Paper of the week: A powerful method for 3D bulk patterning of polymer sheets

Polymer films are ubiquitous in numerous industrial fields such as electronics, biotechnology, optics or portable energy devices. Improving the performances of devices in this broad range of applications most often requires creating 2D- or 3D-structured polymer films in order to combine the material bulk properties and designated interactions with their local environment. For this purpose, methods usually used are based on: (i) phase separation of block copolymers which leads to polymer blend films with an isotropic structure or (ii) radiation-induced graft polymerization to obtain isotropic architecture by an electron beam or γ-ray radiation or an anisotropic structure by swift heavy ion irradiation or by X-rays or Extreme UltraViolet (EUV) light radiation. However, these processes present some limitations such as block copolymer and film synthesis, drastic safety procedures or the high cost of ionising sources.

Graphical abstract: VUV grafting: an efficient method for 3D bulk patterning of polymer sheets

To overcome these drawbacks, Berthelot and co-workers proposed here an innovative process, based on VUV irradiation, which proved efficient not only for surface modification, but also for the bulk modification of industrially relevant polymers such as β-polyvinylidene fluoride (β-PVDF), polyethylene (PE) or fluorinated ethylene propylene (FEP). The authors assumed that VUV irradiation of a PVDF film can induce radical active species at depths up to 50 micrometers, as demonstrated by ESR. Those active species were able to initiate the radical polymerization of a vinylic or acrylate monomer such as acrylic acid through the polymer film, as confirmed by the EDX profile of the film thickness. Similar results were obtained on PE and FEP films, while aromatic polymers such as PET strongly absorbed VUV energy and dissipated it along other pathways. By mixing this process and photolithographic masks, 3D structuration of commercial polymer films was also obtained.

VUV grafting: an efficient method for 3D bulk patterning of polymer sheets by Cecile Baudin, Jean-Philippe Renault, Stephane Esnouf, Serge Palacin and Thomas Berthelot Polym. Chem. 2014, 5, 2990-2996.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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