257 research outputs found
Termodinamica di complessi metallici con polimeri sintetici recanti residui di acido etilen-diammino-diacetico
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Photochemical Modification of a Medical Grade Polyamide Using a Plasma-Based Pre-Treatment
No full textIntroduction: The surface modification of hydrophobic polymers (polyamide 12, PA12) offers a method to increase the hydrophilicity of the surfaces of polymeric medical devices. Plasma is a suitable technology but unfortunately, the modification is reversible, and the hydrophilicity decreases in short time. Otherwise, surface modification with photo-reactive chromophores, namely phenyl azide (PhAz), offers an alternative and irreversible method for the surface hydrophilization.
Methods: The aim of the present work was to combine plasma technology and the azide’s photo-reaction to increase the PA12 hydrophilicity. In the first process step, the polymer surface was activated using plasma reaction. Afterwards, a solution of PhAz was sprayed on the activated polymer surface. Finally, the samples were treated with ultraviolet light to trigger the chemical reaction between the polymer chemical groups and PhAz.
Results: Untreated, plasma-treated, and photo-modified polymers were compared in terms of wettability by means of the contact angle (CA) measurements (immediately, 1 week and a month from the reaction). The hydrophilicity increase of treated surfaces was estimated through “deltaCA”, the decreasing of CA compared to the untreated polymer. Plasma-treated samples were initially very hydrophilic, but hydrophilicity was significantly reduced after 1 week and almost completely lost after 1 month. PhAz-treated samples were significantly more hydrophilic if compared with untreated polymer and after 1-month deltaCA was unchanged. The samples produced by plasma activation followed by treatment with PhAz were very hydrophilic. Some hydrophilicity reduction occurred over time, but after 1 month “deltaCA” was stabilized and still considerably high.
Conclusions: The plasma-based pre-activation process was able to improve the PhAz surface process modification of PA12. Conceivably, new chemical groups generated by the plasma reaction can react with PhAz chromophores and increase the yield of the photochemical reaction, making the polymer surface more hydrophilic if compared with the other processes
Due momenti della critica d'arte latinoamericana del Novecento
No full textThis article aims to analyse the most significant epistemological changes in Latin American criticism between the decades of the 1970s and 90s via the comparison of two of the most important compendiums of Latin American art criticism: America Latina en sus Artes, published by UNESCO in 1974, and Beyond the Fantastic, published by the British Institute InlVA in 1995. In doing so, this article deepens: The consideration of Latin America as a place' from where to announce a discourse about art practices, the relation of the idea of 'Latin American Art' with the questioning of the autonomy of art, and the relation between this idea and the change in the study of art practices, from a discipline as Art History to different fields of studies as 'Visual Studies' and 'Latin American Studies'
Amido-thioether polymers containing pendant carboxylato groups: thermodynamics of protonation and copper(II) complex formation in dilute aqueous solution
No full textSurface modification of polyamide 12 angioplasty balloons by photochemical reaction with an aromatic azide
No full textPolyamide 12 (PA12) is used in a variety of applications when low moisture absorption, good dimensional stability, and toughness are required. Polyamide 12 is one of the polymers most frequently employed to fabricate angioplasty balloon catheters; however, its high hydrophobicity and chemical inertness require the application of coatings to make its surface more hydrophilic and biocompatible. In this work, an alternative method, based on the photochemical reaction of PA12 with a hydrophilic aromatic azide, was developed. Static and dynamic contact angle measurements evidenced that the surface modification process was able to improve PA12 wettability and that the effects were retained even after 12 months from surface treatment. Polyamide 12 modification resulted in an increase of its surface free energy, as evaluated by the van Oss, Good, and Chaudhury method. X-ray photoelectron spectroscopy confirmed the presence of the aromatic azide on PA12 surface. Finally, compliance tests showed that the modification process did not reduce the mechanical performance of balloons
From the Laboratory Image to the Habitat-Image. / De la Imagen de Laboratorio a la imagen-habitat.
No full textA partir de las experiencias vividas en la residencia "laboratorio Eigengrau" del artista Javier Toro, este ensayo reflexiona sobre el modelo del laboratorio científico al interior de los estudios sobre arte
Functionalization of medical device surfaces via photocatalytic reactions
No full textThe ability to tailor polymer surface properties has become a very important and challenging area of science. Most medical devices are constituted of polymeric materials, since they offer a great choice in terms of compromise between processability, properties, and cost. Different polymers are available, with specific mechanical properties and ease to process with known manufacturing technologies. The behavior of these materials with respect to blood, pharmacologic or physiologic solutions, different cells of the human body depends on the chemical structure of the polymer itself and on the conditions and technologies used to process it. Therefore, we focused our research on the development of a technique for modifying the surface properties of a balloon catheter without impacting on its main intended use properties nor on the production processes. Surface modification via photochemical reaction with aromatic azides was successfully performed and monitored by XPS and dynamic contact angle. Reactions of different types of aromatic azides have revealed that the new surface properties depend on the substituent groups present on their structures. The balloons modified according to the present experimental work, can be advantageously used in order to improve the balloon catheter performances in terms of lubricity and biocompatibility
Fuga del tempo, fuga dal tempo: la poesia di Johann Ch. Günther (1695-1723)
No full textThe present article illustrates the presence and the evolution of the escape theme in the poetry of the late-baroque author Johann Christian Günther (1695-1723). This topic is to be found in the frequent lexical references to life's fleeting nature that characterize Guenther's early lyrics as well as in his late production, when he often mentions his desire to flee from a world which is unable to receive his poetical message and, at the same time, from the declining Baroque conventions
Polycarbonates and their use for preparation of bioerosible pharmaceutical matrices
No full textPolycarbonates -[OCO2R1OCO2R2]-a [a = 2-300; R1, R2 = aliph. alicyclic C2-18, polyoxyalkylene residue of -[CHR3(CH2)nO]m-CHR3(CH2)n- (I) (R3 = H, Me; n = 1-3, m = 1-200, or a polyester residue of -[R4CO2]x-[R5CO2]y-R6 (x, y = 1-50; R4, R5 = aliph. C1-4 hydrocarbyl; R6 = aliph. or alicyclic C2-18, polyoxyalkylene residue of I]. are used as bioerosible pharmaceutical matrixes for slow release of the active ingredients. Thus, 1,1'-carbonyldiimidazole was reacted with PEG to obtain diimidazolyl formate which was mixed with 1,6-hexanediol and heated at 60° to obtain a polycarbonate liq
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