标题：Distance Teaching of the Undergraduate Laboratory During Pandemic Time: Dissolution of Cellulose in Mixtures of Ionic Liquids and Dimethyl Sulfoxide and Biopolymer Regeneration as Films
摘要：We report on distance teaching of an experimental project, taught during an advanced chemistry course given to our chemistry-major students (47, divided into eight groups). The project required 12 h to complete, during three weeks. We chose a subject of socio-economic relevance, namely, the physical dissolution of cellulose (Cel), an important step in processing wood-based Cel to fabricate, e.g., fibers and films. The solvents employed were mixtures of DMSO with (green) ionic liquids (ILs) 1-allyl-3-methylimidazolium acetate- (AlMeImAcO) and chloride (AlMeImCl). The former IL dissolves more Cel than the latter, this difference in efficiency was probed using molecular dynamics (MD) simulations. The dissolved biopolymer was dyed with a reactive dye and regenerated as films. The online activities during the classes included showing videos of the experiments done by the instructor; explaining how MD simulations of Cel dissolution were done, and seminars given by the students on themes related to the project. The seminars were on the commercial production of Viscose and Lyocell Cel fibers, dyeing of cellulosic fibers, and properties (light- and washing fastness) of dyed textiles. Additionally, the students were asked to suggest experiments to corroborate, or refute the results of MD simulations. The students appreciated our active learning approach (85.1%); reported that they learned new material and found the seminar themes interesting (80.9%). They indicated that online classes do not replace face-to-face practical classes (59.6%), and that the activities given do not replace the experience acquired by doing the experiment (66.0%). Regarding their local environment, 74.5% considered the conditions at home as good/very good (internet connection and hardware). After returning to face-to-face teaching, we will continue showing videos of the staff while carrying out the experiments, before going to the laboratory. This is a very useful approach to highlight important experimental precautions/protocols e.g., regarding the proper handling of chemicals and equipment. We recommend this project (distance-, or face-to-face teaching) for students of science courses because of its relevance, safety, and low-cost.
关键词：Online teaching;Practical courses;Green solvents;Ionic Liquids;Cellulose Dissolution;Cellulose Film Regeneration;Molecular Dynamics Simulations
