Star-shaped POSS diblock copolymers and their self-assembled films

Novel 16-arm, star-shaped POSS-containing diblock copolymers are first synthesized by methylmethacrylate (MMA) and methacrylisobutyl polyhedral oligomeric silsesquioxane (MA-POSS) using a cetylfunctional initiator of octakis(dibromoethyl) POSS (POSS-(Br)₁₆). Three well-defined copolymers of s-POSS-PMMA_277.3-b-P(MA-POSS)_{5.8,16.4,25.4} are discussed. The introduction of P(MA-POSS) could provide the copolymer with excellent hydrophobic/oleophobic performance and thermal stability. Although the size of core-shell micelles of s-POSS-PMMA_277.3-b-P(MA-POSS) _5.8-25.4 does not increase linearly with increasing MA-POSS content due to different self-assembly behaviors and steric effects, surface roughness (0.44-1.41 nm) and water-hexadecane contact angles (108°/50°-120°/ 58°) of films, as well as thermal stability (T_d = 350-380 °C, T_g = 112-125 °C) and storage modulus (842-1600 MPa) of copolymers increased linearly. The effect of solvents on self-assembled micelles and films indicates that 340-370 nm core-shell micelles, 330-370 nm sun-like stretching micelles and 180-200 nm three-layer-structured micelles are formed in tetrahydrofuran (THF), chloroform (CHCl₃) and butanone (MEK) solution, respectively. The lowest surface free energy (17.48 m Nm^-1) is produced by film casting from THF solution due to the highest surface roughness (1.12 nm) and Si content (6.01%). While, the lowest water absorptive (Δm = 3800 ng cm^-2) and viscoelastic (ΔD/Δf = -0.36) film is produced by CHCl₃ solution, the film casting from MEK solution exhibits the highest water absorption (Δm = 6500 ng cm ^-2) and viscoelasticity (ΔD/Δf = -0.15). This is the first example of a 16-arm, star-shaped POSS diblock copolymers, and can be used as solvent-dependent coatings. This journal is