A Facile Strategy for Non-fluorinated Intrinsic Low-k and Low-loss Dielectric Polymers: Valid Exploitation of Secondary Relaxation Behaviors

Optimization of the Thermally Conductive Low-k Polymer Dielectrics Based on Multisource Free-Volume Effects

Polymers/polymer matrix composites possessing low dielectric constants (low-k polymer dielectrics) contribute to the advance of electronics, for instance, microprocessor chips, mobile phone antennas, and data communication terminals. However, the intrinsic long-chain structural characteristic results in poor thermal conductivities, which draw heat accumulation and undermine the outstanding low-k performance of polymers. Herein, multisource free-volume effects that combine two novel kinds of extra free volume with the known in-cage free volume of polyhedral oligomeric silsesquioxanes (POSSs) are discussed to reduce the capacity for dielectric constant reduction. The multisource free-volume effects of POSSs are associated with the thermal conductive network formed by the hexagonal boron nitride (BN) in the polymer matrix. The results show a decent balance between low-k performance (dielectric constant is 2.08 at 1 MHz and 1.98 at 10 GHz) and thermal conductivity (0.555 W m-1 K-1, 4.91 times the matrix). The results provide a new idea to maximize the free-volume effects of POSSs to optimize dielectric properties together with other desired performances for the dielectrics.

Amorphous Poly (Aryl Ether Ketones) Containing Methylene Groups with Excellent Thermal Resistance, Dielectric Properties and Mechanical Performance

Low-dielectric constant polymers are widely used in various microelectronic materials. With the development of 5G communication technology, there is an urgent need for polymer materials with low dielectric constant at high frequency, good thermal resistance, and mechanical properties. In this study, four novel poly (aryl ether ketone) (PAEK) containing different numbers of methylene groups were synthesized via nucleophilic polycondensation reaction. At 10 GHz, these polymer films exhibit excellent dielectric properties with dielectric constants as low as 2.76. The relationship between the dielectric constant and the number of methylene groups is illustrated by constructing the amorphous accumulation cell model. In addition, methylene groups provided the polymer with favorable mechanical performance, including Young's modulus in the range of 2.17-2.21 GPa, the tensile strength from 82.0 to 88.5 MPa and the elongation at the break achieved 7.94%, respectively. Simultaneously, the polymer maintains good thermal resistance with a glass transition temperature (Tg) reaching 216 °C. The result indicates that the obtained novel PAEK is potentially valuable in the field of high-frequency communications.

Synthesis of a ZSM-5 (core)/SAPO-11 (shell) composite zeolite and its catalytic performance in the methylation of naphthalene with methanol

In the present work, a ZSM-5 (core)/SAPO-11 (shell) composite was prepared by the hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), temperature programmed desorption of ammonia (NH₃-TPD), and other characterization techniques. The catalytic performance of ZSM-5/SAPO-11 for the methylation of naphthalene with methanol was also studied. For comparison, the mechanical mixture was prepared through the blending of ZSM-5 and SAPO-11. The experimental results showed ZSM-5/SAPO-11 has been prepared with good crystallization, and exhibited a core-shell structure, with the ZSM-5 phase as the core and the SAPO-11 phase as the shell. The pore size of ZSM-5/SAPO-11 was between that of ZSM-5 and SAPO-11, and it had fewer acid sites than ZSM-5 and the mechanical mixture but more acid sites than SAPO-11. The excellent catalytic performance of ZSM-5/SAPO-11 was due to suitable pore size and acidity. The formation mechanism of the ZSM-5/SAPO-11 composite zeolite was also discussed.

Comparative Studies of the Dielectric Properties of Polyester Imide Composite Membranes Containing Hydrophilic and Hydrophobic Mesoporous Silica Particles

In this paper, comparative studies of hydrophilic and hydrophobic mesoporous silica particles (MSPs) on the dielectric properties of their derivative polyester imide (PEI) composite membranes were investigated. A series of hydrophilic and hydrophobic MSPs were synthesized with the base-catalyzed sol-gel process of TEOS, MTMS, and APTES at a distinctive feeding ratio with a non-surfactant template of D-(-)-Fructose as the pore-forming agent. Subsequently, the MSPs were blended with the diamine of APAB, followed by introducing the dianhydride of TAHQ with mechanical stirring for 24 h. The obtained viscous solution was subsequently coated onto a copper foil, 36 μm in thickness, followed by performing thermal imidization at specifically programmed heating. The dielectric constant of the prepared membranes was found to show an obvious trend: PEI containing hydrophilic MSPs > PEI > PEI containing hydrophobic MSPs. Moreover, the higher the loading of hydrophilic MSPs, the higher the value of the dielectric constant and loss tangent. On the contrary, the higher the loading of hydrophobic MSPs, the lower the value of the dielectric constant with an almost unchanged loss tangent.