Assessment of Epoxy Functionalized Poly(dimethylsiloxane) Vitrimers Catalyzed with Covalently Attached Amines as Reversible Adhesives

Abstract

In this work, vitrimeric elastomers based on functionalized poly(dimethylsiloxane) are realized. By exploiting reactions of epoxide functional groups with carboxylic acids in the presence of a covalently bonded amine catalyst, dynamic networks are formed to establish their potential in reversible adhesives. The dynamic nature of the networks is characterized thermo‐mechanically, and in tensile tests 85% of the stress at break can be recovered after reprocessing. The covalent adaptable networks are further subjected to damp heat tests, temperature cycling tests, and high temperature storage with the aim to establish the potential and boundaries of the dynamic character of the network after application in harsh environments. The influence of the ageing tests on the reprocessability and mechanical properties is evaluated via infrared spectroscopy and lap‐shear tests. While the damp heat tests (85 °C, 85% relative humidity, and 2000 h duration) lead to hydrolytic bond cleavage of the ester bonds and storage at 120 °C for 930 h oxidizes the hydroxy groups, temperature cycling tests (−40 to 85 °C, 50 cycles) does not degrade the mechanical properties and the dynamic nature of the networks and rejoined lap‐shear specimen exhibit a remaining bond strength of more than 70%.

Influence of Anion and Cation Structures on Ionic Liquid Epoxy-Based Vitrimers

“…While the hydrolytic stability might be increased for PILs compared to pure ILs, the ester cross-links can also be cleaved by hydrolysis, and significant plastification takes place. Therefore, ambient humidity has to be considered for potential applications …”

“…Therefore, ambient humidity has to be considered for potential applications. 31 When comparing the T g values of the dry materials, both anion and cation structures have a significant influence. Exchanging the large Tf 2 N − anion to the more coordinating, smaller BF 4 − and PF 6 − anions increases the T g value from 21 to 44 and 59 °C, respectively.…”

Deciphering the Self-Catalytic Mechanisms of Polymerization and Transesterification in Polybenzoxazine Vitrimers

“…The electron-withdrawing effect, , intramolecular cyclization process, , and proton transfer exchange , are examples of NGP-assisted transesterification. Covalently bonded tertiary amine groups (NR 3 ) acting as base catalysts for dynamic exchange have recently been introduced to develop self-catalytic vitrimers. , NR 3 groups can be incorporated within a network by using amino glycidyl precursors − and primary ,− or tertiary amine-containing , curing agents or also through aza-Michael addition. ,, The position of the catalytic group within the polymer backbone has a significant effect on the kinetics of exchange. Hayashi and Inaba suggested that attaching NR 3 groups on the side groups of the network strands rather than at the cross-link points can significantly enhance the exchange rate of transesterification.…”