The aim of this work was the preparation of the inclusion complex of naproxen with 2hydroxypropyl-β-cyclodextrin (HP-β-CD) in order to improve the physical and chemical properties of naproxen. The molecular inclusion complexes of naproxen with HP-β-CD were prepared by using the co-precipitation method in the solid state with the molar ratio of 1:1. The structure of the obtained complex was characterized by using FTIR, 1 H NMR, UV-Vis and XRD methods. The testing of naproxen photostability by the UV-Vis method indicated the degradation to aromatic ketone, 2-acetyl-6-methoxynaphthalene. FTIR analysis showed that the degradation has started 15 days after the exposure of naproxen to daylight while the inclusion complex of naproxen:2-hydroxypropyl-β-cyclodextrin was photostable for a period of 30 days.

Copolymeric hydrogels of poly(N-isopropylmethacrylamide-co-N-isopropylacrylamide), p(NIPMAM/NIPAM), are synthesized by radical polymerization of N-isopropylmethacrylamide (NIPMAM) and N-isopropylacrylamide (NIPAM) monomers by using the cross-linker ethylen glycol dimethacrylate (EGDM). The synthesized copolymeric p(NIPMAM/NIPAM) hydrogels, starting monomers and the cross-linker were structurally characterized by using Fourier transform infrared spectroscopy (FTIR). The amounts of residual reactants in the synthesized hydrogels were determined by high-pressure liquid chromatography (HPLC). Swelling of p(NIPMAM/NIPAM) hydrogels was investigated in relation to the temperature and pH value of the solution. The obtained values of residual monomer quantities are within acceptable limits and in the range from 2.69 to 5.25 mg g -1 for NIPMAM and 14.55 to 30.80 mg g -1 for NIPAM. The synthesized p(NIPMAM/NIPAM) hydrogels are negatively thermosensitive. The most common mechanisms of transport of a swelling solution in p(NIPMAM/NIPAM) hydrogels are polymer chain relaxation, (Case III), and the anomalous type of diffusion (non-Fickian diffusion). The maximal equilibrium swelling degree of 51.19 was reached by the p(NIPMAM/NIPAM) hydrogel with 1.5 mol% of EGDM at the temperature of 25 o C and pH 4, whereas the lowest one of 0.98 was exhibited by the hydrogel with 3 mol% of EGDM at the temperature of 80 o C and pH 7. Due to their low content of residual reactants and a satisfactory degree of swelling at various pH values, synthesized p(NIPMAM/NIPAM) hydrogels can be applied as carriers for the controlled release of pharmaceutically active substances.

Hydrogels are synthesized by the method of radical polymerization of monomers: N-isopropylacrylamide (NIPAM) and acrylic acid (AA). Characterization of poly(N-isopropylacrylamide-co-acrylic acid) hydrogels, p(NIPAM/AA), has been performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and by determination of the swelling behaviour in aqueous solutions at different temperatures (25, 31 and 37 °C) and pH values (2.2, 4.5, 6 and 6.8). After lyophilisation in the solution at pH 6 and temperature of 25 °C, p(NIPAM/AA) hydrogels have rapidly reached equilibrium degree of swelling, α e , in comparison to non-lyophilized samples. The mechanism of solvent transport within matrix in lyophilized samples corresponds to less Fickian diffusion, whereas Super case II diffusion is characteristic for non-lyophilized samples. p(NIPAM/AA) hydrogel with 1.5 mol% of ethylene glycol dimethacrylate (EGDM) at the temperature of 25 °C and pH 6.8, has reached the highest swelling equilibrium degree, α e = 259.8. The results of swelling studies have shown that p(NIPAM/AA) hydrogels can be classified as superabsorbent polymers (SAPs). For the evaluation of pH and temperature influences on synthesized hydrogels swelling, a full three-level experimental design has been used. Two-factor interaction model (2FI) is the most optimal model of a full three-level experimental design for representing the swelling equilibrium degree of p(NIPAM/AA) hydrogels as a function of investigated parameters, i.e., temperature and pH.

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Hydrogels are three-dimensional polymer networks which have the capacity to retain a large quantity of water or biological fluids in the swollen state. Thermosensitive hydrogels have received special attention of reserachers since they represent a parameter which frequently changes in chemical, biological and physiological systems. Thermosensitive hydrogels have the critical solution temperature, i.e. they exhibit a substantial change in volume with the temperature change. Homopolymers poly(N-isopropylmethacrylamide) (poly(NIPMAM)) and poly(N-isopropylacrylamide) (poly(NIPAM)) are thermosensitive materials which have lately become the subject of intensive study. Monomer N-isopropylmethacrylamide, NIPMAM, enters into copolymerization with monomer N-isopropylacrylamide, NIPAM, in order to create a system with a phase transition temperature approximate to the human body temperature. In literature data there is available information on the synthesis and characterization of microgels, nanogels and copolymers based on NIPMAM and NIPAM. These thermosensitive polymer materials are used in controlled drug delivery and protein immobilization.