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Here, the development of an adhesive is reported – generated via free radical polymerization – which can be degraded upon thermal impact within minutes. The degradation is based on a stimuli responsive moiety (SRM) that is incorporated into the network. The selected SRM is a hetero Diels‐Alder (HDA) moiety that features three key properties. First, the adhesive can be degraded at relatively low temperatures (≈80 °C), second the degradation occurs very rapidly (less than 3 min), and third, the degradation of the network can readily be analyzed and quantified due to its self‐reporting nature. The new reversible self‐reporting adhesion system is characterized in detail starting from molecular studies of the retro HDA reaction. Moreover, the mechanical properties of the network, as well as the adhesion forces, are investigated in detail and compared to common methacrylate‐based systems, demonstrating a significant decrease in mechanic stability at elevated temperatures. The current study thus represents a significant advance of the current state of the art for debonding on demand adhesives, making the system interesting for several fields of application including dental adhesives.

We report the preparation of tetrazole-containing step-growth microparticles, and the subsequent use of photo-induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) reactions on the particles with spatiotemporal control. Microparticles with an average diameter of 4.1 µm and with inherent tetrazole-ene dual-functionality were prepared by a one pot offstoichiometric thiol-Michael addition dispersion polymerization. The NITEC reaction was performed efficiently in the solid phase by UV irradiation, leading to the formation of fluorescent pyrozoline adducts, with an estimated quantum yield of 0.7. Particle concentration independent reaction kinetics were observed and full conversion was reached within 10 min of UV exposure at an intensity of 8 mW cm -2 . Temporal control was demonstrated with either UV or rooftop sunlight irradiation of variable duration. By using two-photon writing with a laser centered around 700 nm wavelength, spatial control was demonstrated with micron-scale resolution via surface patterning of the microparticles. Further, microparticles with exclusive tetrazole functionality were prepared by a onepot, two-step thiol-Michael addition dispersion polymerization. The NITEC reaction between tetrazole-functional particles and acrylates in solution was examined at various tetrazole/alkene molar ratios, and a 10:1 excess of alkenes in solution was found necessary for efficient functionalization.

Here, we report the first-time development of polycarbonate networks with self-reporting thermoreversible bonding/debonding on demand properties. The reversible linkages within the network are based on a Hetero-Diels-Alder (HDA) moiety, which is able to undergo cleavage and rebonding as a function of temperature within minutes. As HDA pair a phosphoryl dithioester and a cyclopentadiene moiety are employed as bonding and debonding take place in the temperature range between 25-120°C. The degradation and rebonding can be readily traced by visible inspection due to the self-reporting nature of the HDA moiety. In order to prove the reversibility, linear polycarbonates (M w = 4.200-20.000 g mol −1 ) including the reversible linkage in each repeating unit were generated and carefully analyzed using size exclusion chromatography (SEC), UV/Vis analysis and high temperature 1 H NMR spectroscopy.Subsequently, polycarbonate networks bearing HDA unitsallowing the networks to be fully degraded into small moleculeswere synthesized, debonded and bonded several times in the temperature range between 25 and 120°C within minutes. The present study thus introduces fully degradable polycarbonate networks based on a facile chemical concept as a viable alternative to networks based on C-C bond formation that disallow a complete degradation.Scheme 1 General concept of the bonding/debonding on demand polycarbonate. The network is formed via the reaction of a triol species (HDA-triol)which is formed via an HDA reaction of the TriCp-linker and PDT-OHwith dimethylcarbonate using TBD as catalyst. The network is then able to bond and debond on demand due to the HDA units within minutes as a function of the applied temperature. PaperPolymer Chemistry 416 | Polym. Chem., 2017, 8, 414-420This journal is

We introduce a new concept for λ-orthogonal photocurable and degradable polymer networks based on disulfone cross-linkers. The methacrylate-based monomer mixture can be cured via irradiation with visible light (400− 520 nm) due to a germanium-based initiator in 10 min. Subsequently, disassembly can be induced via the UV light (350−400 nm) triggered decomposition of a photogenerated amine (PGA) that cleaves the disulfone cross-links of the network completely via a substitution reaction. For the disulfone-based cross-linking, a new dimethacrylate monomer containing the disulfone moiety is synthesized. The cleavage of the S−S bond via a nucleophilic substitution is evidenced using 5 equiv of diethylamine as a nucleophile. In order to achieve an in situ degradation, a UV-degradable PGA is prepared, and its degradation upon UV irradiation as well as its stability under visible light are demonstrated. 1 H NMR spectroscopy in solution revealed a complete degradation of the disulfone in the presence of 5 equiv of the PGA. Finally, a swollen network was prepared and successfully degraded upon UV irradiation within 4 h.

We introduce the facile synthesis of segmented copolymers by a catalyst-free Diels-Alder (DA) reaction at ambient temperature via step-growth and subsequent reversible addition fragmentation chain transfer (RAFT) polymerization. High molecular weight step-growth polymers are readily obtained (M = 40 000 g mol), featuring trithiocarbonate moieties in their chain, which allow monomer insertion via RAFT polymerization yielding high molecular weight species.

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