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Summary: Polyurethane (PU) films with low water contact angle hysteresis (CAH) were prepared by employing less than 0.2 wt.‐% of mono‐ or bihydroxyl‐functionalized polydimethylsiloxane (PDMS) of 60–70 DMS repeat units. A Si content of as low as 0.03 wt.‐% was sufficient to lead to a CAH of 20°. The curing temperature demonstrated strong effects on the wetting behavior of the PDMS‐modified PU films: a relatively low curing temperature (40 °C) resulted in stronger surface segregation of PDMS than higher curing temperatures, giving rise to high water receding CAs and thus low CAH. It was found from angle‐resolved X‐ray photoelectron spectroscopy analysis that the surface silicon content was greater when cured at a lower temperature. The surface of PDMS‐modified PU films was very smooth from AFM observations, but the Si content had strong effects on the surface phase contrast. The chain length of 60–70 DMS repeating units for both mono‐ and bifunctional PDMS appeared to be long enough to prevent the surface reorganization during the CA measurements.Schematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.magnified imageSchematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.

We report on the semicrystalline morphology of injection-molded isotactic polypropylene (iPP)/silica composites prepared via in situ sol−gel technology using hyperbranched polyethoxysiloxane as a silica precursor. The microstructural analysis has been carried out with a combination of small- and wide-angle X-ray scattering and 1H solid-state NMR spectroscopy. The in situ formed silica particles significantly alter the semicrystalline morphology of iPP by improving orientation of the “mother” crystals in the sample core simultaneously with an increase of the “daughter” crystal fraction. Moreover the particles induce formation of thicker crystalline domains and growth of β-crystals in the sample core. The observed morphological modifications can be accounted for by a 2-fold effect of the silica particles, i.e., their action as a nucleating agent of the β-phase, on the one hand, and as a lubrificant reducing the polymer melt viscosity, on the other. Proton spin-diffusion experiment using a double-quantum filter was found suitable for the measurement of the chain mobility gradient in the interface region. The results obtained indicate enhanced polymer chain mobility in the amorphous region in the presence of the silica particles. Finally, the morphology and chain dynamics of the iPP/silica composites are correlated to mechanical properties of the injection-molded samples.

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