Though the stress, strain, and temperature dependence for an ideal rubber is fairly well established, the relation between network structural features like crosslinks, dangling ends, and entanglements and mechanical response is uncertain.... more
Though the stress, strain, and temperature dependence for an ideal rubber is fairly well established, the relation between network structural features like crosslinks, dangling ends, and entanglements and mechanical response is uncertain. The modulus-structure relations recently derived by Miller and Macosko for several types of networks are tested here with a model system: the hydrosilation crosslinking of vinyl-terminated polydimethylsiloxane chains with a tetra-functional silane. Results of shear modulus as a function of extent of reaction and of stoichiometric imbalance are in good agreement with the theory.
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For the first time, order–order and order–disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by... more
For the first time, order–order and order–disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene 1,3 (B) and hexamethylciclotrisiloxane (D3), and subsequently characterized by nuclear magnetic resonance (1H and 13C NMR), size exclusion chromatography (SEC), Fourier Transform
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Block copolymers constitute a fascinating group of polymeric materials belonging to the "soft matter" family. These materials are formed by blocks of polymeric chains from different monomers. In most cases, these blocks are... more
Block copolymers constitute a fascinating group of polymeric materials belonging to the "soft matter" family. These materials are formed by blocks of polymeric chains from different monomers. In most cases, these blocks are thermodynamically incompatible, but the covalent bonds between them impose specific arrangements, generating particular morphologies both in bulk and in solution. In this book, the authors present current research in the study of the phase morphology, material applications and future challenges of block copolymers. Topics discussed include the different experimental skills developed to synthesize model block copolymers; the macromolecular design of stereo block polylactides showing high performance; ion-containing block copolymers and their applications; self-assembled block copolymers for the preparation of advanced materials; the electrical properties of polythylene-b-polyethylene oxide diblock copolymers; and triblock copolymers as tougheners for PMMA matrices.Fil: Ninago, Mario Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Satti, Angel Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Gomez, Leopoldo Raimundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Vega, Daniel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Ciolino, Andrés Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Villar, Marcelo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Valles, Enrique Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
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Publisher Summary This chapter provides an overview of viscoelastic properties of model silicone networks with pendant chains. Model silicone networks, i.e., those prepared by end-linking of functionally terminated polymer chains, are... more
Publisher Summary This chapter provides an overview of viscoelastic properties of model silicone networks with pendant chains. Model silicone networks, i.e., those prepared by end-linking of functionally terminated polymer chains, are extensively utilized to explain the influence of molecular structure on mechanical properties. An important number of studies are focused on the contribution of elastically active chains and trapped entanglements to equilibrium properties. When a rubber network is stretched only those chain sections extending between crosslinking points are permanently oriented by the external stress and contribute to the elastic equilibrium modulus. Dangling chains are temporarily oriented by a deformation, but they can relax, reptating from the free ends towards their permanent junction with the network. At infinite times these chains do not contribute to the elastic force, but they do have a strong effect on time-dependent properties. Model polymer networks are materials prepared in a way that provides independent information on their structure. Synthetic procedures that link long chains of a given linear pre-polymer by their ends are quite successful in obtaining these kinds of materials.
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The synthesis of bidirectional anionic initiators by the reaction between metallic lithium (Li) and naphthalene (Naph), under mild conditions, in non-polar (benzene) or low-polarity media (benzene/THF mixtures) is reported. The efficiency... more
The synthesis of bidirectional anionic initiators by the reaction between metallic lithium (Li) and naphthalene (Naph), under mild conditions, in non-polar (benzene) or low-polarity media (benzene/THF mixtures) is reported. The efficiency of these initiators to provide macromolecules with well-defined structures was demonstrated. Model linear homopolymers from styrene (S) or hexamethyl(ciclotrisiloxane) (D3) monomers were synthesized using classical anionic polymerization (high-vacuum techniques). The model polymers obtained were analyzed using the conventional analytical techniques, and showed narrow molar mass distributions, a broad range of molar masses (from 3000 to 1,000,000 g/mol) and polydispersity indexes (Mw/Mn) lower than 1.1. High molar mass polymers were obtained using pure benzene as solvent, whereas lower molar masses were obtained in benzene/THF mixtures in which the concentration of THF was lower than 10 % v/v. The ratio [Li]/[Naph] and the nature of the reaction medium are the experimental parameters to be controlled to obtain the desired lithium naphthalenides.
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The polypropylene produced in most industrial polymerization processes is a resin which has excellent mechanical properties but broad molecular weight distribution and high molecular weight tails w...
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Research Interests: Engineering, Materials Science, Chemistry, Viscoelasticity, Polymer Chemistry, and 15 moreModeling, Rheology, Molecular modeling, Polymer, Stress relaxation, CHEMICAL SCIENCES, Rheological properties, Molecular Model, Molecular Mass, Molecular weight, Network Model, Rheometer, Theoretical Model, Mean Field Approximation, and Molecular Structure
SE HA SUGERIDO QUE UN DEFECTO EN LOS SISTEMAS DEFENSIVOS LOCALES O SISTEMICOS PODRIA PREDISPONER A INFECCIONES RESPIRATORIAS EN PACIENTES CON ENFERMEDADES OBSTRUCTIVAS DE LAS VIAS AEREAS. ES CONOCIDO QUE ALGUNOS TIPOS DE BRONQUIECTASIAS,... more
SE HA SUGERIDO QUE UN DEFECTO EN LOS SISTEMAS DEFENSIVOS LOCALES O SISTEMICOS PODRIA PREDISPONER A INFECCIONES RESPIRATORIAS EN PACIENTES CON ENFERMEDADES OBSTRUCTIVAS DE LAS VIAS AEREAS. ES CONOCIDO QUE ALGUNOS TIPOS DE BRONQUIECTASIAS, TIENEN SU ORIGEN EN DEFECTOS INMUNOLOGICOS PRIMARIOS QUE AFECTAN FUNDAMENTALMENTE A LA INMUNIDAD HUMORAL. LA PREVALENCIA DE ENFERMEDADES ATOPICAS EN PACIENTES CON DEFICIT PRIMARIO DE INMUNOGLOBULINA A ES MAYOR QUE EN LA POBLACION NORMAL. A PESAR DE SER MAS FRECUENTES LOS DEFICITS DE INMUNIDAD HUMORAL, EXISTE TAMBIEN LA POSIBILIDAD DE QUE EXISTA UNA PROPORCION DEFICIENTE DE CELULAS EFECTORAS DE LA INMUNIDAD. LOS OBJETIVOS DE ESTE TRABAJO SON: 1) COMPARAR ALGUNOS PARAMETROS DE LA INMUNIDAD HUMORAL Y CELULAR EN PACIENTES DIAGNOSTICADOS DE ENFERMEDAD PULMONAR OBSTRUCTIVA CRONICA, ASMA Y BRONQUIECTASIAS, ASI COMO EN UN GRUPO DE PERSONAS SANAS. 2) DETERMINAR LA PREVALENCIA DE LOS DEFICITS PRIMARIOS DE INMUNOGLOBULINAS EN LOS MISMOS ENFERMOS. 3) RELACIONAR LA SITUACION INMUNITARIA DE ESTOS ENFERMOS CON LA EVOLUCION CLINICO FUNCIONAL. SE CONCLUYE QUE: 1. NO EXISTEN DIFERENCIA ESTADISTICAMENTE SIGNIFICATIVAS EN LOS NIVELES DE INMUNOGLOBULINAS, SUBPOBLACIONES LINFOCITARIAS Y FRACCIONES C3 Y C4 DEL COMPLEMENTO ENTRE LOS DIFERENTES GRUPOS DE ENFERMOS. 2. LAS INMUNODEFICIPRIMARIAS CONSTITUYEN UN 20% DE CASOS DE BRONQUIECTASIAS DE CAUSA NO ACLARADA, UN 8% DE LOS CASOS DE ASMA Y UN 1.98 DE LOS CASOS DE EPOC. 3. LOS ESTUDIOS INMUNOLOGICOS DEBEN DE ENTRAR A FORMAR PARTE EN EL PROTOCOLO DE ESTUDIO DE LOS PACIENTES CON BRONQUIECTASIAS DE CAUSA NO ACLARADA, ESPECIALMENTE EN JOVENES, NO FUMADORES Y CON ANTECEDENTES DE PROCESOS INFECCIOSOS DE VIAS ALTAS O BAJAS.
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Research Interests: Engineering, Materials Science, Polymer science, Rheology, Ingenieria y ciencias de los Materiales, and 10 moreCrosslinking, Polyolefins, Polypropylene, Composite Material, CHEMICAL SCIENCES, Extrusion, Extrusion Moulding, Structure-Property Relationships In Materials, Journal of Applied Polymer Science, and Melt Flow Index
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A reaction between a linear polypropylene functionalized with maleic anhydride (PPg) and epoxy resin (bisphenol A diglycidyl ether) was carried out on the molten state to generate long-chain branches (LCB) in the molecular structure of... more
A reaction between a linear polypropylene functionalized with maleic anhydride (PPg) and epoxy resin (bisphenol A diglycidyl ether) was carried out on the molten state to generate long-chain branches (LCB) in the molecular structure of the PPg. Concentrations of epoxy resin (ER) of up to 3.15 wt% were employed to obtain different levels of branching. FTIR spectroscopy analysis indicates that during the reaction, anhydride groups in PPg are consumed and new ester groups are formed. The presence of branches was verified using multiple-detection size-exclusion chromatography and rheology. The degree of long-chain branching induced in PPg augments with increasing concentration of ER. Furthermore, the materials modified with higher content of ER display gel-like behavior. The long-chain branched polymers also display thermo-rheological complexity. Thermal characterization studies show that LCBs have a nucleating effect during crystallization and cause the augment of the crystallization activation energy of PPg.
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The aim of this work was to design and characterize cross-linked hyaluronic acid (HA)-itaconic acid (IT) films loaded with dexamethasone sodium phosphate salt (DEX) for topical therapy of inflammatory ocular surface diseases. Films were... more
The aim of this work was to design and characterize cross-linked hyaluronic acid (HA)-itaconic acid (IT) films loaded with dexamethasone sodium phosphate salt (DEX) for topical therapy of inflammatory ocular surface diseases. Films were chemically cross-linked with polyethylene glycol diglycidyl ether (PEGDE), then physical and mechanical characterization by stress-strain, X-ray diffraction, X-ray fluorescence spectrometry and swelling assays was conducted. A sequential in vitro therapeutic efficacy model was designed to assess changes in interleukin (IL)-6 production in an inflamed human corneal epithelial (HCE) cell line after film exposure. Changes in cell proliferation after film exposure were assessed using the alamarBlue(®) proliferation assay. Experimental findings showed desirable mechanical properties and in vitro efficacy to reduce cell inflammation. A moderately decreased proliferation rate was induced in HCE cells by DEX-loaded films, compared to commercial DEX eye drops...
Research Interests: Chemistry, Inflammation, Cornea, Medicine, Pharmaceutics, and 14 moreDexamethasone, Cell line, In Vitro, Model, Humans, Hyaluronan, Hyaluronic Acid, Polyethylene Glycol, Topical Drug Administration, Ocular, Cell Proliferation, Medicina Clinica, Ophthalmic Solutions, and Pharmacology and pharmaceutical sciences
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A “modified cone and plate” is presented as an alternative geometry for the measurement of material functions in a rotational rheometer. It gives a significant improvement in the quality of the signal for the normal force and makes it... more
A “modified cone and plate” is presented as an alternative geometry for the measurement of material functions in a rotational rheometer. It gives a significant improvement in the quality of the signal for the normal force and makes it possible to reach higher shear rates prior to the point at which the sample fails. A theoretical and experimental study of this new geometry which can be used for normal force and torque measurements has been developed to obtain the first normal stress coefficient and viscosity information.
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The linear viscoelastic behavior of a series of partially hydrogenated polybutadienes (PHPB) obtained by catalytic hydrogenation of an almost monodisperse polybutadiene (PB) was studied experimentally at temperatures above 110 °C. The... more
The linear viscoelastic behavior of a series of partially hydrogenated polybutadienes (PHPB) obtained by catalytic hydrogenation of an almost monodisperse polybutadiene (PB) was studied experimentally at temperatures above 110 °C. The molecular characterization of the polymers used in this study showed that the catalytic hydrogenation of PB produces materials with a bimodal distribution of polymer species for global conversions lower than approximately 90%. All the PHPBs, even the less hydrogenated, are a mixture of a highly hydrogenated PB (with approximately 89% saturation) and unreacted PB. The rheological behavior of the fluids was studied measuring the elastic and viscous moduli at different temperatures in small-amplitude oscillatory shear flow. The two-phase polymer blends show thermorheological complex behavior and an increase in elasticity at low frequencies which may be associated with long relaxation time processes. The dynamic moduli of the pure components in the terminal region is modeled usi...
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Ring-opening homo- and co-polymerization reactions of ϵ-caprolactone were performed by employing anionic polymerization (high vacuum techniques) and lithium silanolates (LS) as initiators. LS were obtained by reaction between... more
Ring-opening homo- and co-polymerization reactions of ϵ-caprolactone were performed by employing anionic polymerization (high vacuum techniques) and lithium silanolates (LS) as initiators. LS were obtained by reaction between hexamethyl(cyclotrisiloxane) and sec-Bu–Li+, or from living poly(dimethylsiloxanyl)lithium chains. The results indicated that LS are efficient initiators for the ring-opening polymerization of ϵ-caprolactone, providing the respective homogeneous polymers in good yields.
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Se generan ramificaciones en polipropilenos comerciales con el objeto de mejorar el procesamiento en flujos elongacionales. La modificación del polipropileno comercial se hace mediante el proceso de procesamiento reactivo con distintos... more
Se generan ramificaciones en polipropilenos comerciales con el objeto de mejorar el procesamiento en flujos elongacionales. La modificación del polipropileno comercial se hace mediante el proceso de procesamiento reactivo con distintos agentes químicos que generan macroradicales en el polímero. Éstos, al recombinarse, generan macromoléculas ramificadas que mejoran las propiedades elongacionales del polímero en estado fundido.Fil: Guapacha Martínez, Jorge Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Failla, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Quinzani, Lidia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Valles, Enrique Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
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ABSTRACT Long-chain branched polypropylenes were synthesized from a maleic anhydride grafted polypropylene (PPg). Different levels of branching were generated by reactive processing using four chain-linking agents: glycerol,... more
ABSTRACT Long-chain branched polypropylenes were synthesized from a maleic anhydride grafted polypropylene (PPg). Different levels of branching were generated by reactive processing using four chain-linking agents: glycerol, 1,4-butanediol, 1,4-phenylenediamine, and the epoxy resin bisphenol-A diglycidyl ether. The results from Fourier transform infrared and size-exclusion chromatography confirm the grafting of the chain-linking agents onto grafted polypropylene and the generation of long-chain branches. In addition, the rheological and morphological results show that 1,4-phenylenediamine produces the largest increment of branching at significantly lower concentrations than the other chain-linking agents. Moreover, 1,4-phenylenediamine gives place to branched polypropylenes with narrower distribution of molecular structures. GRAPHICAL ABSTRACT
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In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerization of propene in the presence of mesoporous SBA-15 silica, which acts as a carrier of the catalytic system (zirconocene as catalyst and... more
In this study, nanocomposites based on polypropylene are synthesized by the in situ polymerization of propene in the presence of mesoporous SBA-15 silica, which acts as a carrier of the catalytic system (zirconocene as catalyst and methylaluminoxane as cocatalyst). The protocol for the immobilization and attainment of hybrid SBA-15 particles involves a pre-stage of contact between the catalyst with cocatalyst before their final functionalization. Two zirconocene catalysts are tested in order to attain materials with different microstructural characteristics, molar masses and regioregularities of chains. Some polypropylene chains are able to be accommodated within the silica mesostructure of these composites. Thus, an endothermic event of small intensity appears during heating calorimetric experiments at approximately 105 °C. The existence of these polypropylene crystals, confined within the nanometric channels of silica, is corroborated by SAXS measurements obtained via the change i...
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Nanocomposites based on isotactic polypropylene (iPP) and mesoporous silica particles of either MCM-41 or SBA-15 were prepared by melt extrusion. The effect of the silica incorporated into an iPP matrix was firstly detected in the... more
Nanocomposites based on isotactic polypropylene (iPP) and mesoporous silica particles of either MCM-41 or SBA-15 were prepared by melt extrusion. The effect of the silica incorporated into an iPP matrix was firstly detected in the degradation behavior and in the rheological response of the resultant composites. Both were ascribed, in principle, to variations in the inclusion of iPP chains within these two mesostructures, with well different pore size. DSC experiments did not provide information on the existence of confinement in the iPP-MCM-41 materials, whereas a small endotherm, located at about 100 °C and attributed to the melting of confined crystallites, is clearly observed in the iPP-SBA-15 composites. Real-time variable-temperature Small Angle X-ray Scattering (SAXS) experiments with synchrotron radiation turned out to be crucial to finding the presence of iPP within MCM-41 pores. From these measurements, precise information was also deduced on the influence of the MCM-41 on ...
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This work aimed to design and characterize cross-linked hyaluronic acid-itaconic acid films loaded with acetazolamide-hydroxypropyl β cyclodextrin-triethanolamine complexes. Films were cross-linked with itaconic acid and... more
This work aimed to design and characterize cross-linked hyaluronic acid-itaconic acid films loaded with acetazolamide-hydroxypropyl β cyclodextrin-triethanolamine complexes. Films were cross-linked with itaconic acid and poly(ethyleneglycol)-diglycidylether. Biopharmaceutical properties were assessed by evaluating in vitro drug release rate, biocompatibility in a human corneal epithelial cell line, bioadhesiveness with pig gastric mucin, in vivo bioadhesion and efficacy. Showed good mechanical properties and oxygen permeability. Proliferation rate of corneal cells was affected by highest acetazolamide concentration. Bioadhesive interaction exhibited a water movement from pig mucin to the film; in vivo experiments showed strong bioadhesion for 8 h and hypotensive effect for almost 20 h. Experimental set showed promising performance and encouraged future studies to optimize formulation. [Formula: see text].