Thermodynamics/hydrodynamics of aqueous polymer solutions and dynamic mechanical characterization of solid films of chitosan, sodium alginate, guar gum, hydroxy ethyl cellulose and hydroxypropyl methylcellulose at different temperatures

Preparation and prediction of physical properties of cellulose acetate and polyamide polymer blend

In this paper the physical properties of the polymer blend of lab synthesized Polyamide (PA) and commercial Cellulose Acetate (CA) was focused. The molecular interactions of CA/PA were investigated thoroughly by means of solubility, viscosity, specific gravity and diffusivity study with different concentrations of the CA/PA combinations and the blend of CA/PA was characterized by optical microscope and differential scanning calorimetry (DSC). Dimethyl formamide (DMF) was selected as solvent for the CA/PA polymer blend at 28°C. The diffusivity result for the polymer blend of CA/PA was suggested slight decrease in diffusivity coefficient with 1:1 blend ratio of CA/PA polymer.

Pharmaceutical applications of dynamic mechanical thermal analysis

The successful development of polymeric drug delivery and biomedical devices requires a comprehensive understanding of the viscoleastic properties of polymers as these have been shown to directly affect clinical efficacy. Dynamic mechanical thermal analysis (DMTA) is an accessible and versatile analytical technique in which an oscillating stress or strain is applied to a sample as a function of oscillatory frequency and temperature. Through cyclic application of a non-destructive stress or strain, a comprehensive understanding of the viscoelastic properties of polymers may be obtained. In this review, we provide a concise overview of the theory of DMTA and the basic instrumental/operating principles. Moreover, the application of DMTA for the characterization of solid pharmaceutical and biomedical systems has been discussed in detail. In particular we have described the potential of DMTA to measure and understand relaxation transitions and miscibility in binary and higher-order systems and describe the more recent applications of the technique for this purpose.

Dynamic mechanical thermal analysis of hypromellose 2910 free films

It is common practice to coat oral solid dosage forms with polymeric materials for controlled release purposes or for practical and aesthetic reasons. Good knowledge of thermo-mechanical film properties or their variation as a function of polymer grade, type and amount of additives or preparation method is of prime importance in developing solid dosage forms. This work focused on the dynamic mechanical thermal characteristics of free films of hypromellose 2910 (also known as HPMC), prepared using three grades of this polymer from two different manufacturers, in order to assess whether polymer chain length or origin affects the mechanical or thermo-mechanical properties of the final films. Hypromellose free films were obtained by casting their aqueous solutions prepared at a specific concentrations in order to obtain the same viscosity for each. The films were stored at room temperature until dried and then examined using a dynamic mechanical analyser. The results of the frequency scans showed no significant differences in the mechanical moduli E' and E″ of the different samples when analysed at room temperature; however, the grade of the polymer affected material transitions during the heating process. Glass transition temperature, apparent activation energy and fragility parameters depended on polymer chain length, while the material brand showed little impact on film performance.

Novel cellulose-based polyelectrolytes synthesized via the click reaction

Novel polyelectrolytes were prepared by conversion of 6-azido-6-deoxycellulose with acetylenedicarboxylic acid dimethyl ester and subsequent saponification. Up to 62% of the azide moieties were converted. The reaction was completed within 48 h using 2 moles of acetylenedicarboxylic acid dimethyl ester per mole of modified anhydroglucose unit. FTIR and NMR spectroscopy were applied to elucidate the molecular structure of the polymers. The polymer degradation was acceptable during this two-step reaction. The resulting biopolymer derivatives were water soluble and reduced the surface tension on water significantly. Moreover, they form ionotropic gels with multivalent metal ions.

Characterization of physical and viscoelastic properties of polymer films for coating applications under different temperature of drying and storage

The increasing tendency to enhance consumer products with added functionality is leading to ever more complex products. Nowadays more and more particulate products are coated to give the product specific functionalities. An appropriate approach is needed to be able to satisfy customer's requirements. In this work, three reference well-known coating agents, namely two grades of hydroxypropyl methylcellulose (HPMC) and one polyvinyl alcohol (PVA) were selected and investigated. Aqueous solutions of such polymers were obtained and viscosity and shear stress were measured function of shear rate, temperature and polymer concentration. The viscosities of the solutions appear to be mainly shear rate independent, they clearly show Newtonian behaviour. Drying and storage conditions influence on morphology and structure of the cast films were evaluated using scanning electron microscope (SEM). Dynamic mechanical thermal analysis (DMTA) experiments were carried out on HPMC and PVA cast films to assess the viscoelastic properties over wide temperature-frequency range. The time-temperature superposition principle was used to determine the shift factor, aT, and to compose a master curve. Magnitudes and profiles of storage modulus, E', loss modulus, E'', and tan delta master curves are discussed with relation to drying and storage conditions. No impact of drying temperature on the polymer properties was observed whereas the effect of storage temperature resulted to be relevant in terms of shifts in glass transition temperature and, only partially, changes in the magnitudes of E' and E''.

Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers. Surface-tension measurements, turbidity measurements and temperature-variable (1)H NMR analysis were combined to investigate the thermal sensitivity of CECTS-g-PDMAs in aqueous solution.