Well-Tailored Norbornene-Based Fluorinated Copolymers toward Modulating Icephobicity and Mechanical Robustness.

Well-tailored construction of icephobic surfaces with mechanical robustness and investigation of the structure-property relationships at the molecular level are highly desirable. Herein, a series of norbornene-based fluorinated polyolefin copolymers (FPOR-x) with varying norbornenyl dodecafluoroheptyl ester (NDFHE) molar fractions (0-100 mol %) were well-designed and fabricated via living ring-opening metathesis polymerization (ROMP) employing NDFHE and norbornenyl pentafluorophenyl ester (NPFPE) as the soft and hard segments, respectively. The mechanical and icephobic properties of the fluorinated copolymers can be regulated by adjusting the soft NDFHE contents. As a result, the well-designed norbornene-based copolymers exhibited a wide range of tunable mechanical properties, including tensile strength ranging from 0.2 to 26.4 MPa, elastic modulus ranging from 0.6 to 593.7 MPa, and breaking elongations ranging from 5718.7% to 3.7%, correlating with the proportion of soft NDFHE content. Furthermore, the synergistic interplay between soft and hard segments, particularly the hardness in the majority and softness in the minority or vice versa, could achieve a significant difference in the local modulus and enhance the propagations of cracks within the three-phase regions (soft regions/hard regions/ice), ultimately leading to a significant reduction in ice shear strength. Notably, FPOR-25% with a tensile strength of 12.0 MPa and an elastic modulus of 227.5 MPa exhibited a remarkably low ice shear strength of 57.7 kPa. This study not only highlights the relationship between the polymer molecular structure and surface icephobic properties but also breaks the limitations of icephobic surfaces with a low modulus.

Flexible Azo-Polyimide-Based Smart Surface with Photoregulatable Surface Micropatterns: Toward Rewritable Information Storage and Wrinkle-Free Device Fabrication.

Stimulus-sensitive materials are of great fascination in surface and interface science owing to their dynamically tunable surface properties and/or morphologies. Herein, we have synthesized an azobenzene-containing polyimide (azo-PI) with enhanced chain flexibility for the fabrication of photosensitive surface patterns on a film/substrate wrinkle system or wrinkle-free devices. The phototriggered cis-trans isomerization kinetics of azobenzene groups in the novel azo-PI with various chain structures were systematically investigated. On the basis of the characteristics of stress relaxation that azobenzene reversible cis-trans isomerization induces in the wrinkled azo-PI film/substrate system, a variety of rewritable visual surface patterns with high resolution and a long legibility time (>30 days) could be easily constructed via visible-light irradiation, enabling the wrinkled azo-PI surfaces to be used as rewritable information storage media. Meanwhile, because of the visible-light irradiation strategy, these photoresponsive surfaces could find potential application in the fabrication of wrinkle-free flexible devices. This study not only sheds light on the influence of the azo-polymer chain structure on its photoresponsive behavior but also provides a versatile strategy for realizing tailor-made smart surface patterns on multilayer functional devices.