Isobutyl Polyhedral Oligomeric Silsesquioxane Research Articles

Low-aggregated multi-color perylene diimide derivatives and their photo-thermal stability in color films

Perylene diimide derivatives (PDIs) have potential applications in organic semiconductor devices owing to their high absorption coefficients and chemical persistency. However, molecular aggregation and inferior thermal stability limit their preparation and application as color-film devices. In addressing this issue, we designed a series of PDIs by introducing different steric hindrance group (propyl isobutyl polyhedral oligomeric silsesquioxane (propyl isobutyl POSS), isoctyl, and 2-octyldodecyl) at the terminal position and electron-donating group (alkoxy, alkyl-substituted phenoxy or alkylamino) at the bay position. Density Functional Theory (DFT) calculations demonstrated that the substitution of propyl isobutyl POSS at the terminal position and electron-donating groups (2,4-di-tert-butylphenoxy, tert-butyloxy, and diethylamino) at bay position of the perylene chromophore had synergistic effect on reducing the aggregation of PDIs, and the bay substitution could achieve PDIs with different colors due to the connection of the substituent group with the conjugated system of the PDIs. Based on the results of calculation, four low-aggregated multi-color PDIs were synthesized for the first time. Their color films displayed excellent photo-thermal stability because of the introduction of propyl isobutyl POSS moieties (Td > 230 °C, color difference ΔE < 3). This work provides important insights into the design of multi-color PDIs with low aggregation and high photo-thermal stabilities, which holds great promise for the organic electronics research field.

Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications.

Herein, the development of new nanocomposite systems is reported based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets (GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS was effectively synthesized via a two-step synthesis protocol, including ultrasonication-assisted reaction and precipitation, and carefully characterized with respect to its chemical and crystalline structure, morphology, and thermal stability. FTIR and XPS spectroscopy analyses revealed that POSS interacts with the residual oxygen moieties of the GNPs through both covalent and noncovalent bonding. The X-ray diffraction pattern of GNP-POSS further revealed that the crystallinity of the GNPs was not altered after their functionalization with POSS. GNP-POSS was successfully incorporated in PU at contents of 1, 3, 5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR analysis of these films confirmed the presence of strong interfacial interactions between the urea groups of PU and the GNP-POSS functionalities. Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal stability and mechanical properties compared to those of the neat PU film. The quasi-static tensile testing of the PU/GNP-POSS samples revealed remarkable enhancements in the tensile strength (from 7.9 for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young's modulus (238-617 MPa), while elongation at break and toughness also showed 14 and 125% improvements, respectively. Finally, the effects of GNP-POSS content on the morphological, quasistatic tensile, and high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite films were also investigated. Overall, the tests performed using a split-Hopkinson pressure bar setup revealed a large increase in the film strength (from 147.6 for the neat PU film to 199 MPa for the PU/GNP-POSS film) and a marginal increase in the energy density of the film (38.1-40.8 kJ/m3). These findings support the suitability of the PU/GNP-POSS nanocomposite films for force protection applications.

Study of Water Sorption in Methacryl-Based Polyhedral Oligomeric Silsesquioxane (POSS) Dental Composites Using Molecular Dynamics Simulations.

Methacrylate-based polyhedral oligomeric silsesquioxane (POSS) is one of the new composites used as a dental resin. Both monofunctional methacryl isobutyl POSS (MIPOSS) and multifunctional methacryl POSS (MAPOSS) are reported to be possible resins that possess the desired properties for using them as dental resins. Our group's previous comparative study on these two resins showed that the MAPOSS composite has superior mechanical properties compared with the MIPOSS composite. In this article, molecular dynamic simulations (MD simulations) are performed to study the water sorption in these two composites. Water sorption in dental composites can have several effects on the material properties, performance, and longevity of dental restorations. Water sorption in MAPOSS and MIPOSS composites is analyzed by studying the hydrogen bonding, cluster analysis, density projection calculations, and diffusion coefficient calculation of water molecules within the resin matrix. MD simulations results are further used to understand the interaction of water molecules with the resin matrix comprehensively, which governs the composite's mechanical properties. The water sorption study showed that the MAPOSS composite has less water sorption capacity than the MIPOSS composite. The practical significance of this study is to find properties that affect dental restoration and longevity, which can help in the design of better materials for dental applications.

Effect of trisilanol isobutyl polyhedral oligomeric silsesquioxane (TPOSS) in recycled PET (rPET) and polypropylene based compound: Investigation on mechanical properties

Recycled polyethylene terephthalate is successfully prepared. This project is involved for “Circular economy” policy. It is successfully prepared into powder form by nano-grinder technique. 10 phr of PP-g-MA and 1 phr to 5 phr of TPOSS are added for compatibilizer and mechanical properties enhancement, respectively. PP-g-MA can form the chemical linkage of the anhydride groups with the polyamide end groups. 20 wt% of recycled polyethylene terephthalate powder and polypropylene based compound is successfully fabricated by melt mixing. Then, it is fabricated by melting spinning technique. Fourier transform infrared presents Si-O-Si linkage in binary blend compound. X-ray diffraction pattern reports that single phase is obtained. Adding TPOSS can be induced to crystallinity enhancement. No significant change of thermal properties was observed from room temperature to 300℃. Scanning electron microscope reports that with the PP-g-MA provides smoothness of surface. Recycled polyethylene terephthalate is uniformly distributed. Melting and crystallization temperatures are reported to be 162℃ to 167℃ and 115℃ to 120℃, respectively. All of throughput rate is reported to be 1.8 g⸳min-1 to 2.3 g⸳min-1. With the existence of TPOSS, the mechanical properties of compound are slightly increased. TPOSS are added for mechanical properties enhancement. The polymer compound presents the excellent properties. It is remarkable to note that recycled polyethylene terephthalate is considered as an excellent candidate for use as raw material for polymer compound production.

Molecular Simulations of Low-Shrinkage Dental Resins Containing Methacryl-Based Polyhedral Oligomeric Silsesquioxane (POSS)

Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress-strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS.

Synthesis of photoactive nanocomposite hydrogels via in-situ photoinitiated thiol-ene click polymerization of acrylates containing norbornene-POSS and norbornene-POSS/Ag NPs

Radical-mediated thiol-ene photopolymerization is a method that has been studied intensively since the beginning of the century due to the nature of click chemistry which can be carried out in a fast, controllable, and easy way under mild environment conditions with no or minimal formation of by-products. In order to improve the properties of the polymeric nanocomposite materials which have been obtained by photopolymerization method and to prepare them for a particular purpose, various nano-sized photo-reactive groups or cross-linking agents have been added to the formulations. The advantage of this study for the preparation of thin-film and hydrogel nanocomposites is based on one-pot thiol-ene photo-click polymerization. The main contribution made by one-component Type II photoinitiator, 2-Mercaptothioxanthone (TX-SH) carries both thiol functionality and chromophoric group on it. Polyhedral oligomeric silsesquioxane (POSS) functionalized with 1 or 3 norbornene units was used as alkene and played a good role in the preparation of nanocomposite hydrogels with/without in-situ formed silver nanoparticles (Ag NPs) with various acrylate content by thiol-ene photo-click polymerization. Especially the good contribution of norbornenylethyl disilanol isobutyl polyhedral oligomeric silsesquioxane (1NBPOSS) or tris-norbornenyl isobutyl polyhedral oligomeric silsesquioxane (3NBPOSS) was seen in terms of conversion percentage of acrylates which was determined by photo differential scanning calorimetry (photo-DSC) and swelling ratios of hydrogels in phosphate buffer solution (PBS) buffer solution. Besides them, obtained nanocomposites displayed good thermal stability values according to the Thermogravimetric analysis (TGA) measurements and scanning electron microscopy (SEM) images confirmed rather small-sized and uniform in-situ formed Ag NPs.

Low dielectric and high performance of epoxy polymer via grafting POSS dangling chains

Polyhedral oligomeric silsesquioxane (POSS) is an ideal nano particle for epoxy polymer to reduce dielectric constant and enhance mechanical properties due to its hollow cage type organic silicon. However, the poor compatibility between POSS and epoxy resin has always been the key factor limiting the amount of addition and the improvement of performance. Herein, a modified epoxy (EGP) with POSS dangling chain is designed, that is, mercaptopropyl isobutyl POSS (POSS-SH) is grafted to diglycidyl ether of 4,4′-diallyl bisphenol-A (DADGEBA) backbone via ‘thiol-ene’ click reaction. Compared with the reported researches, thiol-ene click chemistry shows efficient and controllable, which makes the grafting efficiency of POSS-SH close to 100%. Covalent bond linking between POSS and DADGEBA constrains the aggregation and phase separation of POSS, and the content of used POSS is up to 50%. As expected, the obtained polymer (EGP-x-DDM) cured by 4,4′-diaminodiphenylmethane (DDM) presents low dielectric constant and dielectric loss, as well as tensile strength and tensile modulus are enhanced by 22.9% and 31.6%, respectively. The novel epoxy resin EGP has potential application in the electronic and electrical field.

Design on the corrosion protection of eco-friendly and multifunctional polyhedral oligomeric silsesquioxane functionalized graphene oxide reinforced waterborne polyurethane

This paper explored that the novel waterborne polyurethane (WPU) composite coatings with superior corrosion protection performance was fabricated via intercalating functionalized graphene oxide (GO). The eco-friendly and superhydrophobic aminoethyl aminopropyl isobutyl polyhedral oligomeric silsesquioxane (POSS-NH-NH2) was applied to modify GO via facile one-step chemical grafting. Several analyses such as FT-IR, XRD, Raman, and SEM were performed to verify the successful graft of POSS-NH-NH2 into the GO. Sequentially, the WPU and WPU composite coatings containing GO and functional graphene oxide (PNNG) nanoparticles were prepared and applied on Q235 steel with a thickness of 55 ± 5 µm. The corrosion protection performance of coatings was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization. The results highlighted that well-dispersed and hydrophobic PNNG nanoparticle remarkably enhanced the corrosion protection performance of WPU. In detail, the protection efficiency of WPU composite coatings with 0.1 wt% PNNG reached 99.79% relative to pure WPU. After 21 days’ immersions in 3.5 wt% NaCl aqueous solution, the ǀZ|f=0.01Hz of WPU decreased to 1.96 × 105 Ω cm2 from 1.52 × 107 Ω cm2. However, the ǀZ|f=0.01Hz of WPU with 0.1 wt% PNNG was 1.48 × 108 Ω cm2 after 180 days’ immersions, which was still about 3 orders of magnitude higher than that of WPU.

Characterization of poly(ethylene oxide) modified with different phenyl hepta isobutyl polyhedral oligomeric silsesquioxanes

Poly(ethylene oxide)/polyhedral oligomeric silsesquioxanes (PEO/POSSs) composites were prepared by the melting method. The investigation of their thermal characteristics was performed by the differential scanning calorimetry (DSC), while the investigation of their thermal stability was performed by the non-isothermal thermogravimetry. The glass transition temperatures, the crystallinity and the melting temperature of PEO decrease with the addition of POSS nanoparticles. FTIR analysis also confirms the decrease in PEO’s crystallinity with the addition of POSS. POSS nanoparticles shift the beginning of PEO decomposition toward lower temperatures, while they do not have a significant effect on the maximum decomposition temperature, maximum decomposition rate and the residual mass. Scanning electron microscopy analysis seems to indicate that a poor dispersion of POSS nanoparticles causes this worsening in the thermal behavior of the prepared composites. The non-isothermal decomposition of PEO/POSSs samples is more complex compared to pure PEO. POSS nanoparticles influence the beginning of the PEO’s decomposition process and its activation energy, while the kinetic model of PEO’s thermal decomposition process remains unchanged.

Crystallization behaviors of poly(ethylene terephthalate) (PET) with monosilane isobutyl-polyhedral oligomeric silsesquioxanes (POSS)

The crystallization behaviors of poly(ethylene terephthalate) (PET) with monosilane isobutyl-polyhedral oligomeric silsesquioxanes (POSS) were investigated in detail. It is observed that POSS acts as an effective nucleating agent under appropriate concentration in the PET system. Polarized optical microscopy (POM) results showed that POSS improved the nucleation density of PET. Besides, the transmission electron microscopy (TEM) observation demonstrated POSS dispersed mostly at the nanometer scale throughout the PET matrix. The crystal structures of POSS and PET/POSS were analyzed using wide-angle X-ray diffraction (WAXD). Moreover, non-isothermal crystallization kinetics of PET and PET/POSS were studied using Mo’s method. The PET/POSS system demonstrated the lower value of F(T) than pure PET, indicating that the lower cooling rate was required to attain a specified relative crystallinity for the system. The comparison of the crystallization activation energy (ΔE) showed that the POSS nanoparticles improved the crystallization of PET through an acceleration of the nucleation process. Furthermore, the isothermal crystallization behaviors were also investigated using classic Avrami method. Overall, POSS can act as a nucleating agent and greatly improve the crystallization of PET through accelerating the nucleation process.

Temperature dependence of methanol and ethanol vapor sorption in polyhedral oligomeric silsesquioxane (POSS) containing methacrylate membranes

AbstractThis study aimed to determine the solubility and temperature dependence of methanol and ethanol vapor caused by the difference in the substituents of polyhedral oligomeric silsesquioxane (POSS)‐containing polymethacrylate membranes and the spacer length between the backbone and POSS backbone. Vapor sorption of methanol and ethanol was measured at 25°C, 35°C, and 45°C for three kinds of POSS‐containing polymer membranes, namely, poly(methacryl isobutyl POSS), poly(methacrylate isobutyl POSS), and poly(methacryl phenyl POSS). The primary structures of the three POSS‐containing polymer chains were columnar. The solubility of alcohol vapor on the POSS‐containing polymer membranes followed the mechanism of solid adsorption and not the general dissolution diffusion. The sorption amount at all three temperatures was related to the surface area of the cylindrical primary structure and the solid adsorption property of the alcohol molecule of the POSS substituent. The sorption amount increased because of the large surface area and adsorption property of alcohol molecules. Although a typical glassy polymer shows exothermic mixing and a rubbery polymer displays endothermic mixing, the sample with the POSS substituent of isobutyl group exhibited an unusual behavior of endothermic mixing despite being a glassy polymer.

Novel Unsaturated Polyester Nanocomposites via Hybrid 3D POSS-Modified Graphene Oxide Reinforcement: Electro-Technical Application Perspective.

The latest trends in technologies has shifted the focus to developing innovative methods for comprehensive property enhancement of the polymer composites with facile and undemanding experimental techniques. This work reports an elementary technique to fabricate high-performance unsaturated polyester-based nanocomposites. It focuses on the interactive effect of polyhedral oligomeric silsesquioxanes (POSS)-functionalized graphene oxide (GO) within the unsaturated polymermatrix. The hybrid framework of POSS-functionalized graphene oxide has been configured via peptide bonding between the aminopropyl isobutyl POSS and graphene oxide. The synergistic effect of POSS and graphene oxide paved the way for a mechanism to inculcate a hybrid framework within the unsaturated polyester (UP) via in situ polymerization to develop UP/GO-POSS nanocomposites. The surface-appended POSS within the graphene oxide boosted its dispersion in the UP matrix, furnishing an enhancement in tensile strength of the UP/GO-POSS composites by 61.9%, thermal decomposition temperature (10% mass loss) by 69.8 °C and electrical conductivity by 108 S/m, in contrast to pure UP. In particular, the homogenous influence of the POSS-modified GO could be vindicated in the surging of the limiting oxygen index (%) in the as-prepared nanocomposites. The inclusive property amelioration vindicates the use of fabricated nanocomposites as high-performance nanomaterials in electrotechnical applications.

Near-field scattering enhancement of perylene based aggregates for random lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N’-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide (DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

Improvement of fracture toughness and thermo-mechanical properties of carbon fiber/epoxy composites using polyhedral oligomeric silsesquioxane

The influence of polyhedral oligomeric silsesquioxanes–polyvinylpyrrolidone on the interlaminar fracture toughness of carbon fiber-reinforced composites (CFRPs) is investigated in this study. Baseline composite material is fabricated using novolac epoxy-infused carbon fiber prepreg. Glycidyl isobutyl polyhedral oligomeric silsesquioxanes (GI) is introduced in the CFRP at loading of 1, 3, 5, and 10 wt.% with respect to polyvinylpyrrolidone used as a compatibilizer. Results of the double cantilever beam test indicate an increase of 70% in interlaminar fracture toughness for 5 wt.% GI-POSS loading compared to the baseline composite. Scanning electron microscopy shows polyhedral oligomeric silsesquioxanes enhanced the adhesion between fiber and the resin that leads to the fiber pull-out. Dynamic mechanical analysis result captures the reduction in the storage modulus with addition of polyvinylpyrrolidone due to the plasticization effect. Nonetheless, the introduction of polyhedral oligomeric silsesquioxanes increases the storage modulus for the GI/PVP composite. Additionally, an increase in the glass transition temperature with the reinforcement of polyhedral oligomeric silsesquioxanes is observed.

Mechanistic Insights from Functional Group Exchange Surface Passivation: A Combined Theoretical and Experimental Study

Four different functional groups including amino (−NH2), phosphine (−PH2), hydroxyl (−OH), and thiol (−SH) were combined with POSS (polyhedral oligomeric silsesquioxane) molecules to investigate how functional groups affect the surface passivation of POSS systems. Results from density-functional theory (DFT) calculations indicate that functional group amino (−NH2) with adsorption energy 86 (56) kJ mol–1 is consistently better than that of thiol (−SH) with adsorption energy 68 (43) kJ mol–1 for different passivation mechanisms. Theoretical studies on the analogous POSS–OH and POSS–PH2 systems show similar adsorption energies. Two of the systems were also investigated experimentally; aminopropyl isobutyl POSS (POSS–NH2) and mercaptopropyl isobutyl POSS (POSS–SH) were applied as passivation materials for MAPbI3 (MA = methylammonium) perovskite and (FA)0.85(MA)0.15Pb(I3)0.85(Br3)0.15 (FA = formamidinium) perovskite films. The same conclusion was drawn based on the results from contact angle studies, X-ray dif...

Influence of POSS-PVP in Modification of CFRP Interlaminar Fracture Toughness

The influence of polyhedral oligomeric silsesquioxanes (POSS) – polyvinylpyrrolidone (PVP) on the interlaminar fracture toughness of carbon fiber reinforced composites (CFRP) is investigated in this study. Baseline composite material is fabricated using novlac epoxy infused carbon fiber prepreg. Glycidyl isobutyl POSS (GI) is introduced in the CFRP at loading of 1, 3, 5, and 10 wt. % with respect to PVP used as a compatibilizer. Results of the double cantilever beam test indicates an increase of 70% in interlaminar fracture toughness for 5 wt. % GI-POSS loading compared to the baseline composite. Scanning electron microscopy shows POSS enhanced the adhesion between fiber and the resin that leads to the fiber pull-out. Dynamic mechanical analysis result captures the reduction in the storage modulus with addition of PVP due to the plasticization effect. Nonetheless, the introduction of POSS increases the storage modulus for the GI/PVP composite. Additionally, an increase in the glass transition temperature with the reinforcement of POSS is observed. Keywords: Interlaminar fracture toughness; Carbon Fiber Reinforced

Enhancing the Efficacy of Photodynamic Therapy through a Porphyrin/POSS Alternating Copolymer

AbstractAggregation‐induced quenching (AIQ) of photosensitizers greatly reduces the quantum yield of singlet oxygen generation and mitigates the efficacy of photodynamic therapy (PDT). We have prepared an alternating copolymer starting from 4‐vinylbenzyl‐terminated tetraphenylporphyrin (VBTPP) and maleimide isobutyl polyhedral oligomeric silsesquioxane (MIPOSS), via alternating reversible addition–fragmentation chain transfer (RAFT) polymerization. Porphyrin and POSS are installed on the amphiphilic block copolymers backbone in an alternating fashion and POSS completely inhibits the aggregation of porphyrin units via stacking. The amphiphilic block copolymer can self‐assemble into nanoparticles and its application in PDT treatment was tested. These porphyrin‐containing polymeric nanoparticles display high photochemical yield and phototoxicity in vitro and in vivo, providing a novel strategy to enhance the PDT efficacy.

Enhancing the Efficacy of Photodynamic Therapy through a Porphyrin/POSS Alternating Copolymer.

Aggregation-induced quenching (AIQ) of photosensitizers greatly reduces the quantum yield of singlet oxygen generation and mitigates the efficacy of photodynamic therapy (PDT). We have prepared an alternating copolymer starting from 4-vinylbenzyl-terminated tetraphenylporphyrin (VBTPP) and maleimide isobutyl polyhedral oligomeric silsesquioxane (MIPOSS), via alternating reversible addition-fragmentation chain transfer (RAFT) polymerization. Porphyrin and POSS are installed on the amphiphilic block copolymers backbone in an alternating fashion and POSS completely inhibits the aggregation of porphyrin units via stacking. The amphiphilic block copolymer can self-assemble into nanoparticles and its application in PDT treatment was tested. These porphyrin-containing polymeric nanoparticles display high photochemical yield and phototoxicity in vitro and in vivo, providing a novel strategy to enhance the PDT efficacy.

Synthesis of mesoporous silica spheres utilizing in tandem with POSS-based block copolymer and anion surfactant as dual-template

In this work, novel mesoporous silica spheres were prepared by calcination of golf-shaped silica microspheres, which were fabricated via a typical sol-gel method by using synthetic amphiphilic block copolymer poly(acrylate isobutyl polyhedral oligomeric silsesquioxane)-b-poly(dimethylaminoethyl methacrylate co-styrene)) (PAPOSS-b-(PDMAEMA-co-PSt) and anionic surfactant sodium dodecyl sulfate (SDS) as dual-template. Firstly, three different POSS-based block copolymers were synthesized through subsequent homopolymerization of acrylate isobutyl POSS and chain extension of dimethylaminoethyl methacrylate (DMAEMA) and styrene with various feed ratios via reversible transfer radical polymerization (RAFT). These amphiphilic block polymers and SDS were utilized as cooperative template to golf-shaped silica microspheres. The electrostatic interaction between protonated PDMAEMA segments and anion surfactant as well as the strong interaction between PAPOSS segments and silicon source plays the dominant role in forming golf-shaped silica spheres. Moreover, the surface morphology of silica spheres can be tuned by varying molar ratio of PDMAEMA/PAPOSS. The resulting golf-shaped silica microspheres were further calcined to give mesoporous silica spheres which exhibited a BET surface area of 1031 m2 g−1, a total pore volume of 0.826 cm3 g−1, and a narrow pore size distribution centered at 3.20 nm.

Structural factor of nanoparticles in the stress-induced crystallization of poly(ethylene terephthalate)

The crystallization behavior of poly(ethylene terephthalate) (PET) nanocomposites with clay and trisilanol isobutyl-polyhedral oligomeric silsesquioxane (TPOSS) in the high-speed spinning process was investigated in terms of take-up speed and content of nanoparticles. The spherical TPOSS promoted the crystallization of PET. On the other hand, the plate-like clay with the aspect ratio of 250 suppressed it. At the take-up speed of 3.5 km/min, the crystallinity of the PET nanocomposite containing 1 wt% of clay was 23%, much lower than 48% of neat PET and 57% of the PET nanocomposite containing 2 wt% of TPOSS. The 2D-WAXS analysis revealed that the anisotropic clay nanoparticles aligned parallel to the fiber axis even in the fiber prepared from the free-fall spinning process. Increasing the take-up speed of spinning further increased the degree of orientation of the particle. Because of the suppressed crystallization of PET by the highly oriented clay nanoparticles, the fiber of the PET/clay nanocomposite did not give any characteristic 2D-SAXS pattern over the take-up speed range examined, indicating the absence of tilted lamellar stacks. In the fibers of neat PET and PET/TPOSS nanocomposites, however, an X-shaped 4-point pattern was obtained at low take-up speeds, which was converted to the scattering pattern of an equatorial streak with the inverse triangular scatterings in the meridional direction at high take-up speeds. The transition of the 2D-SAXS pattern shape took place at the take-up speed of 4.5 km/min for neat PET which was shifted to the lower speeds of 4 and 3.5 km/min by adding 1 and 2 wt% of TPOSS, respectively.