The Preparation Of Photo-sensitive And Thermal-sensitive Superhydrophobic Surface

A dual-switchable surface between hydrophobic and superhydrophobic has beenfabricated successfully by combining reversible addition-fragmentation chain transferpolymerization (RAFT) polymeric technology and thiol-NCO click chemistry. Well-definedblock copolymer, poly(7-(6-(acryloyloxy) hexyloxy) coumarin)-b-poly(N-Isopropylacrylamide), was synthesized by RAFT, and then the block copolymer was grafted onto the surfaceof SiO2modified by toluene disocynate (TDI) via thiol-NCO click chemistry. The results ofNMR and FTIR confirmed that the block copolymer (Number average molecular weight (Mn)=9400, Polydispersity index (PDI)=1.22) has been synthesized successfully. The staticcontact angle (CA) of the surface prepared by SiO2/P (7-6-AC)-b-PNIPAAm switches from98±2°to137±2°by adjusting the temperature. Furthermore, the contact angle can alsooscillate between137±2°and157±2°on the irradiation of UV light at365and254nm,respectively. The dual-switchable surfaces exhibit high stability between hydrophilicity andsuperhydrophobicity. Therefore, the method provides a new method to fabricate thedual-stimuli-responsive surface with tunable wettability, reversible switching, and also beeasily extended to other dual-responsive surfaces. This ability to control the wettability by theadjustment of the temperature and UV light has applications in a broad range of fields.The work of this paper mainly includes the following two aspects：(1) We have successfully designed and synthesized a kind of light and temperaturedouble response block polymers. The low molecular weight distribution of block polymermolecular weight is able to be controlled, and it can realize the living controllablepolymerization. The block polymer can through the side chain which containing the coumaringroups can realize the photodimerization and photodepolymerization to change the structuresof the materials at the UV irradiation of365nm and254nm. And this kind of responsivenesshas good reversibility. It can keep the same photo-sensiticity in the multiple cyclicexperiments in three months. So the block polymer can be used for the development ofdurable light response materials.(2) We have successfully prepared the photo-sensitive and thermal-sensitivesuperhydrophobic materials. The superhydrophobic material is based on the materials of14nm silica which decorated with TDI to realize the surface of silica containing the group of–NCO. And then the terminal group C=S of the block polymer which synthesized by theRAFT polymerization method can be restored to–SH at the effect of NaBH4. At the sametime, the–SH group can reacted with the–NCO group by the click chemistry method torealize the block polymer grafted onto the inorganic materials. The static contact angles of the prepared material can change from98±2°to157±2°to come true the hydrophobic statetransit to the superhydrophobic state under the changed condition of temperature and UVirradiation.