Polyethylene glycol/polyhedral oligomeric silsesquioxane as an in situ photocrosslinkable polymeric nanohybrid

Polyhedral oligomeric silsesquioxane (POSS)/poly(ethylene glycol) diacrylate (PEGDA) biodegradable nanohybrids were synthesized in which modified POSS was chemically incorporated into the polymer chain as reinforcing nanoparticles during a blue light photocuring process. First, POSS diacrylate (POSSA) was prepared by the simple reaction of POSS with acryloyl chloride and the product obtained was identified by Fourier transform infrared spectroscopy and ¹³C NMR. Second, POSSA was incorporated into the PEGDA matrix in various concentrations in the presence as well as the absence of a reactive diluent. Finally, some characterizations such as XRD, TEM, equilibrium swelling, viscoelastic behavior, mechanical properties and cytocompatibility tests were performed to evaluate the effectiveness of these nanoparticles within the PEGDA polymer matrix. The results revealed that POSSA acted as a crosslinking agent as well as an inorganic nanofiller to enhance the properties of PEGDA and also that the most effective content of these nanoparticles should be optimized in the range 1.5–3 wt%. This study suggests acrylated POSS as an effective nanoparticle to promote the efficiency of photocured nanohybrids used in medical applications. © 2020 Society of Chemical Industry     

Flame retardancy and thermal stability of polyhedral oligomeric silsesquioxane nanocomposites

The flame retardancy and thermal stability of polyhedral oligomeric silsesquioxane (POSS) nanocomposites are reviewed. Results are summarized and compared on the basis of structure–property relationships. Because of the variability of groups attached on POSS, they exhibit different performance in polymer nanocomposites: metal‐containing POSS show good catalytic charring ability; vinyl‐containing and phenyl‐containing POSS promote the strength of char. Improvements in the cone calorimeter (such as reduced peak heat release rate) are advantages of POSS as preceramics for fire retardancy compared with traditional flame retardants, and it will pave the way to the design of inorganic–organic hybrid polymer nanocomposites with enhanced flame retardancy and thermal stability. Copyright © 2011 John Wiley & Sons, Ltd.     

烯丙基异丁基多面体低聚倍半硅氧烷/聚丁二烯遥爪型纳米杂化材料的制备及表征

采用负离子聚合法,以单官能团笼型烯丙基异丁基多面体低聚倍半硅氧烷(POSS)和丁二烯为单体、正丁基锂为引发剂、环己烷为溶剂及乙基四氢糠基醚为调节剂,制备了烯丙基异丁基POSS/聚丁二烯遥爪型纳米杂化材料,对其结构进行了表征.结果表明,POSS与丁二烯发生了共聚合,实现了活性负离子引发聚合制备POSS/聚丁二烯遥爪型纳米...     

Effect of side chain architecture on dielectric relaxation in polyhedral oligomeric silsesquioxane/polypropylene oxide nanocomposites

Segmental and normal mode dynamics in polyhedral oligomeric silsesquioxane (POSS)/poly(propylene oxide) (PPO) non-reactive and reactive nanocomposites were investigated using a broadband dielectric relaxation spectroscopy (DRS) over wide ranges of frequency and temperature. Three POSS reagents with varying side chain architecture were selected for the study: OctaGlycidyldimethylsilyl (OG), TrisGlycidylEthyl (TG) and MonoGlycidylEthyl (MG). Spectra of OG and TG show a segmental (α) process at lower frequency and a local (β) relaxation at higher frequency, while MG displays only a local relaxation. Neat PPO has both segmental and normal mode (α_N) process. In POSS/PPO non-reactive nanocomposites, the presence of OG and TG causes a decrease in the time scale of α_N and α relaxation, while MG has no impact on the dynamics of PPO. Chemical reactions in POSS/PPO reactive nanocomposites lead to the formation of nanonetworks. Prior to the onset of reaction, POSS nanoparticles promote the motions of PPO chains, decrease the time scale of relaxation and give rise to thermodielectrically simple spectra. During the reaction, however, the network formation leads to spectral broadening and a gradual increase in the time scale of both segmental (α) and normal mode (α_N) relaxation. A detailed account of the effects of structure, concentration and dispersion of POSS in the matrix, molecular weight of PPO, extent of reaction and temperature on the molecular origin, temperature dependence and spectral characteristics of relaxation processes in POSS/PPO nanocomposites is provided.     

Preparation and characterization of styrene/styryl–polyhedral oligomeric silsesquioxane hybrid copolymers

BACKGROUND: Organic–inorganic nanocomposites were prepared by copolymerization of various monomers and polyhedral oligomeric silsesquioxane (POSS) derivatives. Preliminary results showed that styrene/styryl–POSS copolymers could be obtained using CpTiCl₃ catalyst. In the work reported here, the copolymerization of styrene and styryl‐substituted POSS was studied in detail for a more effective catalyst, Cp*TiCl₃. RESULTS: The glass transition temperature (T_g) of the copolymers prepared increased with increasing POSS content. The degradation temperature (T_d) of the copolymers was 60 °C higher than that of syndiotactic polystyrene under nitrogen. Although the thermal properties were improved by incorporation of POSS, the catalytic activity decreased with POSS content. The racemic triad and syndiotactic index of the copolymers decreased with increasing POSS content. Gel permeation chromatograms of the copolymers exhibited multimodal distribution due to the presence of multi‐active centres, which were formed by interaction of Ti with the POSS siloxane linkage. CONCLUSION: With the incorporation of POSS, the thermal properties of polystyrene were improved. The styrene/styryl–POSS copolymers are formed through the various active sites arising from the interactions of Ti with POSS. Copyright © 2008 Society of Chemical Industry     

The synthesis and characterization of polystyrene/magnetic polyhedral oligomeric silsesquioxane (POSS) nanocomposites

Fc-CHCH-C₆H₆-(C₅H₉)₇Si₈O₁₂ (POSS1, Fc: ferrocene) which contain both metal and CC double bond was firstly synthesized by Wittig reaction. The chemical structure of POSS1 was characterized by FTIR, ¹H, ¹³C and ²⁹Si NMR, mass spectrometry and elemental analysis, and the magnetic property of POSS1 have also been studied. Polystyrene composites containing inorganic-organic hybrid polyhedral oligomeric silsesquioxane (POSS1) were prepared by bulk free radical polymerization. XRD and TEM studies indicate that POSS1 is completely dispersed at molecular level in PS matrix when 1 wt% POSS1 is introduced, while some POSS1-rich nanoparticals are present when content of POSS1 is beyond 3 wt%. GPC results show that molecular weight of the PS/POSS1 nanocomposites are increased with addition of POSS1. TGA and TMA data show the thermal stabilities of PS/POSS1 nanocomposites have been improved compared to neat PS. The PS/POSS1 nanocomposites also display higher glass transition temperatures (T_g) in comparison with neat PS. Viscoelastic properties of PS/POSS1 nanocomposites were investigated by DMTA. The results show the storage modulus (E′) values (temperature>T_g) and the loss factor peak values of the PS/POSS1 nanocomposites are higher than that of neat PS. Mechanical properties of the PS/POSS1 nanocomposites are improved compared to the neat PS.     

Synthesis and characterization of polyimide/polyhedral oligomeric silsesquioxane nanocomposites containing quinolyl moiety

A series of functional polyhedral oligomeric silsesquioxane (POSS)/polyimide (PI) nanocomposites were prepared using a two‐step approach. First, octa(aminophenyl)silsesquioxane (OAPS) was mixed with poly(amic acid) (PAA) prepared by reacting bis(4‐amino‐3,5‐dimethylphenyl)‐3‐quinolylmethane and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride. Second, the resulting solution was subjected to thermal imidization. The well‐defined ‘hard particles’ (POSS) and the strong covalent bonds in the amide linkage between the carbon atom of the carboxyl side group in PAA and the nitrogen atom of the amino group in POSS lead to a significant improvement in the thermal and mechanical properties. Homogeneous dispersion of POSS cages in the PI is evident from scanning electron microscopy, which further confirms that the POSS molecule becomes an integral part of the organic‐inorganic inter‐crosslinked network system. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the POSS‐containing nanocomposites are higher than that of the corresponding neat PI system, owing to the significant increase of the crosslinking density in the PI/POSS nanocomposites. Increasing the concentration of OAPS in the PI networks decreases the dielectric constant. Pure PI and PI/POSS systems have good antimicrobial activity. Copyright © 2011 Society of Chemical Industry     

Synthesis of multi-walled carbon nanotube/polyhedral oligomeric silsesquioxane nanohybrid by utilizing click chemistry

A new hybrid material consisting of a polyhedral oligomeric silsesquioxane (POSS) and carbon nanotube (CNT) was synthesized by a simple and versatile approach entailing click coupling between azide moiety-functionalized POSS and alkyne-functionalized multi-walled CNTs. This approach provides a simple and convenient route to efficiently functionalize a wide variety of nanoscale nanostructure materials on the surface of CNTs.     

Formation of nanostructured epoxy networks containing polyhedral oligomeric silsesquioxane (POSS) blocks

Nanostructured epoxy networks, based on DGEBA and poly(oxypropylene)diamine (Jeffamine D), containing nano-sized inorganic blocks, polyhedral oligomeric silsesquioxanes (POSS), were investigated. The POSS were incorporated in the network as crosslinks or as pendant units by using octa- or monoepoxy-POSS monomers, respectively, as well as diepoxides with pendant POSS. The authors focused on investigating the relationship between the network formation process and the final product properties. The reactivity of the epoxy-functional POSS monomers, the hybrid systems' time of gelation, the gel fractions and the phase structure of the networks were determined using ¹H or ¹³C NMR spectroscopy, chemorheology experiments, sol-gel analysis and transmission electron microscopy (TEM).All the POSS epoxides tested show a reduced reactivity if compared to their respective model compounds due to sterical crowding in the neighborhood of their functional groups and due to reduced epoxy group mobility. The incorporation of pendant POSS into networks of the type DGEBA-Jeffamine D-monoepoxy-POSS hence took place only in the late reaction stage. Together with the high tendency of these POSS to aggregation, the kinetics favors the formation of small nano-phase-separated POSS domains, which act as physical crosslinks due to their covalent bonds to the organic matrix. At POSS loadings higher than 70%, topological constraint by POSS leads to a strongly reduced elastic chain mobility, thus additionally strongly reinforcing the networks. The network build-up and gelation of the octaepoxy-POSS-Jeffamine D system were slow compared to the reference DGEBA-Jeffamine D network due to a low octaepoxy-POSS reactivity and due to its strong tendency to cyclization reactions with primary amines. The topology of the amino groups is shown to be very important. In contrast to monoepoxy-POSS, the octaepoxy-POSS becomes dispersed as oligomeric junctions (purely chemical crosslinks) of the network in the cured product. The octaepoxide's reinforcing effect is small and is given only by its high functionality and not by its inorganic nature. The functionality effect is reduced by the mentioned cyclizations.     

聚苯乙烯-丙烯酸丁酯/八异辛基倍半硅氧烷复合乳液的制备及稳定性研究

用细乳液聚合方法制备了聚苯乙烯-丙烯酸丁酯/八异辛基倍半硅氧烷复合乳液(PS t-BA/PO SS),探讨了八异辛基倍半硅氧烷在乳液中的含量对复合乳胶粒的形态、平均粒径及分布以及乳液稳定性的影响。结果表明复合乳胶粒子平均粒径为70~100nm,PO SS的含量对乳胶粒的形态和粒径分布有明显的影响,复合乳液具有良好的稀释稳定性和离心稳定性。     

ABA triblock copolymers containing polyhedral oligomeric silsesquioxane pendant groups: synthesis and unique properties

The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly(3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP=6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase-separated material exhibits a tensile modulus larger than expected (ca. 2×10⁸ Pa) for a continuous rubber phase for temperatures between a pBA-related T_g and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the T_g of the higher T_g phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The T_g of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of T_g in this system.     

甲基笼型倍半硅氧烷/CE杂化复合材料的力学性能

以甲基笼型倍半硅氧烷(POSS)作为氰酸酯树脂(CE)的改性剂,制备出一种POSS/CE杂化复合材料。研究了杂化复合材料中POSS用量对CE结构及力学性能的影响,同时采用红外光谱(FT-IR)法对不同POSS/CE体系的反应性进行了研究。结果表明:POSS的加入对CE的反应性影响不大,有利于POSS/CE杂化体系固化工艺的制定;当杂化体系中w(POSS)=5%时,材料的冲击强度(9.7 kJ/m2)相对最大(提高了49%),弯曲强度(90 MPa)也相对较高,说明适量的POSS对CE具有明显的增韧、增强作用。     

Polysiloxanes containing polyhedral oligomeric silsesquioxane groups in the side chains; synthesis and properties

Linear polysiloxanes having different amounts of polyhedral oligomeric silsequioxane (POSS) side groups were prepared from the hydrosilylation reaction of poly(ethylhydrosiloxane) with different amount of POSS and 1-octene using platinum(0)-divinyl tetramethyldisiloxane as a catayst. 1-Octene and platinum(0)-divinyl tetramethyldisiloxane were found to be very important for the preparation of the linear polymer without any cross-linked structures. The linear polysiloxanes with POSS side groups are soluble in various organic solvents. When the content of POSS-containing monomeric unit is larger than 10 mol%, free standing films can be prepared from a routine solution casting method, although this polysiloxane is not cross-linked.     

Nanotailoring of polyurethane adhesive by polyhedral oligomeric silsesquioxane (POSS)

The development and commercialization of nanoparticles such as nanoclays (NCs), carbon nanotubes (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) offers new possibilities to tailor adhesives at the nanoscale. Four types of POSS, with reactive mono-functional groups of isocyanatopropyl, glycidoxypropyl, aminoethyl and non-reactive octaphenyl, were incorporated in concentrations of 1, 3 and 5 wt% into a polyurethane (PU)-based adhesive. Thermo-mechanical bulk properties were studied using dynamic mechanical analysis (DMA). Adhesive properties were characterized in shear and peel modes. Atomic force microscopy (AFM) was used to study the nanoscale morphology. DMA measurements indicated that the neat PU possessed a glass transition temperature (T _g) of ≈ 30°C. The T _g of PU/POSS-glycidoxypropyl nanocomposite adhesive increased gradually with POSS concentration to 50°C for 5 wt%. PU/POSS-octaphenyl nanocomposite adhesive exhibited an increased T _g by 10°C for 5 wt%. The incorporation of POSS-isocyanatopropyl in the PU had no effect on the T _g. With respect to shear properties of POSS-octaphenyl-, POSS-isocyanatopropyl- and POSS-glycidoxypropyl-based PU nanocomposite adhesives, shear strength improved by 230, 178 and 137%, respectively, compared to neat PU. POSS-aminoethyl exhibited lower shear and peel strengths, while POSS-isocyanatopropyl provided the best balance of both higher shear and peel strengths compared to neat PU. It was concluded that the grafted functional group on the POSS and its reactivity with the PU network components were the decisive factors with respect to the thermo-mechanical, morphological and adhesive properties of the resulting nanocomposite adhesives. Consequently, the POSS/polyurethane based nanocomposite adhesives could be tailored for a large range of applications.     

Montmorillonite intercalated by ammonium of octaaminopropyl polyhedral oligomeric silsesquioxane and its nanocomposites with epoxy resin

The octaammonium chloride salt of octaaminopropyl polyhedral oligomeric silsesquioxane (OapPOSS) was synthesized via the hydrolytic condensation of γ-aminopropyltrimethoxysilane in the methanol solution catalyzed by concentrated hydrochloric acid and was further used as the intercalating agent to modify sodium montmorillonite (MMT). X-ray diffraction (XRD) data indicate that the MMT was successfully intercalated by the ammonium of OapPOSS, as evidenced by the fact that the basal spacing of MMT galleries was expanded from 1.3 to 1.7 nm. The intercalation method used here introduced only the octaammonium POSS salt in contrast to the introduction of all hydrolyzed products from γ-aminopropyltriethoxysilane (APTEOS). The POSS-modified MMT was exploited to prepare the epoxy-MMT nanocomposites. Using a two-step technique, the disorderly exfoliated epoxy-MMT nanocomposites were obtained. XRD studies showed that the formation of the nanocomposites in all the cases with the disappearance of the peaks corresponding to the basal spacing of MMT. Transmission electronic microscopy (TEM) was used to investigate the morphology of the nanocomposites and indicates that the nanocomposites are comprised of a random dispersion of intercalated/exfoliated aggregates throughout the matrix. Differential scanning calorimetry (DSC) indicates that the glass transition temperatures of the as-prepared epoxy-MMT nanocomposites remained invariant in comparison with that of the control epoxy when the POSS-MMT content is less than 10 wt%. However, the nanocomposite containing 15 wt% of POSS-MMT displayed a decreased T_g, which could be attributed to the incomplete curing reaction resulting from the POSS-MMT loading. Thermogravimetric analysis (TGA) shows that the incorporation of POSS-MMT into epoxy networks displayed an apparent improvement in the thermal stability, and the char residue increased with increasing the concentration of POSS-MMT.     

Physical gelation in ethylene-propylene copolymer melts induced by polyhedral oligomeric silsesquioxane (POSS) molecules

The rheological behavior of ethylene-propylene (EP) copolymers containing polyhedral oligomeric silsesquioxane (POSS) molecules was investigated by means of wide-angle X-ray diffraction (WAXD), oscillatory shear, stress and strain controlled rheology in the molten state and dynamic mechanical analysis (DMA) in the solid state. WAXD results showed that the majority of POSS molecules in the EP melt were present in the crystal form. Oscillatory shear results showed that the EP/POSS nanocomposites exhibited a solid-like rheological behavior compared with the liquid-like rheological behavior in the neat resin, i.e. POSS caused physical gelation in EP. While POSS exhibited only a minimum effect on the flow activation energy of EP, the high POSS concentration samples were found to induce higher yield stress than the neat resin. This behavior was similar to the Bingham rheology, indicative of a structured fluid. DMA results indicated that the presence of POSS increased the Young's modulus as well as the T_g of the EP copolymer. These results suggested that two types of interactions contributed to the physical gelation in EP/POSS melts were present: the strong particle-to-particle interactions between the POSS crystals and the weak particle-to-matrix interactions between the POSS crystals and the EP matrix.     

POSS基聚合物的热性能和阻燃性

本文介绍了POSS单体和POSS基聚合物的结构、性能和制备方法。重点阐述了各类POSS基聚合物以及它们的热性能。同时简单介绍了POSS对聚合物阻燃性的影响,分析了POSS提高聚合物热性能和阻燃性的原因,并展望了POSS基聚合物的发展方向。     

笼型倍半硅氧烷改性UPR的固化性能与热性能

采用示差扫描量热仪(DSC),热重分析仪(TGA)及动态力学分析仪(DMA)研究了甲基丙烯酰氧丙基笼型倍半硅氧烷(MAP-POSS)与一缩二乙二醇型UPR、苯乙烯的等温共固化反应及动力学,测试了固化物的热性能和动态力学性能。结果表明,固化过程符合自催化反应机理,当体系中MAP-POSS质量分数为5%时,5%热失重温度和残留量5%时的温度较未加体系分别提高7℃和31℃,玻璃化转变温度降低4.2℃,热降解动力学符合1级反应。     

The effect of sulfonic acid groups within a polyhedral oligomeric silsesquioxane containing cross-linked proton exchange membrane

In this study, polyhedral oligomeric silsesquioxane (POSS) moieties were incorporated into sulfonated poly(ether ether ketone) (SPEEK) to form a new cross-linked proton exchange membrane (PEM). The distribution of the POSS containing cross-linkers with or without sulfonic acid groups dictates the water behavior and connectivity of hydrophilic domains of the PEM. A PEM formed by incorporating 17.5 wt% of the cross-linker (containing POSS macromer and sulfonic acid groups) into SPEEK exhibits high proton conductivity (0.0153 S/cm), low methanol permeability (1.34 × 10⁻⁷ cm²/s), and high selectivity (1.14 × 10⁵ Ss/cm³).     

Synthesis and characterization of polybenzoxazine networks nanocomposites containing multifunctional polyhedral oligomeric silsesquioxane (POSS)

A new class of polybenzoxazine/POSS nanocomposites with network structure is prepared by reacting multifunctional benzoxazine POSS (MBZ-POSS) with benzoxazine monomers (Pa and Ba) at various compositional ratios. Octafunctional cubic silsesquioxane (MBZ-POSS) is used as a curing agent, which is synthesized from eight organic benzoxazine tethers through hydrosilylation of vinyl-terminated benzoxazine monomer (VP-a) with octakis(dimethylsiloxy)silsesquioxane () using a platinum complex catalyst (Pt-dvs). Incorporation of the silsesquioxane core into polybenzoxazine matrix could significantly hinder the mobility of polymer chains and enhance the thermal stability of these hybrid materials. For these nanocomposites, increasing the POSS content in the hybrids is expected to improve its thermal properties with respect to the neat polybenzoxazine. The morphology feature is useful to explain the thermal property changes (T_g and T_d) and AFM images show that the presence of POSS aggregation in larger scales occurs at higher POSS contents. The reason of the heterogeneous phase separation may be from the less compatibility of the inorganic silsesquioxane core with organic benzoxazine species and the homopolymerization of MBZ-POSS. In the course of the formation of the polybenzoxazine/POSS hybrids, POSS particles were separated from the polybenzoxazine rich region, leading to POSS rich domains in the range of 50-1000 nm.