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981.
Today, the technology of microencapsulation of active principles is on top of biomedical advances, because through it we can solve many of the problems caused by current methods of taking medication. Active principle microencapsulation not only solves the problems of drug intake but also controls its dosage. In this study was carried out the development of a protocol for the microencapsulation of ibuprofen by solvent evaporation method. A subsequent application of those microencapsulates to biofunctional textile substrates (cotton, polyamide, acrylic, and polyester) using a finishing process, and finally a study of the release of active principle in two different media (deionized water and physiological serum) has been carried out using samples of the treated fabrics that were submerged into a thermostatized vessel at semi-infinite bath conditions. The determination of active principles released to the bath was determined by a UV spectrophotometer. These experimental results have been analyzed and evaluated, and have therefore allowed to define a controlled drug release system by Fickian diffusion in different media. 相似文献
982.
Sonia Dopico‐García Ana Ares‐Pernas Jorge Otero‐Canabal Mar Castro‐López José M. López‐Vilariño Victoria González‐Rodríguez María J. Abad‐López 《先进技术聚合物》2013,24(8):723-731
Nowadays, there is a growing availability of biodegradable industrial materials intended to food contact applications whose service life behavior needs to be further investigated. This article is focused on the degradation of two materials based on polylactic acid. The correlation between the rate of degradation and the amount of trapped degradation products was investigated applying three characterization techniques in parallel, namely rheology, high‐performance liquid chromatography (HPLC), and matrix‐assisted laser desorption/ionization (MALDI). The rate of degradation was studied through the evaluation of their rheological properties and calculation of the number of average molecular weights, and weight‐average molecular weights. Water‐soluble oligomers and lactic acid were quantified by HPLC‐ultraviolet. Changes in cyclic and linear oligomers were monitored by MALDI‐time‐of‐flight mass spectrometry. Specimens of 4‐mm thickness of each biopolymer were subjected to hydrolysis in deionized water up to 6 months at two temperatures, simulating service conditions of food packaging. The diminution in viscosity and consequently in molecular weight distribution (20–60%) showed the degradation of the molecular structure of both polylactic acids. The chain scission was followed through the increasing values of lactic acid and hydrolyzed oligomers (twofold to eightfold), and the predominant signal of the linear oligomers over the cyclic ones with aging. Rheology, HPLC, and MALDI showed to be complementary tools to better understand the changes in the molecular structure. The obtained results showed the necessity of adding suitable stabilizers for each particular food packaging application. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
983.
The semicontinuous emulsion polymerization of vinyl acetate has been studied. Poly(vinyl alcohol) as a protective colloid and ethoxylated cetyl alcohol as a coemulsifier were used. The conversion and particle diameter were affected by the stirring speed and the coemulsifier distribution between initial reactor charge and continuously introduced monomer. The amount of unreacted monomer oscillates with time. 相似文献
984.
Alejandro Ortega Moñux Steve Greedy Ginés Lifante 《Optical and Quantum Electronics》2013,45(4):307-307
985.
The steady-state fluorescence emission from the local anaesthetic tetracaine (TCA) in water–solvent mixtures and in the presence of α-, β- and γ-cyclodextrin (CD) was investigated at various pH values. Emission was observed from the locally and the intramolecular charge transfer excited states. The TCA–CD system was found to be characterised by 1:1 associate in every case. The association constants of each complex were determined. 相似文献
986.
Jesús M. Arsuaga José Aguado Amaya Arencibia María S. López-Gutiérrez 《Adsorption》2014,20(2-3):311-319
The aim of this work was to investigate the aqueous mercury adsorption in a fixed bed of mesostructured silica SBA-15 functionalized with propylthiol by co-condensation (SBA-15-SH). Powdered synthesized adsorbents were used to prepare pellets with sizes ranging from 0.5 to 1 mm. The physicochemical properties determined from N2 adsorption and chemical analysis were compared for powder and pellets. Batch static experiments were carried out to obtain the equilibrium mercury adsorption isotherms, resulting that although the maximum adsorption capacity was reduced from powder to pellets, the materials maintained high efficiency for mercury removal even at very low aqueous metal concentration. Dynamic experiments were carried out in a fixed bed column by modifying the volumetric flow rate, bed length, inlet concentration, and amount of propylthiol groups incorporated to the adsorbent, and analyzing the temporal scale and the mercury adsorption capacities. The elution of the fixed bed was carried out chemically by circulating an aqueous 2 M hydrobromic acid stream for 2 h so achieving a complete recovery of the mercury previously adsorbed. Simplified dynamic equations of Bohart–Adams and Wolborska were used for modeling the breakthrough curves. 相似文献
987.
988.
989.
H. R. Acevedo-Parra M. R. Torres-Vitela M. M. Castillo-Ortega F. Bautista J. E. Puig S. M. Nuño-Donlucas 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):876-884
The synthesis by emulsion polymerization and the characterization by a battery of techniques of poly(butyl acrylate-co-silver acrylate) [poly(BuAc-co-AgAc)] ionomers are reported here. Reaction rates were fast and conversions around 90% were obtained in less than one hour, regardless of the initial ratio of butyl acrylate and silver acrylate employed (BuAc/AgAc = 90/10, 80/20, 70/30). Particle size was in the range of 176 to 200 nm, depending on the BuAc/AgAc ratio. Ionomers’ formation was corroborated by infrared spectroscopy and inferred by differential scanning calorimetry (DSC). DSC disclosed that the poly(BuAc-co-AgAc) has two glass transition temperatures: one at ca. ?49°C due to relaxation of the ionomer backbone domains rich in BuAc and another ca. 35°C due to the relaxation of the backbone domains where the AgAc-units content was higher. Young moduli increased as the copolymers became richer in AgAc. Antibacterial tests against Escherichia coli with the 90/10 (BuAc/AgAc) ionomer revealed that the bacteria population diminishes from 5 log CFU/mL to less than 0.3 MPN/mL after one hour of contact with the ionomers. Also, we demonstrated that the ionomers are excellent compatibilizers for making semiconductive films of n-dodecylbenzene sulfonic acid-doped polyaniline (PANIDBSA)-poly(BuAc-co-AgAc) and poly(n-butyl methacrylate) (PBMA) blends. The electrical conductivity of the blend films, which were homogeneous, rose as the AgAc content in the films increased. 相似文献
990.
Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo‐heterocycles
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María Inés Flores‐Conde Fabiola N. de la Cruz Julio López J. Óscar C. Jiménez‐Halla Eduardo Peña‐Cabrera Marcos Flores‐Álamo Francisco Delgado Miguel A. Vázquez 《应用有机金属化学》2018,32(3)
The unprecedented reaction of ketone‐containing aromatic pyridinium salts 3a ‐ e and alkynyl Fischer complexes 1a ‐ f proceeds via a mild domino process to provide 4,6‐disubstituted pyran‐2‐ones 5a ‐ k and 2,3,5‐trisubstituted furans 6a ‐ h (45‐97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products. 相似文献