(PVA/AAc) and P(PVA/AAc)-Fe-Ag hydrogels by SEM showed that the pristine hydrogels have a relatively wider pore structure, while a dark particles showed in case of hydrogels loaded metal nanoparticles. Magnetic iron and silver nanoparticles are clearly visible as spherical shapes throughout the surface of the hydrogels. It can be noticed that by increasing the metal concentration from 0.1 to 0.4M, the metal particle increase on the polymeric surface. Furthermore, the metal within the hydrogels observed as dark particles.
7- The EDX data indicate well defined characteristics patterns of the magnetic iron and silver nanoparticles present in the hydrogel. The EDX for iron entrapped into P(PVA/AAc) has higher value than that for silver. On the other hand, the increase in the concentration of both iron and silver content in the polymer leads to a significant increase in the EDX value.
8- Thermogravimetric analysis (TGA) and the rate of thermal decomposition were used to study the thermal analysis of the prepared hydrogels and hydrogels-metal nanoparticles. The observed TGA results confirm the enhancement in the thermal stability by incorporation of the nanometal with the prepared hydrogel.
9- The electron paramagnetic resonance (EPR) results show that the P(PVA/AAc)-Fe has high EPR signal while the P(PVA/AAc)-Fe-Ag has no EPR signal. The disappear of EPR may be due to the formation of a fine layer of silver shell on the core of magnetic iron nanoparticles which prevent the effect of the magnetic field on the magnetic iron nanoparticles.
10- The size of the majority of magnetic iron silver nanoparticles determined by transmission electron microscope (TEM) showed a spherical and uniform distribution of metal nanoparticles through the hydrogel network. The results indicate that, the mean size of P(PVA/AAc)-Fe-Ag nanoparticles at concentrations 0.1 and 0.4 M, equal 10.99 and 12.84 nm, respectively. It also clears evidence that, the mean particle size is increase by increasing the concentration of the metal loaded content.
11- The diameter distribution of metal nanoparticles was also determined by dynamic light scattering (DLS). The particle size was found to be 61.3 and 71.6 nm for P(PVA/AAc)-Fe-Ag (0.1M) and (0.4M) respectively.
12- The release study results of VB12 from P(PVA/AAc) and P(PVA/AAc)-Fe-Ag hydrogels show an excellent pH-dependance. The hydrogels metal nanoparticles revealed a higher VB12 release 6 times than that of the pristine hydrogel. It is clearly indicated that the high VB12 release was found at pH 6.8 thus, the significant change in release with changing pH may be used as basis for explaining the proposed hydrogel system in oral drug delivery applications.
Part 2:
13- P(PVA/AAm) hydrogels were prepared by using gamma irradiation with a composition (20:80) at irradiation dose 20 kGy. To obtain magnetic iron and silver nanoparticles the swollen P(PVA/AAm) hydrogels were immersed in a solution of FeSO4 and AgNO3 at different concentrations then transferred to a reducing agents NH4OH and NaBH4. The effect of the composition and irradiation dose on the hydrogels gelation percent was investigated.
14- The increasing of the AAm ratio in the composition from 20 up to 80, the degree of gelation (%) of P(PVA/AAm) hydrogels was found to be increased. The gelation (%) of P(PVA/AAm) hydrogels was increase by increasing irradiation dose up to 20 kGy then at 30 kGy a slight decrease in the gelation (%) was observed.
15- The swelling of P(PVA/AAm) hydrogels was increase by increasing AAm concentration. The effect of irradiation dose on the swelling (%) showed that, the swelling (%) decrease as the irradiation dose increase up to 40 kGy.
16- The effect of pH on the swelling (%) of P(PVA/AAm) hydrogels exhibits extremely low swelling percent in pH 3 whereas the gel demonstrates a relatively high swelling in pH 6.8. According to fick’s law, the mechanism of the swelling was found to be non-fickian or anomalous diffusion mechanism (0.5<n<1) where the diffusion and relaxation rates are comparable.
17- The results of the swelling of the hydrogel nanoparticles show that the swelling percent of P(PVA/AAm)-Fe-Ag nanoparticles increases by the increasing of pH value from 3 to 6.8 and 10. The swelling capacity value of P(PVA/AAm)-Fe-Ag nanoparticles was more P(PVA/AAm) hydrogel.
18- The chemical interaction between P(PVA/AAm) molecules and magnetic iron, silver nanoparticles was confirmed by FT-IR spectra of the P(PVA/AAm) and the P(PVA/AAm)-Fe-Ag. The presence of the metal nanoparticles in the hydrogel samples leads to the decreasing the intensity of all bands.
19- The examination of the surface morphology of P(PVA/AAm), and P(PVA/AAm)-Fe-Ag hydrogels by SEM was occurred. The pore structure of pristine hydrogels has to be a relatively wider with dark particles in case of hydrogels loaded metal nanoparticles. Magnetic iron and silver nanoparticles are clearly visible as spherical shapes throughout the surface of the hydrogels. The increase of the metal concentration from 0.1 to 0.4M lead to the metal particle increase on the polymeric surface and within the hole of the gel pore as dark particles.
20- The presence of magnetic iron and silver nanoparticles in the hydrogel has been demonstrated by EDX measurements and the results showed that, the EDX for iron entrapped into P(PVA/AAm) has higher value than that for silver. On the other hand, the increase in the metals concentration in the polymer a significant increase in the EDX value was observed.
21- Thermogravimetric analysis (TGA) was used for a thermal analysis study of P(PVA/AAm) hydrogels and P(PVA/AAm)-Fe-Ag nanoparticles. The TGA and the rate of thermal decomposition results show that the thermal stability increases by the incorporation of the iron and silver nanometal within the prepared hydrogel.
22- The magnetic behavior of magnetic iron nanoparticles was characterized by electron paramagnetic resonance (EPR). The EPR signal of P(PVA/AAm)-Fe was found to be higher than that of P(PVA/AAm)-Fe-Ag.
23- The magnetic iron silver nanoparticles size at different metal concentrations was determined by transmission electron microscope (TEM) which showed almost spherical and uniform distribution of metal nanoparticles through the hydrogel network. The mean size of P(PVA/AAm)-Fe-Ag nanoparticles was equal 12.07 and 13.07 nm at concentration 0.1 and 0.4M. The increase of the concentration of the metal loaded content lead to increase the mean particle size increased.
24- The diameter distribution of P(PVA/AAm)-Fe-Ag nanoparticles determined by dynamic light scattering DLS showed that the particle size of P(PVA/AAm)-Fe-Ag (0.1M) and P(PVA/AAm)-Fe-Ag (0.4M) was 81.1 and 90.1 nm respectively.
25- The adsorption capacities of P(PVA/AAm) and P(PVA/AAm)-Fe-Ag hydrogel increased rapidly with the increase of the adsorption time. The adsorption capacity of P(PVA/AAm) was more than that of P(PVA/AAm)-Fe-Ag hydrogel toward Cu+2, methylene blue and methyl green. In addition, the adsorption capacity by P(PVA/AAm) and P(PVA/AAm)-Fe-Ag hydrogels toward methyl green is more than that of methylene blue which may be due to the difference in their structures.
Conclusion
Here, we have demonstrated a highly facile and simple methodology for preparing hydrogel-magnetic iron-silver nanoparticles. For this purpose, a series of P(PVA/AAc) and P(PVA/AAm) hydrogels were prepared by gamma irradiation with different compositions (wt%). Highly stable and uniformly distributed magnetic iron-silver nanoparticles have been obtained with hydrogel networks as nanoreactors. The developed hydrogel metal nanoparticles swelling properties are dependent on the internal network structure and it can be noted that the prepared hydrogels have low swelling percent in the acidic medium and extensive swelling in pH 6.8 and pH 10.
The results indicate that, by transmission electron microscope (TEM), the mean size of P(PVA/AAc)-Fe-Ag nanoparticles ranged between 10.99 and 12.84 nm and for P(PVA/AAm)-Fe-Ag ranged between 12.07 and 13.07 nm.
The introducing of metal nanoparticles to the pristine hydrogel leads to a higher thermal stability, higher magnetic properties and higher swelling capacity. The high response of P(PVA/AAc) and P(PVA/AAc)-Fe-Ag to the swelling at high pH suggesting the use of such hydrogels in drug release applications. The release study results that the highest value of release was at pH 6.8 which can be used for colon drug delivery system.
On the other hand, P(PVA/AAm) and P(PVA/AAm)-Fe-Ag have very high swelling , so it has been successfully to used in environmental remediation by removal of copper ions and dyes.