Deysma Coll

Silicon-containing oligomeric poly(amides) with phthalimidyl-amide side groups: synthesis, characterization and thermal studies

Oligomeric poly(amide)s (PAs) were synthesized from monomeric diacids, which were obtained from phthalic anhydride and the amino acid glycine, l-alanine, l-phenylalanine, l-valine, l-leucine, l-isoleucine and p-aminobenzoic acid. The phthalimidyl acids (IA-1 to IA-7) reacted with 5-amino-isophthalic acid in order to obtain the monomeric diacids (1-7). Furthermore, the monomeric diacid 8 was obtained by direct reaction between phthalic anhydride and 5-amino-isophthalic acid. The isophthalic acid derivatives were reacted with bis(4-aminophenyl)diphenylsilane in order to obtain the PAs. Monomers and polymers were characterized by infrared and 1H-, 13C- and 29Si-NMR spectroscopy, elemental analysis and, when necessary, optical rotation. The results were in agreement with the proposed structures. The yields were generally good, but the η inh values were low, indicating that the polymers were of oligomeric nature, namely, a chain of moderate molecular weight. The polymers were soluble in polar aprotic solvents and some of them were soluble in m-cresol and tetrahydrofuran. The glass transition temperatures (T g) values were obtained by differential scanning calorimetry, showing, in general, a decrease in value when the volume of the side chain of the amino acid moiety was increased. The thermal stability of the polymers was determined by dynamic thermogravimetry, showing good values of thermal decomposition temperatures (TDT), especially for those with aromatic residue in the amino acid, and for PA without amino acid. For PAs in which the side chain of the amino acid was larger, the TDT values were lower, probably due to the lack of symmetry and the length of the side chain, both of which have influence on the thermal stability.

Silarylene-containing oligo(ether-amide)s based on bis(4-(4-amino phenoxy)phenyl)dimethylsilane. Effect of the dicarboxylic acid structure on some properties

Oligo(ether-amide)s (PEAs) based on diphenylsilane and oxyphenyl units were synthesized through a Yamazaki–Higashi phosphorylation polyamidation technique. Thus, three new aromatic monomers were synthesized and characterized: a di(ether-amine), bis(4-(4-aminophenoxy)phenyl)dimethylsilane, and two dicarboxylic acids, bis(4-(4-carboxyphenoxy)phenyl)dimethylsilane and bis(4-(4-carboxyphenoxy)phenyl)diphenylsilane. MALDI-TOF mass spectrometry analyses show that the average molecular masses of the PEAs ranged from 1334 to 2097 m/z. The UV-vis technique was used to determine the optical band gap (Eg) of the oligomers. These values were between 3.91 and 4.57 eV. On the other hand, the conductivity of the samples was measured in the solid state (film) through the “four point method” showing a slight conductor behavior (13.3 and 5.0 S cm−1). Determination of fluorescence emission peaks showed two absorption bands. The first peak is related to a lesser electron-donating nature from an amide group, while the second peak was attributed to the polar solvent. Raman spectroscopy was used to determine the functional group in order to corroborate the structure and the crystallinity degree of the PEAs. Microstructural analyses of the samples were developed by using grazing incidence X-ray diffraction, showing amorphousness in the system studied. AFM micrographs showed that all the samples present certain porosity. On the other hand, the incorporation of flexibility inducing oxyether linkages affected positively the solubility of the PEAs in common organic solvents, and also decreased significantly the values of the glass transition temperature (Tg) and increased the transparency in the UV-vis region. In all cases, the thermal decomposition temperature values (TDT10%) were above 400 °C.

Quantitative Structure–Activity Relationship of Organosulphur Compounds as Soybean 15-Lipoxygenase Inhibitors Using CoMFA and CoMSIA

Three‐dimensional quantitative structure–activity relationship studies were carried out on a series of 28 organosulphur compounds as 15‐lipoxygenase inhibitors using comparative molecular field analysis and comparative molecular similarity indices analysis. Quantitative information on structure–activity relationships is provided for further rational development and direction of selective synthesis. All models were carried out over a training set including 22 compounds. The best comparative molecular field analysis model only included steric field and had a good Q2 = 0.789. Comparative molecular similarity indices analysis overcame the comparative molecular field analysis results: the best comparative molecular similarity indices analysis model also only included steric field and had a Q2 = 0.894. In addition, this model predicted adequately the compounds contained in the test set. Furthermore, plots of steric comparative molecular similarity indices analysis field allowed conclusions to be drawn for the choice of suitable inhibitors. In this sense, our model should prove useful in future 15‐lipoxygenase inhibitor design studies.

Novel aromatic polyimides derived from 2,8-di(3-aminophenyl)dibenzofuran. Synthesis, characterization and evaluation of properties

Three aromatic polyimides (PIs) were prepared from a new aromatic diamine monomer derived from the rigid ring dibenzofuran. All PIs were obtained in high yield and the inherent viscosities were in the range of 0.60 and 0.74 dL g−1. Polyimides derived from 4,4′-hexafluoroisopropyliden diphthalic anhydride (6FDA) and 4,4′-(dimethylsilanediyl) diphthalic anhydride (SiDA) showed excellent solubility in a variety of aprotic polar organic solvents. All PIs showed high thermal stability with thermal decomposition temperature (TDT10%) between 555–590 °C and the glass transition temperatures (Tg) values were between 290 and 315 °C. Polymeric films were obtained from PI-6FDA and PI-SiDA solutions and then contact angle and surface free energy were tested in order to know the hydrophobicity of materials. Likewise, permeability and selectivity analyses were developed where PI-6FDA film offered a reasonably acceptable balance of permselectivity with values close to the Robeson upper-bound (1991), in particular for the CO2/CH4 gas pair.

Silicon-containing poly(esters) with halogenated bulky side groups. Synthesis, characterization and thermal studies

Poly(esters) (PEs) derived from diacids containing bulky side groups, which have an halogenated (Cl, Br) imide ring, an aminoacidic residue (glycine, L-alanine, L-valine) and an amide group were obtained with a silicon-containing diphenol. Also PEs without the aminoacidic residue were obtained. PEs were characterized by IR and NMR spectroscopy, and the results were in agreement with the proposed structures. PEs were obtained with good yields and moderate or high ηinh values. PEs were soluble in aprotic polar solvents and were swollen in other solvents like m-cresol and THF. The Tg values were determined and it was possible to see a tendency in the sense that when the size of the atom (Cl, Br) bonded to the imidic ring is increased, the Tg values decreased, also for those PEs obtained without the aminoacidic residue. The thermal decomposition temperatures showed that only two PEs can be considered as thermostable, considering TDT values above 400 °C at 10% of weight lost. The other PEs showed good thermal stability, showing in general a decrease of the TDT values when the volume of the side group, is increased. PEs showed UV-vis transparency at 400 nm lower than 20%, but between 500 and 600 nm, showed 80% transparency. PEs containing halogen atoms showed flame retardancy in a simple essay, with respect to PEs without halogen atoms in which the combustion was complete.

Aromatic polyimides containing cyclopropylamide fragment as pendant group. A study of the balance between solubility and structural rigidity

Aromatic polyimides (PIs) containing a cyclopropylamide moiety as bulky polar pendant group were prepared in high yield and were structurally characterized. Polyimides containing 4,4’-hexafluoroisopropyliden diphthalic anhydride and bis(3,4-dicarboxyphenyl)dimethylsilane anhydride were soluble in aprotic polar organic solvents, while those PI derived from benzophenone-3,3′,4,4′-tetracarboxylic dianhydride with a keto central unit was insoluble. The relationship between bulky pendant group and the nature of the central moiety of the dianhydride monomer respect to the thermal properties of the PIs was studied. All PIs were thermally stable showing thermal decomposition temperature with the 10% weight loss (TDT10%) between 425-480 ºC. The glass transition temperature (Tg) values range between 265 and 315 °C. Mechanical properties from films of a selected PI were tested too.

Synthesis and characterization of aromatic poly(ether-imide)s based on bis(4-(3,4-dicarboxyphenoxy)phenyl)-R,R-silane anhydrides (R = Me, Ph) – spontaneous formation of surface micropores from THF solutions

Two new aromatic dianhydride monomers containing R,R-diphenylsilane (R = Me or Ph), an ether group and an isobenzofuran-1,3-dione moiety in their structure were prepared and spectroscopically characterized. They were reacted with two silylated aromatic diamines, previously reported, in order to prepare four different aromatic poly(ether-imide)s (PEIs). High yields were obtained for the synthesis of these polymers with an inherent viscosity range between 0.10 and 0.27 dL g−1, corresponding to a viscosimetric average molecular weight (Mv) from 1740 to 9520. PEIs were soluble in a variety of polar aprotic solvents. The thermal decomposition temperatures measured varied between 473 and 526 °C and the glass transition temperature values obtained varied from 164 to 184 °C. All poly(ether-imide)s were transparent in the UV-visible region. Additionally, films of these polymers were prepared by deposition of a solution through a spin coating technique; this process induces a spontaneous micropore formation on the film surface by means of quasi-instantaneous solvent evaporation. The solid samples were morphologically characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM). Thus, shape, distribution and dimensions (diameter and height) of the pores were studied. These parameters varied in agreement with the specific polymer characteristics: molecular weight, solubility and the nature of the R groups inserted into the molecule (phenyl group presence produces larger and deeper pores), among others.

Synthesis and characterization of aromatic poly(amides) based on 3,5-diamino-N-cyclopropylbenzamide

Three aromatic poly(amides) (PAs) were prepared, one of them containing a dimethyldiphenylsilane unit from a new aromatic diamine monomer with a bulky pendant polar group. All PAs were obtained in high yield and the inherent viscosities were in the range of 0.30 and 0.47 dL g−1. The obtained poly(amides) showed excellent solubility in a variety of aprotic polar organic solvents. PAs evidence thermal stability with thermal decomposition temperature (TDT10%) between 300–371 °C and the glass transition temperatures (Tg) values were high (between 215 and 250 °C). PAs containing silicon atom in the main chain captures the highest moles number of water per mole of repeating unit. Contact angles were also tested in order to know the hydrophilicity of the polymer films.

New oligomeric poly(ether-imide)s containing diphenylsilane and dibenzofuran moieties. Synthesis and characterization

ABSTRACT A new aromatic diamine, 2,8-di(4-aminophenyl)dibenzofuran, was synthesized through the Suzuki C-C coupling reaction. This compound and an analoge diamine also based on a dibenzofuran moiety reacted with silylated-dianhydrides to yield three aromatic oligomeric poly(ether-imide)s (PEIs). The new diamine and the oligomers were characterized by elemental analysis, FT-IR, and NMR. Additionally, for the samples, solubility in an organic polar solvent was stablished and inherent viscosity values as an indirect measure of the molecular size were recovered. Some properties of PEIs were established and related to the specific structure of the repeating unit. In this sense, the rigidity/flexibility of the main chain fragments and the volume of groups bonded to silicon atom were responsible for the final properties of the polymers. All PEIs were obtained in high yield, but the inherent viscosities values of the soluble samples were low, indicating probably, low to moderated molecular sizes. The thermal decomposition temperatures measured by TGA varied from 490 to 562°C, and the Tg values ranged between 205 and 218°C. The solubility of all samples was tested in a series of common organic solvents at room temperature and at 40°C. The optical transparency in solution for the soluble samples was also determined.

3D-QSAR Modeling of Non-peptide Antagonists for the Human Luteinizing Hormone-releasing Hormone Receptor

The application of ligand-based drug design methods such as quantitative structure-activity relationship (QSAR) is a mandatory issue in the design of luteinizing hormone-releasing hormone (LHRH) receptor antagonists because the lack of information on the molecular structure for this target protein. The relationship between the structures and the antagonistic activities of 128 non-peptide antagonists for the LHRH receptor were modeled by using the classic QSAR methods comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). The best model included CoMSIA steric, electrostatic, hydrophobic and hydrogen bond donor fields, had a Q2 value of 0.780 and predicted adequately the activity of external compounds. The tridimensional contour maps generated were used to identify the key structural requirements responsible for a high biological activity of the compounds. These features should represent the ligand features involved in interactions with the target protein that modulate their potency as antagonists.