Browsing by Author "Terraza, Claudio A."

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    A new porous organic polymer containing Troger's base units: Evaluation of the catalytic activity in Knoevenagel condensation reaction
    (2021) Rodriguez-Gonzalez, Fidel E.; Niebla, Vladimir; Velazquez-Tundidor, M. V.; Tagle, Luis H.; Martin-Trasanco, Rudy; Coll, Deysma; Ortiz, Pablo A.; Escalona, Nestor; Perez, Edwin; Jessop, Ignacio A.; Terraza, Claudio A.; Tundidor-Camba, Alain
    The classic Tro center dot ger's base polymerization of a diamine and dimethoxymethane with trifluoroacetic acid as catalyst generated a Tro center dot ger's base-type polymer (TBP), which exhibited the absolute insolubility in a variety of organic solvents because of its highly aggregated model. A new porous organic polymer was obtained by a simple Tro center dot ger's base polymerization reaction between a diamine and formaldehyde in the form of acetal in the presence of trifluoroacetic acid as catalyst. Tro center dot ger's base-type polymer (TBP) resulted insoluble in a wide range of organic solvents due to its rigid and aromatic structure. TBP was characterized spectroscopically (FT-IR), thermally and morphologically. As result, a thermostable and amorphous polymer bearing pores ranging between 50 and 300 nm and macro-voids of up to 12 mu m was obtained. Due to the insolubility of the TBP, it was tested as a metal-free heterogeneous catalyst in the Knoevenagel condensation reaction, showing a high efficiency. For this, the optimal catalyst load, reaction time and reuse of the catalyst were studied using benzaldehyde and malononitrile as substrates. Furthermore, aldehydes with variable chain sizes and ethyl cyanoacetate replacing malononitrile were tested as substrate with a high percent of conversion (97-99%).
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    A semi-rigid co-poly(imide) derived from an isomeric mixture of monomers. Assessing gas transport properties in self-standing polymer membrane
    (2024) Cruz, Yennier; Rodriguez, Ary; Rodriguez-Gonzalez, Fidel E.; V. Velazquez-Tundidor, Maria; Niebla, Vladimir; Aguilar-Vega, Manuel; Sulub-Sulub, Rita; Coll, Deysma; Terraza, Claudio A.; Tundidor-Camba, Alain
    Chemical structure and morphology of polymers are directly related with the membrane separation performance. Poly(imide)s (PIs) are the most widely used polymers in the preparation of membranes for gas separation applications; thus, research on the structural design of polymers is of great interest to develop new membranes. In the present work, we reported the synthesis, characterization, and measurement of the gas transport properties of a new co-poly(imide)s (PI-D2a-D2b-6FDA) prepared from a mixture of isomeric diamines. The co-poly(imide) synthetic route involved several steps, starting by a bromination reaction, followed by a double nucleophilic aromatic substitution giving an isomeric mixture of precursors, which suffered a Suzuki-Miyaura C-C crosscoupling reaction followed by the reduction of nitro groups to give two new isomeric diamines. Finally, diamines simultaneously reacted with the dianhydride 6FDA to obtain PI-D2a-D2b-6FDA. The co-poly(imide) had a Mn of 47.7 kDa and a Mw of 74.0 kDa with a PDI of 1.6. The sample exhibited a 10% weight loss at 540 degrees C, Tg of 280 degrees C, BET surface area of 110 m2 g-1, and wide-angle X-ray diffraction (WAXD) interchain d -spacing at 9.5 & Aring; and 6.3 & Aring;. Tensile strength, elongation at break and Young's modulus were 109.6 MPa, 6.66% and 2.18 GPa, respectively. co-Poly(imide) was soluble in various polar aprotic organic solvents such as DMSO, NMP, DMF, DMAc, THF, and chloroform, forming a self -standing dense film whose gas transport properties were measured. Pure gas permeability coefficients for H2, CO2, O2, N2, and CH4, were 47.28, 24.04, 4.35, 1.02, and 0.76 (Barrer), respectively, which follows a decreasing order by the increasing kinetic diameters of the respective gases. Ideal gas selectivities H2/N2, O2/N2, CO2/CH4, and CO2/N2 were 46.4, 4.3, 31.6, and 23.6, respectively. These gas transport properties were compared with the commercial polymer Matrimid (R), showing higher gas permeability coefficients than Matrimid (R).
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    Comparison between poly(azomethine)s and poly(p-phenylvinylene)s containing a di-R-diphenylsilane (R = methyl or phenyl) moiety. Optical, electronic and thermal properties
    (2021) Sobarzo, Patricio A.; Mariman, Andrea P.; Sanchez, Christian O.; Hauyon, Rene A.; Rodriguez-Gonzalez, Fidel E.; Medina, Jean; Jessop, Ignacio A.; Recabarren-Gajardo, Gonzalo; Tundidor-Camba, Alain; Terraza, Claudio A.
    Two new silicon-containing poly(azomethine)s (PAzM-Me and PAzM-Ph) and two new silicon-containing poly(pphenylvinylene)s (PPVSi-Me and PPVSi-Ph) were obtained from 4',4'''-(dimethylsilanediyl)bis([1,1 '-biphenyl]-4-carbaldehyde) and 4',4'''-(diphenyl silanediyl)bis([1,1 '-biphenyl]-4-carbaldehyde) with p-phenylendiamine for PAzMs or phenylenebis(methylene))bis(triphenylphosphonium) bromide for PPVSis. All polymers were structurally characterized by FT-IR, NMR and elemental analysis. The materials showed a high thermal stability (501-538 degrees C) with the TPS-core increasing this parameter. The absorption and emission of PAzMs and PPVSis were closely related with the nature of the silane-core in the backbone. All samples showed wide-band gaps where the TPS-core-based materials evidenced the lower energy transitions; PAzM-Ph (2.83 eV) and PPVSi-Ph (2.81 eV). This work lay the groundwork for new architectures of silane-based poly(azomethine)s and poly(p- phenylvinylene)s derivatives for potential optoelectronic applications.
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    Development of Novel Phase-Change Materials Derived from Methoxy Polyethylene Glycol and Aromatic Acyl Chlorides
    (2023) Angel-Lopez, Alejandro; Norambuena, Angel; Arriaza-Echanes, C.; Terraza, Claudio A.; Tundidor-Camba, Alain; Coll, Deysma; Ortiz, Pablo A.
    In this research, novel, organic, solid-liquid phase-change materials (PCMs) derived from methoxy polyethylene glycol (MPEG) and aromatic acyl chlorides (ACs) were prepared through a condensation reaction. The MPEGs were used as phase-change functional chains with different molecular weights (350, 550, 750, 2000, and 5000 g/mol). The aromatic ACs, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC), were employed as bulky linker cores. Solubility tests demonstrated that this family of PCMs is soluble in protic polar solvents such as H2O and MeOH, and insoluble in nonpolar solvents such as n-hexane. Fourier-ransform infrared spectroscopy (FT-IR UATR) and nuclear magnetic resonance (H-1, C-13, DEPT 135 & DEG;, COSY, HMQC, and HMBC NMR) were used to confirm the bonding of MPEG chains to ACs. The crystalline morphology of the synthesized materials was examined using polarized optical microscopy (POM), revealing the formation of spherulites with Maltese-cross-extinction patterns. Furthermore, it was confirmed that PCMs with higher molecular weights were crystalline at room temperature and exhibited an increased average spherulite size compared to their precursors. Thermal stability tests conducted through thermogravimetric analysis (TGA) indicated decomposition temperatures close to 400 & DEG;C for all PCMs. The phase-change properties were characterized by differential scanning calorimetry (DSC), revealing that the novel PCMs melted and crystallized between -23.7 and 60.2 & DEG;C and -39.9 and 45.9 & DEG;C, respectively. Moreover, the heat absorbed and released by the PCMs ranged from 57.9 to 198.8 J/g and 48.6 to 195.6 J/g, respectively. Additionally, the PCMs exhibited thermal stability after undergoing thermal cycles of melting-crystallization, indicating that energy absorption and release occurred at nearly constant temperatures. This study presents a new family of high-performance organic PCMs and demonstrates that the orientation of substituent groups in the phenylene ring influences supercooling, transition temperatures, and thermal energy storage capacity depending on the MPEG molecular weight.
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    Effect of thiophene, furan moieties and zinc ions on melamine-based porous polyaminals properties and catalytic activity on CO2 cycloaddition reaction
    (2022) Sobarzo, Patricio A.; Tundidor, Alain; Sanz-Perez, Eloy S.; Terraza, Claudio A.; Maya, Eva M.
    A new series of melamine-based porous polyaminals containing thiophene or furan moieties of different size in the polymer network were prepared and fully characterized. The new polyaminals were N-rich polymers with nitrogen content between 10 and 28%, exhibited micro-, meso- or macroporosity, depending on the type and size of the thiophene or furan moiety with specific surface areas in the range of 23-490 m(2)/g. The CO2 uptakes were moderated, between 1 and 5% and those polyaminals with higher CO2 uptake capacity were selected as catalysts to promote the conversion of CO2 into cyclic carbonate and also to prepare the corresponding zinc complexes, which were used as catalysts in the same reaction. The selected catalysts showed good catalytic performance working under much milder reaction conditions (CO2 pressure of 4 bar, 80 degrees C, 0.1 mol % of cocatalyst) than the examples of melamine-based polyaminals published so far for this reaction.
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    Ionenes as Potential Phase Change Materials with Self-Healing Behavior
    (2023) Arriaza-Echanes, Carolina; Velazquez-Tundidor, Maria V.; Angel-Lopez, Alejandro; Norambuena, Angel; Palay, Francisco E.; Terraza, Claudio A.; Tundidor-Camba, Alain; Ortiz, Pablo A.; Coll, Deysma
    Ionenes are poly(ionic liquids) (PILs) comprising a polymer backbone with ionic groups along the structure. Ionenes as solid-solid phase change materials are a recent research field, and some studies have demonstrated their potential in thermal dissipation into electronic devices. Eight ionenes obtained through Menshutkin reactions were synthesized and characterized. The analysis of the thermal tests allowed understanding of how the thermal properties of the polymers depend on the aliphatic nature of the dihalogenated monomer and the carbon chain length. The TGA studies concluded that the ionenes were thermally stable with T10% above 420 degrees C. The DSC tests showed that the prepared ionenes presented solid-solid transitions, and no melting temperature was appreciated, which rules out the possibility of solid-liquid transitions. All ionenes were soluble in common polar aprotic solvents. The hydrophilicity of the synthesized ionenes was studied by the contact angle method, and their total surface energy was calculated. Self-healing behavior was preliminarily explored using a selected sample. Our studies show that the prepared ionenes exhibit properties that make them potential candidates for applications as solid-solid phase change materials.
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    Microwave-assisted melamine-based polyaminals and their application for metal cations adsorption
    (2021) Sandin, Ricardo; Gonzalez-Lucas, Maria; Sobarzo, Patricio A.; Terraza, Claudio A.; Maya, Eva M.
    Three new cross-linked melamine-based polyaminal networks containing phenyl (MA-iPh), pyridine (MA-Py) or thiophene (MA-Th) moieties were easily prepared by microwave irradiation (MW) in shorter reaction times (between 1.5 and 4 h) than conventional heating (72 h). The networks showed high nitrogen content (27-37%), specific surfaces between 34 and 424 m(2)g(-1) and high thermal stability (300 degrees C). The adsorption capacity of these polyaminals was determined over different toxic metals such as Cr(VI), Cu(II), Cd (II) and Pb(II) at different pH. The results showed greater chromium adsorption capacity in acid medium (pH 2), while the divalent cations were mainly adsorbed at pH 5. MA-Py that displayed the highest nitrogen content (37%) and highest specific surface area (424 m(2)g(-1)) also showed the highest adsorption capacities of this series, with values of 27.22, 26.42, and 53.13 mg/g for Cr(VI), Cd(II) and Pb(II); respectively. Additionally, MA-Py and MA-iPh with adsorption capacities of 29.12 and 25.02 mgg 1 for Cr(VI) and Cd(II), were competitive in terms of adsorption capacities regarding commercial ion exchange-resins which shown adsorptions in the range 13.7-21.3 mg/g.
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    New Benzotriazole and Benzodithiophene-Based Conjugated Terpolymer Bearing a Fluorescein Derivative as Side-Group: In-Ternal Forster Resonance Energy Transfer to Improve Organic Solar Cells
    (MDPI, 2022) Jessop, Ignacio A.; Cutipa, Josefa; Perez, Yasmin; Saldias, Cesar; Fuentealba, Denis; Tundidor-Camba, Alain; Terraza, Claudio A.; Camarada, Maria B.; Angel, Felipe A.
    A new benzodithiophene and benzotriazole-based terpolymer bearing a fluorescein derivative as a side group was synthesized and studied for organic solar cell (OSC) applications. This side group was covalently bounded to the backbone through an n-hexyl chain to induce the intramolecular Forster Resonance Energy Transfer (FRET) process and thus improve the photovoltaic performance of the polymeric material. The polymer exhibited good solubility in common organic chlorinated solvents as well as thermal stability (TDT10% > 360 degrees C). Photophysical measurements demonstrated the occurrence of the FRET phenomenon between the lateral group and the terpolymer. The terpolymer exhibited an absorption band centered at 501 nm, an optical bandgap of 2.02 eV, and HOMO and LUMO energy levels of -5.30 eV and -3.28 eV, respectively. A preliminary study on terpolymer-based OSC devices showed a low power-conversion efficiency (PCE) but a higher performance than devices based on an analogous polymer without the fluorescein derivative. These results mean that the design presented here is a promising strategy to improve the performance of polymers used in OSCs.
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    New Hybrid Copper Nanoparticles/Conjugated Polyelectrolyte Composite with Antibacterial Activity
    (2021) Jessop, Ignacio A.; Perez, Yasmin P.; Jachura, Andrea; Nunez, Hipolito; Saldias, Cesar; Isaacs, Mauricio; Tundidor-Camba, Alain; Terraza, Claudio A.; Araya-Duran, Ingrid; Camarada, Maria B.; Carcamo-Vega, Jose J.
    In the search for new materials to fight against antibiotic-resistant bacteria, a hybrid composite from metallic copper nanoparticles (CuNPs) and a novel cationic pi-conjugated polyelectrolyte (CPE) were designed, synthesized, and characterized. The CuNPs were prepared by chemical reduction in the presence of CPE, which acts as a stabilizing agent. Spectroscopic analysis and electron microscopy showed the distinctive band of the metallic CuNP surface plasmon and their random distribution on the CPE laminar surface, respectively. Theoretical calculations on CuNP/CPE deposits suggest that the interaction between both materials occurs through polyelectrolyte side chains, with a small contribution of its backbone electron density. The CuNP/CPE composite showed antibacterial activity against Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative (Escherichia coli and Salmonella enteritidis) bacteria, mainly attributed to the CuNPs' effect and, to a lesser extent, to the cationic CPE.
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    New polyimides containing methyl benzamidobenzoate or dimethyl benzamidoisophthalate as bulky pendant groups. Effects on solubility, thermal and gas transport properties
    (2022) Terraza, Claudio A.; Cruz, Yennier; Rodriguez, Ary; Victoria Velazquez-Tundidor, Maria; Hauyon, Rene A.; Rodriguez-Gonzalez, Fidel E.; Niebla, Vladimir; Aguilar-Vega, Manuel; Sulub-Sulub, Rita; Coll, Deysma; Ortiz, Pablo A.; Perez, Yasmin P.; Comesana-Gandara, Bibiana; Tundidor-Camba, Alain
    This work reports the synthesis of six new polyimides obtained by the reaction of two novel diamine monomers: methyl 4-(3,5-diaminobenzamido)benzoate and dimethyl 5-(3,5-diaminobenzamido)isophthalate, bearing one or two methyl ester groups in their phenyl rings, respectively, with three known dianhydrides, 4,4 '-(hexafluoroisopropylidene) diphatalic anhydride (6FDA), 4,4 '-(dimethylsilanediyl) dipthalic anhydride (SiDA) and 4,4 '-oxydiphthalic anhydride (ODPA). The polyimides were synthesized using the "two-step" method, which first involves forming a poly(amic acid) precursor that is subsequently cyclodehydrated to form the imide linkage. The yields were higher than 95% in all cases, and the structural characterization was performed by spectroscopic techniques like FT-IR, H-1, C-13, and Si-29 NMR. In addition, the effect on the solubility in common organic solvents and thermal and gas transport properties of these polyimides were studied as a function of the nature of the respective side group and the dianhydride used.
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    Polyimides Containing Biphenyl and Troger's Base Units for Gas Separation Membranes
    (2024) Rodriguez, Ary; Tundidor, Maria Victoria Velazquez; Cruz, Yennier; Rodriguez-Gonzalez, Fidel Ernesto; Aguilar-Vega, Manuel J.; Sulub-Sulub, Rita; Ravula, Sudhir; Bara, Jason E.; Terraza, Claudio A.; Tundidor-Camba, Alain
    Two diamine monomers containing biphenyl and Tr & ouml;ger's base units were synthesized, and each diamine that differed by the presence of two -CH3 groups was reacted with commercially 4,4 '-hexafluoroisopropylidene diphthalic anhydride (6FDA) for obtaining two polyimides of intrinsic microporosity (PIM-TB-PI-1 and PIM-TB-PI-2) with structural elements that ensured the formation of contorted and semirigid chains. Both PIM-PIs were soluble in polar aprotic solvents, including tetrahydrofuran and chloroform, showing high thermal stability (T-d > 500 degrees C) and high glass transition temperatures (T-g > 300 degrees C). The surface area and the distance between polymer chains were determined by using N-2 adsorption/desorption and wide-angle X-ray diffraction (XRD) techniques, respectively. PIM-TB-PI-1 showed a surface area of 81 m(2) g(-1) and d-spacing of 5.9 & Aring;, while PIM-TB-PI-2 had slightly higher values (SA = 109 m(2) g(-1) and d-spacing = 6.3 & Aring;). PIM-TB-PI-1 and PIM-TB-PI-2 form dense films that exhibited pure gas permeability coefficients that are 1 order of magnitude higher than Matrimid while they present lower perm-selectivities than the former. This result is related to chain rigidity in PIM-TB-PIs that maintains a distribution of microvoids that are large enough for these gases to diffuse through the interconnected free volume, and the TB units in the main chain of both polymers increase steric hindrance for gas permeability and diffusion. The higher diffusion coefficients of PIM-TB-PI-2, as compared to PIM-TB-PI-1 are related to the presence of -CH3 groups near the imide group, preventing an efficient packing of the polymer chains.
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    Polymers of intrinsic microporosity containing aryl-phthalimide moieties: synthesis, modeling, and membrane gas transport properties
    (2023) Rodriguez-Gonzalez, Fidel E.; Soto, Cenit; Palacio, Laura; Montero-Alejo, Ana L.; Escalona, Nestor; Schott, Eduardo; Comesana-Gandara, Bibiana; Terraza, Claudio A.; Tundidor-Camba, Alain
    High-performance polymers for membrane gas separation require the careful design of the structure-porous relationship. In this work, five phthalimide-based polymers of intrinsic microporosity (PIMs) were obtained via the double nucleophilic aromatic substitution with the commercially available 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane (TTSBI) monomer. The phthalimide monomers were synthesized considering different sizes and positions of the alkyl-substituents to evaluate their influence on the physical properties of the polymers and their potential use as gas separation membranes. Four polymers were soluble in the low-boiling solvents chloroform and tetrahydrofuran, facilitating the casting of self-standing films to evaluate their gas separation properties. The thermally stable membranes showed 5% weight lost between 537 ? and 549 ?. As powders, these four polymers showed apparent BET surface areas ranging from 434 to 661 m(2) g(-1). The experimental BET surface areas correlated with those obtained by molecular simulation models of the synthesized polymers. A linear function is proposed as a tool to predict, with a known uncertainty, the surface area values of this type of polymer from the corresponding computational models. As a trend, increasing the volume of the ortho-substituent in the aryl-phthalimide group increases the permeability of the membranes, reaching generally better performances than Matrimid (R) and close to those of PIM-1, considering their place on the Robeson diagrams of the O-2/N-2, CO2/CH4 and CO2/N-2 gas pairs. Aging studies between 63 and 122 days showed a decrease in permeability, accompanied by the typical increase in selectivity that tends to move the data parallel to the upper Robeson limits.
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    PVDF Composite Membranes with Hydrophobically-Capped CuONPs for Direct-Contact Membrane Distillation
    (2021) Saldias, Cesar; Terraza, Claudio A.; Leiva, Angel; Koschikowski, Joachim; Winter, Daniel; Tundidor-Camba, Alain; Martin-Trasanco, Rudy
    Water scarcity is an imminent problem that humanity is beginning to attempt to solve. Among the several technologies that have been developed to mitigate water scarcity, membrane distillation is of particular note. In the present work, CuO nanoparticles capped with 1-octanethiol (CuONPs@CH) or 1H,1H,2H,2H-perfluorodecanethiol (CuONPs@CF) are prepared. The nanoparticles are characterized by FT-IR and TGA methods. Two weight losses are observed in both cases, with the decomposition of the organic fragments beginning at 158 degrees C and 230 degrees C for CuONPs@CF and CuONPs@CH, respectively. Flat sheet PVDF composite membranes containing nanoparticles are prepared by the casting solution method using nanoparticle concentrations that ranged between 2-20% with a non-woven polyester fabric as support. The obtained membranes showed a thickness of 240 +/- 40 mu m. According to water contact angle (87 degrees for CuONPs@CH and 95 degrees for CuONPs@CF, both at 10% w.t) and roughness (12 pixel for CuONPs@CH and 14 pixels for CuONPs@CF, both at 10% w.t) determinations, the hydrophobicity of membranes changed due to a decrease in surface energy, while, for naked CuONPs, the roughness factor represents the main role. Membranes prepared with capped nanoparticles showed similar porosity (60-64%). SEM micrographs show asymmetric porous membranes with a 200-nm surface pore diameter. The largest finger-like pores in the membranes prepared with CuONPs, CuONPs@CH and CuONPs@CF had values of 63 +/- 10 mu m, 32 +/- 8 mu m, and 45 +/- 10 mu m, respectively. These membranes were submitted to a direct contact membrane distillation module and flux values of 1.8, 2.7, and 3.9 kg(m(2)center dot h)(-1) at Delta T = 30 degrees C were obtained for the CuONPs, CuONPs@CH, and CuONPs@CF, respectively. The membranes showed 100% salt rejection during the testing time (240 min).
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    Spraying Fluorinated Silicon Oxide Nanoparticles on CuONPs@CF-PVDF Membrane: A Simple Method to Achieve Superhydrophobic Surfaces and High Flux in Direct Contact Membrane Distillation
    (2022) Lenac, Zivka; Saldias, Cesar; Terraza, Claudio A.; Leiva, Angel; Koschikowski, Joachim; Winter, Daniel; Tundidor-Camba, Alain; Martin-Trasanco, Rudy
    Desalinization of seawater can be achieved by membrane distillation techniques (MD). In MD, the membranes should be resistant to fouling, robust for extended operating time, and preferably provide a superhydrophobic surface. In this work, we report the preparation and characterization of a robust and superhydrophobic polyvinylidene fluoride membrane containing fluoroalkyl-capped CuONPs (CuONPs@CF) in the inner and fluorinated capped silicon oxide nanoparticles (SiO(2)NPs@CF) on its surface. SiO(2)NPs@CF with a mean diameter of 225 +/- 20 nm were prepared by the sol method using 1H,1H,2H,2H-perfluorodecyltriethoxysilane as a capping agent. Surface modification of the membrane was carried out by spraying SiO(2)NPs@CF (5% wt.) dispersed in a mixture of dimethyl formamide (DMF) and ethanol (EtOH) at different DMF/EtOH % v/v ratios (0, 5, 10, 20, and 50). While ethanol dispersed the nanoparticles in the spraying solution, DMF dissolved the PVDF on the surface and retained the sprayed nanoparticles. According to SEM micrographs and water contact angle measurements, the best results were achieved by depositing the nanoparticles at 10% v/v of DMF/EtOH. Under these conditions, a SiO(2)NPs covered surface was observed with a water contact angle of 168.5 degrees. The water contact angle was retained after the sonication of the membrane, indicating that the modification was successfully achieved. The membrane with SiO(2)NPs@CF showed a flux of 14.3 kg(m(2)center dot h)(-1), 3.4 times higher than the unmodified version. The method presented herein avoids the complicated modification procedure offered by chemical step modification and, due to its simplicity, could be scalable to a commercial membrane.
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    Synthesis and Properties of Poly(imides) and Poly(imides)/Ionic Liquid Composites Bearing a Benzimidazole Moiety
    (2019) Terraza, Claudio A.; Ortiz, Pablo; Tagle, Luis H.; Perez, German; Saldias, Cesar; Rodriguez-Gonzalez, Fidel E.; Cabrera-Barjas, Gustavo; Catalan, Henry; Tundidor-Camba, Alain; Coll, Deysma
    Three new aromatic poly(imides) containing benzimidazole units in the backbone were synthesized and characterized by several spectroscopic techniques. Flexible spacer groups were incorporated into the poly(imides) structure to improve their solubility in organic solvents and their oxidative stabilization. All poly(imides) were thermally stable (T-d5% > 512 degrees C) and had the ability to form dense flexible films. Novel composite films were successfully prepared by loading poly(imide) with ionic liquid ([Bmim]Br) at different concentrations up to 25 wt.%. The resulting materials were characterized according to their morphology and elemental composition (SEM-EDX), water uptake capability, contact angle, and oxidative degradation resistance. Results suggested that poly(imide)/ionic liquid composites would be excellent candidates for future proton conductivity measurements.
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    Synthesis of dimethyl- and diphenylsilane-based oligo(azine)s: Thermal, optical, electronic, and morphological properties
    (2022) Sobarzo, Patricio A.; Jessop, Ignacio A.; Perez, Yasmin; Hauyon, Rene A.; Velazquez-Tundidor, Maria V.; Medina, Jean; Gonzalez, Alexis; Garcia, Luis E.; Gonzalez-Henriquez, Carmen M.; Coll, Deysma; Ortiz, Pablo A.; Tundidor-Camba, Alain; Terraza, Claudio A.
    Four new oligo(azine)s were synthesized from dimethyldiphenylsilane and tetraphenylsilane core-based dialdehydes and hydrazine by high-temperature polycondesation and proposed as materials for optoelectronic applications. The oligo(azine)s were characterized by EA, FT-IR, and NMR. Although most of samples were poorly soluble, TPS-containing PAZ-4 was soluble in aprotic polar solvents. According to SEC and FT-IR studies, the samples were oligomers with up to five repeating units long. TGA showed highly stable samples with TDT10% over 420 degrees C except for PAZ-1 that contains a DMS core along with phenyl units, and thus, the lowest carbon content in the series. From DSC analysis, the substitution of phenyl groups in PAZ-1/3 by biphenyl moieties in PAZ-2/4 allowed to obtain oligo(azine)s with lower T-g values. PAZ-4 showed a UV-A absorption with optical band-gap values of 2.91 and 2.65 eV from UV-vis (solution) and DRS (films), respectively. PL analysis showed a violet emission. PAZ-4 showed resistivity of 29.24 omega cm, similar to wide-band gap materials. Their contact angle measurements showed a critical surface tension of 42.29 dynes/cm, revealing its hydrophobicity. AFM analysis indicated that the PAZ-4 films had homogeneous surfaces. Young's modulus close to 4.46 GPa was established by microindentation for the PAZ-4 thin-films.
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    SYNTHESIS, CHARACTERIZATION AND FILM PREPARATION OF NEW CO-POLYIMIDE BASED ON NEW 3,5-DIAMINO-N-(PYRIDIN-4-YLMETHYL)BENZAMIDE, ODA AND 6FDA
    (2018) Tundidor-Camba, Alain; Saldias, Cesar; Tagle, Luis H.; Terraza, Claudio A.; Coll, Deysma; Perez, German; Aguilar-Vega, Manuel; Abarca, Romina L.; Ortiz, Pablo A.
    This work describes mainly the synthesis and characterization of new co-polyimides obtained from the polycondensation of the dianhydride 4,4'-(hexafluoroisopropylidene)diphtlialic anhydride (6FDA), 4,4'-oxydianiline (ODA) and the new diamine 3,5-diamino-N-(pyridin-4-ylmethyl)benzamide (PyDA). It describes as the different compositions of ODA and PyDA present in the polymers. produce variation on thermal and mechanical properties, which are important characteristics for the development of future nanocomposites derived from these polymers. Both PyDA monomer and polymers were characterized using FT-IR and NMR (H-1, C-13, F-19, dept 135 degrees, COSY, HMBC, HMQC) spectroscopy. The inherent viscosity of polymers is between 0.3 to 1.49 dL/g, they are soluble in aprotic polar solvents, such as: DMSO, DMF and DMA. In addition, all co-polymers showed thermal decomposition temperature and glass transition temperatures above 483 degrees C and 289 degrees C, respectively. Mechanical tests under tension of co-polymer films showed Young's modulus between 2.1-3.9 GPa and tensile strength between 35.5 and 120.0 MPa. On the other hand, an increase in crystallinity and hydrophilicity is observed when increasing the amount of pyridinyl groups.
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    Tetraphenylsilane-based oligo(azomethine)s containing 3,4-ethylenedioxy- thiophene units along their backbone: Optical, electronic, thermal properties and computational simulations
    (2022) Sobarzo, Patricio A.; Gonzalez, Alexis; Jessop, Ignacio A.; Hauyon, Rene A.; Medina, Jean; Garcia, Luis E.; Zarate, Ximena; Gonzalez-Henriquez, Carmen; Schott, Eduardo; Tundidor-Camba, Alain; Terraza, Claudio A.
    A series of three new oligo-poly(azomethine)s (o-PAzMs) were successfully synthesized, incorporating tetra-phenylsilane (TPS) and 3,4-ethylenedioxythiophene (EDOT) moieties with Mn and Mw between 3.9 and 5.4 kDa and 8.3-11.6 kDa, respectively. The silylated o-PAzMs were highly soluble in low-boiling point solvents such as CHCl3, THF, and CH2Cl2. All three materials are highly thermally stable, with onset temperatures of degradation of at least 250 degrees C and with TDT10% between 340 and 460 degrees C. The glass transition temperature values agree with the flexibility of the repetitive units and showed values between 125 and 155 degrees C. The absorption and emission of the o-PAzMs were observed in the blue-violet UV-vis region (350-550 nm) with moderate Stokes shifts (48-71 nm). The oligomers are it-conjugated wide-band gap materials (2.83-2.73 eV), where the high electronic tran-sitions would be associated with disruption of it-conjugation, which is promoted by the TPS core and (d-p)it orbital interactions. This disruption controls the effect from the EDOT unit rich donor on HOMO (-5.79 eV to-5.71 eV) and LUMO (-2.98 eV to-2.89 eV) energy values. Furthermore, DFT and TDDFT calculations were performed to theoretically characterize the observed UV-Vis transitions and frontier molecular orbitals (MOs) energies.
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    Theoretical and Experimental Vibrational Spectroscopic Investigation of Two R1R2-Diphenylsilyl-Containing Monomers and Their Optically Active Derivative Polymer
    (2014) Gonzalez-Henriquez, Carmen M.; Terraza, Claudio A.; Sarabia, Mauricio
    FT-IR and Raman spectra of bis(4-aminophenyl)diphenylsilane (DIA) and a dicarboxylic acid containing the imide function and a L-alanine moiety (L-ALA) and their resultant polymer (PALA) were recorded in the 500-4000 cm(-1) and 400-3800 cm(-1) regions, respectively. The optically active poly(imide-amide) obtained has two sp(3) carbons in the main chain, favoring its flexibility. Raman analysis identifies the fluorescence produced by the electronic conjugation between the aromatic rings and the amidic groups, which affects the molecular fine structure. Thus, the theoretical study of the vibrational patterns has become a support and a complementary technique for the characterization of this fluorescent system. The optimized molecular geometry of the monomers and the polymeric unit using B3LYP and HF methods at the 6-31G(d) level of theory were used for the vibrational assignments. Thus, the small variations between the calculated and experimental vibration values could be related to possible intra- and/or intermolecular interactions or to the existence of a charge transfer phenomena between a donor or acceptor group within the system.
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    Thiophene- and bithiophene-based π-conjugated Schiff base oligomers containing binaphthalene moieties in the backbone. Properties and computational simulations
    (2024) Gonzalez, Alexis F.; Mariman, Andrea P.; Hauyon, Rene A.; Pavez-Lizana, Danitza; Saldias, Cesar; Schott, Eduardo; Zarate, Ximena; Garcia, Luis; Gonzalez-Henriquez, Carmen M.; Jessop, Ignacio A.; Tundidor-Camba, Alain; Sobarzo, Patricio A.; Terraza, Claudio A.
    New pi-conjugated Schiff base oligomers (o-AZdAN1Th and o-AZdAN2Th) based on a binaphthalene core and containing thiophene or bithiophene units in their backbone were synthesized from the reaction between [1,1 '-binaphthalene]-4,4 '-diamine with thiophene-2,5-dicarbaldehyde and [2,2 '-bithiophene]-5,5 '-dicarbaldehyde by a high-temperature polycondensation method. These new materials were slightly soluble in non-protic polar solvents, such as chloroform and dichloromethane. From GPC analysis of the CHCl3-soluble fraction, o-AZdAN1Th was found to be a tetramer, whereas o-AZdAN2Th was a trimer with 1.4 kDa and 1.3 kDa average molecular weight (Mn), respectively. Both samples exhibited high thermal stability with T5% values of 452 degrees C and 456 degrees C and relatively high Tg values of 346 degrees C and 384 degrees C, for o-AZdAN1Th and o-AZdAN2Th, respectively. The samples showed absorptions in the deep-blue (o-AZdAN1Th) and blue (o-AZdAN2Th) regions of the visible spectrum, and emission responses at 387 nm and 447 nm, respectively, with moderate Stokes shifts (77-95 nm). Their optical and electronic properties were similar to those described for thiophene-based materials, with optical bandgap values close to 2.4 eV. HOMO energy values of -5.98 and -5.95 eV and LUMO energy values of -3.87 eV and -3.84 eV were obtained for o-AZdAN1Th and o-AZdAN2Th, respectively. Theoretical DFT and TD-DFT calculations were used to compare the effect of increasing thiophene units along the backbone for the real and also theoretical o-AZdANxTh samples (x = 3 and 4 thiophene units). According to our study, these two new thiophene-based can be proposed for optoelectronic applications.