Azide/Alkyne‐“Click”‐Reactions of Encapsulated Reagents: Toward Self‐Healing Materials

Abstract

The successful encapsulation of reactive components for the azide/alkyne-"click"-reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido-telechelic three-arm star poly(isobutylene) (M(n) = 3900 g · mol⁻¹) as well as trivalent alkynes were encapsulated into micron-sized capsules and embedded into a polymer-matrix (high-molecular weight poly(isobutylene), M(n) = 250,000 g · mol⁻¹). Using (Cu(I)Br(PPh₃)₃) as catalyst for the azide/alkyne-"click"-reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.-% and accordingly 5 wt.-% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self-healing properties.

Polythiourethane microcapsules as novel self-healing systems for epoxy coatings

“…Most common materials used for shell wall are polyureas [8][9][10], polyurethanes [3,11,12], melamine-formaldehyde [13][14][15] and ureaformaldehyde [2,16,17]. They can be obtained using different methods like in situ polymerization [2,[13][14][15][16][17][18][19], interfacial polymerization [3, 8-12, 20, 21], Pickering emulsion [22][23][24], microemulsion polymerization [25,26], solvent evaporation/ Fig. 1 Schematic of second-generation self-healing process: (1) coating with microcapsules before microcrack propagation, (2) microcracks occur, (3) microcapsules rupture and healing agent fills crack area, (4) healing agent reacts with water from environment and functional groups from matrix extraction [27,28] or sol-gel reaction [29,30].…”

Development of optimized autonomous self-healing systems for epoxy materials based on maleimide chemistry

“…The average maximal peak load to break the virgin sample is 58 N in the case of EPON 828, 80 N in the case of RIM (100:30), and 120 N in the case of RIM (100:50). It is clear that EPON 828 is an intrinsically weaker material than RIM (100: 30) and RIM (100:50). However, note that the high apparent strength of the RIM (100:50) arises from plastic deformation of the RIM material due to its relatively low T g (48 °C).…”

Designing semiencapsulation based covalently self‐healable poly(methyl methacrylate) composites by Atom Transfer Radical Polymerization

“…are the prevailing adopted techniques for designing self-healing polymers. [5][6][7][8][9][10][11] Among various healing techniques, covalent bond formation is undoubtedly the most efficient healing technique to ensure sufficient strength for long-term structural applications, as they are the strongest chemical bonds. Although numerous methods are available for making self-healing polymers a few of them leads to formation of covalent bond formation between healing agent and the matrix.…”