Citation: Rouhana, R.; Stommel, M.; Stanko, M.; Muth, M. Novel Method of Carbon Precursor Masking to Generate Controlled Perforations in a Carbon Film. Macromol 2022, 2, 554–561. https://doi.org/10.3390/ macromol2040036 Academic Editor: Ana MaríaDíez-Pascual Received: 14 November 2022 Accepted: 29 November 2022 Published: 5 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Novel Method of Carbon Precursor Masking to Generate Controlled Perforations in a Carbon Film Rami Rouhana 1, * , Markus Stommel 2 , Michael Stanko 1 and Markus Muth 1 1 Chair of Plastics Technology, TU Dortmund University, Leonhard-Euler-Str. 5, 44227 Dortmund, Germany 2 Leibniz Institute of Polymer Research, Hohe Str. 6, 01069 Dresden, Germany * Correspondence: rami.rouhana@tu-dortmund.de; Tel.: +49-231-755-6069 Abstract: A patterned carbon film was produced from Linear Low-Density Polyethylene (LLDPE) by the implementation of a novel method named Chemical Masking Perforation (CMP). The following paper describes this procedure, starting with the sulfonation of the precursor polymer LLDPE with Chlorosulphonic acid to stabilize the material, followed by Fourier-transform infrared spectroscopy (FTIR) evaluation to compare the atomic bonds from the stabilized film as well as from the masked sections of the film. To finalize, the cross-linked film was carbonized in an oven at 950 ◦ C. The outcome of this process was a carbon film with a thickness similar to a carbon fiber diameter of 8 μm with controllable size and distribution. Keywords: sulfonating; composite; thin films; patterned film; cross-linked; polyethylene; carbon film 1. Introduction Carbon films have several applications in many industries such as electronics, nuclear research, nano-devices, and electron microscopy [1–8]. Laser perforation, surface etching, and mechanical stamping are methods developed to generate functional perforation ge- ometries through carbon films [9]. This paper presented a novel method for the perforation and topological patterning of carbon-based material. The resultant perforated carbon films can be used to construct biomimetic platelet matrix composites similar to the structures described in the work of Sakhavand et al. [10,11] and Rouhana and Stommel [12], and structures investigated by Behr et al. [13,14] and Mirkhalaf et al. [15]. Generating periodic porosity in brittle material also allows crack arresting and improves toughness [16–18]. Such structures show high toughness properties compared with bulk ceramics and stiff- ness and strength properties that can be tailored to an intended application. Generating perforated carbon films with an energy-efficient and accurate method could allow the construction of carbon platelet composites and carbon film laminates with varying proper- ties and applications. Successful manufacturing of patterned carbon foils as described by Rouhana and Stommel [12] would allow the design of novel composites with potentially similar mechanical properties as carbon fiber composites. Other properties can also be exploited, such as thermal and electrical conductivity, as explained in the paper of Choi et al. [19], where organic photovoltaic cells were fabricated from carbon nanosheets with PE as the precursor material, reaching conductivity values of 1100 S/cm. Meanwhile, thermal properties can also be enhanced in composite materials using carbon fibers, leading to better thermal conductivity that can be achieved when the fibers have an optimal orientation within the matrix [20]. This can be mitigated by implementing carbon films, which can be better aligned and have a higher-conductivity flat surface. For the manufacturing of high-strength carbon structures, different precursor materials can be used, such as PAN (Polyacrylonitrile), Pitch, Polyolefin, Lignin, and others [21,22]. Those precursor materials are generally shaped in the required form as fiber by spinning methods or films by known extrusion methods [23,24]. After obtaining the Macromol 2022, 2, 554–561. https://doi.org/10.3390/macromol2040036 https://www.mdpi.com/journal/macromol