**8. Conducting polyaniline nanoparticles**

120 Gamma Radiation

electrons to carbonyl groups and formation of radical anion of a very high rate constant and

The process of crosslink occurs due to interaction between two free radical monomers which combine to form intermolecular bond leading to three dimensional net of crosslinked highly molecular polymer, more likely dominate in unsaturated compound or monomer. The

Radiation grafting is a process in which active radical sites are formed on or near the surface of an exciting polymer, followed by polymerization of monomer on these sites. Grafting is accompanied by homopolymerization of the monomer; the material to which the monomer is grafted is described as the backbone, trunk or support. Radiation grafting is used to modify the polymers texture such as film, fibers, fabrics and molding powders. The process of grafting can be expressed as follow; suppose the polymer A is exposed to γ-rays, thus the active free radical sites A\* created randomly along the polymer backbone chain, this free radical initiate a free radical on the monomer B then undergoes grafting polymerization at that active sites. The extension of the attached monomer B upon the base polymer A is termed as the degree of grafting DOG which refers to the mass of the grafted polymer as a percentage of the mass of the original base polymer. Such process can be expressed in

Fig. 2. Schemes for grafting process for polymer A with monomer B using gamma radiation.

Conducting polymers and their composites exhibit excellent optical, electrical, and electrochemical properties and therefore they have potential applications in enhancement the electrode performance of rechargeable batteries and fuel cells, electric energy storage systems in supercapacitors, solar energy conversion, photoelectrochromics, corrosion protection, electromagnetic interference shielding and biosensors (Malinauskas *et al*.,

In this work attempts are made to produce conducting polyaniline (PANI) formed in pallets and dispersed in PVA matrix (films) then their structure, optical properties and electrical conductivity are investigated. However, for the first time the polymerization of pure PANI

crosslinked polymer show strong mechanical strength and high thermal resistance.

the decay of radicals with parallel addition of monomer to the growing chain.

**6. Cross linking** 

**7. Radiation grafting** 

schematic Figure (2).

2005).

PANI has high electrical conductivity that can be controlled by oxidation or protonic doping mechanism during synthesis. PANI is known for its excellent thermal and environmental stability but poor processibility due to insolubility in most common solvents and brittleness that limits its commercial applications. In the composites form with another water soluble polymers such as PVA, poly(vinyl pyrrolidone), poly(acrylic acid) and poly(styrene sulfonic acid) (PSSA) which used as stabilizers, the processibility of PANI could be improve and a functionalized protonic acid can be added into the composites to chemically polymerize PANI. The PANI dispersion can then be cast to form composite film containing PANI nanoparticles. To improve the conductivity further, chemically and electrochemically PANI/ polymer composites have been irradiated with x-rays, gamma radiation, and electron beams (Bodugoz *et al*., 1998; Sevil *et al*., 2003; Wolszczak *et al*., 1996 a and b; Angelopous *et al*. 1990). When ionizing radiation interacts with polymer materials active species such as ions and free radicals are produced and thus, improved the PANI conductivity.

Conducting PANI has been synthesized by chemical and electrochemical methods, which the later is considered the common one because of better purity. Chemically and electrochemically synthesized polyaniline are subjected to many shortcomings such as impurities, solvent toxicity, long tedious process, poor compatibility, insoluble, expensive, low production and difficult in their preparation, etc. However, report on synthesis of PANI nanoparticles using only -irradiation has not been reported until the date of 2007. The advantages of radiation processing is that no metallic catalyst, no oxidizing or reducing agent is needed, synthesis in a solid-state condition, fast and inexpensive, and controllable acquisitions. The synthesis of PVA/PANI nanoparticles by -irradiation doping is proposed in this work.
