Author: Christopher Kriebel
Source: This material is based upon work completed at The University of Akron’s Polymer Engineering Department under the Guidance of Dr. Cavicchi supported by the National Science Foundation under Grant No. EEC-1542358.
Encapsulated polymers have many applications from drug delivery to self-healing materials. Capsules can be designed in a variety of different ways from encapsulating the polymer to using the polymer to form a capsule around the compound. There is a research group out of The University of Akron working on encapsulating an Alkyd polymer inside of a silica shell to be used as an additive in coating agents that will give the coating self-healing properties. In this lesson students will investigate the encapsulation process by using a polymer sodium alginate to form a capsule around fruit juice by crosslinking the polymer when it encounters a calcium lactate solution. The students will then add these capsules to gelatin and test the properties of the capsules and modified gelatin.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Compounds for Synthesizing
Equipment for Synthesizing
Equipment for Testing
This lesson begins with an pre-assessment (Google form) to evaluate what the students know about polymers, what they remember from previously learned content, what they know about future content that will show up in the lesson, and how engineering design works.
Then the teacher will begin the content portion of the lesson using the Google Slides presentation. During the introduction to polymers the teacher will perform the following two demos:
The teacher will continue the content section. When the teacher arrives at the material related to Alkyds and their applications make sure to ask the students how they would solve the problem of graffiti and corrosion before going into detail how the group from The University of Akron approached the problem.
Towards the end of the lesson content explain to the students that they will be engineering their own self-healing material.
Give the students time to get in their groups and work on the pre-lab questions. It is important that they can correctly solve problem number 9 as it will be used in the procedure on day 2.
Students will be working in the laboratory to synthesize their engineered material.
Students will perform a rupture test on their synthesized capsules.
Students can test their material and eat the final product.
Optional Extension: students can re-engineer their material. Extends the lesson one more day.
Assessment: Pre-assessment and Formal Assessment
Students will meet with their groups to work on the pre-lab and plans for there engineered material.
Assessment: Formal assessment of pre-lab questions.
Day 2: Synthesis Procedure and Capsule Rupture Test
Students perform the food spherification synthesis following by making a solution of sodium alginate and fruit juice and then dripping it into a solution of calcium lactate and water. The students will then isolate the alginate spheres. The students will then prepare a gelatin with dissolved calcium lactate added. At this point the students will consult their experimental design notes to see what proportions of calcium gelatin and alginate spheres to add to their sample tray. They must also make a control sample of gelatin to compare to their engineered samples. The samples are then placed into the refrigerator and left overnight.
Assessment: Formal assessment of tables for capsule rupture testing. Formal assessment occurs on day two when the samples are removed from the refrigerator for testing.
Students will complete the discussion and conclusion section of the laboratory worksheet. They will answer specific questions related to the chemistry behind the laboratory experience.
Assessment: Summative assessment of discussion and conclussion
Students can elaborate on their design in the discussion section of the laboratory worksheet.
Students will complete the extension activity and present a new product (conceptual) through a five-minute presentation to the class.
Assessment: Formal assessment of the discussion for elaboration and of the extension activity.
This lesson should be taught along with stoichiometry section specifically when students are required to perform molecular calculations. Prior to this the students should be familiar with the types of chemical bonding, how to represent chemical compounds, quantifying matter, and intermolecular/intramolecular forces. Students need to be comfortable working in groups in a laboratory setting. Students should also be proficient in laboratory safety procedures and techniques.
Common Core Standards:
Students should be able to recognize the physical changes occurring when the sodium alginate and calcium lactate are dissolved into their respective solutions. Students should be able to identify that there is an ionic bond between the calcium ion’s and the alginate polymer that is created when they interact and this ionic bonding is occurring because the calcium has a two plus charge will the sodium was only a one plus, therefore allowing one calcium ion to interact with to alginate strands holding them together.
Students need to be aware of the various intermolecular and intramolecular forces that are also playing a role in the gelatin molds.
Students should be able to calculate the molarity of a solution using the molecular mass of the compound, the mass of the compound added and the total volume of the solution. They should also be able to determine how much of a solution should be added to a specific mass to produce a predetermined molarity.
Students encounter polymers everyday in their life, but vary rarely are they aware of what the polymer is or why it was made. Students may recognize plastics as polymers, but vary few would be able to point to polymers in coating agents. This lesson is designed to make the students aware of polymers in their everyday lives along with introducing how they can be used to engineer solutions to everyday problems. At the end of the lesson the students will need to create a conceptual application for self-healing polymers that can be used in everyday life.
Many times students make solutions at home, but are unaware of what they are actually doing to the concentration of the solution or how that will affect the final product; they just simply follow the directions on the label. This lesson is designed to make them think about the concentration of solutions and how it is affecting their products. They may have to reformulate their design and change the concentration by making a new solution. This is actually a desired outcome of the lesson as the students will have to think critically and understand how the solutions concentration plays an integral role in the final physical properties of their engineered gelatin.
Multiple Assessments should be used throughout this lesson the majority are formal assessments of student progress, understanding, and engineering design. There are opportunities for summative assessment throughout the lesson as well. The assessment opportunities are as follows: