Post Lab Questions
1. Describe a polymer in your words.
A substance which has a molecular structure that is primarily made up of many similar repeating units known as monomers that are bound together.
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2. As the number of initiators increase, what happens to the length of the chains?
The length of the chains increases. Polymerization begins at initiation, and only two molecules are involved in the chain reaction; monomers and initiator molecules. An increase in the number of initiators leads to more activated monomers that can polymerize hence resulting in an increase in the length of the monomers.
3. Predict how the “strength” and “flexibility” of the polymers change as the number of cross-linkers increases.
4. A “branched polymer” is formed when one chain is attached to the body of another chain. A branched polymer resembles the branches of a tree. Rebuild a structure and insert a picture here, so that is shows branching.
Structure of low-density polyethylene
5. What did you have to do with one of the terminal ends to create the branching requested for your polymer?
The introduction of branching required replacement of a substituent such as a hydrogen atom on one of the monomer subunit with a covalently bound chain of the polymers.
6. Below is the structure of the monomer ethylene chloride, the building block of polyvinyl chloride, PVC. Draw a five repeating unit of the polymer. (You will need to draw this by hand and then insert a picture of your work here.)
7. Below is a picture of the polymer known as polyethylene:
What does its monomer look like? Draw its structure here: (You will need to draw this by hand and then insert a picture of your work here.)
Polymers are a unique molecular structure made up of repeating monomers units. Synthesis of polymers takes place in three reactions: initiation reaction, propagation reaction and termination reaction. It requires different molecules such as the monomers to be covalently bound and the initiator molecules. The length of the polymers increases with the number of monomers and initiator molecules. Crosslinking is essential for increasing the strength of polymers however it reduces their flexibility. Branching in polymers occurs through substitution of substituent molecule with a chain of the polymer at one of the carbons of the polymers.