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.

Systematic investigations on the Cu(I)-catalyzed "click" reaction between a three-arm star polymer and low-molecular-weight alkynes are described. Liquid trivalent alkynes ( 2 -7 ) are reacted either with monovalent azidotelechelic polyisobutylene 1b ( M n = 1900 g mol − 1 , PDI = 1.3) in solution, or with the trivalent azidotelechelic polyisobutylene 1a ( M n = 4000 g mol − 1 , PDI = 1.3). A signifi cant autoacceleration is observed leading to increased reaction rates of the mono-, di-, and trisubstituted alkynes. Reaction in the solvent-free state proved to be signifi cantly faster than reaction in solution. Upon testing various Cu(I) catalysts, CuBr(PPh 3 ) 3, tripropargylamine 2 emerges as the ideal component for a room-temperature "click" reaction with the threearm star polyisobutylene 1a .components displaying suffi cient (high) molecular mobility to allow subsequent formation of a supramolecular or covalent network. Thus, liquid components (DCPD or derivatives, liquid epoxides) or molecules with low molecular weights (corresponding to high mobility) are used preferentially, in order to keep the time scale of diffusion suffi ciently short as to allow physical contact between the interacting molecules. We recently have reported [ 13 ] on a chemical self-healing polymer (see Figure 1 ), where two reactive liquid (polymeric) components are embedded into separate capsules, subsequently reacting after rupture of the capsule by mechanical deformation and destruction. In contrast to similar systems reported in the literature, our approach uses the azide/alkyne "click" reaction [14][15][16] as the underlying chemical "addition" reaction to effect crosslinking between a multivalent (polymeric) liquid azide 1a and the trivalent alkynes 2 and 6 (see Scheme 1 ). To effect the encapsulation of polymer 1a , an emulsion method was developed, generating urea/formaldehyde capsules with incorporated (fl uorescently) labeled polymer. The two different capsules were then embedded into a polymeric matrix containing added Cu(I) catalyst and base, leading to effect a separate location of the capsules in the matrix, which release their contents after mechanically induced rupture and subsequent crosslinking reaction. The so-induced "click" reaction leads to a measureable reaction rate of several days at temperatures of 40 ° C. The present

No abstract