1. Introduction

Polymer solutions like PVA solutions are important in applied electrochemistry due to their applications in electrodes,especially when doped with transition metals ^(1,2) Transition metals plus polymer solutions improve the conducting properties and play important role in forming thin films ⁽³⁾. Conductivity and refractive index measurements explain the ion - ion, ion – solvent Interactions and the association of ions in different media ^(4,5). Estimation of the optical and mechanical properties of polymers in absence and presence of metals are very important to give relations between the optomechanical characterizations ⁽⁶⁾. The aim of this work is to evaluate the optical and mechanical properties of PVA in presence of CoCl₂ and solutions in presence and absence of both PVA (polyvinyl alcohol) and 44% by weight ethanol – water mixtures together or separately.

2. Experimental

Cobalt chloride from Merck Co. and polyvinyl alcohol (PVA), M.W 17,000, water soluble polymer from Arondate laborations were provided. The ethanol was BDH supplement and water used was secondly distilled one. 5 ml of bidistilled water were put in test tubes, then different concentrations of solid CoCl₂ were added and dissolved. Also another solutions were prepared by adding different con- centrations of CoCl₂ to 44% by weight ethanol-water solventsin absence and presence of 10% (by weight) PVA. The solutions were left for more than one day in water thermostat of the type (Polyscience 8105, USA) at 298.15 K. The densities were measured by taking 1ml of the prepared solutions and put in specific gravity bottle (1 ml capacity) and weight them by the use of Mettler Toledo USA four digital balance with accuracy of plus, minus 0.001 gram. The densities have been used for evaluating the solvated radii ⁽⁷⁾. The refractive indices of the different solutions used here in this work were measured using a refractometer of the type ATAGO-3T (No 5250) at 298.15 K.

3. Results and Discussions

From densities of CoCl₂ aqueous solutions in absence and presenceof 10% by weight PVA, the molar volumes were evaluated by dividing the molecular weight of CoCl₂ by densities, and the evaluated volumes (V) are represented in Table 1.

From the experimental refractive indices (n), the molar refraction (R_M) were calcu44% by weight lated

By applying ⁽⁸⁾ eq.1.

(1)

Where V is the measured molar volumes.The evaluated R_M values are listed also in Table 1. The specific refractivities of the isotropic dielectric (ε ) were calculated by using de Vries equation ^(9,10) as seen in eq.2.

(2)

Where d are the densities of the solutions. The mean values of the molecular dipole polarizability(α) i.e the dipole moment induced by electric field were calculated from Lorenz-Lorenz formula ⁽¹¹⁾ following equation (3)

(3)

The number of molecular chains (N),the molduli of elasticity E and Shear modulus G were calculated by using equations (4), (5) and (6) after Fouda and Gomaa and Mognashi ^(10-12).

(4)

(5)

(6)

Where k is Boltzman^,s constant , T the absolute temperature , N_A is the Avogadro^,s number and M is the molecular weight of CoCl₂

Table 1. Densities (d),molar volume (V),refractive index (n), molar refraction (RM), specific refractivity ( ε ) number of chain molecules ( N ).polarizability (α ).elastic modulus (E) and Shear modulus (G) for CoCl2 in aqueous solutions at 298.15K

Table 2. Densities (d),molar volume (V),refractive index (n), molar refraction (RM), specific refractivity ( ε ) number of chain molecules ( N ).polarizability (α ).elastic modulus (E) and Shear modulus (G) for CoCl2 in 44 % by weight ethanol water solutions at 298.15K

Table 3. Densities (d),molar volume (V),refractive index (n), molar refraction (RM), specific refractivity ( ε ) number of chain molecules ( N ).polarizability (α ).elastic modulus (E) and Shear modulus (G) for 10% PVA + CoCl2 in aqueous solutions at 298.15K

Table 4. Densities (d),molar volume (V),refractive index (n), molar refraction (RM), specific refractivity (ε) number of chain molecules (N).polarizability (α).elastic modulus (E) and Shear modulus (G) for 10% PVA + CoCl2 in 44 % mixed ethanol water solvents at 298.15K

All the measured and evaluated data for CoCl₂ aqueous solutions (Table 1), CoCl₂ in mixed ethanol-water solvents (Table2) and 10% polyvinylalcohol + CoCl₂ in absence of 44 % ethanol-water mixed solvents (Table 3) and in presence of 44 % mixed ethanol-water solvents (Table 4), are evaluated at 298.15 K. In comparing the four given tables we can conclude that both the optical and mechanical properties of CoCl₂ are increased by using mixed 44% ethanol-water solvents and 10 % PVA. CoCl₂ + 10% PVA + 44% ethanol-water solutions show the biggest optical and mechanical properties from all the used media.The organic solvents increase the salvation parameters ^(13-15) affecting the optical and mechanical properties.

Therefore the optical and mechanical properties of PVA solutions can easily be improved by the addition CoCl₂ and 44 % ethanol-water solutions.

4. Conclusions

The optomechanical properties of PVA increase in presence of CoCl₂+44% ethanol by weight due to the increase in molar refraction (R_M), specific refractivity (ε), molecular polarizability (α), elastic modulus (E) and Shear modulus (G ).