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The synthesis, characterization and degradation of a hybrid chitosan (CTS)/glycidyl methacrylate (GMA) material are reported. These versatile materials (natural-synthetic materials) are potential candidates for dental restoratives. All materials were characterized by infrared spectroscopy (FT-IR), X-ray diffraction and thermal (DSC) analysis. Particular attention was paid to the thermal stability and chemical resistance of the hybrid CTS materials. From dynamical rheological tests, it was concluded that CTS-GMA solutions behave as physical hydrogels. These pH-sensitive gels are an example of stimuli-responsive polymers, also known as 'smart polymers'.

This work reports on the synthesis and ring-opening metathesis polymerization (ROMP) of new structural isomers based on norbornene dicarboximides bearing trifluoromethyl moieties, specifically, N-2-trifluoromethylphenyl- exo- endo-norbornene-5,6-dicarboximide (2a) and N-3-trifluoromethylphenyl- exo- endo-norbornene-5,6-dicarboximide (2b) using tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (I), bis(tricyclohexylphosphine) benzylidene ruthenium (IV) dichloride (II), and bis(tricyclohexylphosphine) p-fluorophenylvinylidene ruthenium (II) dichloride (III). It is observed that the –CF3 moiety attached to the ortho position of the aromatic ring increases the thermal and mechanical properties of the polymer, whereas the meta substitution has the opposite effect. A comparative study of gas transport in membranes based on these fluorinated polynorbornenes showed that the –CF3 ortho substitution increases the permeability of the polymer membrane as a consequence of the increase of both the gas solubility and the gas diffusion. In contrast, the gas permeability coefficients of the meta-substituted polymer membrane are rather similar to those of the non-fluorinated one attributed to a lower fractional free volume. The meta-substituted polymer membrane besides showing the largest permselectivity coefficients of all the isomers studied here was also found to have one of the largest permselectivity coefficients reported to date for separating hydrogen/propylene in glassy polynorbornene dicarboximides.

Poly(methyl methacrylate) (PMMA) is one of the most commonly plastics used as dental-base material, due to its good biological compatibility and mechanical properties. Chitosan has wide application in chemical, biochemical and biomedical fields of research. In this work, chitosan (CTS) was functionalized with glycidyl methacrylate (GMA), to ease a further reaction with MMA. The resulting co-polymer was finally blended with PMMA and poly(butyl acrylate) PBA which works as a damper, the polymers were cured by UV to obtain the final resin. Characterization of UV-cured resins was carried out by thermal measurements, X-ray diffraction, atomic force microscopy (AFM), micro and nanoindentation, water absorption and elution in water. As a result a higher thermal stability of the final resin compared with the precursor co-polymer ((CTS-GMA)-g-PMMA) was obtained. The resin presented roughness in the nanometer scale and nanoparticles embedded in the acrylic matrix producing a tough material. However, XRD measurements show that all materials are in an amorphous state. Values of hardness and elastic modulus results were very near to those of the dentine. The results of elution in water of the tested resin samples show them as clinically acceptable as a dental base material.

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The sol-gel technique was used to incorporate rhodamine 6GDN (Rh 6GDN) into thin layers of SiO 2 and into an organic-inorganic hybrid matrix (OIHM). The OIHM is composed of a mixture of SiO 2 and an acrylic copolymer. The Rh 6GDN was also incorporated into poly(methyl methacrylate) (PMMA) matrices. To investigate the influence of the different matrices on the optical behavior of the Rh 6GDN-colored layers on glass substrates, the optical absorption and photoluminescence were measured and analyzed. The absorption spectra show the presence of two main bands related to the monomer and dimer absorption, the relative intensity of these band depends on the type of matrix and on the hydrolyzation/condensation time. The strongest luminescence intensity was observed when the dye was embedded in the PMMA matrix; it was 20% larger than that observed in the OIHM layers. The weakest luminescence corresponds to the dye in the SiO 2 matrix, which was up to 90% below the values observed when PMMA matrices were used. The absorption spectra of the dye show an unusual intense band at a wavelength of 310 nm when it is embedded in the PMMA matrix. A band in this position, which emits at 308 nm, is desirable for excimer laser applications. A simple quantum mechanical model is used, which treats the dye molecules as two-dimensional potential wells for delocalized electrons. The model fits reasonably well the experimental optical transitions determined from absorption and fluorescence spectra.

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