This paper presents an affordable methodology for the analysis of the crosslinking, by polycondensation reaction, between maltodextrin and citric acid under thermal processing. This methodology is based on three complementary analytical techniques: Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and rheometry. FTIR has been found to be a powerful technique for the characterization of both the esterification reaction and other non-covalent interactions between maltodextrin and citric acid. TGA has been mainly applied to quantify the progress of the polycondensation reaction. Rheometry has been extensively used to understand the crosslink formation resulting from the polycondensation process between maltodextrin and citric acid, allowing the determination of the gel time. Furthermore, these techniques have revealed added value when used as complementary techniques. For instance, the FTIR results supported the conclusions from the study of polycondensation reaction progress by TGA. Similarly, the TGA results about the polycondensation reaction temperature are consistent with the rheology study. Overall, the insightfulness and accuracy of the methodology presented in this paper make it very useful as a tool to optimize industrial processing of materials which apply binding systems based on maltodextrin and citric acid.

Hydrophilic copolymers with high refractive index and bactericide properties based on quaternary ammonium salts monomers and methacrylates bearing benzothiazole moieties have been developed for application as foldable intraocular lenses. Composition of the systems was adjusted to get materials with optimized flexibility, wettability, and refractive properties. All the materials have been characterized in terms of optical properties, glass transition temperature, water content, and wettability. Water contact values oscillated between 37 and 15% and refractive index values in the wet state between 1.49 and 1.53, depending on composition. Glass transition temperature interval was 63-77 degrees C. Values of surface free energy of the solid ranged from 49 to 54 mN/m, characteristic of IOL hydrogel materials. Bactericide properties of the quaternary ammonium salts methacrylates were higher than that of the benzothiazole derivative, showing inhibition halos as high as 23-25 mm in antibiogram tests against S. epidermidis and P. aeruginosa , strains found in the ocular cavity and responsible for most postsurgical endolphthalmitis. Biocompatibility of the systems was evaluated in cell cultures using human fibroblasts. Cellular viability was higher than 90%, and close to 100% in many cases, for the extracts of selected formulations collected at different periods of time.

For short-term cardiovascular application, segmented polyurethanes (SPUs) based on 4,4-methylenebis(cyclohexyl isocyanate) (HMDI), polytetramethylenglycol (PTMG) and 1,4-butanediol (BD) were synthesized and characterized by spectroscopy (FT-IR, (1)H-NMR) and thermal (TGA, DMA, DSC) and mechanical techniques. The segmented nature of the SPUs was not easily established by spectroscopic means; however, TGA allowed the quantification of the rigid segments content by the significant mass loss between 348 and 356 degrees C. The alpha transition was detected by DMA and related to the T(g) of the soft segments at -50 degrees C, while DSC showed the presence of an endothermic transition above 80 degrees C attributed to the melting of rigid segments. Two types of composites were prepared using the synthesized SPUs and Lycra (either T162B or T162C). The first one consisted of a two layers casting laminated while the second one was a classic unidirectional fibre-reinforced material. Laminate composites prepared with SPU containing 23.9% and 33.9% of rigid segments and Lycra T162C exhibited a higher tensile modulus but lower tensile strength than composites prepared with Tecoflex SG-80A (39.7% of rigid segments). The energy of adhesion between layers on these composites ranged from 475 to 2150 J. Fibre-reinforced SPUs exhibited higher moduli than the two layer laminated composites with increasing amounts of rigid segments in the matrix and by increasing Lycra T162C content (up to 10%). This behaviour was explained by SEM, which showed a good fibre-matrix bonding.

Abstract:The preparation, characterization, and in vitro release of Ibuprofen from Al 2 O 3 , poly(L-lactic acid) (PLLA), and polymethylmethacrylate (PMMA) composites are described. The release process of the anti-inflammatory drug after the immersion of composites in a buffered solution is analyzed. The rate of Ibuprofen release is related to the crystalline or amorphous form of the drug. The presence of a ceramic component, ␣-Al 2 O 3 , and a biodegradable polymer, PLLA, facilitates both Ibuprofen crystallization and drug release. In addition, these composite systems modulate the release of the stereoisomers R(−) and S(+) of the drug.