| Abstract
| - Block copolymers with semifluorinated monodendron side groups were synthesized byattachment of a first generation 2- or 3-armed monodendron acid chloride to a hydroxylated poly(styrene-b-1,2/3,4-isoprene). A convergent growth strategy was developed to synthesize the monodendron groupsin good yield using an approach that could be extended to higher generation monodendrons. High extentsof attachment were achieved despite the steric effects of the bulky monodendron side groups. The resultingpolymers formed a smectic B mesophase at room temperature as determined by WAXS data. The transitiontemperatures, mesophase range, and enthalpy of the smectic B−isotropic transition were all affected byside-group structural factors such as flexible spacer length, mesogen length, and monodendron core. Thecritical surface tensions of the resulting semifluorinated polymers were as low as ∼8 mN/m as determinedby Zisman analysis. Surface stability of polymer films in a polar liquid environment was stronglydependent on the extent of attachment exhibited by the semifluorinated groups. The monodendron −CF2−helix within 1 nm of the surfaces has a net orientation normal to the surface as measured by near-edgeX-ray absorption fine structure (NEXAFS) methods, but the orientational order parameter Shelix is muchhigher for the 2-armed monodendrons than for the 3-armed monodendrons. In both cases Shelix seemsinsensitive to monodendron attachment density along the isoprene block. We suggest that packingfrustration of the monodendron subunits produces surfaces with spontaneous curvature that differsdepending on whether the monodendrons are 2- or 3-armed. The more highly curved surface topology ofthe 3-armed monodendrons may provide a partial explanation for its decreased orientational order.
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