Dual-switchable surfaces between hydrophobic and superhydrophobic fabricated by the combination of click chemistry and RAFT

Abstract

The wetting properties of superhydrophobic surfaces have received worldwide and tremendous attention [1] since the dual hierarchical structure of the lotus leaf was discovered [2]. Lotus-Leaf-like superhydrophobic surfaces, exhibit an amazing property for not only being wetted by water leading to a self-cleaning effect [3], but also for their great advantages in applications. In recent years, superhydrophobic surfaces are widely used in the human body implant materials [4], microfluidic tools [5], Calix azacrown [6], tunable optical lenses [7], labon-chip systems [8]. The wettability of the surface is influenced by its chemical composition and morphology [9], because chemical composition determines the surface free energy, and a lower surface energy leads to higher hydrophobicity. Additionally, the hierarchical structure (micro roughness covered with nano roughness) was not only necessary for a high contact angle (CA) but essential for the stability of the water-solid and water-air interfaces [10] Received 1 January 2014; accepted in revised form 1 April 2014Abstract. A dual-switchable surface between hydrophobic and superhydrophobic has been fabricated successfully by combining reversible addition-fragmentation chain transfer polymerization (RAFT) polymeric technology and thiol-NCO click chemistry. Well-defined block copolymer, poly(7-(6-(acryloyloxy) hexyloxy) coumarin)-b-poly(N-Isopropylacryl amide), was synthesized by RAFT, and then the block copolymer was grafted onto the surface of SiO 2 modified by toluene disocynate (TDI) via thiol-NCO click chemistry. The results of nuclear magnetic resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopies confirmed that the block copolymer (Number average molecular weight (M n ) = 9400, polydispersity index (PDI) = 1.22) has been synthesized successfully. The static contact angle (CA) of the surface prepared by SiO 2 /P (7-6-AC)-b-PNIPAAm switches from 98±2 to 137±2° by adjusting the temperature. Furthermore, the contact angle can also oscillate between 137±2 and 157±2° on the irradiation of UV light at 365 and 254 nm, respectively. The dual-switchable surfaces exhibit high stability between hydrophilicity and superhydrophobicity. Therefore, the method provides a new method to fabricate the dual-stimuli-responsive surface with tunable wettability, reversible switching, and also be easily extended to other dual-responsive surfaces. This ability to control the wettability by the adjustment of the temperature and UV light has applications in a broad range of fields.

Fabrication of polyaniline coated iron oxide hybrid particles and their dual stimuli-response under electric and magnetic fields

“…The reversible phase transitions as a response to external stimuli, such as pH, temperature, ionic strength, shear, electric or magnetic fields become a significant area of materials research [1][2][3][4][5][6][7][8]. Electric or magnetic stimuli-responsive suspension systems are particularly noticeable because their dramatic changes in shear viscosity and yield stress under a range of conditions is useful for rheology control applications.…”

Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications

“…The combination of CRP techniques (ATRP, [ 214 ] RAFT, [ 215 ] etc.) and coupling reactions has been useful in grafting PMMA, PS, PNiPAAm, poly(N-vinylcarbazole), poly(7-(6-(acryloyloxy) hexyloxy) coumarin), etc.…”

Inspired smart materials with external stimuli responsive wettability: a review

“…211 A temperature and UV light-responsive surface with switchable wettability between hydrophobicity and superhydrophobicity has been fabricated successfully by graing a block copolymer of poly(7-(6-(acryloyloxy)hexyloxy)coumarin)-b-poly(N-isopropylacryl amide), generated via combining reversible addition-fragmentation chain transfer polymerization (RAFT) onto an SiO 2 surface modied by toluene diisocyanate (TDI). 212 Moreover, a superhydrophobic aligned-ZnO-nanorod array surface, which exhibited a patterned wettability transition from the Cassie to the Wenzel state via a photoelectric cooperative wetting process was also reported. 213 In addition, considering more complex environments, for example the human body, multi-responsive smart surfaces urgently need to be explored.…”