Synthesis of new unsymmetrical diamine and polyimides: structure–property relationship and applications of polyimides

Supramolecular Phthalimide Networks Via Tandem Diels-Alder Reaction-Aromatization Using Biomass-Derived Furanic Dienes

The design and synthesis of phthalimide derivatives are important goals for applications in fields such as pharmaceutical science and optoelectronics. In the present study, a facile and convenient synthetic pathway (no heat or acid/catalyst needed) is devised to produce phthalimides from a biomass-derived furan by directly introducing an N-carbamate group at the C-2 position of the furan ring via thermal Curtius rearrangement. The electron-donating N-carbamate group increases the energy level of the highest occupied molecular orbital of the furan diene, resulting in a significant increase of the rate of the Diels-Alder reaction with maleimide compared to the conventional furfuryl furan. Interestingly, the Diels-Alder adduct smoothly undergoes aromatization (dehydration) to generate the phthalimide motif. It is shown that the biomass-derived phthalimides can produce supramolecular gels and act as sensors of basic anions like F^- and CN^- . The novel synthetic pathway to phthalimide derivatives from a biomass-derived furan can potentially be used to develop novel phthalimide motifs for a variety of applications.

Effect of the Dianhydride/Branched Diamine Ratio on the Architecture and Room Temperature Healing Behavior of Polyetherimides

Traditional polyetherimides (PEIs) are commonly synthesized from an aromatic diamine and an aromatic dianhydride (e.g., 3,4'-oxidianiline (ODA) and 4,4'-oxidiphtalic anhydride (ODPA)) leading to the imide linkage and outstanding chemical, thermal and mechanical properties yet lacking any self-healing functionality. In this work, we have replaced the traditional aromatic diamine by a branched aliphatic fatty dimer diamine (DD1). This led to a whole family of self-healing polymers not containing reversible chemical bonds, capable of healing at (near) room temperature yet maintaining very high elastomeric-like mechanical properties (up to 6 MPa stress and 570% strain at break). In this work, we present the effect of the DD1/ODPA ratio on the general performance and healing behavior of a room temperature healing polyetherimide. A dedicated analysis suggests that healing proceeds in three steps: (i) an initial adhesive step leading to the formation of a relatively weak interface; (ii) a second step at long healing times leading to the formation of an interphase with different properties than the bulk material and (iii) disappearance of the damaged zone leading to full healing. We argue that the fast interfacial adhesive step is due to van der Waals interactions of long dangling alkyl chains followed by an interphase formation due to polymer chain interdiffusion. An increase in DD1/ODPA ratio leads to an increase in the healing kinetics and displacement shift of the first healing step toward lower temperatures. An excess of DD1 leads to the cross-linking of the polymer thereby restricting the necessary mobility for the interphase formation and limiting the self-healing behavior. The results here presented offer a new route for the development of room temperature self-healing thermoplastic elastomers with improved mechanical properties using fatty dimer diamines.

Poly(ether–imide)s with flexible linkages and kinks

Four new aromatic diimide–diol monomers were synthesized from bisphenol A dianhydride and hydroxyamines. The poly(ether–imide)s (PEI-1 to PEI-4) were synthesized from these diols and 4,4′-difluorobenzophenone-IV via carbonyl-activated aromatic nucleophilic fluoro displacement reaction. The chemical structures of the monomers and PEIs were confirmed by Fourier transform infrared spectrometer and proton nuclear magnetic resonance spectroscopies. The PEIs synthesized here were amorphous and soluble in polar aprotic solvents and low-boiling organic solvents. The PEIs had good thermal stability, 10% weight loss occurred in the temperatures range of 400–448°C, and char yields at 800°C under nitrogen atmosphere was in the range of 14–22%. The limiting oxygen index values of PEIs were in the range of 23.1–26.3, and such PEIs can be used as self-extinguishing polymers. The dielectric constants of the PEIs were in the range of 3.30–4.00, and such PEIs can be used as electrical insulation materials for systems operating at high temperature for long time.

Synthesis and characterization of organosoluble, transparent, and hydrophobic fluorinated polyimides derived from 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene

A novel aromatic fluorinated diamine monomer, 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene, was synthesized by coupling of 2-isopropylaniline and 4-(trifluoromethyl)benzaldehyde and its structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, and mass spectrometry, and then used to prepare a series of fluorinated polyimides (FPIs) by polycondensation reaction with various commercial dianhydrides via conventional one-step method. The obtained FPIs present excellent solubility in most organic solvents and enough to cast into tough and flexible films. All the FPI films show good optical transparency and light color with the cutoff wavelengths in range of 307–362 nm and the average transmittance above 86%. These polymer films also exhibit high glass transition temperature in range of 261–331°C and thermal stability with 10% weigh loss above 463°C under nitrogen atmosphere. Furthermore, they exhibit outstanding mechanical properties with tensile strengths of 65.9–94.3 MPa, elongation at break of 11.4–13.8%, Young’s modulus of 1.6–1.9 GPa, and low dielectric constants in range of 2.75–3.10 at 1 MHz as well as prominent hydrophobicity with the contact angle in the range of 87.3–93.9°.

Synthesis of diol monomers and organosoluble fluorinated polyimides with low dielectric

Four diimide–diol monomers were synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride and aminophenol/aminonaphthol. The structures of the monomers were characterized by spectroscopic analysis. A series of fluorinated polyimides (FPI-1 to FPI-8) were synthesized from these new diols and 4,4′-difluorobenzophenone/4,4′-dichlorodiphenyl sulphone, through nucleophilic displacement reaction. The FPIs were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, thermogravimetry, differential scanning calorimetry, solution viscosity, solubility test, and dielectric properties test. FPIs were amorphous and showed good solubility due to the presence of >C(CF3)2 unit and flexible groups in the polyimides backbone. These FPIs also showed good thermal stability and the 10% weight loss occurred in the range 353–505°C. The limiting oxygen index values of FPIs were in the range of 31.5–39.1 and such FPIs can be used as self-extinguishing polymers. These FPIs have a dielectric constant in the range of 3.10–4.23 and can be used as high temperature electrical insulation materials.