Search Results (13)

In order to improve the dielectric properties of existing thermosetting resins, taking advantage of reactive fillers is a simple and feasible option. In this paper, we synthesized a new double epoxycyclohexane double-decker silsesquioxane (DEDDSQ), in which the structure of aliphatic epoxy resin introduced into DDSQ successfully, and the resulting structure of DEDDESQ is confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS). Cyanate ester resin was selected as the case study for the application of DEDDSQ as reactive fillers. A CE/E51/DEDDSQ nanocomposite was fabricated by incorporating a small proportion of E51 resin and DEDDSQ into cyanate ester resin to enhance its comprehensive properties. X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) analyses demonstrated that DEDDSQ dispersed uniformly within the resin matrix. Dynamic mechanical analysis (DMA) demonstrated that the CE/E51/8.0DEDDSQ nanocomposites exhibit excellent thermal properties. The glass transition temperature (T_g) of the nanocomposite was measured to be 264 °C, indicating its excellent thermal stability. Dielectric property measurements showed that the addition of DEDDSQ reduced the dielectric constant of the cyanate ester resin, with the CE/E51/8.0DEPOSS nanocomposite exhibiting a dielectric constant of 2.47 at 1 MHz. Full article

A series of di-functional benzoxazine (BZ) monomers was synthesized, specifically the double-decker silsesquioxane (DDSQ) cage structure (DDSQ-BZ). Comparative analyses were conducted between DDSQ-BZ monomers and the most commonly utilized bisphenol A-functionalized bifunctional benzoxazine (BPA-BZ) monomer. DDSQ-BZ compounds possess better thermal properties such as high char yield and high thermal decomposition temperature (T_d10) after thermal ring-opening polymerization (ROP) because the inorganic DDSQ cage nanostructure features a nano-reinforcement effect. In addition, blending inorganic DDSQ-BZ compounds with epoxy resin was explored to form organic/inorganic hybrids with enhanced thermal and mechanical properties following thermal ROP. The improvement in mechanical properties is primarily attributed to the network structure formed by the cross-linking between DDSQ-BZ and the epoxy resin during thermal ROP, as well as hydrogen bonding interactions formed between the hydroxyl groups generated during thermal ROP and the Si-O-Si bonds in the DDSQ structure. Full article

Rapid developments in materials engineering are accompanied by the equally rapid development of new technologies, which are now increasingly used in various branches of our life. The current research trend concerns the development of methods for obtaining new materials engineering systems and searching for relationships between the structure and physicochemical properties. A recent increase in the demand for well-defined and thermally stable systems has highlighted the importance of polyhedral oligomeric silsesquioxane (POSS) and double-decker silsesquioxane (DDSQ) architectures. This short review focuses on these two groups of silsesquioxane-based materials and their selected applications. This fascinating field of hybrid species has attracted considerable attention due to their daily applications with unique capabilities and their great potential, among others, in biomaterials as components of hydrogel networks, components in biofabrication techniques, and promising building blocks of DDSQ-based biohybrids. Moreover, they constitute attractive systems applied in materials engineering, including flame retardant nanocomposites and components of the heterogeneous Ziegler-Natta-type catalytic system. Full article

This study synthesized two azide-functionalized monomers through p-dichloro xylene and double-decker silsesquioxane (DDSQ) units with NaN₃ to form DB-N₃ and DDSQ-N₃ monomers, respectively. In addition, five different propargyl-functionalized monomers were also prepared from hydroquinone, bisphenol A, bis(4-hydroxyphenyl)methanone, 2,4-dihydroxybenzaldehyde (then reacted with hydrazine hydrate solution) and 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethene with propargyl bromide to form P-B, P-BPA, P-CO, P-NP, and P-TPE monomers, respectively. As a result, various DDSQ-based main chain copolymers could be synthesized using Cu(I)-catalyzed click polymerization through DDSQ-N₃ with different propargyl-functionalized monomers, of which the chemical structure and molecular weight could be confirmed by using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) analyses. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy analyses also could characterize the thermal stability, morphology, and optical behaviors of these DDSQ-based copolymers. All results indicate that the incorporation of an inorganic DDSQ cage could improve the thermal stability such as thermal decomposition temperature and char yield, because of the DDSQ dispersion homogeneously in the copolymer matrix, and this would then affect the optical properties of NP and TPE units in this work. Full article

We present a smart and efficient methodology for the synthesis of a variety of fluorinated silsesquioxanes (SQs) with diverse Si-O-Si core architecture. The protocol is based on an easy-to-handle and selective hydrosilylation reaction. An investigation on the placement of the reactive Si-HC=CH₂ vs. Si-H in the silsesquioxane, as well as silane vs. olefin structure, respectively, on the progress and selectivity of the hydrosilylation process, was studied. Two alternative synthetic pathways for obtaining a variety of fluorine-functionalized silsesquioxanes were developed. As a result, a series of mono- and octa- T₈ SQs, tri- ‘open-cage’ T₇ SQs, in addition to di- and tetrafunctionalized double-decker silsesquioxane (DDSQ) derivatives, were obtained selectively with high yields. All products were characterized by spectroscopic (NMR, FTIR) techniques. Selected samples were subjected to the measurements revealing their dielectric permittivity in a wide range of temperatures (from −100 °C to 100 °C) and electric field frequencies (10⁰–10⁶ Hz). Full article

In this study a new type of bifunctional epoxy compound (DDSQ-EP) based on double-decker silsesquioxane (DDSQ) was synthesized by process of alkaline hydrolysis condensation of phenyltrimethoxysilane and corner capping reaction with dichloromethylvinylsilane, followed by epoxidation reaction of vinyl groups. The resultant structures were confirmed using Fourier transform infrared spectrometry, nuclear magnetic resonance spectrometry and time-of-flight mass spectrometry, respectively. The DDSQ-EP was incorporated into polybenzoxazine to obtain the PBZ/DDSQ-EP nanocomposites. The uniform dispersion of DDSQ-EP in the nanocomposites was verified by X-ray diffraction and scanning electron microscope. The reactions occurred during the curing of the composites and were investigated using infrared spectroscopy of segmented cures. Dynamic mechanical analysis and thermal gravimetric analysis indicated that the storage modulus, glass transition temperature and thermal stability of PBZ/DDSQ-EP were increased in comparison with pure benzoxazine resins. Assessment of dielectric properties demonstrated that the dielectric permittivity and dielectric loss of polybenzoxazine decreased slightly because of the addition of DDSQ-EP. Full article

In this study, we prepared a difunctionalized cyanate ester double-decker silsesquioxane (DDSQ-OCN) cage with a char yield and thermal decomposition temperature (T_d) which were both much higher than those of a typical bisphenol A dicyanate ester (BADCy, without the DDSQ cage) after thermal polymerization. Here, the inorganic DDSQ nanomaterial improved the thermal behavior through a nano-reinforcement effect. Blending the inorganic DDSQ-OCN cage into the epoxy resin improved its thermal and mechanical stabilities after the ring-opening polymerization of the epoxy units during thermal polymerization. The enhancement in the physical properties arose from the copolymerization of the epoxy and OCN units to form the organic/inorganic covalently bonded network structure, as well as the hydrogen bonding of the OH groups of the epoxy with the SiOSi moieties of the DDSQ units. For example, the epoxy/DDSQ-OCN = 1/1 hybrid, prepared without Cu(II)-acac as a catalyst, exhibited a glass transition temperature, thermal decomposition temperature (T_d), and char yield (166 °C, 427 °C, and 51.0 wt%, respectively) that were significantly higher than those obtained when applying typical organic curing agents in the epoxy resin. The addition of Cu(II)-acac into the epoxy/BADCy and epoxy/DDSQ-OCN hybrids decreased the thermal stability (as characterized by the values of T_d and the char yields) because the crosslinking density and post-hardening also decreased during thermal polymerization; nevertheless, it accelerated the thermal polymerization to a lower curing peak temperature, which is potentially useful for real applications as epoxy molding compounds. Full article

In this study, we synthesized bismaleimide into a functionalized double-decker silsesquioxane (DDSQ) cage. This was achieved by hydrosilylation of DDSQ with nadic anhydride (ND), reacting it with excess p-phenylenediamine to obtain DDSQ-ND-NH₂, and treating with maleic anhydride (MA), which finally created a DDSQ-BMI cage structure. We observed that the thermal decomposition temperature (T_d) and char yield were both increased upon increasing the thermal polymerization temperature, and that these two values were both significantly higher than pure BMI without the DDSQ cage structure since the inorganic DDSQ nanoparticle could strongly enhance the thermal stability based on the nano-reinforcement effect. Based on FTIR, TGA, and DMA analyses, it was found that blending epoxy resin with the DDSQ-BMI cage to form epoxy/DDSQ-BMI hybrids could also enhance the thermal and mechanical properties of epoxy resin due to the organic/inorganic network formation created by the ring-opening polymerization of the epoxy group and the addition polymerization of the BMI group due to the combination of the inorganic DDSQ cage structure and hydrogen bonding effect. The epoxy/DDSQ-BMI = 1/1 hybrid system displayed high T_g value (188 °C), T_d value (397 °C), and char yield (40.4 wt%), which was much higher than that of the typical DGEBA type epoxy resin with various organic curing agents. Full article

A synthesis of a series of mono-T₈ and difunctionalized double-decker silsesquioxanes bearing substituted triazole ring(s) has been reported within this work. The catalytic protocol for their formation is based on the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) process. Diverse alkynes were in the scope of our interest—i.e., aryl, hetaryl, alkyl, silyl, or germyl—and the latter was shown to be the first example of terminal germane alkyne which is reactive in the applied process’ conditions. From the pallet of 15 compounds, three of them with pyridine-triazole and thiophenyl-triazole moiety attached to T₈ or DDSQ core were verified in terms of their coordinating properties towards selected transition metals, i.e., Pd(II), Pt(II), and Rh(I). The studies resulted in the formation of four SQs based coordination compounds that were obtained in high yields up to 93% and their thorough spectroscopic characterization is presented. To our knowledge, this is the first example of the DDSQ-based molecular complex possessing bidentate pyridine-triazole ligand binding two Pd(II) ions. Full article

A series of innovative thermosetting polymer nanocomposites comprising of polysiloxane-imide-containing benzoxazine (PSiBZ) as the matrix and double-decker silsesquioxane (DDSQ) epoxy or polyhedral oligomeric silsesquioxane (POSS) epoxy were prepared for improving thermosetting performance. Thermomechanical and dynamic mechanical characterizations indicated that both DDSQ and POSS could effectively lower the coefficient of thermal expansion by up to approximately 34% and considerably increase the storage modulus (up to 183%). Therefore, DDSQ and POSS are promising materials for low-stress encapsulation for electronic packaging applications. Full article

In this study we incorporated various amounts of a double-decker silsesquioxane (DDSQ) into phenolic/DDSQ hybrids, which we prepared from a bifunctionalized phenolic DDSQ derivative (DDSQ-4OH), phenol, and CH₂O under basic conditions (with DDSQ-4OH itself prepared through hydrosilylation of nadic anhydride with DDSQ and subsequent reaction with 4-aminophenol). We characterized these phenolic/DDSQ hybrids using Fourier transform infrared spectroscopy; ¹H, ¹³C, and ²⁹Si nuclear magnetic resonance spectroscopy; X-ray photoelectron spectroscopy (XPS); and thermogravimetric analysis. The thermal decomposition temperature and char yield both increased significantly upon increasing the DDSQ content, with the DDSQ units providing an inorganic protection layer on the phenolic surface, as confirmed through XPS analyses. We obtained carbon/DDSQ hybrids from the phenolic/DDSQ hybrids after thermal curing and calcination at 900 °C; these carbon/DDSQ hybrids displayed electrochemical properties superior to those of previously reported counterparts. Full article

In this study, we synthesized two main chain–type block copolymers featuring hydrogen bond donor and acceptor segments through atom transfer radical polymerization (ATRP) using a bifunctionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the initiator. Hydrosilylation of vinylbenzyl chloride at the two corners of a double-decker silsesquioxane (DDSQ) provided the bifunctionalized benzyl chloride initiator VBC-DDSQ-VBC, which we applied as a platform to prepare a main chain–type polystyrene homopolymer (PS-DDSQ-PS), the diblock copolymer poly(styrene–b–4-vinylpyridine) (P4VP-b-PS-DDSQ-PS-b-P4VP), and the diblock copolymer poly(styrene–b–tert-butoxystyrene) (PtBuOS-b-PS-DDSQ-PS-b-PtBuOS) through sequential ATRP. Selective hydrolysis of the tert-butoxyl units of PtBuOS-b-PS-DDSQ-PS-b-PtBuOS yielded the strongly hydrogen bonding diblock copolymer poly (styrene-b-vinylphenol) (PVPh-b-PS-DDSQ-PS-b-PVPh). We used Fourier transfer infrared spectroscopy, nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, mass-analyzed laser desorption ionization mass spectrometry, and transmission electron microscopy to investigate the chemical structures, thermal behavior, and self-assembled nanostructures formed by these main chain–type block copolymers based on DDSQ. Full article

The preparation of hybrid nanocomposite materials derived from polyhedral oligomeric silsesquioxane (POSS) nanoparticles and polyimide (PI) has recently attracted much attention from both academia and industry, because such materials can display low water absorption, high thermal stability, good mechanical characteristics, low dielectric constant, flame retardance, chemical resistance, thermo-redox stability, surface hydrophobicity, and excellent electrical properties. Herein, we discussed the various methods that have been used to insert POSS nanoparticles into PI matrices, through covalent chemical bonding and physical blending, as well as the influence of the POSS units on the physical properties of the PIs. Full article