Browsing by Author "Niebla, Vladimir"

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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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    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.