A series of semiaromatic polyimides containing polyhedral oligomeric silsesquioxane (POSS) in main chain (POSS−PIs) from a double-decker-shaped silsesquioxane diamine (DDSQ−diamine) (4) with various aromatic tetracarboxylic dianhydrides were prepared and the structures were characterized by IR and NMR spectra. A double-decker-shaped silsesquioxane dianhydride (DDSQDA) (3) was synthesized by hydrosilylation reaction from double-decker-shaped silsesquioxane (DDSQ) (1) and cis-5-norbornene-endo-2,3-dicarboxylic anhydride (2), which then reacted with 4,4‘-oxydianiline (ODA) to produce the DDSQ-diamine. The POSS−PIs possessed good thermal stability and mechanical properties, low water absorption, and alkali resistance as well as low dielectric constant. The 5% weight loss temperatures (T d 5) in air were observed at 495−514 °C. The polymer films had good mechanical properties with elongation at breakage of 2.9−6.0%, in which POSS−PI 8c derived from 4,4‘-oxydiphthalic anhydride (ODPA) exhibits the highest elongation of 6.0%. The water absorption of POSS−PI 8b (<1%) was much lower than that of PI from pyromellitic dianhydride (PMDA)/ODA (6.0%). POSS−PIs 8 possessed excellent alkaline and acid resistance. POSS−PI 8b kept its flexible mechanical properties when immersed in 5% NaOH solution at 40 °C for 72 h. The dielectric constant of POSS−PI 8c measured by precision impedance method was 2.36.

Hyperbranched polymers possess unique characteristics such as low viscosity, high solubility in organic solvents and a high degree of functionality at the terminal position. However, hyperbranched polymers also possess weak mechanical properties. In this study, hyperbranched poly(ether sulfone)s (HBPES) possessing sulfonic acid moieties at the terminal position were prepared by reacting electrophilic sulfonium ions with electron-rich benzene rings from two kinds of AB 2 monomers. To address the weakness of HBPES, hybrid materials containing linear and hyperbranched PES were investigated. Linear and hyperbranched multiblock copolymers were successfully prepared by reacting oligomeric linear PES and AB 2 monomers. From the multiblock copolymers, linear and hyperbranched PES blends were prepared and applied as ion-exchange membranes for fuel cells. Films containing various ratios of linear and hyperbranched PES terminated by sulfonyl chloride groups were prepared via casting from a solution of DMAc. The results indicated that tethers between linear and hyperbranched polymers were important for controlling the size of the phases and for preventing the dissolution of HBPES in water; thus, linear and hyperbranched polymers were crosslinked by simply heating blends of both films. Finally, hybrid films containing sulfonic acid groups were obtained by hydrolyzing the sulfonyl chloride moieties. The resultant films showed ion-exchange capacities that were comparable to that of a Nafion 117 membrane (Dupont, Tokyo, Japan).

Oxidation of the surface of syndiotactic 1,2-polybutadiene (PBD) films with aqueous KMnO4/K2CO3 at room temperature produced PBD-ox, containing a range of oxidized functionality. When heated against water, the surface of PBD-ox became more hydrophobic, a result contrary to what would be expected if enthalpic forces dominated the reconstruction. Initially, the hydrophilicity of the surface varied reversibly as a function of temperature, reflecting reversible changes in the relative concentrations of hydrophilic and hydrophobic groups at the interface. Eventually, however, the surface remained hydrophilic against water, independent of temperature. The temperature dependence of this phenomenon suggests the importance of entropy in determining the state of minimum interfacial free energy in this system. This entropic effect is attributable to rubber elasticity arising from crystallinity in the polymer, and its loss is associated with a change in the amount and type of crystallinity.

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