Thermal and Mechanical Properties of Microporous Polyurethanes Modified with Reduced Graphene Oxide

Microporous polyurethanes (MPU) were modified by adding 0.25%–1.25 wt% of reduced graphene oxide (RGO). The materials were prepared without solvent via in situ polymerization. From a technological point of view, it is very important to obtain functional materials by using reacting compounds only. The thermal characteristics of obtained MPU were investigated using TGA, DSC, and DMA techniques. In comparison to nonmodified microporous polyurethane, the thermal stability and mechanical properties of the modified systems have significantly improved. The temperature corresponding to the maximum degradation rate (Tmax) for nanocomposites containing 1% and 1.25 wt% of RGO was 51°C higher than that observed for pure microporous PU system. The increase of tensile strength was also observed for matrix with the addition of 0.5 wt% RGO nanofiller

Polyurethane Nanocomposites Containing Reduced Graphene Oxide, FTIR, Raman, and XRD Studies

Recently, graphene and other graphene-based materials have become an essential part of composite science and technology. Their unique properties are not only restricted to graphene but also shared with derivative compounds like graphene oxide, reduced graphene oxide, functionalized graphene, and so forth. One of the most structurally important materials, graphene oxide (GO), is prepared by the oxidation of graphite. Though removal of the oxide groups can create vacancies and structural defects, reduced graphene oxide (rGO) is used in composites as effective filler similar to GO. Authors developed a new polyurethane nanocomposite using a derivative of grapheme, thermally reduced graphene oxide (rGO), to modify the matrix of polyurethane elastomers, by rGO

The Role of Hydrogen Bonding in Paracetamol–Solvent and Paracetamol–Hydrogel Matrix Interactions

The photophysical and photochemical properties of antipyretic drug – paracetamol (PAR) and its two analogs with different substituents (acetanilide (ACT) and N-ethylaniline (NEA)) in 14 solvents of different polarity were investigated by the use of steady–state spectroscopic technique and quantum–chemical calculations. As expected, the results show that the spectroscopic behavior of PAR, ACT, and NEA is highly dependent on the nature of the solute–solvent interactions (non-specific (dipole-dipole) and specific (hydrogen bonding)). To characterize these interactions, the multiparameter regression analysis proposed by Catalán was used. In order to obtain a deeper insight into the electronic and optical properties of the studied molecules, the difference of the dipole moments of a molecule in the ground and excited state were determined using the theory proposed by Lippert, Mataga, McRae, Bakhshiev, Bilot, and Kawski. Additionally, the influence of the solute polarizability on the determined dipole moments was discussed. The results of the solvatochromic studies were related to the observations of the release kinetics of PAR, ACT, and NEA from polyurethane hydrogels. The release kinetics was analyzed using the Korsmayer-Peppas and Hopfenberg models. Finally, the influence of the functional groups of the investigated compounds on the release time from the hydrogel matrix was analyzed

The Role of Hydrogen Bonding in Paracetamol–Solvent and Paracetamol–Hydrogel Matrix Interactions

The photophysical and photochemical properties of antipyretic drug – paracetamol (PAR) and its two analogs with different substituents (acetanilide (ACT) and N-ethylaniline (NEA)) in 14 solvents of different polarity were investigated by the use of steady–state spectroscopic technique and quantum–chemical calculations. As expected, the results show that the spectroscopic behavior of PAR, ACT, and NEA is highly dependent on the nature of the solute–solvent interactions (non-specific (dipole-dipole) and specific (hydrogen bonding)). To characterize these interactions, the multiparameter regression analysis proposed by Catalán was used. In order to obtain a deeper insight into the electronic and optical properties of the studied molecules, the difference of the dipole moments of a molecule in the ground and excited state were determined using the theory proposed by Lippert, Mataga, McRae, Bakhshiev, Bilot, and Kawski. Additionally, the influence of the solute polarizability on the determined dipole moments was discussed. The results of the solvatochromic studies were related to the observations of the release kinetics of PAR, ACT, and NEA from polyurethane hydrogels. The release kinetics was analyzed using the Korsmayer-Peppas and Hopfenberg models. Finally, the influence of the functional groups of the investigated compounds on the release time from the hydrogel matrix was analyzed.</jats:p

Transport Mechanism of Paracetamol (Acetaminophen) in Polyurethane Nanocomposite Hydrogel Patches&mdash;Cloisite&reg; 30B Influence on the Drug Release and Swelling Processes

This article describes the swelling and release mechanisms of paracetamol in polyurethane nanocomposite hydrogels containing Cloisite&reg; 30B (organically modified montmorillonite). The transport mechanism, swelling and release processes of the active substance in nanocomposite matrix were studied using gravimetric and UV-Vis spectroscopic methods. Swelling and release processes depend on the amount of clay nanoparticles in these systems and the degree of crosslinking of PU/PEG/Cloisite&reg; 30B hydrogel nanocomposites. The presence of clay causes, on the one hand, a reduction in free volumes in the polymer matrices, making the swelling process less effective; on the other hand, the high swelling and self-aggregation behavior of Cloisite&reg; 30B and the interactions of paracetamol both with it and with the matrix, cause a change in the transport mechanism from anomalous diffusion to Fickian-like diffusion. A more insightful interpretation of the swelling and release profiles of the active substance was proposed, taking into account the &ldquo;double swelling&rdquo; process, barrier effect, and aggregation of clay. It was also proven that in the case of modification of polymer matrices with nanoparticles, the appropriate selection of their concentration is crucial, due to the potential possibility of controlling the swelling and release processes in drug delivery patches

Polymer-Dependent Layer Structures in Montmorillonite Nanocomposites

We have studied structural differences among tetrahedral and octahedral sodium Montmorillonite layer arrangements in naturally occurring and synthetic montmorillonite clay minerals, as well as their poly(ethylene oxide) and poly(ε-coprolatone) polymer nanocomposites