An Introductory Polymer Chemistry Course for Plastics Technology

Penn State-Erie offers one of three undergraduate degree programs in plastics engineering technology in the country, which has seen considerable growt...
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In the Classroom edited by

Computer Bulletin Board

Steven D. Gammon

An Introductory Polymer Chemistry Course for Plastics Technology Students

University of Idaho Moscow, ID 83844

Mary G. Chisholm* School of Science, Penn State Erie, The Behrend College, Erie, PA 16563; [email protected] Paul E. Koch School of Engineering and Engineering Technology, Penn State Erie, The Behrend College, Erie, PA 16563

Background Penn State Erie, The Behrend College, offers a unique four-year program in plastics engineering technology in which the educational focus is on the practical application of engineering principles and new technologies to the production of plastics. Students receive a solid foundation in the basic sciences, and recently, as a result of the success and steady growth of the program, the curriculum was revised and the chemistry component was strengthened. The plastics technology faculty wanted to introduce a course in applied organic polymer chemistry, taught by an organic chemist, which could be developed to include a laboratory and which would offer students the opportunity to include more chemistry in their senior research projects. Presenting an introductory polymer chemistry course to technology students posed some unusual challenges. A course based on traditional polymer chemistry was inappropriate because the first two years of the curriculum evolve around the fundamentals of plastics processing and the properties of plastics. Students have received one course in general chemistry as freshmen, a course introducing the nature of plastics with a little organic chemistry taught by an engineer, and a year of non-calculus physics. Their computer literacy and laboratory skills are good at this stage in their education, so a new polymer chemistry course that drew heavily on both had great appeal. This would be a terminal course in polymer chemistry and we expected that the level of chemophobia would be high. Finally, there is very little precedent for such a polymer chemistry course, since this program is one of only three undergraduate programs in plastics engineering technology in the country accredited by the Technology Accreditation Commission of the Accreditation Board for Engineering and Technology (TAC/ABET). Our program meets the requirements for accreditation with just one course in general chemistry and without the course described here. The program sees itself in a position to play a leadership role in curriculum development and is seeking to expand the chemistry component. Materials For a decade or more we have been told that if a learning experience is to be successful for students, they must become involved as active participants (1, 2). The National Science Foundation has directed several major initiatives in its course and curriculum development (CCD) program, in which

students participate actively in the learning process (3, 4 ). We decided that although this course would not contain a laboratory component initially, we would teach it so that students could learn introductory organic chemistry by active participation. They would learn about basic bonding, molecular geometry, and bond energies by using molecular modeling software. They would learn about the impact of stereochemistry on the properties of plastics by building stereoisomers with a kit and drawing them using a modeling program. By being able to visualize structures in both 2D and 3D forms and by manipulating a molecule using a computer, students would have access to several methods to help them learn about molecular structure and properties. The importance of teaching polymer chemistry at the undergraduate level has been debated by the Committee on Professional Training of the American Chemical Society and it is currently one of several options recommended by the ACS for an approved chemistry program. Concerns about the role of polymer chemistry in the undergraduate curriculum were the subject of the symposium “The State of the Art in Polymer Chemistry” at a national meeting of the ACS in 1981 (5). Jefferson and Phillips described a polymer science course for chemical technology students (6 ), but none of these programs are directed toward students whose educational goals emphasize the application of technology to the production and processing of plastics. The choice of a textbook had no good solution. We examined many outstanding introductory polymer texts (7–11), but none met the needs of our students because they all assume a knowledge of basic organic chemistry. Most had very few problems and none had worked problems. They did not provide supplementary study tools, which made them appear very austere alongside the enticing graphics of Alchemy and the Macrogalleria Web site (12). We reluctantly decided not to use a textbook, instead relying heavily on the Macrogalleria Web site for the polymer chemistry component and Alchemy for teaching structure, bonding, and stereochemistry in organic chemistry. Our fundamental challenge was teaching our students to think at the molecular level. They had been trained to think about polymers at the macroscopic and bulk levels because they had encountered them in the lab, where they discovered that the properties of a material affect its performance. Armed with SciPolymer/Alchemy (13), a model kit, and the address of the Macrogalleria Web site, but without a textbook, we were ready to begin.

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The Software Alchemy is a comprehensive molecular discovery system and modeling program, so we were able to use it as a standalone program for drawing and manipulating simple molecules to teach introductory structure, geometry, and energy concepts. The 2D sketch and 3D modeling modes were particularly valuable because students were able to sketch quite complicated molecules quickly, convert them to 3D mode, and perform a series of manipulations that showed them how a molecule would behave as a polymer. They could change the tacticity by a click of the mouse, rotate bonds to gain some insight into entanglement, or enable the dipole moment calculator to see the effects of polarity. They could monitor their changes by examining the energy content of each conformation they made. Once the basics were mastered, students could draw any polymer, real or imaginary, in Alchemy, add it to the SciPolymer database, and examine its physical properties, which are automatically calculated by SciPolymer. SciPolymer is a software package that can predict polymer properties on the basis of structure–property (QSAR) relationships. It consists of three databases: 630 polymers, each of which has up to 33 experimental and calculated physical properties listed, 300 monomers, and 150 substituents. SciPolymer is interfaced with Alchemy 2000 so that any polymer in the database can be drawn in Alchemy by a click of the mouse. In addition, any new polymer can be drawn in Alchemy and added to the SciPolymer database, and its physical properties will be automatically calculated. This package was originally targeted toward the research and development faction of the polymer design industry, but it is also a unique and, in our experience, a highly effective teaching tool. The tools and underlying theory used to calculate the various polymer properties were described by Bicerano (14 ). SciPolymer contains four integrated sets of routines: 1. The database contains properties, descriptors, and names of polymers, which can be edited. 2. The database can be searched, sorted, and filtered to generate sets of polymers specified by the user.

Box 1. Course Outline Part 1. Introduction to structure, bonding, geometry, polarity, energy concepts. Stereochemistry: conformational, geometric, and configurational isomerism and their impact on polymer properties. The concept of tacticity. The systematic and nonsystematic naming of polymers. Simple relationships between structure and properties. Discussion of selected physical properties: molecular weight, hardness, crystallinity, thermal properties, solubility. Part 2. Analysis of plastics emphasizing modern instrumental methods. Determination of molecular weight using viscometry, gel permeation chromatography, MALDI mass spectrometr y. Determination of thermal properties using differential scanning calorimetry. Determination of structure using infrared and nuclear magnetic resonance spectroscopy. Part 3. Synthesis of polymers. Addition reactions: radical, cationic, and anionic addition. The use of Ziegler–Natta and metallocene catalysts. Condensation reactions. Use of simple thermodynamic relationships to describe reaction rates, equilibrium, and optimization of conditions for polymerization and formation of solutions.

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3. Search results can be graphed, sorted for comparison, and, exported to Excel. Existing and new compounds can be drawn by accessing Alchemy from within SciPolymer. 4. New polymers can be created, added to the polymer database, and visualized in Alchemy. Batch mode copolymers and substituted polymers can be constructed and examined rapidly. All new polymers that are added to the database can have their properties examined automatically.

The strength of SciPolymer lies in its ability to design an infinite number of new polymers and provide empirical information about their properties. We have taken the drawing and design components of the two software packages and used them to teach a computer-based course in polymer chemistry, which emphasizes structure-property relationships. Course Content The course content was chosen to meet certain criteria appropriate for technology students. It would be marketed to them more as an engineering course than as a chemistry course. Students would be asked to build things (molecules), test them (with Alchemy), and determine how their products could be used (with SciPolymer). There would be a major design component to the course, for which the student would create a new plastic to perform a specific function and then evaluate the material to see how well it would perform. They would learn how to analyze plastic materials using modern instruments. Based on these principles, the course was divided into three parts, shown in Box 1. The class met three times a week and about one class period a week was spent in the computer lab, where many of the introductory concepts were learned by drawing and visualizing simple molecules in Alchemy. The naming of polymers was taught by selecting compounds in SciPolymer and drawing them in Alchemy using the interface. One of the fields in the database contains the names of the polymers in it. Much of Parts 2 and 3 were taught using the Macrogalleria Web site as a resource, described by its authors as “a cyberwonderland of polymer fun.” It requires the Chime and Shockwave plug-ins, providing it with animation, which complements the capabilities of Alchemy very well. It is laid out in the form of a shopping mall with five floors, each floor providing increasingly complex information about polymers. It is very structure oriented, which helped students make the transition from the macroscopic to the molecular level. We used frequent classroom demonstrations to illustrate some polymer properties such as solubility, and glass transition temperature using liquid nitrogen. We showed the class the instruments we own, ran some spectra, and carried out some simple polymer reactions such as the nylon rope trick (15). We found the descriptions of polymer synthesis, particularly the sections on metallocene and Ziegler–Natta catalysis, very useful, because they were written in an informal and straightforward manner that students were able to understand.

Examples of Assignments Using SciPolymer/Alchemy Introductory exercises to teach students the capabilities of the software. Perform a series of sort and filter routines.

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Examine selected properties of the search results by graphing and tabulating data. Draw a selection of simple molecules and polymers in Alchemy and import them into SciPolymer. Examine their physical properties. Students were encouraged to be imaginative in this exercise. Examination of stereochemical properties of simple polymers using a hand-held modeling kit. Draw the same structures in Alchemy and perform a series of energy observations to discover the properties of related stereoisomers. Draw examples of polymers with polar, bulky, and long pendant groups in alchemy (about 20 repeat units were used). Draw both the isotactic and syndiotactic forms, make changes in their conformation by rotating bonds, and examine the energy content of the different isomers. Build sets of copolymers in which one monomer is always the same, and select the second monomer to meet a series of criteria. Comment on selected properties of the new polymers. Build a series of related substituted polymers. Vary the substituents and the position and frequency of substitution. Comment on selected properties of the new compounds. Examine the properties of a series of polymers built from the monomers of a very hard and a very soft polymer. Suggest possible applications of the new polymers. For the final design project students were asked to create a plastic for a product with a very specific application, which they should specify at the outset. They were given instructions on how to build a database of 64 new polymers that were new homopolymers and copolymers, all with a series of substitutions. They had to justify their choice of monomers and substituents. They were asked to evaluate their results for the application they had chosen and finally determine whether they should take their efforts to their boss to convince him or her to make an investment to go into production for the new material. Students displayed considerable imagination in their selections, which included small objects such as golf tee pegs and fishing lures, plastic beer bottles, football helmets, and a wide variety of plastic auto components. Box 2. Introductory Survey—Getting to Know You 1. Functional groups. (a) What is a functional group? (b) Why are they important? (c) Draw the structure of a functional group with its name that you have heard about. 2. What is a free radical? Draw one. 3. Can you draw the structure of polystyrene, polyvinyl chloride and an isoprene-based rubber? Give it a shot. 4. If that was too easy, how about drawing the monomers of nylon. 5. Check the terms that you have heard of. Check again those terms you can define: stereochemistry tacticity gel permeation chromatography block copolymer

6. 7. 8. 9.

geometric isomerism glass transition temperature condensation polymerization molecular mechanics

What are you hoping to get out of this course? Do you expect it to be easy/difficult? Do you think it is an important course in the program? How much time do you expect to spend each week studying outside the classroom? 10.Give a couple of one-word descriptors or a phrase that best describes your feelings towards chemistry and where it fits into this program.

An unexpected problem we encountered very early in using SciPolymer was that students were not familiar with many of the physical properties listed in the database, so they were not certain what the values meant. If they wanted to measure hardness or permeability, for example, they were not sure which of the many physical constants listed was the best to use, or what the values were telling them. They tended to select properties they were familiar with, such as density or glass transition temperature, which frequently were inappropriate for what they wanted. Tg is not a good predictor of thermal stability and density is a poor predictor of hardness. They often did not realize that the molecular weight (given for the monomer) told them very little about the properties of their new polymer. It turned out to be necessary for us to spend time explaining what many of the physical properties listed in the database actually measured because the students had not encountered many of them in previous courses. Some, such as the steric hindrance factor, are very empirical, but since we had discussed steric hindrance in class, students were curious about what the constant told them. They ended up with a better understanding of the diversity of the physical properties of polymers than if SciPolymer had not been used. Assessment The enrollment in this course was 40 the first time it was taught and 50 the following year; it is currently 65. Many students are nontraditional and have jobs in the plastics industry, and some are working full time. Their career goals range from progressing to graduate school to seeking a job in a local molding company to operate equipment.

Student Evaluation Student input was sought at both the beginning and the end of the course. We thought it would be helpful to have some measure of students’ expectations and their perception of how this course fitted into their career goals before we started. The informal introductory questionnaire, shown in Box 2, was intended to discover how much students had retained from previous chemistry courses. Responses were more varied than we expected. They ranged from enthusiastic to very apprehensive, from serious to frivolous, from a willingness to learn to hostility. The greatest surprise was how little students appeared to have retained from previous courses. The first five questions were answered very poorly, although students should have been able to give the correct answer to all of them. Answers to question 10 frequently expressed the sentiment “difficult but important” or, with more feeling, “the backbone of the program, but I am clueless”. A few students clearly resented having to take a course they expected to find difficult, which they felt had no value to them, or which they would never use. The course evaluation (Box 3), passed out at the end of the semester, contained many revealing comments. Students were asked to respond on a scale of 1 (strongly disagree) to 5 (strongly agree). The numerical average of the responses is misleading because the opinions were very polarized. However, some useful facts did emerge. The students felt unprepared for this course and thought that the other courses were not well positioned to help them succeed in this one. There is a year between chemistry courses in the program. Some incon-

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Box 3. Student Evaluation of CHEM 202 (selected questions) We are anxious to receive feedback from you after the first offering of CHEM 202 is complete. We are interested in what you think of the course content, the course objectives as defined and as you saw them, the emphasis on different topics, etc. This course will evolve and part of a successful evolution depends upon comments from students. The next time it is taught it will be different from the first time. You can help to make it a better course. Keep in mind that this is an introductory course in polymer chemistry for technology students, and as such, certain topics belong in the syllabus. How they are taught, however can be varied. Please try to evaluate the course and not the instructor. Response: 1 = disagree, 5 = agree 1. The amount of material on polymer synthesis was about right. 2.7 2. The SciPolymer software was helpful. 2.6 3. The use of 3D plastic models was helpful. 3.1 4. The courses in chemistry (3) should be taught in consecutive semesters. 4.1 5. Our background does not prepare us well for CHEM 202. 3.8 6. There should be additional courses in chemistry in the program. 2.4 7. More assignments using SciPolymer would be helpful. 2.6 8. There should be a separate lab/computer course for 1–2 credits. 2.7 9. This material is of no use to me in my anticipated job/ additional studies. 2.9 10. Although I don’t see much use for this material in the near future, I should take a course in polymer chemistry. 3.0 11. This course should be optional. 3.6 12. If the program is to acquire a national reputation for excellence, then a course like this is essential. 3.5 13. The course was not sufficiently rigorous for a nationally accredited program. 1.8 14. The course content was appropriate. 2.7 15. Please give your anticipated grade.

sistencies appeared: the majority thought that the polymer chemistry course should be optional, but thought that if the program has national recognition, then polymer chemistry should be required. SciPolymer received a mixed review. Students who had superior computer skills thought it was a helpful way to learn introductory chemistry because it led directly to the concept of structure–property relationships. Students with weaker computer skills became frustrated with the amount of time they needed to spend on homework assignments and thought that SciPolymer was taking time way from more important assignments. Most students found the course quite difficult, but felt that the effort was worthwhile. Some resented taking so much chemistry because they did not see any value in the course that complemented their career goals. This group was intensely sensitive to jobs, careers, salaries, and the relevance of all the courses to their needs. For a student who plans to operate and maintain blow-molding equipment after graduation, the chemistry of polymers is somewhat erudite; whereas for students planning to go on to graduate school, their chemistry background is minimal.

Faculty Evaluation The overriding challenge of this course is how to teach introductory polymer chemistry to students who have had only one course in chemistry and a minimal amount of organic chemistry taught in an engineering course. Many students are highly motivated because the rewards of success are substantial. The job placement record for graduates from the program is close to a hundred percent, with starting 1150

Table 1. Grade Distribution % of Students Getting Grade

No. of Year Students

A

B

C

D

1997

40

21

29

29

16

5

1998

50

33

22

25

8

12

F

salaries as high as $45,000. For the less motivated students the challenge of a polymer chemistry course can be overwhelming when they see their peers succeeding, and they regard the course as an unjust obstacle to their career goals. The grade distribution for 1997–98 is shown in Table 1. The first time the course was taught, the distribution was a typical bell curve, but the second time it was taught the class polarized: more students failed (they need a C in the course to graduate), although we tried to incorporate some changes suggested from our experiences during the first year. The amount of time spent in the computer lab was increased and more help sessions on the software were held. The meeting time for the class was changed to 8.00 a.m. the second year, which caused many student complaints and class attendance suffered. We believe that the change in meeting time accounted for some of the increase in number of lower grades. The use of SciPolymer/Alchemy is pivotal in this course. We chose to use it because we thought that students would learn to think at the molecular level more quickly than if we used a textbook approach, particularly when polymer chemistry text books assume a knowledge of introductory organic chemistry. The software is not particularly difficult to learn. Students with good computer skills liked the way they were learning chemistry, and their progress was not impaired by the software. Students who learned the software more slowly would benefit more if they could use the same software in additional courses. It is difficult for some students to become proficient in the use of SciPolymer in a single course. When it is incorporated into additional courses and its capabilities are reinforced and expanded, then its value as a teaching tool will be increased. The Macrogalleria Web site filled most of the void produced by not using a textbook. It avoids a discussion of basic organic chemistry, but covers some complex subjects in a very upbeat manner that the students liked. Its strength lay in its writing style, which motivated students to read about polymer properties and synthesis where a textbook might have failed. Assessment of the course is difficult because of the broad range of student career goals it must accommodate. As the program grows, new options may be developed and the chemistry requirement between options will vary. One course in polymer chemistry cannot satisfy the needs of every student in the program. For the current curriculum, we plan to continue teaching the course using SciPolymer/Alchemy and the Macrogalleria, and we believe that this course has added an important new dimension to the program Future Plans The value of an introductory polymer chemistry course for technology students would increase if it contained a laboratory component. This is a frequent comment by students who are accustomed to taking courses that include an integrated

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In the Classroom

laboratory. Plans for a laboratory component are underway. Students will compare the results of physical tests carried out on materials in the lab, some of which they might try to make themselves, to those in the database. We plan to make SciPolymer available to students so they can increase the use of chemistry in their senior design projects. This will expand the scope of the topics that students can tackle in their senior year. In addition, the School of Engineering operates the Plastics Technology Deployment Center, whose mission is to provide local plastics companies with technical support, education, and training. The addition of SciPolymer to its software capabilities will enable small companies to embark on design projects in consultation with the program faculty and qualified students. This will give them access to state-of-theart polymer design software, which can predict new polymer properties based on structure–property relationships. Conclusion Using a hands-on computer-aided approach to teach a course in introductory polymer chemistry has resulted in a higher acceptance of introductory chemistry, as measured by student evaluations, than was found in general chemistry, where a more conventional approach was used. SciPolymer/ Alchemy gives students the opportunity to use skills acquired in polymer chemistry in other laboratory and design courses. One reason we teach the course in this way is that we hope students will retain and use their skills in polymer chemistry better than if we used a textbook-based approach. We would like to motivate a higher percentage of the students in the course because many believed chemistry was important but were unable to find the course very relevant. Our experience supports the recommendations of recent curriculum reform, that students will benefit if they can be active participants in the learning process. The issue of how much polymer chemistry should be taught in a plastics engineering technology program can only be answered by pointing out that this program meets the requirements for accreditation without the course in polymer chemistry described in this article. Acknowledgments This paper was presented at the 15th Biennial Conference on Chemical Education, University of Waterloo, ON, August 1998. Acquisition of SciPolymer/Alchemy was made possible in part by grants from the joint education committee of the Division of Polymer Chemistry and Polymeric Materials (POLYED) and the Fund for Excellence in Learning and

Teaching, The Pennsylvania State University. We gratefully acknowledge the advice and support of Joseph Votano of SciVision during the development of this course. Literature Cited 1. Advisory Committee to the National Science Foundation Directorate for Education and Human Resources. Shaping the Future: New Expectations for Undergraduate Education in Science, Mathematics, Engineering and Technology; National Science Foundation: Washington DC, 1996; http:// www.ehr.nsf.gov/EHR/DUE/documents/review/96139/start.htm (accessed Jun 2000). 2. Eiseman, J. W.; Fairweather, J. S.; Rosenblum, S.; Britton, E. Evaluation of the Division of Undergraduate Education’s Course and Curriculum Development Program. Final Report for the Division of Research, Evaluation and Communication Directorate for Educational and Human Resources, National Science Foundation: Washington DC, 1998. http://www.ehr.nsf.gov/ EHR/REC/pubs/ccd/finalrpt.pdf (accessed Jun 2000). 3. Anthony, S.; Mernitz, H.; Spencer, B.; Gutwill, J.; Kegley, S.; Molinaro, M. J. Chem. Educ. 1998, 75, 322–324. 4. Landis, C. R.; Peace, E. G.; Sharberg, M. A.; Branz, S.; Spencer, J. N.; Ricci, R. W.; Zumdhal, S. A.; Shaw, D. J. J. Chem. Educ. 1998, 75, 741–744. 5. Papers presented at the Division of Chemical Education Symposium, State of the Art for Chemical Educators III: Polymer Chemistry; J. Chem. Educ. 1981, 58, 836–950. 6. Jefferson, A.; Phillips, D. N. J. Chem. Educ. 1999, 76, 232–235. 7. Campbell, I. M. Introduction to Synthetic Polymers, Oxford University Press: Oxford, UK, 1994. 8. Challa, G. Polymer Chemistry, An Introduction; Ellis Horwood: New York, 1993. 9. Cowie, J. M. G. Polymer Chemistry and Physics of Modern Materials, 2nd ed.; Chapman and Hall: New York, 1991. 10. Nicholson, J. W. The Chemistry of Polymers, 2nd ed.; Royal Society of Chemistry: Cambridge, UK, 1997. 11. Rosen, S. L. Fundamental Principles of Polymeric Materials, 2nd ed.; Wiley: New York, 1993. 12. The Macrogalleria: http://www.psrc.usm.edu/macrog/index.htm (accessed Jun 2000). 13. SciPolymer, version 3.0/Alchemy 2000, version 2.0; SciVision, Inc., Burlington, MA. 14. Bicerano, J. Prediction of Polymer Properties; Dekker: New York, 1993. 15. Shakhashiri, B. Z. Chemical Demonstrations. A Handbook for Chemistry Teachers; University of Wisconsin Press: Madison, 1983; Vol. 1, pp 213–215.

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