Polymer Chemistry Exam 1
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What does the number average degree of polymerization represent, in words not math symbols?
The average number of monomers per polymer chain.
What does the number average molecular weight represent, in words, not math symbols?
The average molecular weight of a polymer chain
Without explaining what the two individual terms mean, what does this math as a whole represent: (Nx) * (x)
The total number of monomers present in the sample
Without explaining what the two individual terms mean, what does this math as a whole represent: (Mx) * (Nx)
The total mass of the sample
Without explaining what the three individual terms mean, what does this math as a whole represent: (Mo)(x)(Nx)
The total mass of the sample
Without explaining what the three individual terms mean, what does this math as a whole represent: (Mo)(x)
The molecular weight of a single polymer chain with a degree of polymerization x
Lower case “x” in polymer chemistry notation usually represents what?
Degree of polymerization
Lower case “n” in polymer chemistry notation usually represents what?
Number of repeat units
(Mo) in polymer chemistry notation usually represents what?
The molecular weight of an (incorporated) monomer.
(Mx) in polymer chemistry notation usually represents what?
The molecular weight of a single polymer chain whose degree of polymerization is x
(Nx) in polymer chemistry notation usually represents what?
The total number of chains whose degree of polymerization is x.
(Wx) in polymer chemistry notation usually represents what?
The total mass of ALL chains whose degree of polymerization is x
What is the mathematical relationship between number of repeat units and degree of polymerization?
Degree of polymerization = (Number of repeat units) * (Number of monomers PER repeat unit)
Conceptually, what is the difference between a number average and a weight average?
The weight average gives extra importance to longer chains by summing up quantities proportional to the SQUARE of the chain lengths instead of just summing up things that are proportional to chain length.
Describe a stepwise type of polymerization
A polymerization mechanism where chains of any length can combine with each other, as long as the function groups of the respective chains can react.
Describe an addition polymerization propagation
When a polymer chain with an active site grows by adding a single monomer to the active site. The active site is then transferred to that newly added monomer.
What is another name for a stepwise polymerization mechanism that creates a byproduct?
An elimination mechanism. Or a condensation polymerization if the byproduct is water, which it often is.
What are the three steps of an addition polymerization?
Initiation, propagation, deactivation
For an addition polymerization, what are two examples of deactivations which are terminations?
Termination by combination, Termination by disproportionation
What is the difference between a deactivation that is a termination and one that isn’t?
In a termination, the active site no longer exists anywhere. In the other types of deactivation the active site is just transferred off of the current chain to somewhere else.
In an addition polymerization, if the active site gets transferred in a deactivation step, what can it be transferred TO?
A monomer Another polymer chain A different region of the same chain The solvent A chain transfer agent
When many long branches sprout from a single monomer, what type of polymer geometry results?
A star polymer
A polymer whose branches very often quickly lead to other branches is what type of polymer geometry?
A dendrimer
A polymer with tertiary branch points spaced close together is what type of polymer geometry?
A comb polymer