Thermally Stabilized Blue Luminescent Poly(p‐phenylene)s Covered with Polyhedral Oligomeric Silsesquioxanes

A novel series of poly(p‐phenylene)s (PPPs) with polyhedral oligomeric silsesquioxanes (POSSs) on their side chains was prepared. The obtained POSS‐modified PPPs are as follows: 25POSS‐PPP ( 2b , containing 25 mol‐% of POSS units in all side chains), 50POSS‐PPP ( 2c , containing 50 mol‐% of POSS units in all side chains), 100POSS‐PPP ( 2d , containing 100 mol‐% of POSS units in all side chains), and 0POSS‐PPP ( 2a , as a blank polymer). Films polymer 2d showed the same absorption and photoluminescence (PL) spectra as those in CHCl₃ solution, indicating that bulky POSS units strongly suppressed intermolecular aggregation of the PPP backbone. Polymer 2d showed the same PL spectra even after thermal annealing at 150 °C for 6 h. This enhancement of PL stability is due to the significant effect of the bulky POSS units.

     

Liquid‐crystalline organic–inorganic hybrid polymers with functionalized silsesquioxanes

Liquid‐crystalline (LC) hybrid polymers with functionalized silsesquioxanes with various proportions of LC monomer were synthesized by the reaction of polyhedral oligomeric silsesquioxane (POSS) macromonomer with methacrylate monomer having an LC moiety under common free‐radical conditions. The obtained LC hybrid polymers were soluble in common solvents such as tetrahydrofuran, toluene, and chloroform, and their structures were characterized with Fourier transform infrared, ¹H NMR, and ²⁹Si NMR. The thermal stability of the hybrid polymers was increased with an increasing ratio of POSS moieties as the inorganic part. Because of the steric hindrance caused by the bulkiness of the POSS macromonomer, the number‐average molecular weight of the hybrid polymers gradually decreased as the molar percentage of POSS in the feed increased. Their liquid crystallinities were very dependent on the POSS segments of the hybrid polymers behaving as hard, compact components. The hybrid polymer with 90 mol % LC moiety (Cube‐LC90) showed liquid crystallinity, larger glass‐transition temperatures, and better stability with respect to the LC homopolymer. The results of differential scanning calorimetry and optical polarizing microscopy showed that Cube‐LC90 had a smectic‐mesophase‐like fine‐grained texture. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4035–4043, 2001     

A novel use of Ti‐POSS as initiator of L‐lactide ring‐opening polymerization

The efficacy of a metal‐silsesquioxane, namely, heptaisobutyl (isopropoxyde)titanium‐polyhedral oligomeric silsesquioxanes (Ti‐POSS), as initiator of the ring‐opening polymerization of L ‐lactide (LLA) has been assessed. Indeed, as demonstrated by proton nuclear magnetic resonance (¹H NMR) spectroscopy and gel permeation chromatography (GPC) measurements, a well‐controlled polymerization occurs via a coordination‐insertion mechanism. Moreover, the above reaction leads to the direct insertion of the silsesquioxane molecule into the polymer backbone, thus producing a hybrid system. Differential scanning calorimetry measurements demonstrated that in comparison with a commercial poly‐L ‐lactide (PLLA), the polymers prepared with Ti‐POSS exhibit a higher crystallinity. Indeed, the presence of silsesquioxane molecules, attached to one end of the polymer chains, has been found to appreciably affect the crystal nucleation density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of semitelechelic POSS‐polymethacrylate hybrids by thiol‐mediated controlled radical polymerization with unusual thermal behaviors

We have developed an efficient and versatile method for the synthesis of polyhedral oligomeric silsesquioxanes (POSS)‐polymethacrylate hybrids, such as POSS‐poly(methyl methacrylate) (POSS‐PMMA), POSS‐poly(ethyl methacrylate) (POSS‐PEMA), and POSS‐poly(benzyl methacrylate) (POSS‐PBzMA) of controllable molecular weights and low polydispersities by thiol‐mediated radical polymerization at elevated temperature (100 °C). By tuning the reactant concentrations and degree of polymerization of the grafted polymethacrylate chains, POSS content in these hybrid materials could be varied. MALDI‐TOF‐MS analysis of the hybrid molecule shows that the nanoscale POSS moiety is connected to the end of polymethacrylate chain through the sulfur atom bridge. These hybrid materials were further characterized using various techniques such as FTIR, XRD, NMR, TGA, and DSC. In all synthesized hybrids, the incorporation of POSS moiety at the end of polymethacrylate chain resulted in the decrease of glass transition temperature (T_g) compared to that of neat polymethacrylates of comparable molecular weights. Surprisingly, POSS‐PMMA hybrids only with relatively high POSS content (～ 10 and 16 wt %) showed physical aging behavior as reveled by DSC study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1111–1123, 2008     

Synthesis and characterization of novel PDMS nanocomposites using POSS derivatives as cross‐linking filler

We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both the cross‐linker and filler within a polydimethylsiloxane (PDMS) polymer matrix. These polymer composites were prepared through the reaction of octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting of two pendant hepta(isobutyl)POSS molecules attached to a central octasilane‐POSS core, were also used in the fabrication of the PDMS composites. The chemical incorporation of these POSS cross‐linkers into the PDMS network was verified by solid‐state ¹H magic angle spinning NMR. Based on dynamic mechanical analysis, the PDMS nanocomposites prepared with the octafunctional OS‐POSS cross‐linker exhibited enhanced mechanical properties relative to polymer systems prepared with the tetrafunctional TDSS cross‐linker at equivalent loading levels. The observed improvements in mechanical properties can be attributed to the increased dimensionality of the POSS cross‐linker. The PDMS elastomers synthesized from the larger super‐POSS molecule showed improved mechanical properties relative to both the TDSS and OS‐POSS composites due to the increased volume‐fraction of POSS filler in the polymer matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2589–2596, 2009     

Janus POSS Based on Mixed [2:6] Octakis‐Adduct Regioisomers

A series of regioisomeric Janus‐type polyhedral oligomeric silsesquioxanes (POSS) with multiple, mixed surface functional groups has been successfully synthesized based on the cubic T₈‐POSS framework in two consecutive thiol–ene reactions. The first thiol–ene addition of β‐mercaptoethanol leads to a statistical mixture of multi‐adducts where the regioisomers of bis‐adducts (ortho, meta, and para isomers) can be isolated at synthetically useful quantities by flash column chromatography. Then, the second thiol–ene reaction readily installs a variety of functional groups onto the remaining vinyl groups of each regioisomer, providing an easy access to precisely defined, hetero‐bifunctional Janus POSS nano‐building blocks. The configurations and structures of the products have been unambiguously proven by using ¹H, ¹³C, and ²⁹Si NMR spectroscopy as well as MALDI‐TOF mass spectrometry.     

Side‐chain effect of octa‐substituted POSS fillers on refraction in polymer composites

To investigate the relationship between the chemical structures of the side chains of polyoctahedral oligomeric silsesquioxanes (POSS) fillers and the ability to decrease the refractive indices of the polymer composites, we examined the influence on the degree of polymer chain packing by the existence of the octa‐substituted POSS derivatives. The polymer composites containing methyl‐, ethyl‐, vinyl‐, isobutyl‐, octyl‐, octadecyl‐, cyclopentyl‐, and phenyl‐substituted POSS in poly(methyl methacrylate) (PMMA) were prepared. The packing coefficients of the PMMA composites containing POSS derivatives were evaluated from molar refractions and refractive indices of the films with the Lorentz–Lorenz equation. We found that the ethyl group shows the lowest values of the packing coefficients and a significant effect in reducing the refractive indices of the polymer composites. Finally, in summary, it was shown that POSS molecules can intrinsically offer to reduce a packing. In addition, less entanglement and smaller interactions between polymer chains and the substitution groups are favorable to release a packing, resulting in decreases in refractive indices. Our findings described here are the first efforts to quantitatively evaluate the ability of POSS fillers to lower refractive indices at the molecular level. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A hybrid‐type,chiral π‐conjugated polymer wrapped with polyhedral oligomeric silsesquioxanes

A novel hybrid‐type chiral binaphthyl‐based polyarylene derivative with polyhedral oligomeric silsesquioxanes (POSS) units 2a was prepared by Suzuki–Miyaura coupling polymerization from a chiral (R)‐6,6′‐dibromo‐2,2′‐diPOSS‐substituted 1,1′‐binaphthyl derivative 1a and p‐biphenylene diboronic acid. As a reference, a binaphthyl‐based polyarylene derivative without POSS unit 2b was also prepared. The obtained polymers were studied with thermogravimetric analysis, optical rotations, circular dichroism (CD), ultraviolet‐visible, and photoluminescence (PL) spectra. Gel permeation chromatography measurements of 2a and 2b showed that their number‐average molecular weights were 13,300 and 16,500, respectively. The thermal stability of POSS‐modified polymer 2a (temperature of 10% weight loss; T₁₀ = 380 °C) was extremely high compared with that of polymer without POSS unit 2b (T₁₀ = 335 °C) due to the siliceous bulky POSS segments on the side chains. The specific optical rotation [α]_D was ?66.7° (c 0.06, CHCl₃) for 2a and ?62.3° (c 0.06, CHCl₃) for 2b . The CD spectra showed that these two polymers had very similar and strong Cotton effects. Film polymer 2a showed almost the same PL spectrum as that in dilute CHCl₃ solution, indicating that bulky POSS units strongly suppressed intermolecular aggregation of the π‐conjugated polymer backbone. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6035–6040, 2008     

Aliphatic Polyester/polyhedral Oligomeric Silsesquioxanes Hybrid Networks via Copper‐free 1,3‐dipolar Cycloaddition Click Reaction

In this study, we describe the preparation and characterization of a new class of thermoset hybrid networks containing aliphatic polyester and polyhedral oligomeric silsesquioxanes (POSS). The copper‐free 1,3‐dipolar cycloaddition click reaction of internal alkyne functionalized aliphatic polyester and multifunctional azido POSS with different concentrations led to highly crosslinked thermoset networks. The click reactions performed under ambient conditions (i.e., in tetrahydrofuran at room temperature for 1 day) in the absence of any catalyst. The chemical composition of hybrid networks and homogenous distribution of POSS molecules were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy with energy dispersive spectroscopy. The swelling ratios of hybrid networks were commonly decreased by increasing POSS‐N₃ content and by changing polar solvents to apolar solvents. Thermogravimetric analysis results demonstrated that the thermal stability of hybrid networks increased with higher POSS feeding ratio. Tensile tests were applied to evaluate the mechanical properties of hybrid networks. Compared to neat aliphatic polyester, the mechanical properties of hybrid networks significantly improved. For instance, the tensile strength were enhanced from 5 MPa to 19 MPa by increasing the concentration of azido functionalized POSS from 10 to 40. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2222–2227     

Functionalization of surface‐grafted polymethylhydrosiloxane thin films with alkyl side chains

Thin films of crosslinked polymethylhydrosiloxane (PMHS) have been grafted on silica using the sol–gel process allowing further functionalization by effective quantitative hydrosilylation of SiH groups by olefins within the network. Postfunctionalization gives the polysiloxane network with n‐alkyl side chains. The PMHS coating was prepared by room temperature polycondensation of a mixture of methyldiethoxysilane HSiMe(OEt)₂ monomer and triethoxysilane HSi(OEt)₃ (TH) as crosslinker. The surface‐attached films are chemically stable and covalently bonded to the silica surface. Subsequently, films were functionalized without delamination. We showed by FTIR spectroscopy how the crosslinking ratio and the molecular size of the alkenes precursors influence the extent of the hydrosilylation reaction of SiH groups in the PMHS network. We have determined that quasi‐full olefin addition catalyzed by a platinum complex occurred within soft networks of less than 5% TH with 1‐alkenes CH₂?CH(CH₂)_n‐2CH₃ of various alkyl chain lengths (n = 5, 11, 17). Powders of PMHS gel were also modified with 1‐alkenes by hydrosilylation. The SiH groups within the soft gel (5% crosslinked) were fully functionalized as shown by ²⁹Si and ¹H solid‐state NMR. The structure of functionalized polysiloxane with n‐octadecyl and n‐dodecyl side chains was studied by FTIR, wide angle X‐ray diffraction, and DSC showing crystallization of the long n‐alkyl chains in the network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3546–3562, 2008     

Thermally curable organic/inorganic hybrid polymers as gate dielectrics for organic thin‐film transistors

New low‐temperature curable organic/inorganic hybrid polymers were designed and synthesized as gate dielectrics for organic thin‐film transistors (OTFTs). Allyl alcohols were introduced to polyhedral oligomeric silsesquioxane (POSS) via hydrosilyation to produce an alcohol‐functionalized POSS derivative (POSS‐OH). POSS‐OH was then reacted with hexamethoxymethylmelamine at carrying molar ratios at 80 °C in the presence of a catalytic amount of p‐toluenesulfonic acid to give highly cross‐linked network polymers (POSS‐MM). The prepared thin films were smooth and hard after the thermal cross‐linking reaction and had very low leakage currents (<10^?8 A/cm²) with no significant absorption over the visible spectral range. Pentacene‐based OTFTs using the synthesized insulators as gate dielectric layers had higher hole mobilities (up to 0.36 cm²/Vs) than a device using thermally cross‐linked poly(vinyl phenol) and melamine as the gate dielectric layer (0.18 cm²/Vs). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3260–3268     

Novel polymer nanocomposites based on polystyrene and Ti‐functionalized polyhedral silsesquioxanes

Ti‐based polyhedral silsesquioxanes (Ti‐POSSs) have been prepared and dispersed in polystyrene (PS), by in situ polymerization, and the resulting materials have been characterized by several experimental techniques including both scanning (SEM) and transmission (TEM) electron microscopy, wide angle X‐ray diffraction (WAXD), X‐ray photospectroscopy (XPS), and thermogravimetric analysis (TGA/DTG). TEM and SEM analyses proved that PS nanocomposites of the samples based on heptaisobutyl‐Ti‐POSS (HEI‐Ti‐POSS) are formed, where HEI‐Ti‐POSS cages are directly linked to the macromolecules via Ti‐C bonds. The presence of HEI‐Ti‐POSS enhances the thermo‐oxidative stability of PS‐based nanocomposites and does not significantly affect the polymer molecular mass. Copyright © 2009 John Wiley & Sons, Ltd.     

Morphology‐Controlled Self‐Assembly of an Organic/Inorganic Hybrid Porphyrin Derivative Containing Polyhedral Oligomeric Silsesquioxane (POSS)

An organic/inorganic hybrid porphyrin derivative, namely, metal‐free tetrakisphenyl porphyrin–polyhedral oligomeric silsesquioxanes (H₂TPP‐POSS) was synthesized by azide–alkyne click chemistry. The self‐assembly behavior of H₂TPP‐POSS was systematically studied in CHCl₃ at different concentrations and in solvents with different polarities. Novel nanovesicles could be obtained through the self‐assembly of H₂TPP‐POSS in CHCl₃ at a concentration lower than 10^?4 m. Diffuse microrods formed at a concentration higher than 10^?4 M . Additionally, the polarity of the solvent also greatly influenced the assembled morphologies, and a series of assembled morphologies, including crescent‐shaped micelles, spherical micelles, doughnut‐shaped vesicles, and ordered square sheets, could form in solvents with different polarities.     

The First Europium(III) β‐Diketonate Complex Functionalized Polyhedral Oligomeric Silsesquioxane

The first europium(III) β‐diketonate complex functionalized polyhedral oligomeric silsesquioxane (POSS) has been obtained by immobilization of such a complex at a silicon vertex of the POSS cage through the complexation of Eu³⁺ ions with thenoyltrifluoroacetone‐functionalized POSS. The new molecular hybrid material is liquid at room temperature, and shows bright‐red emission when irradiated with UV light due to energy transfer from the thenoyltrifluoroacetone ligand to the coordinated Eu³⁺ ions. Thermal analysis has revealed a significant improvement in the thermal stability of the material compared with tris(2‐thenoyltrifluoroacetonate)europium(III) dihydrate, [Eu(TTA)₃] ? 2 H₂O. In the context of recent advances in printable electronic technology, this novel luminescent organic liquid with the characteristic emission of Eu³⁺ may potentially be useful in the development of next‐generation organic devices such as flexible displays.     

POSS end‐linked peptide‐functionalized poly(ɛ‐caprolactone)s and their inclusion complexes with α‐cyclodextrin

In this report, we have synthesized organic/inorganic hybrid peptide–poly(?‐caprolactone) (PCL) conjugates via ring opening polymerization (ROP) of ?‐caprolactone (CL) in the presence of two sequence defined peptide initiators, namely POSS‐Leu‐Aib‐Leu‐NH₂ (POSS: polyhedral oligomeric silsesquioxane; Leu: Leucine; Aib: α‐aminoisobutyric acid) and OMe‐Leu‐Aib‐Leu‐NH₂. Covalent attachment of peptide segments with the PCLs were examined by ¹H and ²⁹Si NMR spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) and FTIR spectroscopy. Supramolecular inclusion complexations of synthesized peptide‐PCL conjugates with α‐cyclodextrin (α‐CyD) were studied to understand the effect of POSS/OMe‐peptide moieties at the PCL chain ends. Inclusion complexation of peptide‐PCL conjugates with α‐CyD produced linear polypseudorotaxane, confirmed by ¹H NMR, FTIR, powder X‐ray diffraction (PXRD), polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Extent of α‐CyD threading onto the hybrid peptide‐PCL conjugated polymers is less than that of α‐CyD threaded onto the linear PCL. Thus, PCL chains were not fully covered by the host α‐CyD molecules due to the bulky POSS/OMe‐peptide moieties connected with the one edge of the PCL chains. PXRD experiment reveals channel like structures by the synthesized inclusion complexes (ICs). Spherulitic morphologies of POSS/OMe‐peptide‐PCL conjugates were fully destroyed after inclusion complexation with α‐CyD and tiny nanoobjects were produced. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3643–3651.     

Energy transfer along a sequence controlled hybrid polymer

The present work provides an ideal model for intra‐chain energy transfer study in conjugated polymer through shielding the polymer backbone by using bulky polyhedral oligomeric silsesquioxanes (POSS). POSS provides a circumference shielding of the polymer backbone to prevent closed packing of the polymer chains, allowing the intra‐chain energy transfer dominating in large concentration range. Bi‐functional POSS (B‐POSS) is specially designed to separate donor (fluorene) and acceptor (benzothiadiazole) within the polymer chain. The dynamics of energy transfer in poly(fluorene‐POSS‐alt‐POSS‐benzothiodiazole) (PTBtTbOFl₃) is studied by steady state as well as time resolved fluorescence spectroscopy at different donor/acceptor ratios. Results reveal that POSS can effectively shield inter‐chains energy transfer of the polymers, suggesting it is an effective model for energy transfer study with less inter‐chains effects. PTBtTbOFl₃ works as a chemosensors is also reported in the detection of explosive derivatives. These results provide insights for optimizing nanostructured materials for use in optoelectronic devices. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1225–1233     

Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating

In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g^?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.     

Cubic Polyhedral Oligomeric Silsesquioxane Based Functional Materials: Synthesis,Assembly, and Applications

Organically modified cubic polyhedral oligomeric silsesquioxanes (POSS) have attracted increasing attention in the design of novel functional hybrid materials for applications such as porous materials, liquid crystals, semiconductors, high‐temperature lubricants, fuel cells, and lithium batteries. The nanosized POSS moiety can be conveniently modified on the periphery with a variety of functional groups to lead to hybrid materials with desired functions. In addition, suitable mono‐functionalized POSS derivatives can be incorporated into polymers as side chains via various synthetic strategies to offer a wide class of functional polymeric materials with tunable physical properties for targeted applications. In this Focus Review, we aim to summarize the recent developments on the chemistry and applications of POSS‐based molecules and polymers. Moreover, the properties as well as assembly behavior of the POSS‐based functional hybrid materials will be reviewed, and the relationship of the performance of the hybrid materials with the intrinsic nature of the POSS unit will be addressed.     

Preparation of carboxyl‐functionalized polyhedral oligomeric silsesquioxane by a structural transformation reaction from soluble rod‐like polysilsesquioxane

Carboxyl‐functionalized polyhedral oligomeric silsesquioxane (SQ; POSS‐COOH ) was successfully prepared by a structural transformation reaction, that is, a process of heating and concentrating soluble carboxyl‐functionalized rod‐like polySQ (PolySQ ‐COOH ) using the aqueous superacid trifluoromethanesulfonic acid (HOTf) as the catalyst and solvent. The obtained POSS‐COOH was a mixture of a cage‐like decamer (T₁₀‐POSS), which was the main product, and an octamer (T₈‐POSS) and a dodecamer (T₁₂‐POSS), which were the minor products. The product obtained by heating and concentrating PolySQ‐COOH using aqueous hydrochloric acid (HCl) as the catalyst and solvent was soluble polySQ rather than POSS. For comparison, heating and concentrating POSS‐COOH in aqueous HOTf and HCl were performed, which yielded POSS‐COOH and PolySQ‐COOH , respectively. Based on these results, the process of heating and concentrating each starting material ( PolySQ‐COOH and POSS‐COOH ) in aqueous HOTf afforded POSS‐COOH , and a similar process in aqueous HCl yielded PolySQ‐COOH . © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2511–2518     

Flame retardant epoxy composites with epoxy‐containing polyhedral oligomeric silsesquioxanes

A kind of polyhedral oligomeric silsesquioxanes (POSS) containing the propoxyl‐epoxy and phenyl groups (pr‐ep‐Ph‐POSS) was synthesized via hydrolytic condensation reaction. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry identified the structure of the pr‐ep‐Ph‐POSS, including major caged Si₆O₉ (T6), Si₁₀O₁₅ (T10), Si₁₂O₁₈ (T12), etc. The pr‐ep‐Ph‐POSS was applied into the epoxy resin to achieve EP/pr‐ep‐Ph‐POSS composites. Thermogravimetric analysis indicated that EP/pr‐ep‐Ph‐POSS showed excellent thermal properties than pure EP. The fire behaviors of EP/pr‐ep‐Ph‐POSS composites were evaluated based on the cone calorimetry, limiting oxygen index (LOI), UL‐94 vertical burning test, and smoke density test. The smoke density decreased by ~30%, the LOI value reached to 26.4%, dripping was inhibited, and the peak of heat release rate decreased by ~62%. X‐ray photoelectron spectroscopy analysis and FTIR indicated that protective‐barrier effect is the main flame‐retardant mode of action for pr‐ep‐Ph‐POSS, due to the formation of the Si‐O‐Si, Si‐O‐C, and Si‐C condensed phase, which improve the thermal stability, strength, and integrity of the char layer.