Self‐healing nanocomposites from silica − polymer core − shell nanoparticles

Abstract

A copolymer containing butyl methacrylate in a 10-fold excess and furan-protected maleimidopropyl methacrylate was synthesized via atom transfer radical polymerization (ATRP). Maleimide functionalities served as dienophiles for reversible crosslinking by Diels − Alder (DA) reactions. As counterpart to the linear polymer, silica − polymer core − shell nanoparticles with grafted furfuryl groups were prepared by surface-initiated ATRP. Rheological measurements during the DA reaction at 80 • C showed an increase in storage modulus due to crosslinking within the nanocomposite. DSC allowed the detection of the endothermic retro-DA reaction above 120 • C, which provided the possibility to self-heal scratches. Repeated curing/decrosslinking was detected using UV−visible spectroscopy and revealed the reproducibility of the thermoreversible crosslinking reaction, which is a prerequisite for the self-healing mechanism. Finally, the scratch-healing abilities of the material were verified on composite films.

Self-healing polymer nanocomposites based on Diels-Alder-reactions with silica nanoparticles: The role of the polymer matrix

“…[22] furfuryl methacrylate (FMA, 5), the protected maleimide monomer -3-(3,5-dioxo-10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-en-4-yl)-propyl 2-methylprop-2-enoate (pMiMA, 6), poly[(butyl methacrylate)-co-(protected maleimidopropylmethacrylate)] (pMiMAcoBMA, P1) and FMAcoBMA (P2) were synthesized using literature known procedures. [16,21] …”

“…The filtrate was concentrated, and the residue was distilled to afford 11-bromo-1-undecene. Yield: 16 2-(11-Undecenyl)-furan (2). THF (abs., 80 mL) was cooled to 0 °C and n-butyllithium (20 mL, 2.5 M solution in hexanes, 48.0 mmol) was added while stirring under argon.…”

“…A C C E P T E D ACCEPTED MANUSCRIPT 16 high filler concentration was necessary to obtain the best ratio of crosslinking groups. Therefore the effect of crosslinking is not so high compared to the other systems.…”

“…The BMA to FMA respectively MiMA ratio was 10:1 which was verified by 1 H NMR spectroscopy. [16] Synthesis of Undecenylfuranand N-propylmaleimide modified Polydimethylsiloxanes (S1-S6) Commercially available H-terminated polydimethylsiloxanes (S1-E&S2-E), methylhydrosiloxanedimethylsiloxane copolymers (S3-E) (SiMe3 terminated), and polymethylhydrosiloxanes (S4-E) (SiMe3 terminated) were treated with 2-(11-undecenyl)-furan (2) in a hydrosilation reaction applying Karstedt catalyst in toluene (Scheme 4) at 100 °C to reach quantitative yield. In case of polymethylhydrosiloxanes the reaction time has to be increased to 12 h and a twofold amount of solvent was used, because the system gets highly viscous during the reaction.…”

“…[16] Furfurylmethacrylat and protected maleimidopropylmethacrylat were used as comonomers in the polymerization reaction. Comonomer or R = Scheme 3: Synthesis of DA-group modified polybutylmethacrylates P1 and P2 [16] By choosing the amount of diene or dienophil-bearing comonomers the degree of substitution was tailored. The BMA to FMA respectively MiMA ratio was 10:1 which was verified by 1 H NMR spectroscopy.…”