Article pubs.acs.org/jchemeduc
Polymer Day: Outreach Experiments for High School Students Jeffrey M. Ting,†,§ Ralm G. Ricarte,†,∥ Deborah K. Schneiderman,‡,∥ Stacey A. Saba,† Yaming Jiang,† Marc A. Hillmyer,‡ Frank S. Bates,† Theresa M. Reineke,‡ Christopher W. Macosko,† and Timothy P. Lodge*,†,‡ †
Department of Chemical Engineering and Materials Science and ‡Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States S Supporting Information *
ABSTRACT: We present a collection of hands-on experiments that collectively teach precollege students fundamental concepts of polymer synthesis and characterization. These interactive experiments are performed annually as part of an allday outreach event for high school students that can inform the development of ongoing polymer education efforts in a university setting. The Advanced Polymer Synthesis experiment aims to introduce broad concepts of polymer synthesis. Techniques such as ring-opening polymerization are explained and demonstrated. The Block Polymer Micellization experiment extends this idea to block polymers for drug delivery applications. Students are taught the idea of self-assembly and prepare micelles to encapsulate β-carotene in water with flash nanoprecipitation. In terms of materials characterization, the vast physical properties space of polymers is explored. The Happy− Sad Spheres experiment provides an interactive demonstration of the glass transition temperature, while the Polymer Swelling/ Rheology experiment features the interesting properties of cross-linked and entangled polymers. Evaluation surveys showed positive feedback from students in learning polymer concepts through this program. Overall, the simple principles taught by these outreach experiments can be easily incorporated into modern laboratory curricula with broad implications for disseminating public knowledge and promoting continued interest in polymer science and engineering. KEYWORDS: High School/Introductory Chemistry, Polymer Chemistry, Public Understanding/Outreach, Hands-On Learning/Manipulatives, Polymerization, Synthesis, Micelles, Materials Science
■
INTRODUCTION The tremendous breadth, relevance, and impact of polymers span nearly all aspects of modern life, ranging from important commodity products like car tires and diapers to highly specialized materials in energy, medicine, and electronics. However, in terms of education for the public, the familiarity of these polymeric materials in such a wide array of applications can create a general disconnection between their practical utility and a deeper understanding of underlying structure−property relationships. For example, high school students may understand that common polymers such as rubber bands are stretchable while plastic cups are not, but they may not recognize that these properties are attributed to differences in molar mass or chemical structure. In an unconventional teaching curriculum, Burmeister and Eilks reported an example of incorporating consumer test methods (product testing and comparison in compliance with standards) into a student lesson plan that focused equally on polymer chemistry and societal impact.1 Nearly 100 high school student participants were tasked to evaluate the competition between economic benefits and environmental concerns for poly(vinyl chloride), poly(ethylene terephthalate), and thermoplastic starches. Follow-up questionnaires revealed that the © XXXX American Chemical Society and Division of Chemical Education, Inc.
majority of the students’ preconceptions toward plastics and sustainability were changed, including a newfound recognition of the importance of chemical considerations in polymer processing to address societal needs. The American Chemical Society Committee on Professional Training (ACS CPT) recently prepared the 2015 ACS Guidelines for undergraduate curricula to include the preparation and characterization of polymeric materials.2 In particular, inquiry-driven and open-ended investigations in laboratory settings were encouraged to be more widely implemented. More broadly, toward the goal of inspiring young students to pursue careers in science, technology, engineering, and mathematics (STEM) in university settings, three main criteria have been proposed by Graham et al.:3 (i) early exposure to research project experience, (ii) active learning in coursework, and (iii) participation in STEM learning communities. With Special Issue: Polymer Concepts across the Curriculum Received: October 19, 2016 Revised: April 8, 2017
A
DOI: 10.1021/acs.jchemed.6b00767 J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Article
respect to criterion iii, chemistry-oriented outreach programs have been widely established across higher education institutions.4−6 To teach polymer principles, outreach efforts typically involve hands-on demonstrations, ranging from single experiments7,8 to multiweek programs.9,10 At the University of Minnesota, the annual Discover STEM outreach program aims to engage high school students in a university environment during a week-long summer camp, where each day centers on a different STEM theme.11 This is a unique intermediate between the conventional stand-alone and multiweek programs. Of the scheduled days, “Polymer Day: You Make It, You Break It” (hereafter called “Polymer Day”) was conceived under the National Science Foundation Materials Research Science and Engineering Center (MRSEC) Program in 2007 to highlight the rich aspects of polymer science and engineering at an ageappropriate level. In a day-long event, high school students participate in seven hands-on, complementary experiments led by graduate students and postdoctoral researchers. The morning activities introduce students to what polymers are and how they can be made, whereas the afternoon experiments involve understanding and assessing material properties of various familiar polymers. Herein we describe the learning objectives, materials, procedures, and outcomes of four main Polymer Day experiments: Advanced Polymer Synthesis, Block Polymer Micellization, Happy−Sad Spheres, and Polymer Swelling/Rheology. These interactive experiments demonstrate different applications of polymers with an emphasis on teaching elements of synthesis and characterization. The remaining experiments (Epoxy Tensile Bars, Mechanical Properties, Polyurethane Foams, and Silly Goop) are discussed in the Supporting Information. At the end of Polymer Day, students are surveyed to evaluate instructor performance and short-term retention of concepts. We conclude with a brief discussion of the effectiveness of this program using these metrics and an outlook on polymer education in the coming decade. For polymer science educators, these demonstrations can be easily performed in modern university laboratories to provide a comprehensive overview of the advancing polymer science landscape. Furthermore, nearly all of the experiments can be conducted on the benchtop without the need for specialized equipment; alternative experiment ideas are provided where this may not be the case. Although these experiments were created with the intent of being performed concurrently, the protocols are readily adaptable to a variety of stand-alone settings for precollege- or college-level students. For teachers that would like to incorporate these experiments in their curricula, a comprehensive glossary of basic polymer terms and jargon published by the International Union of Pure and Applied Chemistry (IUPAC) provides an excellent complementary resource to the setup and discussion in this work.13
exposure to moisture. Hexamethylenediamine is toxic, corrosive, and incompatible with strong oxidants. Sodium hydroxide is corrosive. Sebacoyl chloride is corrosive and hydrolyzes in water to generate hydrogen chloride. Cyclohexane, used to dissolve the sebacoyl chloride, is highly flammable, toxic to aquatic life, and a skin irritant and can be fatal if inhaled. Because of these significant hazards, the nylon synthesis demonstration should be conducted in a fume hood. Block Polymer Micellization
β-Carotene, an orange dye, is a mild skin and eye irritant. Poly(ethylene oxide)-b-poly(lactic acid) (PEO-b-PLA) may cause mild skin irritation. Exposed areas of skin or eyes should be flushed continuously with water. If a flash nanoprecipitation device is unavailable, a simplified preparation method can be employed. Gea et al.14 previously reported the preparation of β-carotene-loaded micelles in chitosan-graf t-poly(lactide). Here, β-carotene was predissolved in tetrahydrofuran and added dropwise into a solution of water containing the fully dissolved polymer under sonication. To remove the organic solvent, the solution was then subjected to rotary evaporation and filtered to remove free β-carotene. For block polymer micelle characterization, if a dynamic light scattering apparatus is unavailable, students can learn the same qualitative lesson by using hand-held laser pointers. This involves a simple visual test to gauge whether assembled particles are present in the solution: Figure S-3 in the Supporting Information shows representative photographs of this phenomenon. If students and teachers use this method, laser safety concerns are important to address. Common hand-held laser pointers are rated at
