Shape-Memory Assisted Scratch-Healing of Transparent Thiol-Ene Coatings

Abstract

A photopolymerizable thiol-ene composition was prepared as a mixture of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT), with 1 wt. % of 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator. A systematic analytical analysis that investigated the crosslinked PETMP-TTT polymer coatings employed Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, differential scanning calorimetry, thermogravimetric analysis, pencil hardness, thermo-mechanical cyclic tensile, scratch testing, and atomic force microscopy. These coatings exhibited high optical transparency and shape-memory that assisted scratch-healing properties. Scratches produced on the PETMP-TTT polymer coatings with different constant loadings (1.2 N, 1.5 N, and 2.7 N) were completely healed after the external stimulus was applied. The strain recovery ratio and total strain recovery ratio for PETMP-TTT polymer were found to be better than 94 ± 1% and 97 ± 1%, respectively. The crosslinked PETMP-TTT polymer network was also capable of initiating scratch recovery at ambient temperature conditions.

Recovery Behavior of Microstructured Thiol-Ene Shape-Memory Film

“…Heat treatment for recovery process of the deformed PETMP-TTT films was performed in an oven at 100 • C (i.e., recovery temperature) for 1 h under an air atmosphere. It is worth mentioning that glass transition temperature (T g ) for the particular thiol-ene composition is 41 ± 1 • C, as reported in our previous work [26]. The glassy transition is the primary mechanism that governs the shape-memory behavior of PETMP-TTT film.…”

“…Photopolymerizable thiol-ene composition was prepared as reported previously [26]. A photoinitiator was briefly dissolved in a warm PETMP at 60 • C in an amber glass jar, then the calculated amount of TTT was added, avoiding direct day or artificial light.…”

“…In 2010, Nair et al first described the use of thiol-ene photopolymers as shape-memory polymer systems exhibiting excellent shape fixity and distinct shape-memory actuation response [17]. Recently, our group designed a thiol-ene shape-memory-assisted scratch-healing polymer system that not only responds to the temperature changes as the external stimulus, but is also capable of initiating scratch recovery at ambient temperature conditions [26].…”

Hot Embossing of Micro-Pyramids into Thermoset Thiol-Ene Film

“…Thiol-ene polymer systems are of particular interest as they present numerous advantages including fast polymerization, low volume shrinkage, homogeneity of the polymer network, flexibility and high optical transparency of the polymerized films [ 32 , 33 ]. It was reported that thiol-ene polymer networks exhibit a good shape recovery and self-healing effect [ 34 ]. Recently, our group demonstrated an efficient recovery of microstructured thiol-ene films fabricated via casting and a UV polymerization technique on silicon substrates textured using electron beam lithography [ 35 ].…”

A Facile and Highly Efficient Route to Amphiphilic Star‐Like Rod‐Coil Block Copolymer via a Combination of Atom Transfer Radical Polymerization with Thiol–Ene Click Chemistry

“…Over the past two decades, the versatility of thiol–ene click chemistry has been greatly exploited in polymer and materials science 25–29. The ability to combine thiol–ene chemistry with other functionalization reactions and polymerization techniques allows enhanced control and specificity in macromolecular architectures, providing the access to multifunctional materials (e.g., block copolymers,30 dendrimers,31 biomaterials,32 cross‐linked materials,33 and colloidal nanoparticles34,35). The thiol–ene crosslinking of multifunctional thiols with nonactivated CC double bonds is currently utilized in surface coating due to many advantages (e.g., regioselectivity, quantitative yields, facile synthetic strategies, and tolerance to many solvents or reaction conditions) over other synthetic methods, especially those employing heavy‐metal catalysts 31,36–39.…”