Polybenzoxazine nanocomposites containing 3,13‐Diglycidyl double‐decker silsesquioxane

3,13‐Diglycidyloxypropyloctaphenyl double‐decker silsesquioxane (3,13‐diglydidyl DDSQ) was synthesized via hydrosilylation between 3,13‐dihydrooctaphenyl double‐decker silsesquioxane (3,13‐dihydro DDSQ) and allyl glycidyl ether. This novel difunctional polyhedral oligomeric silsesquioxanes (POSS) macromer was incorporated into polybenzoxazine (PBZ) thermosets to obtain the organic–inorganic nanocomposites. Compared to control PBZ, the organic–inorganic nanocomposites displayed the enhanced glass transition temperatures (T _g's). Under the identical condition, the organic–inorganic nanocomposites exhibited the stable rubbery plateaus in the measurements by dynamic mechanical thermal analysis, which was in marked contrast to control PBZ thermoset. The enhanced T _g's and improved dynamic mechanical properties are attributable to the formation of the additional crosslinking between PBZ and the difunctional POSS macromer and the nanoreinforcement of POSS cages on PBZ networks. Thermogravimetric analysis indicates that the organic–inorganic nanocomposites displayed improved thermal stability. POLYM. COMPOS., 38:827–836, 2017. © 2015 Society of Plastics Engineers     

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     

Low dielectric and high thermal conductivity epoxy nanocomposites filled with NH2‐POSS/n‐BN hybrid fillers

Hybrid fillers of mono‐amine polyhedral oligomeric silsesquioxane/nanosized boron nitride (NH₂‐POSS/n‐BN) were performed to fabricate NH₂‐POSS/n‐BN/epoxy nanocomposites. Results revealed that the dielectric constant and dielectric loss values were decreased with the increasing addition of NH₂‐POSS obviously, but increased with the increasing addition of BN fillers. For a given loading of NH₂‐POSS (5 wt %), the thermal conductivities of NH₂‐POSS/n‐BN/epoxy nanocomposites were improved with the increasing addition of n‐BN fillers, and the thermal conductivity of the nanocomposites was 1.28 W/mK with 20 wt % n‐BN fillers. Meantime, the thermal stability of the NH₂‐POSS/n‐BN/epoxy nanocomposites was also increased with the increasing addition of n‐BN fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41951.     

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     

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     

Rheological behavior and mechanical properties of PVC/MAP‐POSS nanocomposites

The polyhedral oligomeric silsesquioxanes which contains methylacryloylpropyl groups (MAP‐POSS) was synthesized. The MAP‐POSS/PVC nanocomposites were prepared. The influences of composition, shear rate' shear stress on melting rheological behavior of MAP‐POSS/PVC nanocomposites were discussed. The dynamic mechanical properties, mechanical properties, and morphology were determined by DMA, material tester and SEM, respectively. The result shows that the plastic times decreases and melt viscosity increases with increasing MAP‐POSS content. The n has a maximal value at 5 wt% MAP‐POSS content, but have best impact strength at 3%. MAP‐POSS can use as process aid and impact aid of PVC at appropriate contents. POLYM. COMPOS., 31:1822–1827, 2010. © 2010 Society of Plastics Engineers.     

Crystallization behavior of ultrahigh‐molecular‐weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites prepared by ethylene in situ polymerization

A [3‐t‐Bu‐2‐O? C₆H₃CH?N(C₆F₅)]₂TiCl₂ catalyst (bis(phenoxyimine)titanium dichloride complex – FI catalyst) was immobilized on disilanolisobutyl polyhedral oligomeric silsesquioxane (OH‐POSS) to prepare ultrahigh molecular‐weight polyethylene (UHMWPE)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites during ethylene in situ polymerization. The dispersion state of POSS in the UHMWPE matrix was characterized by X‐ray diffraction measurements and transmission electron microscopy. It was shown that the OH‐POSS achieved uniformed dispersion in the UHMWPE matrix, although its polarity was unmatched. The isothermal and nonisothermal crystallization behavior of the nanocomposites was investigated by means of differential scanning calorimetry. The crystallization rate of the nanocomposites was enhanced because of the incorporation of POSS during the isothermal crystallization. POSS acted as a nucleus for the initial nucleation and the subsequent growth of the crystallites. For nonisothermal studies, POSS showed an increase in the crystallinity. The crystallization rate of the nanocomposites decreased because the presence of POSS hindered the crystal growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40847.     

Octa(aminophenyl) polyhedral oligomeric silsesquioxane/boron‐containing phenol–formaldehyde resin nanocomposites: Synthesis,cured, and thermal properties

Octa(aminophenyl) polyhedral oligomeric silsesquioxane (OAP‐POSS) and boron‐containing phenol‐formaldehyde resin (BPFR) were synthesized, respectively. The BPFR nanocomposites with different OAP‐POSS content (wt%) were prepared, and their properties were characterized. The results show that the thermal degradation process of this nanocomposites can be divided into three stages, and they are all following the first order mechanism. The residual ratio and thermal degradation activation energy E_a of 9 wt% OAP‐POSS/BPFR nanocomposites are both better than others and the E_a increase gradually in three stages, which is 93.3, 134.0, and 181.9 kJ mol⁻¹, respectively. Its residual ratio at 900°C is 36.48%. The mechanical loss peak temperature T_p is 228°C for 12 wt% OAP‐POSSS/BPFR nanocomposites, which is higher 48°C than pure BPFR. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synthesis,structure, and properties of high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

The organic–inorganic hybrid nanocomposites from high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR, thermal gravity analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS‐POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

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     

Morphology and mechanical properties of high density polyethylene‐POSS hybrid nanocomposites obtained by reactive blending

The high density polyethylene‐polyhedral oligomeric silsesquioxane (HDPE‐POSS) organic–inorganic hybrids were obtained and their properties studied. The hybrids were prepared by grafting of POSS on polyethylene chains during reactive melt‐blending of HDPE, maleic anhydride functionalized HDPE and amine‐functionalized POSS, taking advantage of the high efficiency of amine‐anhydride reaction in the molten state. The structure, morphology, and physical properties of the obtained hybrids and blends were studied to find the influence of POSS chemical structure and grafting degree on the morphological characteristics and mechanical properties of hybrid nanocomposites. It was found that grafting of POSS cages on HDPE chains leads to the POSS dispersion at the molecular level. On the contrary, when POSS was mixed with plain HDPE any grafting of POSS on polyethylene chains was not possible, which resulted in phase‐separated blend. The mechanical tests revealed that modification of polyethylene by grafting with POSS molecules does not affect significantly its mechanical properties, both static and dynamic, except ultimate strain, which is lower in hybrids and their blends than in plain HDPE. The impact properties (Izod impact strength) were slightly improved by grafting of HDPE with POSS. HDPE‐g‐POSS hybrids demonstrated also much enhanced thermo‐oxidative stability comparing to plain polyethylene. POLYM. ENG. SCI., 55:2058–2072, 2015. © 2014 Society of Plastics Engineers     

Highly soluble polyamide–polyhedral oligomeric silsesquioxane hybrid nanocomposites: Synthesis and characterization

A method of preparing linear polyamide‐polyhedral oligomeric silsesquioxane (PA‐POSS) hybrid nanocomposites in a reactor using thionyl chloride/triethylamine (TEA) as the activating agent was investigated. Soluble polyamic acid (PAA) having carboxylic acid end groups were first synthesized by condensation reaction of 2,2‐ bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2‐bis[4‐(4‐aminophenoxy)phenyl]‐1,1,1,3,3,3‐hexafluoropropane, (6FODA). The PAA was acylated by SOCl₂/TEA and followed by the addition of different mole percentages of aminopropyl heptacyclopentyl POSS (AP‐POSS) and 3‐(trifluoromethyl) aniline to get the PA‐POSS hybrid nanocomposites. The chemical structure of PA‐POSS hybrid nanocomposites were investigated by ATR‐FTIR and NMR spectroscopic techniques. Thermal and morphological properties of PA‐POSS were influenced by changing the percentage of POSS and investigated by thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Wide angle X‐ray diffraction and contact angle measurements. The PA‐POSS with hexafluoroisopropylidene and POSS groups have higher bulk density resulting in higher free volume and then increasing the solubility property. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Application of polyhedral oligomeric silsesquioxane to the stabilization and performance enhancement of poly(4‐methyl‐2‐pentyne) nanocomposite membranes for natural gas conditioning

The application of octatrimethylsiloxy polyhedral oligomeric silsesquioxane (POSS) nanoparticles was investigated in the fabrication of novel reverse‐selective poly(4‐methyl‐2‐pentyne) (PMP) nanocomposite membranes for the separation of heavier hydrocarbons from methane. Generally, PMP and PMP–fumed silica (FS) nanocomposite membranes suffer severe physical aging with approximately 40% permeation flux reduction over 120 days. A straightforward strategy was introduced to suppress the physical aging of PMP and also to improve the thermal stability without compromising the selectivities and permeabilities through the incorporation of a functionalized POSS–FS binary filler system. Fourier transform infrared spectroscopy and scanning electron microscopy proved productive interactions between the fillers and polymer, with a fair compatibility between them. Thermogravimetric analysis confirmed that the thermal stability of the neat PMP was enhanced by the incorporation of the fillers into the nanocomposites. The addition of POSS and FS led to improved operational performance, such as in the permeability and selectivity, over the neat PMP. The permeation stabilities of the PMP–POSS and PMP–FS–POSS nanocomposite membranes were clearly improved over a long time (120 days). The permeation data indicated that the PMP–3 wt % POSS–20 wt % FS nanocomposite membrane is promising for C₃H₈/N₂ and C₃H₈/CH₄ separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45158.     

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     

Influence of different percentages of N‐phenylaminopropyl—poss on the degradation kinetic of epoxy resin

In the present study, nanocomposites were prepared with different contents (1, 2, 5, 10% by weight) of polyhedral oligomeric silsesquioxane—POSS n‐phenylaminopropyl in an epoxy matrix. The samples were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). TGA analyses were performed at different heating rates to allow for the prediction of the kinetic parameters of degradation. XRD analyses were used to calculate the average molecular interchain spacing. TGA analysis showed that the presence of POSS increased the thermal stability of the nanocomposites. An increase in the activation energy on degradation was evidenced through the kinetic parameters, especially for the 10% POSS. Moreover, the addition of POSS changed the kinetic mechanism of the deceleratory mode (F_n) in favor of the diffusion (D_n) process. The diffusion mechanism is corroborated by the XRD analyses that showed the increase of distance between chains when was added POSS. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Synthesis of PS‐g‐POSS hybrid graft copolymer by click coupling via ”graft onto” strategy

Polystyrene (PS)‐incorporated polyhedral oligomeric silsesquioxanes (POSS) organic–inorganic hybrid graft copolymer could be achieved by click coupling reaction between alkyne groups in POSS and azido groups in PS via “graft onto” strategy. Alkyne‐functionalized POSS was synthesized via thiol‐ene facile click reaction and subsequent amidation reaction with very high yield. Azido‐multifunctionalized PS could be synthesized by chloromethylation and subsequent azido reaction. The chemical structures of PS‐(CH₂Cl)_m, PS‐(CH₂N₃)_m, and PS‐g‐POSS were determined by Fourier transform infrared and ¹H NMR characterization. PS‐g‐POSS presented a better hydrophobic property with contact angle of 113° than that of PS (85°). And PS‐g‐POSS with ≤5% of grafting degree had lower glass transition temperature (T_g) than that of PS and then it increased up to 112°C with grafting degree. An obvious aggregation of POSS phase with 10–80 nm in size was formed in PS‐g‐POSS matrix. In addition, 5 wt % of PS‐g‐POSS was added to general purpose polystyrene (GPPS) to remarkably improve its tensile strength from 45 to 57 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization and CO2 sorption properties of poly[methacryloxypropylheptacyclopentyl‐T8‐silsesquioxane‐ co‐3‐methacryloxypropyltris(trimethylsiloxy)silane]

Poly[methacryloxypropylheptacyclopentyl‐T8‐silsesquioxane (MAPOSS)‐co‐3‐methacryloxypropyltris(trimethylsiloxy)silane (SiMA)] was synthesized through free radical polymerization. The physical and carbon dioxide (CO₂) sorption properties of the copolymer membranes were investigated in terms of the MAPOSS content. As the MAPOSS content increases, the membrane density increased, suggesting a decrease in the fractional free volume. In addition, the thermal stability was improved with increasing the MAPOSS content. These are because of the polyhedraloligomericilsesquioxane (POSS) units that restrict the high mobility of poly(SiMA) segments. The glass transition temperature, T_g of the copolymers was single T_g based on the differential scanning calorimetry, suggesting that the copolymers were random and not phase separation. Based on the CO₂ sorption measurement, the POSS units play a role in reducing Henry's dissolution by suppressing the mobility of the poly(SiMA) component, while POSS units increase the nonequilibrium excess free volume, which contributes to the Langmuir dissolution. Based on these results, the introduction of MAPOSS unit is one of the effective ways to improved the thermal stability and CO₂ sorption property due to the enhancement of the polymer rigidity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Epoxy‐functionalized polyhedral oligomeric silsesquioxane/cyanate ester resin organic–inorganic hybrids with enhanced mechanical and thermal properties

A series of cyanate ester resin (CE) based organic–inorganic hybrids containing different contents (0, 5, 10, 15 and 20 wt%) of epoxy‐functionalized polyhedral oligomeric silsesquioxane (POSS‐Ep) were prepared by casting and curing. The hybrid resin systems were studied by the gel time test to evaluate the effect of POSS‐Ep on the curing reactivity of CE. The impact and flexural strengths of the hybrids were investigated. The micromorphological, dynamic mechanical and thermal properties of the hybrids were studied by SEM, dynamic mechanical analysis (DMA) and TGA, respectively. Results showed that POSS‐Ep prolonged the gel time of CE. CE10 containing 10 wt% POSS‐Ep displayed not only the optimum impact strength but the optimum flexural strength. SEM results revealed that the improvement of mechanical properties was attributed to the large amount of tough whirls and fiber‐like pull‐outs observed on the fracture surfaces of CE10. DMA results indicated that POSS‐CE tended to decrease E′ of the hybrids in the glassy state but to increase E′ of the hybrids in the rubbery state. TGA results showed that CE10 also possesses the best thermal stability. The initial temperature of decomposition (T_i) of CE10 is 426 °C, 44 °C higher than that of pristine CE. © 2013 Society of Chemical Industry