Bernard Sillion

Soluble sulfonated naphthalenic polyimides as materials for proton exchange membranes

Series of sequenced sulfonated naphthalenic polyimides with improved solubility were prepared by polycondensation in m-cresol using aromatic diamines containing phenylether bonds and/or bulky groups. Sulfonated polyimides were characterized by NMR and IR spectroscopies. Membranes were prepared by solution casting method and characterized by determining the ion-exchange capacity, water swelling, proton conductivity whereas the morphology of polymer membranes was studied by small angle neutron scattering.

Synthesis and characterization of a linear CARDO polyimide from (5,5′-bisisobenzofuran)-1,1′,3,3′-tetrone and 4,4′-(9H-fluoren-9-ylidene)bisphenylamine

Abstract Starting from an aromatic diamine, 4,4′-(9H-fluoren-9-ylidene)bisphenylamine (FBPA), we have synthesized a series of linear polyimides by polycondensation with different molar proportions of (5,5′-bisisobenzofuran)-1,1′,3,3′-tetrone (BTDA). The polymers were anhydride end-capped or phenylimide end-capped. Owing to the presence of lateral fluorene groups (CARDO structure), the fully cyclized FBPA/BTDA polyimides exhibited good solubility in many solvents such as N,N-dimethylformamide, N-methylpyrrolidone, m-cresol, dimethylsulphoxide and N,N-dimethylacetamide. A detailed study of the FBPA/BTDA chemical structure and molecular weight was performed by 13C nuclear magnetic resonance and size exclusion chromatography. The thermal and mechanical properties of polymer films were then investigated. The glass transition temperature determined from thermomechanical analysis ranged from 350 to 380°C and the Youngs modulus measured from tensile tests was about 2.5 GPa at room temperature and 1.7 GPa at 200°C. Thermogravimetric analyses and water uptake determination showed the high decomposition temperature, near to 400°C under argon, and the low water absorption (lower than 1 wt%) of the FBPA/BTDA polyimides.

Polyimide-modified epoxy system: time-temperature-transformation diagrams, mechanical and thermal properties

Abstract A hot-melt processable thermoset was prepared by blending tetraglycidyl-4,4′-diaminodiphenylmethane/4,4′-diaminodiphenylsulfone epoxy resin and a high- T g thermoplastic polyimide. The polyimide was synthesized from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-(9 H -fluoren-9-ylidene)bisphenylamine to form a linear structure initially miscible with the neat epoxy resin. The thermal polymerization study, including determination of time-temperature-transformation cure diagrams, pointed out a lowering in crosslink density of epoxy network probably due to the polyimide viscosity effect. After cure, no phase separation could be observed by scanning electron microscopy and only one T g was detected by dynamic mechanical analysis, showing full miscibility between the blend components. The consequences of the thermoplastic incorporation (polyimide concentration = 10 wt%) were a slight increase in T g value ( ΔT g = +5°C) and rather limited improvements in stress at rupture (50%) and strain-energy release rate G Ic (27%) compared to the unmodified epoxy matrix.

Thermosetting oligomers containing maleimides and nadimides end-groups

In the field of high thermomechanical performance polymers, linear and thermosetting systems offer complementary properties. Among the thermosetting materials, BMIs and BNIs have been extensively studied and are now commercially available. In this chapter, firstly the main preparation and characterization methods are reviewed, and then the chemistry of the polymerization processes is discussed for both families. For the BMIs, due to the electrophilic character of their double bond, different polymerization pathways have been published, which is not the case for BNIs. Special attention has been paid to thermal polymerization which has already been used in industrial achievements; however, on the other hand, the structure of these materials has been considered for the purpose of establishing relationships between processability, stability and thermomechanical properties.

Polypentamethylnadimides obtained by Diels-Alder reaction

Abstract The reactions between benzylbromide or α,α′-dibromo-meta-xylene (DBMX) and sodium 1,2,3,4,5-pentamethylcycopenta-1,3-dienide (CpMe5⊝, Na⊕) give only the expected pentamathylcyclopentadiene derivatives with a good yields. These products lead to endo isomer adducts via a Diels–Alder reaction with maleimide. New low molecular weight polypentamethylnadimides were obtained in this way from the Diels–Alder polymerization of bispentamethylcyclopentadiene monomers and commercial or synthetic bismaleimides. The polyadducts were characterised by size exclusion chromatography (SEC), matrix assisted laser desorption ionization-time of flight (MALDI-TOF), nuclear magnetic resonance (NMR) and thermogravimetric analyses (TGA). The low molecular weight was attributed to methyl steric hindrance. For the lowest molecular weight products, two different endcapped oligomers were observed.

Thermal polymerization of arylacetylenes: 1. Study of a monofunctional model compound

Abstract The thermal polymerization of arylacetylene compounds has been studied from a monofunctional model compound, 4-(hexyloxy)phenylacetylene I. I was synthesized and bulk polymerized under several experimental conditions. The reaction products were analysed by chromatography, spectroscopy and spectrometry techniques. The observed average polymerization degree is low. The lowest molecular weight compounds were isolated and identified: they are two naphthalenic dimers and three benzenic trimers. They represent 30 wt% of the whole polymerization product. We have shown also that the thermal polymerization of I is temperature and time dependent and that a depolymerization process takes place at high temperature.

Mechanism of endo-exo isomerization of nadimide end-capped oligomers

Before polymerization, nadimide end-capped polyimide oligomers exist in the endo form. During the cure, an endo-exo equilibrium takes place. This paper discusses the relationship between endo-exo isomerization and the reverse-Diels-Alder reaction of the nadinaide system. As a consequence of the experimental results, an explanation for cyclopentadiene evolution during the polymerization of nadimide systems is given.

Synthesis and Characterization of Aromatic Polyimides Bearing Nonlinear Optical Chromophores

The syntheses and characterizations of two aromatic polyimides with nonlinear optical (NLO) chromophore side chains were investigated through a two-step synthetic route. These two polymers were prepared by polycondensation of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) with 4-(4-amino, 2-hydroxy) phenoxyaniline (HODA) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP), respectively. First the poly(hydroxy)imides were prepared by direct thermal imidization. The resulting polyimides bearing hydroxy groups were found to react easily with the terminal hydroxy group of the chromophore (Disperse Red1 (DR1)) via the Mitsunobu reaction. The high content of chromophore for the polyimide with 6FAP diamine was confirmed by UV spectroscopy and ellipsometry spectroscopy measures. The resulting NLO polyimides possess high glass transition temperatures (Tg > 185°C), excellent solubilities and processabilities even though the extent of chromophore grafting is up to 95 mol%. The second harmonic coefficient (d 33) at the wavelength of 1320 nm is close to 30 pm V−1. The thermal and temporal stabilities of the NLO properties were investigated. The relaxation temperature of the SHG signal measured at the 50% decay of the initial SHG signal (I 2ω /2 at 2°C min−1) was 168°C for the polyimide based on HODA and 157°C for the polyimide based on 6FAP.

Aromatic and Heterocyclic Polymers—What Future?

This paper discusses the evolution observed in the field of high performance polymers and tries to forecast the future in different domains. The paper is divided into four sections: 1. From the 1960s to the 21st century. 2. What’s new in chemistry and why? 3. What could be the future for high performance polymers in structural applications, electrical industries, electronic and electro-optical industries, membrane technologies, fuel cell membranes and other fields such as conductive polymers. 4. Concluding remarks.

Negative-type soluble photosensitive polyimides derived from benzhroltetracarboxylic dianhydride: synthesis and characterization

Abstract The present paper deals with the synthesis and the characterization of negative-type soluble photosensitive polyimides based on benzhydroltetracarboxylic dianhydride. These polymers were prepared either by a thermal or chemical imidization, and the photoreactive methacryloyl group was introduced through the reaction between the hydroxyl group and the isocyanate group of methacryloyl isocyanate to yield a carbamate linkage. Bis(4-aminophenyl)methane, bis(3,5-dimethyl-4-aminophenyl)methane and bis(3-methyl-5-isopropyl-4-aminophenyl)methane were used as aromatic diamines, and 1,1,1,3,3,3-hexafluoropropane-2,2-di(4′-phthalic anhydride) as aromatic dianhydride, 4- N,N -Dimethylamino-3′,5′-diaminobenzophenone was also used in order to produce an autophotosensitive polymer. The resulting methacryloyl carbamate-modified polyimides were found to be soluble in polar solvents and they were characterized by infrared and 1 H and 13 C nuclear magnetic resonance spectroscopies. Inherent viscosities, glass transition temperatures, thermal behaviour and dielectric constants were also determined.