POSS‐based molecular hybrids with low dielectric constant: Effect of chemical structure and molecular architecture

Three kinds of hybrids with different architectures including dumbbell‐type, bead‐type, and cross‐linked structure, were prepared via the Heck reaction between octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) and different bromo‐substituted aromatic amide monomers. The molecular architecture can be successfully achieved by simply varying the feed ratio of OV‐POSS to monomers. Their structure and properties were characterized by FTIR, ¹H NMR, ²⁹Si NMR, provide the expansion for FTIR and NMR] All the POSS‐based hybrids exhibited good thermal stability and low dielectric constant properties. The relationship between chemical structure, molecular architecture, and the dielectric constant of these hybrids were investigated in detail. The results show that POSS content dominated the low dielectric constant of the hybrids, while the chemical structure of organic chains and molecular architecture also play an important role on the formation of low dielectric constant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42292.     

Synthesis of eugenol‐based polybenzoxazine–POSS nanocomposites for low dielectric applications

Nanocomposites of eugenol‐based polybenzoxazines/amine containing polyhedral oligomeric silsesquioxane (POSS) have been prepared through copolymerization of allyl‐containing benzoxazine compounds and amine containing POSS. Their structures, curing behaviour, and thermomechanical properties were characterized by Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, X‐ray diffraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The nanoscale dispersion of POSS cores in the nanocomposites was verified by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy studies. The results from DMA and TGA show that the thermal stability, crosslink density and flame retardance of the nanocomposites increased when small amounts of POSS cores (5 wt%) were incorporated into the system. Further the POSS incorporation reduces the dielectric constant of the benzoxazines to about 1.32. Hence, the prepared nanocomposites could be used as ultra‐low‐k materials for advanced microelectronics. POLYM. COMPOS., 36:1973–1982, 2015. © 2014 Society of Plastics Engineer     

Kinetic studies of POSS–DGEBA precursors derived from monoamine functional POSS using dynamic dielectric sensing and nuclear magnetic resonance

Incorporation of pre‐reacted monofunctional polyhedral oligomeric silsesquioxane (POSS)–epoxy adducts dramatically improves dispersion of POSS in epoxy–amine networks. The relationship between reaction kinetics and mechanism for formation of POSS–epoxy adducts versus reaction temperature was investigated. Reactivities of epoxy–monoamine functional POSS molecules were determined using in situ reaction monitoring by dynamic dielectric sensing and ²⁹Si NMR spectroscopy. The amine‐functional POSS–epoxy isothermal reaction showed reduced reactivity due to reduced molecular mobility, that is, diffusion limitations. Kinetic parameters were determined by fitting ²⁹Si NMR data to the model of Kamal that was extended to include diffusion. Fitting of this model to experimental data showed very good agreement over the entire conversion range for pre‐reaction between amine‐functionalized POSS and epoxy. An autocatalytic mechanism, the same as that for the neat epoxy–amine systems, was indicated. Gel permeation chromatography, scanning electron microscopy and transmission electron microscopy were used to investigate molecular weight evolution and morphology of final networks cured by 4,4′ diaminodiphenyl sulfone using pre‐reacted POSS–epoxy adducts. POSS aggregate size decreased with increased pre‐reaction temperature; more homogenous POSS dispersion was observed with higher pre‐reaction temperature. Dynamic mechanical analysis demonstrated that T_g of composites decreased slightly compared to that of the neat matrix and there appeared to be little change in microstructural heterogeneity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45994.     

Preparation and properties of high‐performance polysilsesquioxanes/bismaleimide‐triazine hybrids

A novel kind of high‐performance hybrids (coded as POSS‐NH₂/BT) with significantly decreased curing temperature, lowered dielectric constant and loss, and improved thermal resistance were developed, which were prepared by copolymerizing bismaleimide with cage octa(aminopropylsilsesquioxane) (POSS‐NH₂) to produce POSS‐containing maleimide, and then co‐reacted with 2,2′‐bis(4‐cyanatophenyl) isopropylidene. The curing behavior and typical properties of cured POSS‐NH₂/BT were systematically investigated. Results show that POSS‐NH₂/BT hybrids have lower curing temperatures than BT resin because of the additional reactions between  OCN and amine groups. Compared with BT resin, all hybrids show improved dielectric properties. Specifically, hybrids have slightly decreased dielectric constants and similar dependence of dielectric constant on frequency over the whole frequency from 10 to 10⁶ Hz; more interestingly, the dielectric loss of hybrids is only 25% of that of BT resin at the frequency lower than 10⁵ Hz, whereas all hybrids and BT resin have almost equal dielectric loss when the frequency is higher than 10⁵ Hz. In addition, POSS‐NH₂/BT hybrids also show good thermal and thermo‐oxidative stability compared with BT resin. All these differences in macroproperties are attributed to the difference in chemical structure between POSS‐NH₂/BT hybrids and BT resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(acetoxystyrene-co-isobutylstyryl POSS) Nanocomposites: Characterization and Molecular Interaction

The poly(acetoxystyrene-co-isobutyl styryl polyhedral oligomeric silsesquioxanes)s (PAS-POSS) were synthesized by free radical polymerization and characterized by FTIR, high resolution NMR, FTIR, GPC, and DSC. The results show that the POSS content can be controlled by varying the POSS feed ratios. The interactions between organic components and inorganic POSS core, and the effects of inorganic POSS core on the properties of the resulting hybrids were investigated by high resolution solid state ¹³C NMR, ²⁹Si NMR and FTIR spectra. The results provide detailed understandings of the effects of POSS moiety on properties of hybrid polymers.     

A novel hybrid functional nanoparticle and its effects on the dielectric,mechanical, and thermal properties of cyanate ester

A novel hybrid functional nanoparticle (denoted POSS‐MPS) was synthesized by aminopropyl‐functionalized mesoporous silica (AP‐MPS) with glycidyl polyhedral oligomeric silsesquioxane (G‐POSS). The G‐POSS was employed as molecular caps to envelop the MPS and improve the interaction with the polymer matrix. The POSS‐MPS hybrids were designed to improve the properties of cyanate ester (CE) without affecting its inherent properties. The POSS‐MPS/CE composites exhibited excellent improvement in dielectric properties, mechanical properties, and thermal properties due to increase of voids volume in the composites and reinforcement of interface interaction between organic and inorganic phase. The dielectric constant (κ) and loss factor (tan δ) of composites with 4 phr of POSS‐MPS reduced to 2.78 and 0.008 in comparison to pure CE with the value of 3.27 and 0.012, respectively. Moreover, the composites exhibited 14.3, 4.9, 57.5, and 8.7% enhancement in flexural strength, flexural modulus, impact strength, and glass transition temperature (T_g) in comparison to pure CE, respectively. The results manifested that introduction of POSS‐MPS into CE exhibited toughening and reinforcing effects on the composites. POLYM. COMPOS., 37:2142–2151, 2016. © 2015 Society of Plastics Engineers     

Preparation and properties of ethylene/POSS copolymer with rac‐Et(Ind)2ZrCl2 catalyst

The various monovinyl‐functional polyhedral oligomeric silsesquioxane (POSS) monomers had been copolymerized with ethylene (E) using rac‐Et(Ind)₂ZrCl₂ and a modified methylaluminoxane (MMAO) cocatalyst. The unreacted POSS monomer could be removed completely by washing the copolymerization product with n‐hexane. And the copolymers were characterized with ¹H NMR, TEM, DSC, TGA, and GPC to know the composition, thermal properties, molecular weight and its distribution, respectively. According to ¹H NMR data, the monomer reactivity ratios of various POSS monomers were calculated by the Fineman‐Ross and Kelen‐Tudos methods. Thermogravimetric analysis of E/POSS copolymers exhibited an improved thermal stability with a higher degradation temperature and char yields, demonstrating that the inclusion of inorganic POSS nanoparticles made the organic polymer matrix more thermally robust. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and thermal property of hybrid nanocomposites by free radical copolymerization of styrene with octavinyl polyhedral oligomeric silsesquioxane

The poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution ¹H NMR, ²⁹Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the ¹H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic T_g and T_dec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Morphology and mechanical properties of polypropylene‐POSS hybrid nanocomposites obtained by reactive blending

The polypropylene‐polyhedral oligomeric silsesquioxane (PP‐POSS) organic–inorganic hybrids were obtained and studied. The hybrids were prepared by grafting of POSS on PP chains during a reactive melt‐blending of polypropylene (iPP), maleic anhydride functionalized PP (PP‐g‐MA), and amine‐functionalized POSS (aminopropylheptaisobutyl‐POSS, ambPOSS, aminopropylheptaisooctyl‐POSS, amoPOSS, or aminoethylaminopropylheptaisobutyl‐POSS, am2bPOSS), taking advantage of the high efficiency of amino‐anhydride reaction in the molten state. The structure, morphology, and physical properties of the obtained hybrids and blends were studied by means of wide‐ and small‐angle X‐ray scattering, dynamic scanning calorimetry, scanning electron microscopy, dynamic mechanical thermal analysis, as well as tensile and impact experiments. The influence of POSS chemical structure and grafting degree on the morphological characteristics and mechanical properties was investigated. It was found that grafting of POSS cages on PP chains leads to the POSS dispersion on the molecular level. On contrary, when POSS was mixed with plain iPP any grafting of POSS on iPP chains was impossible, which resulted in phase‐separated blend with crystallites of POSS dispersed in iPP matrix. The mechanical tests revealed that modification of polypropylene by grafting with POSS molecules does not affect significantly its mechanical properties, both static and dynamic, except ultimate strain, which is markedly lower in hybrids and their blends than in plain iPP. Also the impact properties of PP were practically not improved by modification with POSS. POLYM. COMPOS., 34:929–941, 2013. © 2013 Society of Plastics Engineers     

Thermal and dielectric properties of newly developed L-tryptophan-based optically active polyimide and its POSS nanocomposites

A new chiral diamine L-methyl-2-[(3,5-diaminobenzoyl)amino]-3-(1H-indol-3yl)propanoate was synthesized using L-tryptophan (essential amino acid) as starting material. The structure of the synthesized diamine was supported by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H and ¹³C-NMR) and mass spectral techniques. The diamine was polymerized with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride via thermal imidization method to produce thermally stable chiral polyimide (PI) with low dielectric constant. Additionally, polyimide nanocomposites were also prepared by incorporating amino functionalized polyhedral oligomeric silsesquioxane (POSS) into the PI matrix. The polyimide and PI/POSS nanocomposites were characterized by FT-IR spectroscopy. The PI was found to have specific optical rotation of –41.4°. The inherent viscosity was found to be 0.77 dLg^?1 indicating that a high molecular weight PI was formed. Surface morphology of the neat PI and nanocomposites was studied by scanning electron microscopy, transmission electron microscopy and atomic force microscopy (AFM) that reveal uniform distribution of the nanoparticles in the PI matrix. DSC analysis indicates that the T_g of the PI and its nanocomposites are in the range of 222–250 °C. The T_10% was found to be in the range of 402.4–470.5 °C for the PI and its nanocomposites. The dielectric constant values are in the range of 3.5–2.1.     

Reactive melt blending of PS‐POSS hybrid nanocomposites

Hybrid nanocomposites of polystyrene (PS) and methacryl phenyl polyhedral oligomeric silsesquioxane (POSS) were synthesized by reactive melt blending in the mixing chamber of a torque rheometer using dicumyl peroxide (DCP) as a free radical initiator and styrene monomer as a chain transfer agent. The effects of mixing intensity and composition on the molecular structure and morphology of the PS‐POSS hybrid nanocomposites were investigated. The degree of POSS hybridization (α_POSS) was found to increase with the POSS content, DCP/POSS ratio, and rotor speed. For the PS‐POSS materials processed in the absence of styrene monomer, an increase in the α_POSS led to a reduction in the molecular weight by PS chain scission, as a consequence of the free radical initiation. On the other hand, the use of styrene monomer as a chain transfer agent reduces the steric hindrance in the hybridization reaction between POSS and PS, enhancing the degree of POSS hybridization and avoiding PS degradation. The PS‐POSS morphology consists of nanoscale POSS clusters and particles and microscale crystalline POSS aggregates. PS‐POSS with higher α_POSS values and lower amounts of nonbound POSS showed improved POSS dispersion, characterized by smaller interfacial thickness (t) and greater Porod inhomogeneity lengths (l_p). The processing‐molecular structure–morphology correlations analyzed in this study allow the POSS dispersion level in the PS‐POSS materials to be tuned by controlling the reactive melt blending through the choice of the processing conditions. These insights are very useful for the development of PS‐POSS materials with optimized performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effects of structure of POSS on the properties of POSS/PMMA hybrid materials

Octa‐vinyl polyhedral oligomeric silsesquioxane (V‐POSS) and octa‐(methacryloxy) propyl polyhedral oligomeric silsesquioxane (M‐POSS) were incorporated into PMMA to prepare POSS/PMMA hybrid materials at molecular level via in situ polymerization. The resulting hybrid materials showed only swelling instead of solution in ethyl acetate, while pristine PMMA completely dissolved in ethyl acetate; moreover, the M‐POSS/PMMA hybrid materials exhibited more excellent resistance to solvent stress cracking. An excellent transparency was observed for all hybrid materials. Incorporation of V‐POSS and M‐POSS significantly improved thermal properties of PMMA. The thermal decomposition temperature of hybrid materials was enhanced except a slightly compromised initial decomposition temperature. The hybrid materials prepared with 0.2–0.6 mol% M‐POSS or V‐POSS improved the reinforcing and toughening properties in comparison to pristine PMMA. Also, the incorporation of POSS decreased the dielectric constant and dielectric loss of the hybrid materials with more voids introduced into the composites no matter the structure of POSS. POLYM. ENG. SCI., 55:565–572, 2015. © 2014 Society of Plastics Engineers     

聚合物/笼型倍半硅氧烷复合材料应用研究进展

综述了聚合物/笼型倍半硅氧烷（POSS）复合材料在阻燃材料、低介电材料和发光材料等方面的应用研究进展,展望了聚合物/POSS复合材料的发展前景并指出了其需研究解决的问题。     

Synthesis and thermal characterization of new dumbbell shaped POSS/PS nanocomposites: Influence of the symmetrical structure of the nanoparticles on the dispersion/aggregation in the polymer matrix

A series of three novel dumbbell shaped polyhedral oligomeric silsesquioxanes (POSS)/ polystyrene (PS) nanocomposites, at different POSS contents (3%, 5% and 10% w/w), was synthesized and characterized in order to investigate the effects of this new bridged structure on the filler‐polymer interaction and then on the thermal behavior of the obtained polymer nanostructured materials (PNMs). Nanocomposites were synthesized by in situ polymerization of styrene and the actual POSS concentration in the obtained PNMs was checked by ¹H NMR spectroscopy. Scanning electron microscopy (SEM) and FTIR spectroscopy evidenced, at the same time, the presence of filler‐polymer interactions and auto‐aggregation phenomena. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates in both inert and oxidative atmospheres. The characteristic parameters of thermal stability, namely temperature at 5% mass loss and the apparent activation energy of degradation, for the various nanocomposites were determined and an increase in the initial decomposition temperatures of PNMs with increasing the POSS contents was observed. The results are discussed and interpreted. POLYM. COMPOS., 36:1394–1400, 2015. © 2014 Society of Plastics Engineers     

Synthesis and characterization of polyurethane hybrids: Influence of the polydimethylsiloxane linear chain and silsesquioxane cubic structure on the thermal and mechanical properties of polyurethane hybrids

The structural effects of polydimethylsiloxane (PDMS) or polyhedral oligosilsesquioxanes (POSSs) on the thermomechanical properties of polyurethane (PU) networks were studied. An ester–amine‐functionalized silsesquioxane and a PDMS macromer were synthesized, and the macromer (10 wt %) was crosslinked with the PU prepolymer to obtain PU networks. The synthesized macromers and hybrids were characterized with Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, and ²⁹Si‐NMR spectroscopy techniques. The influence of POSS cubes on the thermal and mechanical properties of the polymer network films was studied comparatively with the similarly functionalized PDMS linear chain via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The degradation pattern of the POSS‐incorporated PU nanocomposites was almost the same as that of the PU network synthesized from the linear PDMS macromer. The differences in the char yields and activation energies of the hybrids reflected the enhancement of the thermal properties of the nanohybrids. The TGA and DSC curves of the macromers suggested that the thermal properties of the macromers not only depended on either the PDMS or POSS inorganic core but also depended on the organic peripheral attached to the inorganic core. The glass‐transition temperatures of the nanohybrids were higher than those of the linear‐PDMS‐incorporated hybrids. The storage modulus values increased 3‐fold upon the incorporation of POSS rigid groups into the PU hybrids in comparison with the flexible PDMS‐chain‐incorporated PU hybrids. The DMA measurements showed a long‐range rubbery plateau region for all the PU hybrids, with high storage modulus and tan δ values showing the structural homogeneity of the crosslinked networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxane) hybrid nanocomposites: Preparation,thermal properties,and Tg improvement mechanism

A series of poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxanes) (PVP‐POSS) organic–inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high‐resolution ¹H‐NMR, solid‐state ²⁹Si‐NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis of ²⁹Si‐NMR spectra, average numbers of reacted vinyl groups of each octavinyl‐POSS macromer are calculated to be 5–7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (T_g and T_dec) primarily due to crosslinking structure and dipole–dipole interaction between POSS cores and PVP carbonyl groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of poly(HEMA‐co‐MMA)‐g‐POSS nanocomposites by combination of reversible addition fragmentation chain transfer polymerization and click chemistry

New hybrid poly(hydroxyethyl methacrylate‐co‐methyl methacrylate)‐g‐polyhedral oligosilsesquioxane [poly(HEMA‐co‐MMA)‐g‐POSS] nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and click chemistry using a grafting to protocol. Initially, the random copolymer poly(HEMA‐co‐MMA) was prepared by RAFT polymerization of HEMA and MMA. Alkynyl side groups were introduced onto the polymeric backbones by esterification reaction between 4‐pentynoic acid and the hydroxyl groups on poly(HEMA‐co‐MMA). Azide‐substituted POSS (POSS? N₃) was prepared by the reaction of chloropropyl‐heptaisobutyl‐substituted POSS with NaN₃. The click reaction of poly(HEMA‐co‐MMA)‐alkyne and POSS? N₃ using CuBr/PMDEATA as a catalyst afforded poly(HEMA‐co‐MMA)‐g‐POSS. The structure of the organic/inorganic hybrid material was investigated by Fourier transformed infrared, ¹H‐NMR, and ²⁹Si‐NMR. The elemental mapping analysis of the hybrid using X‐ray photoelectron spectroscopy and EDX also suggest the formation of poly(HEMA‐co‐MMA)‐anchored POSS nanocomposites. The XRD spectrum of the nanocomposites gives evidence that the incorporation of POSS moiety leads to a hybrid physical structure. The morphological feature of the hybrid nanocomposites as captured by field emission scanning electron microscopy and transmission electron microscopic analyses indicate that a thick layer of polymer brushes was immobilized on the POSS cubic nanostructures. The gel permeation chromatography analysis of poly(HEMA‐co‐MMA) and poly(HEMA‐co‐MMA)‐g‐POSS further suggests the preparation of nanocomposites by the combination of RAFT and click chemistry. The thermogravimetric analysis revealed that the thermal property of the poly(HEMA‐co‐MMA) copolymer was significantly improved by the inclusion of POSS in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of poly(vinyl pyrrolidone‐co‐isobutylstyryl polyhedral oligomeric silsesquioxane) nanocomposites

Poly(vinyl pyrrolidone‐co‐isobutyl styryl polyhedral oligomeric silsesquioxane)s (PVP–POSS) were synthesized by one‐step polymerization and characterized using FTIR, high‐resolution ¹H‐NMR, solid‐state ¹³C‐NMR, ²⁹Si‐NMR, GPC, and DSC. The POSS content can be controlled by varying the POSS feed ratio. The T_g of the PVP–POSS hybrid is influenced by three main factors: (1) a diluent role of the POSS in reducing the self‐association of the PVP; (2) a strong interaction between the POSS siloxane and the PVP carbonyl, and (3) physical aggregation of nanosized POSS. At a relatively low POSS content, the role as diluent dominates, resulting in a decrease in T_g. At a relatively high POSS content, the last two factors dominate and result in T_g increase of the PVP–POSS hybrid. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2208–2215, 2004     

Synthesis and characterization of poly(dimethylsiloxane‐urethane) nanocomposites: Effect of (in)completely condensed silsesquioxanes on thermal,morphological, and mechanical properties

The structural properties of completely condensed and incompletely condensed silsesquioxane in the polyurethane nanocomposites containing 17.5 wt % of silsesquioxane was investigated by FTIR, TGA, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and DMA techniques. FTIR spectra shows the existence of hydrogen bonding in the PU‐POSS system. The intensity of hydrogen bonding decreases with the increase in POSS‐H loading suggesting the prevention of the formation of hydrogen bonding by the addition of POSS‐H molecule. SEM analysis reveals the incompatibility of POSS‐H molecule in the PU matrices exhibiting greater extent of phase separation and a large number of POSS aggregates on the addition of POSS‐H molecule in the PU‐POSS matrices. The TGA thermograms show that the POSS‐PU hybrids possess excellent thermal stabilities. However, the incorporation of POSS‐H molecule leads to a decrease in the thermal properties and only the char yield values increase with the increase in the POSS‐H content in the PU‐POSS hybrids. The XRD pattern reveals that the crystalline structure of POSS molecules are destroyed by the polymer matrices in the PU‐POSS hybrid films. The decrease in the bending storage modulus E′ values with the increase in the POSS‐H content proves the retardation of hydrogen bonding formation by the POSS‐H molecule in the PU‐POSS hybrid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Degradation kinetic of epoxy nanocomposites containing different percentage of epoxycyclohexyl—POSS

In this study, epoxy nanocomposites containing 0.5, 1, 2, and 5% (m/m) of epoxycyclohexyl—POSS were prepared by mechanical mixture. The samples were characterized by gel content, thermogravimetric analysis (TGA), transmission electron microscopy, and scanning electron microscopy (SEM). TGA analysis was carried out at different heating rates (5, 10, 20, and 40°C min⁻¹) aiming to evaluate the decomposition by Avrami, Flynn‐Wall‐Ozawa and Criado kinetic models. It was constated an increase in the gel fraction and dispersion of the nanocages only for the sample containing 5% POSS. The degradation study showed two distinct stages of weight loss and only for the first stage a shift in the temperature up POSS incorporation was observed. The Avrami kinetic parameters showed that the incorporation of POSS does not affect the degradation rate constant; however, there is an increase in the time required for the degradation reaction occurs. Also, it was observed an increase in the activation energy values for the sample containing 5% (m/m) of POSS. The degradation kinetic mechanisms in presence of POSS was changed from deceleratory mode (F₁) for diffusion (D_n) in the range corresponded to the second stage of weight loss. SEM analysis showed that the morphology of the epoxy resin was modified by the POSS presence, and for 5% (m/m) of POSS was constated a more homogeneous morphology in relation to other samples. © 2012 Society of Plastics Engineers