Ramón Pamies

Universidad Politécnica de Cartagena | UPCT · Department of Material and Manufacture Engineering

Aqueous solutions of a thermoresponsive amphiphilic diblock copolymer, containing poly(N-isopropylacrylamide), in the presence of the anionic sodium dodecyl sulfate (SDS) surfactant can undergo a temperature-induced transition from loose intermicellar clusters to collapsed core-shell nanostructures. The polymer-surfactant mixtures have been charact...

A bead-and-spring model has been used to simulate the behavior of thermoresponsive asymmetric diblock amphiphilic copolymers with aid of Monte Carlo simulations. The alteration of the thermodynamic conditions was mimicked by using a Lennard-Jones potential, which was related to the measured temperatures by comparison with experimental data for aque...

The behavior of dilute solutions of linear polyelectrolyte molecules both at equilibrium and under shear flow is modeled by using the Brownian dynamics simulation technique. The mathematical polymer model consists of a bead-and-spring chain with charged beads that interact through a screened Debye–Hückel potential as well as through FENE spring for...

Effects of temperature on the association behavior in aqueous solutions of a series of thermosensitive poly(N-isopropylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide) triblock copolymers (PNIPAAM(m)-b-PEG(n)-b-PNIPAAM(m)) with the length of the PNIPAAM block fixed (m approximate to 67) and with different lengths of the PEG...

In this article, we report a study of the adsorption of a charged thermoresponsive poly(N-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride) [abbreviated as PNIPAAM24-b-PAMPTMA(+)18] block copolymer onto gold nanoparticles by means of dynamic light scattering (DLS), zeta-potential measurements, cryo-TEM, rheology small-a...

New nanocomposites based on biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) are processed via extrusion, using low content of calcined hydrotalcite (CHT) and cloisite 20A (C20A) as additives (3 wt%). The aim of this work is to characterize the thermal and viscoelastic response of the structures induced by the presence of the additive...

In this work, we present an ongoing redesign of the IMAM Romeo 41 biplane fighter aircraft. This antique plane is no longer operating and the only available information for the reconstruction was the maintenance manual, a catalogue with most of the pieces and old pictures. We aim the recreation of this aircraft with the aid of SolidWorks software....

In this study, we prepared plastic films composed of modified layered double hydroxides (LDHs), which were incorporated into a low-density polyethylene (LDPE) matrix. The sunscreen additive sulfonic phenylbenzimidazole acid sodium salt was incorporated as counter-anion in the interlayer of a nanoclay by means of ion-exchange reactions to improve th...

Three diprotic ionic liquids (PILs) containing bis(2-hydroxyethyl) ammonium cations and citrate (DCi), lactate (DL), or salycilate (DSa) hydroxy/carboxylate anions were studied as lubricants for Ti6Al4V–sapphire contact. At room temperature, the neat PILs are non-Newtonian fluids, which show up to a 70% friction coefficient reduction with respect t...

The triprotic ammonium carboxylate ionic liquid crystal (2-hydroxyethyl)ammonium oleate (MO) has been studied as a neat lubricant and as a lubricant additive in two base oils, PAO6 and 100N. The lubricants have been used in commercially pure copper-OFHC copper balls on disk reciprocating sliding contact at room temperature. Neat MO presents a very...

The development of new technologies strongly depends on the design of new materials. The combination of dissimilar materials opens a wide variety of opportunities to create composites with novel functions, properties, and applications [1]. Polymers are the most commonly used matrices due to their low density, simplicity of handling, low cost, and g...

The main purpose of the present study is to improve the tribological performance of aqueous lubricants with the use of ecofriendly, fatty acid-derived additives. The protic ionic liquid crystal bis(2-hydroxyethyl)ammonium stearate (DES) has been added to 50:50 water+ethylene glycol (W–EG) to obtain (W–EG)+0.5%DES; (W–EG)+1%DES and (W–EG)+2%DES emul...

A new series of nanofluids based on graphene dispersed in 2-hydroxyethylammonium lactate (ML) ionic liquid was developed. Concentrations of 0.1, 0.5 and 1 wt. % of graphene were studied and these dispersions were stable after 2 months. Raman spectra showed a strong interaction between ML and graphene. The effect of the concentration of graphene and...

Polylactic acid (PLA)-based nanocomposites were prepared by twin-screw extrusion. Graphene oxide (GO) and an ionic liquid (IL) were used as additives separately and simultaneously. The characterization of the samples was carried out by means of Fourier transform infrared (FT-IR) and Raman spectroscopies, thermogravimetric analysis (TGA), and differ...

Bis(2-hydroxyethyl) ammonium stearate (DES) protic ionic liquid crystal (PILC) has been added in 1 wt.% and 2 wt.% proportion to di-bis(2-hydroxyethyl) ammonium succinate (DSU) protic ionic liquid (PIL) to obtain (DSU+1%DES) and (DSU+2%DES) lubricant blends. The new blends are non-Newtonian fluids with liquid crystalline domains. Addition of (DES)...

The effect of microencapsulated phase‐change materials (MPCM) on the rheological properties of pre‐set geopolymer and Portland cement mortars was examined. Microcapsules with hydrophilic and hydrophobic shells were compared. The shear rate dependency of the viscosities fitted well to a double Carreau model. The zero shear viscosities are higher for...

To reduce pollution and global warming, the energy consumption needs to be decreased. Incorporation of Phase Change Materials (PCMs) into building materials can help lower the energy needed to cool and warm buildings, while keeping the indoor temperature at a comfortable level. However, incorporation of PCMs into construction materials alter their...

The thermoresponsive nature of aqueous solutions of poly(N‐isopropylacrylamide) (PNIPAAM) star polymers containing 2, 3, 4, and 6 arms has been investigated by turbidity, dynamic light scattering, rheology, and rheo‐SALS. Simulations of the thermosensitive nature of the single star polymers have also been conducted. Some of the samples form aggrega...

Graphene (0.5 wt.%) was dispersed in the hydrophobic room-temperature ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (IL) to obtain a new non-Newtonian (IL + G) nanolubricant. Thin layers of IL and (IL + G) lubricants were deposited on stainless steel disks by spin coating. The tribological performance of the new thin...

The rheological behavior of bis[(2-hydroxyethyl)ammonium] palmitate (DPA) fatty acid-derived ionic liquid crystal (ILC) and its dispersions in water has been determined. Neat DPA shows non-Newtonian behavior, with a temperature-thickening effect in the mesomorphic state. The dispersion of 1 wt% DPA in water yields a Newtonian fluid, with viscosity...

This review is focused on the recent developments of nanocomposite materials that combine a thermoplastic matrix with different forms of graphene or graphene oxide nanofillers. In all cases, the manufacturing method of the composite materials has been melt-processing, in particular, twin-screw extrusion, which can then be followed by injection mold...

When developing materials for lunar construction, it is essential to minimize the weight of components that have to be brought in from Earth. All necessary ingredients for geopolymers could potentially be sourced on the lunar surface, which is why the material might be an efficient construction material for infrastructure on the moon. Finding a che...

In this study, we have synthesized new double layered hydroxides to be incorporated to low density polyethylene thermoplastic matrix. These new composites present promising applications as materials to build greenhouses due to the enhancement of their optical properties. A characterization of the modified nanoclay has been performed by means of X-r...

Fatty acids are natural products which have been studied as green lubricants. Ionic liquids are considered efficient friction reducing and wear preventing lubricants and lubricant additives. Fatty acid-derived ionic liquids have shown potential as neat lubricant and additives. Protic ionic liquid crystals (PILCs) are protic ionic liquids (PILs) whe...

Polymethylmethacrylate (PMMA) and nanocomposites containing 0.5 wt.% graphene oxide (GO), graphene oxide-multiwalled carbon nanotubes (NT) or graphene oxide-ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate (IL) (PMMA+GO; PMMA+GO-NT; PMMA+GO-IL) were processed by a single step twin-screw micro-extrusion. The effect of two extrusion tempera...

The present work intends to provide a brief account of the most recent advances in the use of ionic liquid crystals (ILCs) in the field of tribology, that is, the development of new lubricants with the ability to reduce the coefficients of friction and the wear rates of materials under sliding conditions. After a definition of ILCs and their relati...

The design of micro-and nano-composites is an increasing technology that improves the optical, mechanical, and electrical properties of polymeric materials with promising applications in different fields, such as nanotechnology, agriculture, or biomedicine. Rheology is a powerful tool that provides crucial knowledge regarding the interaction betwee...

Dispersions of three different types of carbon nanotubes in a 1 wt.% proportion in the low viscosity 1-ethyl-3-methylimidazolium ([EMIM][DCA]) ionic liquid have been obtained. The neat ionic liquid presents Newtonian behavior, but the addition of carbon nanotubes increases the viscosity with respect to [EMIM][DCA] in the following order: Single-Wa...

The effect of frost conditions on the physical and mechanical properties of geopolymer concrete (GPC) and Portland cement concrete (PCC) containing two different micro-encapsulated phase change materials (MPCM) was examined. Microstructural studies revealed that the freeze-thaw induced concrete deterioration can be contributed to microcracks appear...

In this paper we represent a study reporting the numerical simulation of small-diameter pipes extrusion process. Polypropylene and low density polyethylene were chosen as plastics and a selected transverse head as a tool in the simulations. The aim of the study is to examine the distribution of temperature in the individual sections of the bagasse...

Molybdenum chalcogenides present interesting properties beyond their superconducting critical temperatures and upper critical magnetic fields, making them suitable for potential applications in tribology, batteries, catalysis, or thermopower. In this study, Mo15S19 nanoparticles with an average diameter of 10 nm were synthesized via the reaction of...

A mix design procedure for geopolymer concrete (GPC) was developed in order to maintain a high compressive strength after adding micro-encapsulated phase change materials (MPCM). The most relevant factors which affect the properties of fly ash/slag based GPC containing MPCM are considered. Class F fly ash and slag, sodium hydroxide and sodium silic...

New dispersions of few-layers graphene (G) in 1-ethyl-3-methylimidazolium ([EMIM]) ionic liquids (ILs) with dicyanamide ([DCA]) or bis(trifluoromethylsulfonyl)imide ([TFSI]) anions have been obtained by mechanical mixing and sonication. IL+0.5 wt% G dispersions show constant viscosity values from 357K (for IL = [EMIM][DCA]) or from 385K (for IL = [...

The effect of micro-encapsulated phase change materials (MPCM) in solid and liquid states on the mechanical properties and microstructure of geopolymer and Portland cement concretes is investigated. Geopolymer concrete (GPC) and Portland cement concrete (PCC) containing different amounts of MPCM were prepared and cured at both 20 °C and 40 °C. The...

La presente invención se refiere a una dispersión que comprende el líquido iónico dicianamida de 1-etil-3-metilimidazolio y partículas de grafeno sin modificar dispersas en dicho líquido iónico. La dispersión de las partículas de grafeno sin modificar en el líquido iónico da lugar a un fluido libre de elementos tóxicos y cuya viscosidad aumenta con...

The rheological behavior of 1-ethyl-3-methylimidazolium tosylate (EMIMTsO) and its dispersions with aligned and nonaligned multiwalled carbon nanotubes (MWCNTs) has been studied. Raman spectroscopy analysis has been carried out to characterize the samples. The effects of concentration, types of carbon nanotubes (CNTs), and temperature on the viscol...

New hybrid complexes composed by a thermoresponsive copolymer and gold nanoparticles (Rh = 22 nm) have been characterized by dynamic light scattering (DLS) and UV-visible spectroscopy. A cationic thermoresponsive triblock copolymer, methoxy-poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly((3-acrylamidopropyl) trimethyl ammonium ch...

In this work, we present a rheological characterization of pure IL and dispersions of two different types of MWCNTs in 1-ethyl-3-methylimidazolium tosylate (EMIMTsO). We have studied the shear effect on EMIMTsO-MWCNTs dispersions at different temperatures. Studies have been carried out for two different MWCNT regime concentrations in IL. Therefore,...

Chitosan (CS) is a biocompatible polysaccharide with positive charge that is widely used as a coating agent for negatively charged nanoparticles. However, the types of structures that emerge by combining CS and nanoparticles as well as their behaviour are still poorly understood. In this work, we characterize the nanocomposites formed by gold nanop...

The evaluation of the effect of saline aqueous media in the aggregation of colloidal gold nanoparticles (AuNP) suspensions has been followed by means of both dynamic light scattering and UV–Vis spectroscopy techniques. A wide range of ionic strengths from 0 to 1 M has been covered for suspensions of AuNPs with a hydrodynamic radius of 6.5 nm. The g...

The adsorption of a series of four poly(N-isopropylacrylamide)-based copolymers composed of a hydrophilic block of methoxy poly(ethylene glycol) (MPEG) with a variable length and a PNIPAAM block of fixed size (MPEGn -b-PNIPAAM71) onto flat and spherical citrate-coated gold surfaces has been investigated. The adsorption onto planar surfaces was stud...

The characterization of a series of four poly(N-isopropylacrylamide)-based copolymers with a hydrophilic block of poly(ethylene glycol) with a variable length (MPEGn -b-PNIPAAM71) has been performed by means of analytical ultracentrifugation. Molecular mass, partial specific volume, sedimentation coefficient (s), and hydrodynamic radius (R h) have...

The adsorption of two positively charged hydroxyethylcellulose derivatives with 7 and 60 mol % positively charged groups and a cationic, hydrophobically modified hydroxyethylcellulose containing 1 mol % hydrophobic groups and 7 mol % charged groups onto flat and spherical citrate-coated gold surfaces of different sizes has been investigated. The pl...

A broad study of the viscous behavior of three different sodium alginates in dilute and non-dilute solution in the presence of different electrolytes has been performed. In dilute solutions, we have determined the molecular weight of three different samples of sodium alginate from the same source through the Mark–Houwink–Sakurada equation. We have...

A computer programs suite, SIMUFLEX, has been constructed for the calculation of solution properties of flexible macromolecules modeled as bead-and-connector models of arbitrary topology. The suite consists mainly of two independent programs, BROWFLEX that generates the macromolecular trajectory by using the Brownian dynamics technique and ANAFLEX...

Temperature-induced phase transition of three low-molecular-weight samples (Mw < 1.2 × 104) of poly(N-isopropylacrylamide) was studied with the aid of turbidimetry, dynamic light scattering, and rheology. We have demonstrated that the lower critical solution temperature depends on the length of the chain and the concentration of the polymer in the...

This review elucidates several aspects on the behavior of charged polysaccharides and mucin. Viscosification of dilute aqueous solutions of hyaluronan (HA) occurs in the course of time at low shear flow, whereas shear thinning as time evolves is found at moderate shear rates. Hydrogen bonds and electrostatic interaction play an important role for t...

Temperature-induced intermicellar structures in aqueous solutions of the thermoresponsive methoxypoly(ethylene glycol)-block-poly(N-isopropylacrylamide) (MPEGn-b-NIPAAM71) copolymer that exhibit a lower critical solution temperature were studied by means of turbidimetry, dynamic light scattering (DLS), shear viscosity, and rheo small-angle light sc...

The determination of the intrinsic viscosity by single-point determinations, like that based on the Solomon–Ciuta equation, have been proposed as efficient alternatives to dilution procedures. With a basis on theoretical analysis and computer simulation, we evaluate the systematic and global bias of the Solomon–Ciuta result and show how it depends...

A combination of turbidity, light scattering, and steady shear viscosity experiments has revealed that aqueous solutions of an amphiphilic diblock copolymer or a negatively charged triblock copolymer, both containing poly(N-isopropylacrylamide), can undergo a temperature-induced transition from loose intermicellar clusters to collapsed core-shell n...

A temporary network formed by associative polymers with many sticky groups is represented by the bead-and-spring chain model and its dynamics is studied using Brownian dynamics simulation. The model contains neither the network topology nor explicit interactions between chains. Instead, appropriate transition rules are employed to represent the att...

The authors used the bead-and-spring model and the Brownian dynamics simulation technique including hydrodynamic interaction to study the behavior of dilute polyelectrolyte solutions under elongational flow. First they carried out simulations to determine the longest relaxation time of a polyelectrolyte, finding that the relaxation time depends on...

The longest relaxation time of polymer chains with varying topology (linear, regular star and ring) and flexibility (hard and soft connectors) is computed numerically by using two approaches: decay of certain property values after cessation of a perturbation (electric field or flow field) and fit of the time correlation function of some characteris...

The formation of associative networks in semidilute aqueous solutions of hydrophobically modified hydroxyethylcellulose (HM-HEC) is dependent on intermolecular hydrophobic interactions. Addition of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) monomers to the system provides decoupling of these associations via inclusion complex formation with the p...

A bead and spring model is considered for the Brownian dynamics simulation of the behavior of cyclic polymer chains (rings) in a dilute solution under shear or elongational flow. Finite extensibility, excluded volume, and hydrodynamic interaction are taken into account to make the polymer model as realistic as possible. In shear flow, the deformati...

A bead and spring model is considered for the Brownian dynamics simulation of the behavior of regular star polymer chains in a dilute solution under both shear flow and extensional (or elongational) flow. Finite extensibility, excluded volume, and hydrodynamic interaction are taken into account to make the polymer model as realistic as possible. Th...

The non-Newtonian behavior of dilute polymer solutions is investigated by computer simulation of a bead-and-spring model, using the Brownian dynamics technique to evaluate the shear rate dependence of the intrinsic viscosity. This behavior is a consequence of the combined effects of hydrodynamic interaction, excluded volume, and finite extensibilit...