Alain Tundidor-Camba

Synthesis of Oligomeric Silicon-containing Poly(imide-amide)s Derived from Trimellitic Anhydride and Amino-Acids. Vibration Spectral, Optical, Thermal and Morphological Characterization

Poly(imide-amide)s (PIAs) were synthesized from diacids, which were obtained by trimellitic anhydride and glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and p-aminobenzoic acid, and bis(4-aminophenyl)diphenylsilane. Compounds were characterized by elemental analysis, optical activity, IR and NMR spectroscopies. Yields were good, but ηinh values were low, showing materials of oligomeric nature, confirmed by MALDI-TOF spectrometry. PIAs were soluble in polar aprotic solvents, while those derived from amino acids with bulky side groups were soluble in CHCl3 and acetone. The wavenumber of vibrational bands were compared by Infrared and Raman spectroscopy. However, the high fluorescence emitted for PIAs, difficult to predict the vibrations of certain functional groups by Raman spectroscopy. The incorporation of chiral, amide and imide moieties interrupt the conjugation and increase the flexibility of the system. In addition, the adjacent phenyl units from the silicon-containing diamine, disfavors the planar conformation, which affects the optical properties showing an insulator behavior. DSC analyses showed that PIA-VII of aromatic nature had the higher glass transition temperature (Tg) value. For the other PIAs the Tg values decreased when volume of the side groups was increased, with the exception of PIA-VI derived from L-isoleucine. The thermal decomposition temperatures showed that only PIA-VII derived from p-aminobenzoic acid was thermostable. For the other PIAs it was possible to see a decrease of the TDT values when the size of the side chain is increased. The size and shape of the polymeric particles were studied by Scanning Electronic Microscopy (SEM), showing a relation between structure, incorporation of rigid aromatic rings and voluminous group into the system.

Silicon-containing oligomeric poly(imido-amides) with amino moieties. Synthesis, characterization and thermal studies

Silicon-containing oligomeric poly(imido-amides) (PIAs) were synthesized from dicarboxylic imido-acids containing a Si atom, which were obtained from dianhydrides and the amino acids glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and p-aminobenzoic acid (I–III-(a–g)), were polymerized with the diamine bis(4-aminophenyl)diphenylsilane. Monomeric dicarboxylic imido-acids and PIAs were characterized by IR and 1H, 13C and 29Si NMR spectroscopy and, when necessary, optical rotation, and the results were in agreement with the proposed structures. The yields were very good, greater than 90%, but the ηinh values were low, indicating that PIAs were of oligomeric nature, especially those derived from dicarboxylic imido-acids with aromatic groups bonded to the Si central atom. PIAs were soluble in polar aprotic solvents, and also in other organic solvents like m-cresol, tetrahydrofuran, and several in CHCl3 and acetone, due to the inclusion of Si atoms and amino acidic residues in the main chain. The glass transition temperature (Tg) values were obtained by DSC, and showed a tendency in the sense that when the side chain of the amino acidic residue is increased, the Tg values decrease, as the higher volume of the side chain implies a higher chain separation and consequently a higher free rotation of them. PIAs including glycine or p-aminobenzoic acid residues, without side groups, showed higher Tg values due to an increase of the molecular rigidity. The thermal stability was determined by dynamic thermogravimetry showing that almost all PIAs were thermally stable, with TDT10% values greater than 400 °C. The most stable PIAs were those including the p-aminobenzoic residue in the main chain. The groups, methyl or phenyl, bonded to the Si atom of the carboxylic imide-acids residue did not show an important influence. The UV-vis transparency was studied showing that the increase of the aromatic content decreases the UV-vis transparency. PIAs derived from carboxylic imide-acids containing only phenyl groups bonded to the Si atom, were non-transparent.

Silarylene-containing poly(ether-amide)s obtained by Yamazaki–Higashi phosphorylation technique: use of bis(4-(4-aminophenoxy)phenyl)ethylmethyl silane

Abstract Aromatic poly(ether-amide)s (PEAs) based on -(R1,R2)diphenylsilane- and oxyether units were synthesized by direct polycondensation of a diamine and two dicarboxylic acids. For this, the diamine bis(4-(4-aminophenoxy)phenyl)ethylmethylsilane was obtained by reduction of the respective dinitro compound, which was synthesized by nucleophilic aromatic halogen displacement from 1-fluoro-4-nitrobenzene with bis(4-hydroxyphenyl)ethylmethylsilane in basic medium. New silicon-containing aromatic diamine and the PEAs were characterized by elemental analysis, FT-IR, 1H, 13C and 29Si NMR spectroscopy and the results were in agreement with the proposed structures. The incorporation of aliphatic units such as methyl and/or ethyl groups on the silicon atoms affected positively the solubility of the PEAs in organic polar solvents. When their thermal and optical properties were compared with two PEAs of similar structure, containing phenyl groups bonded to the silicon atoms, it was observed a decrease of the glass transition temperature and transmittance values, maintaining a high thermal resistance.

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.

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.

SYNTHESIS, CHARACTERIZATION AND THERMAL STUDIES OF WHOLLY AROMATIC POLY(IMIDE-AMIDES) CONTAINING SI AND/OR GE IN THE MAIN CHAIN

Poly(imide-amides) (PIAs) containing the heteroatoms Si and/or Ge in the main chain were obtained from diacids, which were synthesized from trimellitic anhydride and the diamines bis(4-aminophenyl)diphenylsilane or bis(4-aminophenyl)diphenylgermane. With the same diamines the polymers containing the heteroatoms Si and Ge in the main chain were obtained. Polymers were soluble in aprotic polar solvents and characterized by IR and 1H, 13C and 29Si NMR spectroscopy, and the results were in agreement with the proposed structures. Low inherent viscosity values (h inh ) (0.04 – 0.12 dL/g) were obtained, indicating the presence of oligomeric species. The Tg values were obtained by differential scanning calorimetry (DSC), and the results did not show a relation with the nature of the heteroatoms, in the sense that the polymers with Si should have higher Tg values than those with Ge due to the lower volume of the former atom. Also, the low values of h inh associated to low molecular weight species, have important influence on Tg values. The thermal decomposition temperatures were obtained by dynamic thermogravimetry. These analyses showed that the highest thermal decomposition temperature (TDT) values were obtained for PIA-II and PIA-III with Si and Ge in the repeating unit, and the lowest TDT values with two Si atoms in the unit.

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.