The Recent Advances of Polymer-POSS Nanocomposites With Low Dielectric Constant

This study provides a comprehensive overview of the preparation methods for polyhedral oligomeric silsesquioxane (POSS) monomers and polymer/POSS nanocomposites. It focuses on the latest advancements in using POSS to design polymer nanocomposites with reduced dielectric constants. The study emphasizes exploring the potential of POSS, either alone or in combination with other materials, to decrease the dielectric constant and dielectric loss of various polymers, including polyimides, bismaleimide resins, poly(aryl ether)s, polybenzoxazines, benzocyclobutene resins, polyolefins, cyanate ester resins, and epoxy resins. In addition, the research investigates the impact of incorporating POSS on improving the thermal properties, mechanical properties, surface properties, and other aspects of these polymers. The entire study is divided into two parts, discussing systematically the role of POSS in reducing dielectric constants during the preparation of POSS composites using both physical blending and chemical synthesis methods. The goal of this research is to provide valuable strategies for designing a new generation of low dielectric constant materials suitable for large-scale integrated circuits in the semiconductor materials domain.

Effect of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes on Structure-Property Relationships of Thermostable Hybrid Cyanate Ester Resin Based Nanocomposites

Nanocomposites of cyanate ester resin (CER) filled with three different reactive amino-functionalized polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized. The addition of a small quantity (0.1 wt.%) of amino-POSS chemically grafted to the CER network led to the increasing thermal stability of the CER matrix by 12-15 °C, depending on the type of amino-POSS. A significant increase of the glass transition temperature, Tg (DSC data), and the temperature of α relaxation, Tα (DMTA data), by 45-55 °C of the CER matrix with loading of nanofillers was evidenced. CER/POSS films exhibited a higher storage modulus than that of neat CER in the temperature range investigated. It was evidenced that CER/aminopropylisobutyl (APIB)-POSS, CER/N-phenylaminopropyl (NPAP)-POSS, and CER/aminoethyl aminopropylisobutyl (AEAPIB)-POSS nanocomposites induced a more homogenous α relaxation phenomenon with higher Tα values and an enhanced nanocomposite elastic behavior. The value of the storage modulus, E', at 25 °C increased from 2.72 GPa for the pure CER matrix to 2.99-3.24 GPa for the nanocomposites with amino-functionalized POSS nanoparticles. Furthermore, CER/amino-POSS nanocomposites possessed a higher specific surface area, gas permeability (CO2, He), and diffusion coefficients (CO2) values than those for neat CER, due to an increasing free volume of the nanocomposites studied that is very important for their gas transport properties. Permeability grew by about 2 (He) and 3.5-4 times (CO2), respectively, and the diffusion coefficient of CO2 increased approximately twice for CER/amino-POSS nanocomposites in comparison with the neat CER network. The efficiency of amino-functionalized POSS in improving the thermal and transport properties of the CER/amino-POSS nanocomposites increased in a raw of reactive POSS containing one primary (APIB-POSS) < eight secondary (NPAP-POSS) < one secondary and one primary (AEAPIB-POSS) amino groups. APIB-POSS had the least strongly pronounced effect, since it could form covalent bonds with the CER network only by a reaction of one -NH2 group, while AEAPIB-POSS displayed the most highly marked effect, since it could easily be incorporated into the CER network via a reaction of -NH2 and -NH- groups with -O-C≡N groups from CER.

Effects of trace phenolic hydroxyl groups on the cure behaviours and properties of cyanate esters

To improve the curing properties of cyanate esters and retain their heat resistance, dielectric properties and adhesion properties, modified cyanate copolymers were prepared by blending bisphenol A cyanate (BADCy) ester with phenol, hydroquinone (HO), resorcinol and phloroglucinol (LO). Differential scanning calorimetry analysis (DSC) and Fourier transform infrared spectroscopy were used to investigate the cure behaviours of the prepared compounds. The prepared materials were compared with the BADCy ester containing trace of cobalt acetylacetonate (CoAt). The CoAt/BADCy blend modified by HO exhibited better curing properties. The exothermic peak temperature ( T p) of the CoAt/BADCy blend dropped to 169°C after introducing 1 wt% HO, likely due to the hydroxyl functional groups at the para position of the benzene ring resulting in higher symmetry and reactivity for the HO. In addition, compared with original CoAt/BADCy, the cyanate esters modified by phenolic hydroxyl groups demonstrated higher adhesive properties and a similar glass transition temperature (approximately 290°C) as well as stable dielectric properties. The experimental results indicate potential applications of the cyanate ester under high-temperature conditions.

Study on the Relationships between Microscopic Cross-Linked Network Structure and Properties of Cyanate Ester Self-Reinforced Composites

Bisphenol A dicyanate (BADCy) resin microparticles were prepared by precipitation polymerization synthesis and were homogeneously dispersed in a BADCy prepolymer matrix to prepare a BADCy self-reinforced composites. The active functional groups of the BADCy resin microparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy. The results of an FT-IR curve showed that the BADCy resin microparticles had a triazine ring functional group and also had an active reactive group -OCN, which can initiate a reaction with the matrix. The structure of the BADCy resin microparticles was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From the TEM results, the BADCy resin microparticles dispersed in the solvent were nano-sized and distributed at 40-60 nm. However, from the SEM results, agglomeration occurred after drying, the BADCy resin particels were micron-sized and distributed between 0.3 μm and 0.6 μm. The BADCy resin prepolymer was synthesized in our laboratory. A BADCy self-reinforced composite was prepared by using BADCy resin microparticles as a reinforcement phase. This corresponds to a composite in which the matrix and reinforcement phase are made from different morphologies of the same monomer. The DSC curve showed that the heat flow of the microparticles is different from the matrix during the curing reaction, this means the cured materials should be a microscopic two-phase structure. The added BADCy resin microparticles as reaction sites induced the formation of a more complete and regular cured polymer structure, optimizing the cross-linked network as well as increasing the interplay between the BADCy resin microparticles and prepolymer matrix. Relative to the neat BADCy resin material, the tensile strength, flexural strength, compressive strength and impact strength increased by 98.1%, 40.2%, 27.4%, and 85.4%, respectively. A particle toughening mechanism can be used to explain the improvement of toughness. The reduction in the dielectric constant showed that the cross-linked network of the self-reinforced composite was more symmetrical and less polar than the neat resin material, which supports the enhanced mechanical properties of the self-reinforced composite. In addition, the thermal behavior of the self-reinforced composite was characterized by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The results of DMTA also establishes a basis for enhancing mechanical properties of the self-reinforced composite.

Toughening of POSS-MPS composites with low dielectric constant prepared with structure controllable micro/mesoporous nanoparticles

In this work, we developed a modified calcination and extraction method to obtain controllable micro/mesoporous nanoparticle samples POSS–MPS, which were synthesized through glycidyl polyhedral oligomeric silsesquioxane (G-POSS) grafting with aminopropyl-functionalized mesoporous silica (AP-MPS). The POSS–MPS was introduced into the cyanate ester (CE) matrix to optimize the dielectric properties and enhance the toughness of the POSS–MPS/CE nanocomposite. The structure of the hybrid was characterized by FTIR and SEM. The dispersion properties, mechanical properties, dielectric properties and thermal performance were also studied. The results showed that both the C-POSS–MPS and E-POSS–MPS uniformly distribute in the CE matrix with the content of 0.5–4 wt%. The impact strength increased 52% and 60% separately with 2 wt% C-POSS–MPS and E-POSS–MPS addition respectively. The introduction of E-POSS–MPS particles can significantly decrease the dielectric loss value of the POSS–MPS/CE composites to 0.00498, which is of potential in wave transparent composites and structures.

A promising method to improve the performance of CE composites via combining advantages of POSS and MPS.

Covalent incorporation of aminated carbon nanotubes into epoxy resin network

In order to expand applied field of epoxy resin, its mechanical properties have to be improved. Carbon nanotube (CNT) is regarded as an exceptional toughening agent for polymers. However, poor dispersion quality of CNT in polymer matrix and weak interfacial force between them commonly lead to low reinforcing efficiency. This article presented a study on the mechanical properties of epoxy composite reinforced with aminated CNT (CNT-NH2). The amination of CNT was achieved via a wet chemical procedure using 1,6-diaminohexane (DAH) as amine source. Fourier transform infrared spectroscopy, zeta potential test, and thermogravimetric analysis were employed to investigate the as-prepared CNT-NH2. The results show that DAH has been successfully grafted onto the surface of CNT. Scanning electron microscopic images show that CNT-NH2 is homogenously dispersed in epoxy matrix. Mechanical properties tests suggest that the tensile strength and fracture toughness of the obtained CNT-NH2/epoxy composite are all enhanced compared with cured pure epoxy resin. The tensile strength and fracture toughness of the as-prepared CNT-NH2/epoxy composite with 0.8 wt% CNT-NH2 show 42% and 95% improvement, respectively. These results indicate that CNT-NH2 is a promising toughening agent for enhancing the mechanical properties of epoxy resin.

The study on the compatibility of epoxy resin with liquid oxygen

Lightweight liquid oxygen (LOX) tank has attracted much attention recently, and epoxy resin is considered to be one of the most likely candidate materials. In this work, polymer wafer made from bisphenol-A epoxy resin was firstly treated with LOX, and then its macroscopic morphology, microscopic structure, and chemical composition were analyzed by atomic force microscopy and Fourier transformed infrared spectroscopy. Finally, its compatibility with LOX was studied by mechanical impact test. The results showed that LOX treatment has little influence on the macroscopic morphology and chemical composition of the epoxy resin wafer, but has a large influence on its microstructure and compatibility with LOX. With the increase of immersion time, the surface roughness, the number, length, and depth of the cracks appeared on the sample surface were all increased. The reaction caused by mechanical impact became more frequent and intense. Finally, possible damage mechanism was discussed.