Independent Two Way Switching of the Wetting Behavior of Cellulose‐Derived Nanoparticle Surface Coatings by Light and by Temperature

Abstract

light-triggered changes in the polarity of a material are of interest, as the switching mechanism does not rely on diffusion, as is the case with the pH-or electrolyteinduced switching of polyelectrolytes. [18] However, one of the major challenges of light-responsive spiropyran that has yet to be solved is the rather slow dynamics of the molecular rearrangements (i.e., slow switching behavior) and the oxidative degradation that can occur during the process. Another group of photoresponsive polarity-switching materials are known as donor acceptor Stenhouse adducts (DASAs). DASAs were discovered recently and have gained an increasing amount of attention in a broad range of fields, generating literal toolboxes for the fast implementation into existing systems to add further functionalities. [19][20][21][22][23][24][25][26][27] These compounds are derived from furfural, a commodity chemical and plant by-product, which is a great step toward sustainable building blocks for photoswitchable compounds. Initial studies focusing on the incorporation of the photoresponsive DASA domain into polymer matrices have been carried out, and the products of which displayed a photoinduced change in wetting behavior based around the mechanism displayed in Figure 1a. [28,29] Both studies found that there was no observable back-switching for DASAs on surfaces, which stands in sharp contrast to the fast switching observed for these molecules in solution. A newer study has reported that second-generation DASA-containing polymers could be switched back within hours, triggered by the glass transition of the matrix polymer. [30] Very recently Zheng et al. reported the reversible switching of a silica nanoparticle bound poly dopamine based DASA system, which could, once immobilized on a polydimethylsiloxane substrate, induce a change in water contact angle (WCA) of up to ≈40°. [31] We have been working in the recent past on cellulose-ester and hydroxypropyl cellulose (HPC)-ester polymers, which can be tailored with respect to their thermal behavior (T g ), and such materials can be applied as nanoparticle coatings on planar surfaces. [32,33] When cellulose-or HPC-ester nanoparticles are being coated onto a planar solid or porous (e.g., paper) substrate, superhydrophobic surface properties with WCAs exceeding 150° can be observed through a combination of roughness (a film consisting of nanoparticles) and low surface energy. Through thermal treatment, the nanoparticle structure Recently, donor acceptor Stenhouse adducts (DASAs) have received interest as photoresponsive polarity switches. In this work, a range of DASAs are synthesized and combined with nanoparticles from hydroxypropyl cellulose stearic acid ester to yield a photoresponsive composite material. This composite is spray-coated onto porous paper substrates, forming an interface that is initially superhydrophobic and can be switched by a visible light trigger to become hydrophilic. Subsequently, this hydrophilic state can be switched back to regain a hydrophobic surface by heating abo...

Smart Surfaces with Tunable Wettability

“…Further, by introducing micro and nanoscale hierarchical surface structures, Feng et al showed the reversible wetting switching between superhydrophilic and superhydrophobic states on TiO 2 nanorod films by cooperating micro and nano hierarchical surface structures together with a photosensitive material coating and the wettability change was quite similar to as reported in their previous work [49]. Morphology of hierarchical surface structures with micro and nano features can be clearly visualized from the SEM images shown in Figure 7e, f. Due to intrinsic photocatalytic property and reversible wettability switch, TiO 2 has also attracted much attention for its various applications, such as antifogging and self-cleaning [51][52][53][54][55]. Another simple approach to produce rough TiO 2 films was based on CF 4 plasma etching technique, which was adopted by Zhang et al to produce superhydrophilic and superhydrophobic patterns by UV irradiation using a photomask [56].…”

Visible Light—Responsive Drug Delivery Nanoparticle via Donor–Acceptor Stenhouse Adducts (DASA)

“…The photoisomerization of DASAs results in changes in solubility, polarity, and structure which are attractive for applications in many fields of chemistry. To date, these applications have included drug delivery, [ 19–21 ] surface modifications, [ 22,23 ] photo‐patterning, [ 24–26 ] catalyst recycling, [ 27 ] gate and molecular logic, [ 28–30 ] sensors, [ 31–35 ] nanoreactors, [ 36 ] and aggregation induced emission (AIE) materials. [ 37 ]…”

Extending Cellulose-Based Polymers Application in Additive Manufacturing Technology: A Review of Recent Approaches

“…The developed composite could be switched reversibly between hydrophobic and hydrophilic properties through exposure to visible light. The coating can be applied onto papers and allow the production of paper-based fluid timers [ 162 ]. The incorporation of CNC and 2-bromoisobuuturyl bromide into 6-[4-(4-methoxyphenyl-azo) phenoxy] hexyl methacrylate produced a photo-responsive composite that changes in color through the irradiation to light with the wavelength of 350 nm [ 163 ].…”