Both aminopropylisobutyl polyhedral oligomeric silsesquioxane (NH2-POSS) and hydrazine monohydrate were utilized to functionalize graphene oxide (GO), and to obtain chemically modified graphene (CMG), which was then used for preparing thermally conductive CMG/polyimide (CMG/PI) nanocomposites via a sequential in situ polymerization and electrospinning-hot press technology NH2-POSS molecules were grafted on the GO surface, and CMG was obtained by the reaction between NH2-POSS and GO The thermal conductivity coefficient (λ), glass transition temperature (Tg) and heat resistance index (THRI) of the prepared CMG/PI nanocomposites were all increased with increasing the CMG loading The λ value of the CMG/PI nanocomposites with 5 wt% CMG was significantly improved to 105 W m−1 K−1, about 4 times higher than that of the pristine PI matrix (028 W m−1 K−1) The corresponding Tg and THRI values were also increased to 2130 and 2823 °C, respectively Moreover, an improved thermal conductivity model was proposed and predicted the λ values of the nanocomposites more precisely than those obtained from the typical Maxwell, Russell and Bruggemen classical models

Significantly enhanced and precisely modeled thermal conductivity in polyimide nanocomposites with chemically modified graphene via in situ polymerization and electrospinning-hot press technology

Micrometer boron nitride/polyamide acid ( m BN/PAA) compound was firstly fabricated via in -situ polymerization, performed to obtain the m BN/PAA electrospun fibers by electrospinning technology, finally to fabricate the dielectric thermally conductive m BN/polyimide ( m BN/PI) composites via thermal-imidization followed by hot press method. The obtained m BN/PI composite with 30 wt% m BN presents relatively highly thermally conductive coefficient ( λ ), excellent dielectric constant ( e ) & dielectric loss tangent (tan  δ ), and extremely outstanding thermal stability, λ of 0.696 W/m K, e of 3.77, tan  δ of 0.007, T Heat-resistance index ( T HRI ) of 279 °C and glass transition temperature ( T g ) of 240 °C, which presents a great potential for packaging in integration and miniaturization of microelectronic devices.

Dielectric thermally conductive boron nitride/polyimide composites with outstanding thermal stabilities via in-situ polymerization-electrospinning-hot press method

To achieve polymer-based composites for electronic packaging with low dielectric constant, low dielectric loss tangent and high thermal conductivity, silane coupling agent KH550 modified hexagonal boron nitride (hBN) platelets were introduced into PTFE matrix via a cold pressing and sintering method. The effect of surface treatment on the morphology, thermal conductivity and dielectric properties of the composites was investigated. The results revealed that after surface treatment, the interfacial adhension between hBN platelets and PTFE matrix was improved and the in-plane orientation degree of hBN platelets in PTFE matrix decreased, which effectively improvd the thermal conductivity of the composites. The thermal conductivity of hBN-KH550/PTFE composite with 30 vol% filler content is 0.722 W/mK, which is 2.7 folds of pure PTFE. Moreover, the enhanced interfacial adhension and reduced surface hydrophilicity of hBN platelets significantly decreased the interfacial polarization, resulting in not only lower dielectric constant and dielectric loss tangent but also weaker frequency-dependence.

Improved thermal conductivity and dielectric properties of hBN/PTFE composites via surface treatment by silane coupling agent

Stress controllability in thermal and electrical conductivity is important for flexible piezoresistive devices. Due to the strength‐elasticity trade‐off, comprehensive investigation of stress‐controllable conduction in elastic high‐modulus polymers is challenging. Here presented is a 3D elastic graphene‐crosslinked carbon nanotube sponge/polyimide (Gw‐CNT/PI) nanocomposite. Graphene welding at the junction enables both phonon and electron transfer as well as avoids interfacial slippage during cyclic compression. The uniform Gw‐CNT/PI comprising a high‐modulus PI deposited on a porous templated network combines stress‐controllable thermal/electrical conductivity and cyclic elastic deformation. The uniform composites show different variation trends controlled by the porosity due to different phonon and electron conduction mechanisms. A relatively high k (3.24 W m−1 K−1, 1620% higher than PI) and suitable compressibility (16.5% under 1 MPa compression) enables the application of the composite in flexible elastic thermal interface conductors, which is further analyzed by finite element simulations. The interconnected network favors a high stress‐sensitive electrical conductivity (sensitivity, 973% at 9.6% strain). Thus, the Gw‐CNT/PI composite can be an important candidate material for piezoresistive sensors upon porosity optimization based on stress‐controllable thermal or electrical conductivity. The results provide insights toward controlling the stress‐induced thermal/electrical conductivities of 3D interconnected templated composite networks for piezoresistive conductors or sensors.

Stress Controllability in Thermal and Electrical Conductivity of 3D Elastic Graphene-Crosslinked Carbon Nanotube Sponge/Polyimide Nanocomposite

Recent progress in polymer/two-dimensional nanosheets composites with novel performances

Polyimide/reduced graphene oxide (PI/r-GO) core–shell structured microspheres were fabricated by in-situ reduction of graphene oxide (GO), which was coated on the surface of PI microspheres via hydrogen bonding and π–π stacking interaction. The highly ordered 3D core–shell structure of PI/r-GO microspheres with graphene shell thickness of 3 nm was well characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and Raman spectra. The glass transition temperature (Tg) of PI/r-GO microspheres was slightly increased because of the interaction of r-GO and PI matrix while the temperature at 5% weight loss (T5%) of PI/r-GO microspheres was decreased due to the side effect of reductant hydrazine hydrate. The PI/r-GO nanocomposites exhibited highly electrical conductivity with percolation threshold of 0.15 vol% and ultimate conductivity of 1.4 × 10−2 S/m. Besides, the thermal conductivity of PI/r-GO nanocomposites with 2% weight content of r-GO could reach up to 0.26 W/m K.

A facile assembly of polyimide/graphene core–shell structured nanocomposites with both high electrical and thermal conductivities

A series of cardo poly(ether sulfone imide)s (PESI-C) containing bulky phthalide groups were prepared via aromatic nucleophilic substitution reaction of phenolphthalein with 4,4′-difluorodiphenyl s

Synthesis of organosoluble and transparent phenolphthalein-based cardo poly(ether sulfone imide)s via aromatic nucleophilic substitution polymerization:

Two series of cardo polyimides with 1,4‐diaminocyclohexane of different trans / cis ratios were synthesized. They exhibited excellent solubility, high glass transition temperature and good transparency.

Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4‐diaminocyclohexane via aromatic nucleophilic substitution polymerization

The invention discloses transparent polyimide resin which is obtained through condensation polymerization of a 1, 4-bis(2, 3-dicarboxylphenoxy)cyclohexane dianhydride monomer and a primary diamine monomer. Phthalic anhydride structures at two ends of the dianhydride monomer keep the high reaction activity of dianhydride, and an alicyclic structure with a distorted middle space structure has relatively large free volume and steric hindrance, so that the formation of charge transfer complexes in polyimide molecules and among the molecules is effectively inhibited, and the transparency and glass transition temperature of a polymer are increased. The obtained polyimide resin has the glass transition temperature of 200-300 DEG C, the ultraviolet absorption cutoff wavelength of 370-380nm and the light transmissivity at the wavelength of 450nm of 75-90%. The transparent polyimide resin has a better application prospect in the fields such as flexible substrate materials of solar cells, substrate materials of flexible transparent conducting films, liquid crystal display materials and the like. The invention also discloses a dianhydride monomer which can be used for preparing the transparent polyimide resin.

Transparent polyimide resin and preparation method thereof

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A facile assembly of polyimide/graphene core–shell structured nanocomposites with both high electrical and thermal conductivities

Synthesis of organosoluble and transparent phenolphthalein-based cardo poly(ether sulfone imide)s via aromatic nucleophilic substitution polymerization:

Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4‐diaminocyclohexane via aromatic nucleophilic substitution polymerization

Transparent polyimide resin and preparation method thereof