Synthesis, Characterization, and Surface Morphology of Pendant Polyhedral Oligomeric Silsesquioxane Perfluorocyclobutyl Aryl Ether Copolymers

Abstract

The synthesis and characterization of solution processable, semi-fluorinated perfluorocyclobutyl (PFCB) aryl ether polymers possessing covalently bound pendant polyhedral oligomeric silsesquioxanes (POSS) cages is reported. The synthesis of POSS aryl trifluorovinyl ether (TFVE) monomers was accomplished by the condensation of commercial monosilanolalkyl-POSS with a TFVE-functionalized chlorosilane. POSS TFVE monomers were elucidated by 1H, 19F, 13C, and 29Si NMR spectroscopy, ATR-FTIR analysis, and elemental (C, H, and F) combustion analysis. Bulk thermal copolymerization of POSS TFVE monomers afforded random and block PFCB aryl ether copolymers functionalized with various POSS loadings. Quantitative monomer conversion was monitored by 19F NMR, which produced copolymer number-average molecular weights (Mn) of (19.5−24.9) × 103 (in CHCl3 using polystyrene as standard) determined by gel permeation chromatography (GPC). Thermal properties of POSS PFCB aryl ether copolymers were evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Transmission electron microscope (TEM) analysis of spin cast optically transparent, flexible POSS PFCB aryl ether copolymer films revealed the presence of 5−20 nm-sized POSS agglomerates. Optical profilometer analysis of spin and drop cast film surfaces exhibited a modest increase in surface roughness of POSS PFCB aryl ether copolymers as compared to PFCB aryl ether homopolymers without POSS inclusion. The POSS copolymers exhibited a modest increase in hydrophobicity as measured by static water contact angle analysis. Synthesis, characterization, thermal analysis, and unique surface features of POSS PFCB aryl ether copolymers are discussed.