A new type of low dielectric polyimide/poly(silsesquioxane)-like (PI/PSSQ-like) hybrid nanocomposite material is successfully prepared from the polyimide (ODA±ODPA) precursor containing phenyltrialkoxysilane (PTS) at two chain ends and monoaryltrialkoxysilane with a self-catalyzed sol±gel process. We employ p-aminophenyltrimethoxysilane (APTS) to provide bonding between the PTS and ODPA±ODA phase. It is shown by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) that the PSSQ-like domain sizes with uniform size are fairly well separated in the hybrid ®lms. The silica domain sizes of 5000-PIS and 5000-PIS±50-PTS ®lms are in the range of 30±100 nm, of 5000-PIS±100-PTS and 10000-PIS±100-PTS in the range of 80±200 and 300±600 nm, respectively. The dielectric constant can be 2.79 for 5000-PIS±140-PTS with fairly good mechanical properties. The PI/PSSQ-like hybrid ®lms have higher onset decomposition temperature and char yield in thermogravimetric analysis (TGA) and higher T g in differential scanning calorimetry (DSC) than the pure PI. Moreover, the PI/PSSQ-like hybrid ®lms have excellent transparency even under high PTS content. In the series of X-PIS hybrid ®lms, the coef®cient of thermal expansion (CTE) below T g increases with the PI block chain length, but in the series of X-PIS±y-PTS ®lms, it slightly increases with the PTS content. However, above T g the CTE of X-PIS and X-PIS±24-PTS is much lower than that of the pure PI. The dielectric constant and water absorption of X-PIS±y-PTS ®lms decrease with the PTS content because of the higher free volume and hydrophobicity. q

Coupling agent-functionalized boron nitride (f-BN) and glycidyl methacrylate-grafted graphene (g-TrG) are simultaneously blended with polyimide (PI) to fabricate a flexible, electrically insulating and thermally conductive PI composite film. The silk-like g-TrG successfully fills in the gap between PI and f-BN to complete the thermal conduction network. In addition, the strong interaction between surface functional groups on f-BN and g-TrG contributes to the effective phonon transfer in the PI matrix. The thermal conductivity (TC) of the PI/f-BN composite films containing additional 1 wt % of g-TrG is at least doubled to the value of PI/f-BN and as high as 16 times to that of the pure PI. The hybrid film PI/f-BN-50/g-TrG-1 exhibits excellent flexibility, sufficient insulating property, the highest TC of 2.11 W/mK, and ultralow coefficient of thermal expansion of 11 ppm/K, which are perfect conditions for future flexible substrate materials requiring efficient heat dissipation.

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Polyimide (PI) nanocomposites with both enhanced thermal conductivity and dimensional stability were achieved by incorporating glycidyl methacrylate‐grafted graphene oxide (g‐GO) in the PI matrix. The PI/g‐GO nanocomposites exhibited linear enhancement in thermal conductivity when the amount of incorporated g‐GO was less than 10 wt%. With the addition of 10 wt% of g‐GO to PI (PI/g‐GO‐10), the thermal conductivity increased to 0.81 W m−1 K−1 compared to 0.13 W m−1 K−1 for pure PI. Moreover, the PI/g‐GO‐10 composite exhibited a low coefficient of thermal expansion (CTE) of 29 ppm °C−1. The values of CTE and thermal conductivity continuously decreased and increased, respectively, as the g‐GO content increased to 20 wt%. Combined with excellent thermal stability and high mechanical strength, the highly thermally conducting PI/g‐GO‐10 nanocomposite is a potential substrate material for modern flexible printed circuits requiring efficient heat transfer capability.

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