In Situ Oxygen-Atom Erosion Study of Polyhedral Oligomeric Silsesquioxane-Siloxane Copolymer

Gonzalez, Rene I.; Phillips, Shawn H.; Hoflund, Gar B.

doi:10.2514/2.3606

Cited by 131 publications

(115 citation statements)

References 22 publications

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“…21 In contrast, fully condensed polyhedral oligomeric silsesquioxane (POSS) molecules (Figure 1), such as a closed cage POSS ( Figure 1A) (R 8 T 8 , where T is a silsesquioxane unit and R is alkyl), are nonamphiphilic. 23,24 Given both the theoretical and experimental interest in POSS as a versatile hybrid organic-inorganic material with a core-shell structure, [25][26][27][28][29][30][31][32] and the fact that open cage [33][34][35][36] trisilanol-POSS structures ( Figure 1B) are amphiphilic (T 7 R 7 (OH) 3 , where R is variable), combining POSS with PEG could lead to interesting amphiphiles.…”

Section: Introductionmentioning

confidence: 99%

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Lee

Deng

et al. 2007

Macromolecules

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Combining two non-surface-active building blocks, oligomeric poly(ethylene glycol) (PEG) and a completely hydrophobic polyhedral oligomeric silsesquioxane (POSS) cage, creates amphiphilic telechelic polymers (POSS-PEG-POSS), which exhibit surface activity at the air/water (A/W) interface. POSS moieties serve as the hydrophobic groups for hydrophilic PEG chains of different number-average molar mass (1, 2, 3.4, 8, and 10 kg mol -1 ). For short PEG chains (1, 2, and 3.4 kg mol -1 ), insoluble monolayers form, whereas POSS end groups were not sufficiently hydrophobic to keep higher molar mass hydrophilic PEG blocks (8 and 10 kg mol -1 ) at the A/W interface. Thermodynamic analyses of the 1, 2, and 3.4 kg mol -1 POSS-PEG-POSS via surface pressurearea per monomer isotherms indicate that the POSS end groups reside at the A/W interface and that the PEG chains are squeezed into the subphase with increasing surface pressure. This conclusion is supported by X-ray reflectivity studies on Y-type Langmuir-Blodgett multilayer films which reveal a double-layer structure with a double-layer spacing of about 3.52 nm. These findings provide a strategy for producing new surface active species from non-surface-active precursors.

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Section: Introductionmentioning

confidence: 99%

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Lee

Deng

et al. 2007

Macromolecules

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“…[29] For various exposures, the step heights (or etch depths) of POSS-PI films were plotted as a function of the step height of the Kapton H ® film. [23] The derivative functions indicated that the 3.5 and 7.0 wt % Si 8 This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States and increased in depth to 1.4 µm after the second exposure. The top of the SiO 2 -coated Kapton HN ® image was exposed to AO and only had erosion in the scratched area with unaffected neighboring silica-coated Kapton HN ® , demonstrating the effects of damage to silica coatings on Kapton ® .…”

Section: Resultsmentioning

confidence: 99%

“…These POSS-copolymers are self-passivating by the formation of a silica layer upon exposure to AO. Evidence of a SiO 2 passivation layer has been shown by X-ray photoelectron spectroscopy studies on AO exposed 3.5, 7.0, and 8.75 weight % Si 8 O 11 main chain (MC)-POSS-PI samples with erosion yields of 3.7, 0.98, and 0.3 percent, respectively, of the erosion yield for Kapton H ® at a fluence of 8.5 x 10 20 O atoms cm -2 .…”

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confidence: 99%

“…[1] It has been well established through space flight experiments in low Earth orbit (LEO) and ground-based simulations of atomic oxygen (AO) effects on LEO, that polymeric materials undergo severe degradation as a result of this aggressive environment encountered in LEO. [2][3][4][5][6][7][8][9][10] In this high vacuum, yet harsh environment, materials are subjected to solar radiation, thermal cycling which can range from -50 ˚C to 150 ˚C, bombardment by low and high-energy charged particles, and high fluxes of AO. [11] These harsh conditions necessitate the design of space-survivable materials.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Characterization of Space-Survivable POSS-Kapton (Trademark) Polyimides (Preprint)

Tomczak¹,

Minton²,

Brunsvold³

et al. 2007

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“…[16]) This fluence is based on the etch depth of the Kapton H reference sample ( 25.4 microns, 1 mil) which has an accepted erosion yield, R e , of 3.00 x 10 -24 cm 3 /atom. [11].…”

Section: Profilometry and Atomic Oxygen Etching Experimentsmentioning

confidence: 99%

Properties and Improved Space Survivability of POSS (Polyhedral Oligomeric Silsesquioxane) Polyimides

et al. 2004

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Kapton polyimide (PI) is widely used on the exterior of spacecraft as a thermal insulator. Atomic oxygen (AO) in lower earth orbit (LEO) causes severe degradation in Kapton resulting in reduced spacecraft lifetimes. One solution is to coat the polymer surface with SiO 2 since this coating is known to impart remarkable oxidation resistance. Imperfections in the SiO 2 application process and micrometeoroid / debris impact in orbit damage the SiO 2 coating, leading to erosion of Kapton.A self passivating, self healing silica layer protecting underlying Kapton upon exposure to AO may result from the nanodispersion of silicon and oxygen within the polymer matrix. Polyhedral oligomeric silsesquioxane (POSS) is composed of an inorganic cage structure with a 2:3 Si:O ratio surrounded by tailorable organic groups and is a possible delivery system for nanodispersed silica. A POSS dianiline was copolymerized with pyromellitic dianhydride and 4,4?-oxydianiline resulting in POSS Kapton Polyimide. The glass transition temperature (Tg) of 5 to 25 weight % POSS Polyimide was determined to be slightly lower, 5 -10 %, than that of unmodified polyimides (414 ºC). Furthermore the room temperature modulus of polyimide is unaffected by POSS, and the modulus at temperatures greater than the Tg of the polyimide is doubled by the incorporation of 20 wt % POSS.To simulate LEO conditions, POSS PI films underwent exposure to a hyperthermal O-atom beam. Surface analysis of exposed and unexposed films conducted with X-ray photoelectron spectroscopy, atomic force microscopy, and surface profilometry support the formation of a SiO 2 self healing passivation layer upon AO exposure. This is exemplified by erosion rates of 10 and 20 weight % POSS PI samples which were 3.7 and 0.98 percent, respectively, of the erosion rate for Kapton H at a fluence of 8.5 x 10 20 O atoms cm -2 . This data corresponds to an erosion yield for 10 wt % POSS PI of 4.8 % of Kapton H. In a separate exposure, at a fluence of 7.33 x 10 20 O atoms cm -2 , 25 wt % POSS Polyimide showed the erosion yield of about 1.1 % of that of Kapton H. Also, recently at a lower fluence of 2.03 x 10 20 O atoms cm -2 , in going from 20 to 25 wt % POSS PI the erosion was decreased by a factor of 2 with an erosion yield too minor to be measured for 25 wt % POSS PI.

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In Situ Oxygen-Atom Erosion Study of Polyhedral Oligomeric Silsesquioxane-Siloxane Copolymer

Cited by 131 publications

References 22 publications

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Synthesis and Characterization of Space-Survivable POSS-Kapton (Trademark) Polyimides (Preprint)

Properties and Improved Space Survivability of POSS (Polyhedral Oligomeric Silsesquioxane) Polyimides

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