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This work involves the preparation and characterization of alginate nanoparticles (Alg NPs) as a new transdermal carrier for site particular transport of glucosamine sulfate (GS). The GS–Alg NPs were examined through transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dielectric spectroscopy. GS–Alg NPs was efficiently prepared via ionic gelation method which generates favorable conditions for the entrapment of hydrophilic drugs. The TEM studies revealed that GS–Alg NPs are discrete and have spherical shapes. FTIR studies showed a spectral change of the characteristic absorptions bands of Alg NPs after encapsulation with GS because of the amine groups of GS and the carboxylic acid groups of Alg. The DSC data showed changes in the thermal behavior of GS–Alg NPs after the addition of GS indicating signs of main chemical interaction among the drug (GS) and the polymer (Alg). The absence of the drug melting endothermic peak within the DSC thermogram of GS–Alg NPs indicating that GS is molecularly dispersed in the NPs and not crystallize. From the dielectric study, it was found modifications within the dielectric loss (ε″) and conductivity (σ) values after the addition of GS. The ε″ and σ values of Alg NPs decreased after the addition of GS which indicated the successful encapsulation of GS within Alg NPs. Furthermore, the dielectric study indicated an increase of the activation energy and the relaxation time for the first process in the GS–Alg NPs as compared to Alg NPs. Consequently, the existing observations indicated an initiation of electrostatic interaction among the amine group of GS and carboxyl group of Alg indicating the successful encapsulation of GS inside Alg NPs which could provide favorable circumstance for the encapsulation of GS for topical management.

Dielectric investigations were carried out on styrene-butadiene rubber cured by an increase in either the sulfur content or curing time in a wide range of frequencies from 100 Hz up to 10 MHz and at room temperature (Ϸ25°C). After subtraction, the losses due to the MaxwellWagner effect, the dielectric data showed deviation from the Debye formula but were found to be fitted in the frequency domain by the Havriliak-Nagami function, which is a combination of Cole-Cole and Cole-Davidson functions. This function describes the relaxation mechanisms of the aggregates caused by the movement of the main chain that were expected to be formed by the addition of the different ingredients to the investigated rubber. These mechanisms are also discussed in terms of the distribution function of Frö hlich between two limiting values of relaxation times 1 and 2 . The relaxation times obtained from both functions increased with an increase in either sulfur content or curing time. The data obtained are discussed in terms of the crosslinking density determined from the Flory-Rehner relation. The effect of thermal aging on such systems was also studied, and the data obtained were compared with those before aging. This investigation led us to conclude that to get an end product that is highly resistant to thermal aging, the system should be cured for a time greater than 30 min with the addition of more than 5 phr sulfur.

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