Chain folding - lamella This animation is about the crystalline lamella formation in the single chains. Prior Viewing: helical structure Future Viewing: Spherulite formation Title of the concept Author: K. Jagadeeshwar Research Scholar (PhD) IIT Madras

Learning objectives After interacting with this Learning Object, the learner will be able to: Know the chain folding in polymers Know about the energy and entropy during the folding Learn about the formation of lamella

1 Master Layout (Part 1) 2 3 4 5 This animation contains 3 parts Part 1: polymer chain folding with temperature Part2: Formation of stack of chains - lamella Part 3: Models of lamella Polymer chain folding during the crystallization process 2 3 4 5

Definition 1 Most polymers don’t stretch out fully instead they fold by themselves after they stretch to a distance in the process of crystallization, when the temperature is reduced . 2 3 4 5

3 3 Part 1, Step 1: Part 1, Step 1: 1 1 Crystallization 2 2 4 4 5 5 Fig 2 3 3 4 4 Fig 1 5 5

Part 1, Step 1: 1 Crystallization 2 Fig 4 3 4 Fig 3 5

Part 1, Step 1: 1 Crystallization 2 3 Fig 6 4 Fig 5 5

Part 1, Step 1: 1 Crystallization 2 Fig 8 3 4 Fig 7 5

Description of the action Part 1, Step 1: 1 Description of the action Audio narration Fig 1 has to appear on the screen. Fig 2 later. Fig 1 has to slowly move to the form of Fig 3 as the red mark in the Fig 2 reduces and become equal to that of Fig 4. Fig 3 then change slowly and become as in Fig 5 as the red mark in Fig 2 reduce and become equal to Fig 6. Fig 5 change slowly and to become figure 7 as the red mark in Fig 6 further decrease as shown in Fig 8. ( Note: Change of Polymer chain Fig 1 and the temperature indication in the thermometer, the red line, should change simultaneously in the animation). When you press the next button it has to go to the next part. The polymer chain that appeared on the screen is above it’s melting point temperature. When it is cooled, it starts to form a crystal. At the time of crystallization, these chains wanted to stretch out. Only few can stretch out perfectly in the form of a straight line. Others, fold back themselves after stretching for a short distance. 2 3 4 5

Part 2, Step 1: 1 2 3 4 Fig 9 5

Part 2, Step 1: 1 LAMELLA 2 3 4 Fig 10 5

Description of the action Part 2, Step 1: 1 Description of the action Audio narration Fig 9 is to be drawn in free form as shown in the animation and Fig 10 has to appear immediately after the animation. When you press the next button it has to go to the part 3. Polymer chains not only fold by themselves at the time of crystallization, they also form stacks of the folded chains, which are called as lamella. 2 3 4 5

Part 3, Step 1: 1 2 3 4 Fig 11 5

Description of the action Part 3, Step 1: 1 Description of the action Audio narration Fig 11, the entire diagram is to be drawn in free form and the lines showed in blue color has to hang on freely and should be moving (waving). When you press next button it has to go to next animation in part 3 itself to step 2. Polymer chains are indecisive. Part of it will be in the crystalline lamella and the part lies in the amorphous region outside the lamella. 2 3 4 5

Part 3, Step 2: 1 2 3 4 Switchboard Model Fig 12 5

Description of the action Part 3, Step 1: 1 Description of the action Audio narration Fig 12, the loop line that came out should increase in its size and then come back to its original stage.( like a bubble is blown and then air is removed inside). When you click next it has to go to next step in part 3. The lamella have chains that go out and come back in to the original position where they have started. 2 3 4 5

Part 3, Step 2: 1 2 3 4 Switchboard Model Fig 13 5

Description of the action Part 3, Step 1: 1 Description of the action Audio narration Fig 13, the lines that are colored blue has to be made as shown in the animation. Initially all the blue lines have to wave freely and then the two lines have to disappear forming the third line as shown in the animation. The lamella have chains where the outgoing chain comes back in the position somewhere away where it was left. These models are quite common and are called switchboard models. 2 3 4 5

APPENDIX 1 Questionnaire: How does a polymer chain fold during the crystallization process? Random 2. Regular 3. Zig-zag 4. None The regularly arranged stack of polymer is referred to as Single cell 2. Unit cell 3. Lamella 4. None Give an example of lamellar model To know more: What happens when polymers fold themselves and form lamella which leads to the formation of spherulite. Refer Learning Object: Spherulite formation

Links for further reading APPENDIX 2 Reference websites: http://www.pslc.ws/macrog/crystal.htm http://willson.cm.utexas.edu/Teaching/Chem367L392N/Files/Crys tallinity%20in%20Polymers.pdf Books: Polymer crystallization  By Jerold M. Schultz Research papers: Phase Transitions and Structure Of Crystalline Polymers Bernard Lotz Institut Charles Sadron (CNRS - ULP), 6, rue Boussingault, 67083 STRASBOURG (France)