Fluids confined in a nanoscale space behave differently than in the bulk due to strong interactions between fluid molecules and solid atoms. Here, we observed water confined inside "open" hydrophilized carbon nanotubes (CNT), with diameter of tens of nanometers, using transmission electron microscopy (TEM). A 1-7 nm water film adhering to most of the inner wall surface was observed and remained stable in the high vacuum (order of 10 Pa) of the TEM. The superstability of this film was attributed to a combination of curvature, nanoroughness, and confinement resulting in a lower vapor pressure for water and hence inhibiting its vaporization. Occasional, suspended ultrathin water film with thickness of 3-20 nm were found and remained stable inside the CNT. This film thickness is 1 order of magnitude smaller than the critical film thickness (about 40 nm) reported by the Derjaguin-Landau-Verwey-Overbeek theory and previous experimental investigations. The stability of the suspended ultrathin water film is attributed to the additional molecular interactions due to the extended water meniscus, which balances the rest of the disjoining pressures.

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Stretchable polymer semiconductors are essential materials to realize soft skin-like electronics. However, most high-mobility semiconducting polymers suffer from poor stretchability and strain-dependent charge carrier mobility. Herein, we report an approach to improve the stretchability of semiconducting polymers while maintaining charge carrier mobility. The strain independent performance was accomplished by incorporating a nontoxic small molecule, namely triacetin (TA), into high-mobility conjugated polymers. We observed that TA molecules substantially increased the stretchability of the high-mobility semiconducting polymer diketopyrrolopyrrole-thienyl-vinyl-thiophene (DPP-TVT), with a crack onset strain >100%, while the neat DPP-TVT polymer only shows a low crack onset strain <25%. The organic field-effect transistor (OFET) devices fabricated using the TA blend films maintain similar charge carrier mobility compared to the neat DPP-TVT-based devices. The influences of TA additive were further characterized, which included reduced glass transition temperature of polymer backbones, decreased modulus, and breakage of the polymer chain aggregations. The TA additive functions as a plasticizer residing in between lamellae layers of semiconducting polymers, which helps to preserve the crystalline molecular packing under deformation. We demonstrated the applicability of this approach by improving the stretchability of various semiconducting polymers using TA and its analog tricaproin. Last, a stretchable OFET array was fabricated with TA blended films, and it showed a well-maintained charge carrier mobility even after 1000 stretch–release cycles at 50% strain.

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