Advanced Aromatic Polymers with Excellent Antiatomic Oxygen Performance Derived from Molecular Precursor Strategy and Copolymerization of Polyhedral Oligomeric Silsesquioxane

Abstract

In this contribution, the advanced aromatic polymers with excellent antiatomic oxygen (AO) performance were designed and synthesized using molecular precursor strategy and copolymerization of polyhedral oligomeric silsesquioxane (POSS). A soluble poly(p-phenylene benzobisoxazole) (PBO) precursor, that is, TBS-PBO (tert-butyldimethylsilyl was denoted as TBS), was designed to overcome the poor solubility of PBO in organic solvents. Then the new copolymer of TBS-PBO-POSS was synthesized by the copolymerization of TBS-PBO and POSS, which possessed good solubility and film-forming ability in common organic solvents, such as N-methylpyrrolidone, N,N-dimethylacetamide, and dimethyl sulfoxide. More importantly, the TBS-PBO-POSS films exhibited outstanding antiatomic oxygen properties because of the incorporation of POSS monomers with cagelike structure into the main chain of copolymer, which drastically reduced the AO-induced erosion owing to the formation of the passivating silica layer on the surface of polymers. When the TBS-PBO-POSS films were exposed to AO effective fluences of 1.5495×10(20) atom cm(-2) (5 h) and 4.6486×10(20) atom cm(-2) (15 h), the relative mass loss was merely 0.19% and 0.41%, respectively. This work provides a new perspective and efficient strategy for the molecular design of aromatic heterocyclic polymers possessing excellent combination properties including processing convenience and antioxidative and mechanical properties, which can be employed as potential candidates to endure the aggressive environment encountered in low earth orbits.

Tribological properties of the polyacrylate/PTFE coating modified by POSS in the space environment

“…Figure (a) shows that the surface morphology of the coating before irradiation is undamaged, with a smooth and continuous surface, whereas the surface of the coating after UV and EI irradiations [Figures (b,c)] is clearly different with many pores and debris, suggesting severe erosion and breaks in the surface structure. In addition, the surfaces gradually changed into the “carpet‐like” structures when the coatings were exposed to AO [Figure (d)], which can be mainly attributed to the strong erosion and degradation of the organic materials in the coating surface . In contrast, the OvPOSS/PMB/PTFE does not exhibit visible changes in the surface morphology apart from small holes and debris after UV and EI irradiation [Figure (f,g)].…”

“…In addition, the surfaces gradually changed into the "carpet-like" structures when the coatings were exposed to AO [ Figure 7(d)], which can be mainly attributed to the strong erosion and degradation of the organic materials in the coating surface. 12,25,35 In contrast, the OvPOSS/ PMB/PTFE does not exhibit visible changes in the surface morphology apart from small holes and debris after UV and EI irradiation [ Figure 7(f,g)]. More importantly, the OvPOSS/PMB/PTFE coatings show a smooth surface in comparison with the pristine coating after AO irradiation.…”

“…Compared with the traditional inorganic nanofiller‐containing composite materials, POSS with functional groups can be covalently grafted onto polymer chains at the molecular level. Therefore, multifunctional POSS can be incorporated into the main chain of polymers as a crosslinking agent to improve the crosslinking density, thermal stability, mechanical properties . More importantly, POSS are incorporated into the lubricating coatings by chemical reaction, which solves the issues from the dispersion and agglomeration of the inorganic nanoparticles in the polymer matrix .…”

“…Therefore, multifunctional POSS can be incorporated into the main chain of polymers as a crosslinking agent to improve the crosslinking density, thermal stability, mechanical properties. 25,26 More importantly, POSS are incorporated into the lubricating coatings by chemical reaction, which solves the issues from the dispersion and agglomeration of the inorganic nanoparticles in the polymer matrix. 27 Different multifunctional POSS have been incorporated into various kinds of polymers to obtain organic-inorganic nanocomposites with improved thermal stability, mechanical properties, and wear resistance.…”

Mechanically Robust Atomic Oxygen‐Resistant Coatings Capable of Autonomously Healing Damage in Low Earth Orbit Space Environment

“…POSS has a cage‐like rigid structure with Si‐O‐Si linkages and exhibits excellent AO‐resistant properties. [3i,j,9] The tetrahedral Si vertices were grafted with UPy groups that can dimerize strongly through self‐complementary quadruple hydrogen‐bonding interactions ( Figure a). The synthesis of UPy‐POSS is described in details in the Supporting Information and its structure was confirmed with 1 H NMR, 13 C NMR, 29 Si NMR Fourier transform infrared and CP/MAS 29 Si NMR spectroscopy (Figures S1–S7, Supporting Information).…”