Polyhedral Oligomeric Silsesquioxane Macromers Research Articles

Poly(hydroxyl urethane)s with Double Decker Silsesquioxanes in the Main Chains: Synthesis, Shape Recovery, and Reprocessing Properties

3,13-Di(cyclic carbonate) double decker silsesquioxane, a new difunctional polyhedral oligomeric silsesquioxane (POSS), was successfully synthesized. By using this POSS macromer, the organic–inorga...

Polyhedral oligomeric silsesquioxane-capped poly(N-vinyl pyrrolidone) amphiphiles: synthesis, self-assembly, and use as porogen of nanoporous poly(vinylidene fluoride)

In this contribution, we reported the synthesis of polyhedral oligomeric silsesquioxane (POSS)-capped poly(N-vinyl pyrrolidone) (PVPy) via reversible addition-fragmentation chain transfer/macromolecular design via interchange of xanthate (RAFT/MADIX) polymerization. First, a POSS macromer bearing xanthate moiety was synthesized and was then used as the chain transfer agent to mediate the radical polymerization of N-vinylpyrrolidone (NVP). By controlling the mass ratios of the POSS-CTA to NVP, a series of the POSS-capped PVPy amphiphiles were successfully synthesized with various molecular weights. It was found that in bulks, the POSS-capped PVPy was microphase-separated and the POSS end groups were self-organized into the spherical microdomains with the size of 10~100 nm in diameter. In the solvent selective for PVPy (e.g., water), the POSS-capped PVPy was capable of self-assembling into the spherical micelles with an average diameter of 20~50 nm as evidenced by dynamic laser scattering (DLS) and transmission electron microscopy (TEM). Owing to the amphiphilicity, POSS-capped PVPy also displayed the self-assembly behavior in poly(vinylidene fluoride) (PVDF), in which the POSS cages were aggregated into 10~30 nm microdomains. In the nanocomposites of PVDF with POSS-capped PVPy, the spherical POSS microdomains were readily etched by using hydrofluoric acid, leaving the nanopores in the materials.

Synthesis of POSS-containing fluorosilicone block copolymers via RAFT polymerization for application as non-wetting coating materials

Abstract By using a polydimethylsiloxane (PDMS) macro-chain transfer agent with trithiocarbonate groups at both ends, fluorosilicone block copolymers containing polyhedral oligomeric silsesquioxane (POSS) were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. Acryloisobutyl POSS (APOSS) and 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) were sequentially introduced into the copolymers. The obtained triblock copolymers PDMS-b-(PAPOSS)2 exhibited a low polydispersity index (PDI) of less than 1.42 in the first 6 h of polymerization, but the PDI value became broader later because of the steric hindrance of the POSS macromer. The POSS-containing fluorosilicone pentablock copolymers with a PDI of about 2.0, which were prepared by the further RAFT polymerization of HFBA, showed clear microphase separation. The average roughness values of the copolymer films were enhanced by introducing POSS, and a certain POSS content led to a significant decrease of the receding contact angle. Measurements of water contact angles and ice shear strengths demonstrated that the non-wetting properties of the copolymer films were improved by the incorporation of both POSS and fluorine blocks. The block copolymers combine the advantages of POSS, PDMS and fluoropolymers, and can be potentially applied as non-wetting coating materials for anti-icing or anti-frosting.

Organic-inorganic copolymers with double-decker silsesquioxane in the main chains by polymerization via click chemistry

A series of novel organic–inorganic copolymers with polyhedral oligomeric silsesquioxane (POSS) in the main chains were synthesized via the copper-catalyzed Huisgen 1,3-dipolar cycloaddition polymerization approach. Toward this end, we synthesized 3,13-azidopropyloctaphenyl double-decked silsesquioxane (DDSQ). This difunctional POSS macromer was used to copolymerize with α,ω-dialkynyl-terminated oligoethylenes with variable number of ethylene units. The organic–inorganic copolymers were obtained with the mass fraction of POSS up to 79%. Gel permeation chromatography showed that the high-molecular-weight copolymers were successfully obtained in all the cases. Differential scanning calorimetry showed that the amplitude of glass transitions for these copolymers was very feeble, suggesting that the segmental motions responsible for the glass transitions was highly restricted with DDSQ cages in the main chains. Thermogravimetric analysis showed that the organic–inorganic hybrid copolymers displayed extremely high thermal stability. Contact angle measurements showed that these organic–inorganic copolymers are highly hydrophobic and possessed very low surface energy. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4221–4232

Synthesis and characterization of epoxy modified cyanate ester POSS nanocomposites

Polyhedral oligomeric silsesquioxane (POSS) viz; namely, Octa functional silsesquioxanes [octa amino (OAPS) and octa glycidyl (OG)] reinforced epoxy modified cyanate ester nanocomposites were prepared through intercrosslinked network. The intercrosslinking formation between cyanate ester and POSS was confirmed by Fourier transform infrared spectroscopy. The morphology of nanocomposites was studied using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and atomic force microscopy techniques. The electrical properties of the nanocomposites were evaluated by impedance analyzer. The influences of POSS macromer on the thermal and mechanical properties of epoxy modified cyanate ester nanocomposites were also addressed. The thermogravimetric analysis indicates that the thermal stability of the nanocomposites increases with increasing percentage of both types of POSS macromer. The dielectric constant and dielectric loss are decreased with increasing POSS concentration in the epoxy modified cyanate ester nanocomposites.

Self‐supporting Polymer from a POSS Derivative

A new polyhedral oligomeric silsesquioxane macromer, octakis[N-(6-aminopyridin-2-yl)undecanamide-10-dimethyl-siloxy]silsesquioxane (POSS-C11-Py), containing eight diaminopyridine arms, is able to self-assemble to form a physically crosslinked polymer-like structure with good mechanical properties (tensile strength = 46.1 MPa, tensile modulus = 0.58 GPa, elongation = 49.3%) through quadruple hydrogen bonding interactions between these arms. POSS-C11-Py is the first organic/inorganic supermolecule possessing polymer-like mechanical properties as a result of self-complementary interactions, providing a potential route toward the design and fabrication of polymer-like supramolecular materials.

Organic-inorganic poly(hydroxyether of bisphenol A) copolymers with double-decker silsesquioxane in the main chains

In this communication, we reported the synthesis of organic-inorganic poly(hydroxyether of bisphenol A) (PH) copolymers with polyhedral oligomeric silsesquioxane (POSS) in the main chains via direct polymerization between diepoxy and bisphenol A. Toward this end, a novel diepoxy POSS macromer, i.e., 3,13-diglycidyloxypropyloctaphenyl double-decker silsesquioxane (denoted diglycidyloxypropyl DDSQ) was synthesized via the hydrosilylation between 3,13-dihydrooctaphenyl double-decker silsesquioxane (denoted dihydro DDSQ) and allyl glycidyl ether. Both diglycidyloxypropyl DDSQ and diglycidyl ether of bisphenol A (DGEBA) were used as the diepoxy monomers. By adjusting the ratio of diglycidyloxypropyl DDSQ to DGEBA, the PH copolymers with variable content of POSS in the main chains were obtained. It is found that with the direct polymerization the PH copolymers with POSS in the main chains of polymers can be successfully obtained while the content of diglycidyloxypropyl DDSQ was not very high. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the glass transition temperatures (Tg) of the organic-inorganic PH copolymers were quite dependent on the contents of POSS in the copolymers. Thermogravimetric analysis (TGA) indicates that the stability of the copolymers was significantly improved in terms of the temperatures at the maximum rate of degradation and the yields of degradation residues. Owing to the presence of POSS in the main chains, the surface hydrophobicity of the organic-inorganic copolymers was significantly improved compared to control PH.

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 17.5wt% of the cross-linker (containing POSS macromer and sulfonic acid groups) into SPEEK exhibits high proton conductivity (0.0153S/cm), low methanol permeability (1.34×10−7cm2/s), and high selectivity (1.14×105Ss/cm3).

Organic–inorganic hybrid hydrogels involving poly(N‐isopropylacrylamide) and polyhedral oligomeric silsesquioxane: Preparation and rapid thermoresponsive properties

Abstract3‐Acryloxypropylhepta(3,3,3‐trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS) was synthesized and used as a modifier to improve the thermal response rates of poly(N‐isopropylacrylamide) (PNIPAM) hydrogel. The radical copolymerization among N‐isopropylacrylamide (NIPAM), the POSS macromer and N,N′‐methylenebisacrylamide was performed to prepare the POSS‐containing PNIPAM cross‐linked networks. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) showed that the POSS‐containing PNIPAM networks displayed the enhanced glass transition temperatures (Tg's) and improved thermal stability when compared with plain PNIPAM network. The POSS‐containing PNIPAM hydrogels exhibited temperature‐responsive behavior as the plain PNIPAM hydrogels. It is noted that with the moderate contents of POSS, the POSS‐containing PNIPAM hydrogels displayed much faster response rates in terms of swelling, deswelling, and re‐swelling experiments than plain PNIPAM hydrogel. The improved thermoresponsive properties of hydrogels have been interpreted on the basis of the formation of the specific microphase‐separated morphology in the hydrogels, that is, the POSS structural units in the hybrid hydrogels were self‐assembled into the highly hydrophobic nanodomains, which behave as the microporogens and promote the contact of PNIPAM chains and water. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 504–516, 2009

Poly(ethylene imine) hybrids containing polyhedral oligomeric silsesquioxanes: Preparation, structure and properties

Both octaglycidyletherpropyl polyhedral oligomeric silsesquioxane and hepta(3,3,3-trifluoropropyl)glycidyletherpropyl polyhedral oligomeric silsesquioxane were synthesized via the hydrosilylation reactions between octahydrosilsesquioxane [and/or hepta(3,3,3-trifluoropropyl)hydrosilsesquioxane] and allyl glycidyl ether. The polyhedral oligomeric silsesquioxane (POSS) macromers were characterized by means of Fourier transform infrared and nuclear magnetic resonance spectroscopy. The inter-component macromolecular reactions between the POSS macromers and poly(ethylene imine) (PEI) were employed to prepare the POSS-containing organic–inorganic PEI hybrids. The inclusion of octaglycidyletherpropyl POSS into PEI results in the formation of the organic–inorganic hybrid networks whereas the introducing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS to PEI affords the linear POSS-grafted PEI copolymers. Differential scanning calorimetry and thermogravimetric analysis show that the POSS-containing PEI hybrids displayed increased glass transition temperatures ( T g’s) and enhanced thermal stability compared to the plain PEI. These PEI hybrid composites can be significantly swollen with water without dissolving, suggesting the formation of hydrogels. The PEI hydrogels containing octaglycidyletherpropyl POSS is in reality the chemically-crosslinked hydrogels whereas the those containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS displayed the behavior of physical hydrogels. The formation of physical hydrogels is ascribed to the microphase-separated morphology in the hybrids. In addition, the hybrids containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS exhibited the typical amphiphilicity as evidenced by the increase in surface hydrophobilicity.

Characterization of negative-type photoresists containing polyhedral oligomeric silsesquioxane methacrylate

A series of negative-type photoresists made by blending with various contents of polyhedral oligomeric silsesquioxane (POSS) methacrylate were prepared and characterized. These POSS macromers tend to crystallize or aggregate to form their own domains within the photoresist matrix. Sensitivity of the POSS modified photoresist is significantly improved with the increase of the POSS content. Results from photo-DSC analyses indicate that both induction time and peak maximum of heat flux are reduced by blending with POSS macromer. Addition of the proper amount (<13 wt%) of POSS can effectively increase photo-polymerization rate and exothermic heat. Hydrogen bonding interaction between the hydroxyl of photoresist and the siloxane of POSS tends to attract methacrylate double bonds surrounding POSS particles locally and thus enhances the rate of photo-polymerization and sensitivity.

Synthesis, characterization, and properties of chain terminated polyhedral oligomeric silsesquioxane-functionalized perfluorocyclobutyl aryl ether copolymers

A new class of perfluorocyclobutyl (PFCB) polymers covalently functionalized with polyhedral oligomeric silsesquioxane (POSS) is presented. Three discreetly functionalized POSS monomers possessing thermally reactive trifluorovinyl aryl ether (TFVE) were prepared in good yields. The POSS TFVE monomers were prepared by initial corner-capping of cyclopentyl (–C 5H 9), iso-butyl (–CH 2CH(CH 3) 2), or trifluoropropyl (–CH 2CH 2CF 3) functionalized POSS trisilanols with acetoxyethyltrichlorosilane followed by sequential acid-catalyzed deprotection and coupling with 4-(trifluorovinyloxy)benzoic acid. TFVE-functionalized POSS monomers were thermally polymerized with 4,4′-bis(4-trifluorovinyloxy)biphenyl or 2,2-bis(4-trifluorovinyloxybiphenyl)-1,1,1,3,3,3-hexafluoropropane monomers via a condensate-free, [2 + 2] step-growth polymerization. The polymerization afforded solution processable PFCB polymers with POSS macromer installed on the polymer chain ends. POSS monomers and their corresponding copolymers were characterized by 1H, 13C, 19F, and 29Si NMR, GPC, ATR-FTIR, and elemental combustion analysis. GPC trace analysis showed agreeable number-average molecular weight for various weight percent of cyclopentyl or iso-butyl and trifluoropropyl chain terminated POSS PFCB copolymers. DSC analysis showed the introduction of increasing POSS weight percent in the endcapped PFCB copolymers lowers the glass transition temperatures as high as 31 °C. On the other hand, the trifluoropropyl POSS endcapped PFCB polymer glass transition temperature was unaffected when copolymerized with the more fluorinated 2,2-bis(4-trifluorovinyloxybiphenyl)-1,1,1,3,3,3-hexafluoropropane monomer. TGA analysis of POSS PFCB copolymers showed step-wise decomposition of copolymers resulting from the initial degradation of the POSS cages at 297–355 °C in nitrogen and air which was confirmed by pyrolysis coupled with GC–MS. This initial weight loss was proportional to the weight percent of POSS incorporated into the polymer. The balance of decomposition was observed at 450–563 °C in nitrogen and air which is higher than the PFCB homopolymers in most cases. Polymer surface characterization was performed on spin cast transparent, flexible films. These composite films exhibited good POSS dispersion within the matrix PFCB polymer as was shown by TEM analysis.

Crystallization and morphology study of polyhedral oligomeric silsesquioxane (POSS)/polysiloxane elastomer composites prepared by melt blending

Composites of poly(methylvinylsiloxane) (“silicone”) elastomers with polyhedral oligomeric silsesquioxane (POSS) were prepared by melt blending. One goal was to establish conditions that would lead to morphologies different from that of a simple filler dispersed in a polymer matrix for the purposes of reinforcement. To this end, the study focused on the dispersion and state of POSS in silicone rubber blends as determined by X-ray diffraction (XRD), polarizing optical microscopy (POM), scanning electron microscopy (SEM), and analysis using a rubber processing analyzer (RPA). Of particular interest were the thermal stability of POSS macromers, and the effects of mixing temperature and subsequent vulcanization of the polysiloxane. The results showed that highly crystalline POSS macromers could undergo condensation reactions at 230 °C in air, leading to partially amorphous structures. Also, POSS crystals apparently dissolved in the polysiloxane at high temperatures and POSS crystals with hexahedral or flake-like structures recrystallized out upon cooling. Both crystallites and POSS molecules co-existed in these blends, with the amount of dispersed molecular POSS being increased at higher temperatures. The POSS molecules exhibited some physical interactions with the polysiloxane uncross-linked chains, but phase separation was induced by the process of cross-linking. In this curing process, POSS molecules could react with the polysiloxane, resulting in decreases in cross-link density. The original POSS crystals could also be dissolved in the polysiloxane during the initial curing stages, but recrystallization upon cooling gave regenerated crystals that were roughly spherical.

Chemical Substituent Effects on Morphological Transitions in Styrene−Butadiene−Styrene Triblock Copolymer Grafted with Polyhedral Oligomeric Silsesquioxanes

A series of hybrid organic/inorganic triblock copolymers of polystyrene−butadiene−polystyrene (SBS) grafted with polyhedral oligomeric silsesquioxane (POSS) molecules with different chemical constituents were synthesized by a hydrosilation method. Four POSS macromers, R‘R7Si8O12, were designed to contain a single silane functional group, R‘, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block and seven identical organic groups, R. Small-angle X-ray scattering and rheological techniques were used to study the effect of sterically similar, yet electronically different, organic R groups, cyclopentyl (Cp), cyclohexyl (Cy), cyclohexenyl (Cye), and phenyl (Ph), on the morphology of SBS triblock copolymer and the order−disorder transition behavior. It was observed that POSS with phenyl moiety, when grafted to the polybutadiene (PB) phase, appears to show favorable interaction with the polystyrene (PS) phase; effectively, the Ph-POSS is plasticizing the SBS due to an effect wh...

Hybrid inorganic/organic crosslinked resins containing polyhedral oligomeric silsesquioxanes

AbstractThe incorporation of both monofunctional and multifunctional polyhedral oligomeric silsesquioxane (POSS) derivatives into crosslinked resins has been conducted as a route to synthesize hybrid organic/inorganic nanocomposites. The central cores of POSS molecules contain an inorganic cage with (SiO1.5)n stoichiometry where n=8,10 and 12. Each Si atom is capped with one H or R function giving an organic outer shell surrounding the nanometer‐sized inorganic inner cage. By including polymerizable functions on the R groups, a hybrid organic/inorganic macromer is obtained which can be copolymerized with organic monomers to create thermoplastic or thermoset systems. We have focused on incorporating POSS derivatives into crosslinking resins of the following types: (1) dicyclopentadiene (2) epoxies (3) vinyl esters (4) styrene‐DVB (5) MMA/1,4‐butane dimethacrylate (6) phenolics and (7) cyanate esters. One goal has been to determine if molecular dispersion of the POSS macromers has been achieved or if various degrees of aggregation occur during crosslinked resin formation. As network formation proceeds, a kinetic race between POSS molecular incorporation into the network versus phase separation into POSS‐rich regions (which then polymerize) occurs. Ultimately, we hope to determine the effects of such microstructural features on properties. Combustion of these hybrids creates a SiO2‐like surface layer that retards flame spread. Dynamic mechanical properties have been studied.

Viscoelastic and Mechanical Properties of Epoxy/Multifunctional Polyhedral Oligomeric Silsesquioxane Nanocomposites and Epoxy/Ladderlike Polyphenylsilsesquioxane Blends

Aliphatic epoxy composites with multifunctional polyhedral oligomeric silsesquioxane (POSS) ((C6H5CHCHO)4(Si8O12)(CHCHC6H5)4) nanophases (epoxy/POSS 95/5 and 75/25) and epoxy blends with the prepolymer of ladderlike polyphenylsilsesquioxane (PPSQ) (95/5, 90/10, and 85/15) were prepared by solution casting and then curing. These composites and blends were studied by dynamic mechanical thermal analysis (DMTA) and mechanical testing. The POSS units incorporated into the epoxy network are well dispersed in the composite, probably on the molecular scale, even at high POSS content (25 wt %) based on TEM observations. However, the aliphatic epoxy/PPSQ blends exhibit good miscibility only at low PPSQ content (≤10 wt %). Phase separation was clearly observed when the PPSQ content was 15%. Incorporation of the POSS macromer into this epoxy network by curing at upper temperatures of 120 and 150 °C broadened the temperature range of glass transition of the resulting composites but has almost no influence on their Tg ...

Polyhedral Oligomeric Silsesquioxane (POSS) Polymers and Copolymers: A Review

This review describes the synthesis and properties of homopolymers and copolymers of monomers containing inorganic–organic hybrid polyhedral oligomeric silsesquioxane (POSS) structures. Monomers, such as styryl-POSS, methacrylate-POSS, norbornyl-POSS, vinyl-POSS, epoxy-POSS, and siloxane-POSS, are included. Both monofunctional and multifunctional monomers are included. Thermoplastic and thermoset systems are considered. Thermal, rheological, and dynamic mechanical properties are described. The synthesis of POSS macromers (monomers) is briefly described. POSS chemicals have been used to prepare nanosized designed novel composites with a variety of potential applications. This review, covering 111 references, is descriptive and not designed to be totally comprehensive. However, the major existing reviews of certain subtopics are noted, allowing the reader to gain a general introduction while providing the information to permit more comprehensive coverage.

Viscoelastic and morphological behavior of hybrid styryl-based polyhedral oligomeric silsesquioxane (POSS) copolymers

We report on the viscoelastic behavior of linear thermoplastic nonpolar hybrid inorganic-organic polymers. These materials have been synthesized through copolymerization of an oligomeric inorganic macromer with 4-methylstyrene where the inorganic portion of the material is a well-defined polyhedral oligosilsesquioxane (POSS), R7(Si8O12)(CH2CH2C6H4CH|CH2), with R A c-C6H11 or c-C5H9. A series of 4-methyl styrene copolymers with approximately 4, 8, and 16 mol % POSS macromer incorporation were investigated. Rheological measurements show that the polymer dynamics are profoundly affected as the percent of POSS increases. In particular, a high-temperature rubbery plateau develops (where a terminal zone is not observed), despite the fact that the parent poly 4-methylstyrene is unentangled. It is also observed that the thermal properties are influenced as the percent of POSS incorporation in- creases, with increases in the glass and decomposition temperatures. The results sug- gest that interchain interactions between the massive inorganic groups are responsible for the retardation of polymer chain motion, a mechanism similar to the ''sticky repta- tion'' model conceived for hydrogen-bonded elastomers and developed by Leibler et al. (Macromolecules, 24, 4701 (1991)).Control over the interchain interactions would also give rise to the observed increases in glass transition and the establishment of a rubbery plateau. q 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1857-1872, 1998

Viscoelastic and morphological behavior of hybrid styryl‐based polyhedral oligomeric silsesquioxane (POSS) copolymers

We report on the viscoelastic behavior of linear thermoplastic nonpolar hybrid inorganic–organic polymers. These materials have been synthesized through copolymerization of an oligomeric inorganic macromer with 4-methylstyrene where the inorganic portion of the material is a well-defined polyhedral oligosilsesquioxane (POSS), R7(Si8O12)(CH2CH2C6H4CCH2), with R = c-C6H11 or c-C5H9. A series of 4-methyl styrene copolymers with approximately 4, 8, and 16 mol % POSS macromer incorporation were investigated. Rheological measurements show that the polymer dynamics are profoundly affected as the percent of POSS increases. In particular, a high-temperature rubbery plateau develops (where a terminal zone is not observed), despite the fact that the parent poly 4-methylstyrene is unentangled. It is also observed that the thermal properties are influenced as the percent of POSS incorporation increases, with increases in the glass and decomposition temperatures. The results suggest that interchain interactions between the massive inorganic groups are responsible for the retardation of polymer chain motion, a mechanism similar to the “sticky reptation” model conceived for hydrogen-bonded elastomers and developed by Leibler et al. [Macromolecules, 24, 4701 (1991)]. Control over the interchain interactions would also give rise to the observed increases in glass transition and the establishment of a rubbery plateau. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1857–1872, 1998

Thermoplastics Modified with Nanoscale Inorganic Macromers

AbstractWe have taken a unique approach to the synthesis and study of hybrid organic/inorganic materials. Our method involves synthesizing nano-size inorganic P1R7Si8O12 clusters which contain seven inert “R” groups for solubility and only one functional “P” group for polymerization. This strategy permits the synthesis of melt processable, linear hybrid polymers containing pendent inorganic clusters and allows us to study the effect these clusters have on chain motions and polymer properties. The synthesis of norbomenyl-based polyhedral oligomeric silsesquioxane (POSS) macromers, their ring opening metathesis copolymerizations with varying amounts of norbornene, and analysis of the effect of the pendent POSS group is presented. The mechanical relaxation behavior and microstructure of norbornyl-POSS hybrid copolymers have been examined for their dependencies on the mole fraction of POSS-norbornyl monomer, as well as for potential sensitivity to the seven inert “R” groups present in each POSS macromer. POSS copolymerization is observed to enhance the α-relaxation temperature, Tα, in proportion to the mole fraction of POSS-norbornyl comonomer. Interestingly, however, the magnitude of this dependence is larger for POSS-norbornyl comonomer possessing cyclohexyl groups (CyPOSS) than for cyclopentyl groups (CpPOSS). While POSS copolymerization yields only slight enhancement of the tensile storage modulus measured near room temperature, at temperatures lower than a strong mechanical relaxation (β-relaxation near T = -75 °C), there is a significant POSS-reinforcement of the storage modulus.