On the Schwarzschild Effect in 3D Two‐Photon Laser Lithography
International audience; The two‐photon Schwarzschild effect in photoresists suitable for 3D laser lithography is revisited. The study ranges over seven orders of magnitude in exposure time (from 1 µs to 10 s) and investigates a wide variety of different photoresist compositions. For short exposure times (“regime I”), the laser power at the polymerization threshold can scale with the inverse square root of the exposure time, as naively to be expected for two‐photon absorption. Substantial deviations occur, however, for low photoinitiator concentrations. For intermediate exposure times (“regime II”), a Schwarzschild‐type of behavior is found, as discussed previously. For very long exposure ti…
Wavelength-Selective Softening of Hydrogel Networks.
Photoresponsive hydrogels hold key potential in advanced biomedical applications including tissue engineering, regenerative medicine, and drug delivery, as well as intricately engineered functions such as biosensing, soft robotics, and bioelectronics. Herein, the wavelength-dependent degradation of bio-orthogonal poly(ethylene glycol) hydrogels is reported, using three selective activation levels. Specifically, three chromophores are exploited, that is, ortho-nitrobenzene, dimethyl aminobenzene, and bimane, each absorbing light at different wavelengths. By examining their photochemical action plots, the wavelength-dependent reactivity of the photocleavable moieties is determined. The wavele…
The Next 100 Years of Polymer Science
International audience; The year 2020 marks the 100th anniversary of the first article on poly merization, published by Hermann Staudinger. It is Staudinger who realized that polymers consist of long chains of covalently linked building blocks. Polymers have had a tremendous impact on the society ever since this initial publication. People live in a world that is almost impossible to imagine without synthetic polymers. But what does the future hold for polymer science? In this article, the editors and advisory board of Macromolecular Chemistry and Physics reflect on this question.