Polymer Chemistry Exam 2 Flashcards
What does the following equal?
Extent of Reaction
Conceptually, what does “Extent of Reaction”mean?
On a scale of zero to one, how many of the possible linking reactions have occurred so far.
What sort of information do you need in order to calculate the extent of reaction?
- You need to know what the limiting reagent is
- You need to know how many functional groups of the limiting reagent you started with.
- You need to know how many functional groups of the limiting reagent have (or have not) reacted at this time.
Express the current molarity of limiting reagent group as a function of its starting molarity and the current extent of reaction.
Amount now = (1 - p) * (Starting Amount)
The following integrated rate law is valid for what sort of reactions? And if you were to plot a graph whose slope is the rate constant, what would your x and y values be?
This is valid for a stepwise reaction of A-B or of equal amounts of A-A and B-B monomers. It works for uncatalyzed or catalyzed reactions, but not for SELF-catalyzed reactions.
y values: 1 / (1-p)
x values: [A]0 * t
The following integrated rate law is valid for what sort of reactions? And if you were to plot a graph whose slope is the rate constant, what would your x and y values be?
This is valid for a stepwise reaction of A-B or of equal amounts of A-A and B-B monomers which is self-catalyzed.
y values: 1 / (1-p)^2
x values: 2 * [A]o ^2 * t
Express the following in terms of extent of reaction
1 / (1-p)
What are the variables in this formula, and when is it valid?
It calculates the theoretical number average degree of polymerization, given an extent of reaction.
It is valid whenever it is a polymerization of A-B monomers or of equal amounts of A-A and B-B monomers via a stepwise reaction.
What are the variables in this formula and when is it valid?
It calculates the number average molecular weight given the extent of reaction and molecular weight of an average monomer.
It is valid whenever it is a polymerization of A-B monomers or equal amounts of A-A and B-B monomers via a stepwise reaction.
What do the variables represent in this equation and when is it valid?
It calculates the number average degree of polymerization.
p = Extent of reaction
It is valid in all of the following:
(1) In a stepwise polymerization of A-B
(2) In a stepwise polymerization of A-A with B-B provided that A is the limiting group.
(3) In a stepwise reaction with equal amounts of A-A and B-B and some monofunctional B monomers
What are the variables in this equation, and what does this calculate?
p = extent of reaction, x = degree of polymerization.
For a stepwise polymerization of A-B monomers, it calculates the mole fraction of chains of length x present at a given extent of reaction. This is equivalent to the probability that a chain selected at random has this length.
What are the variables in this equation, and when is it valid?
p is extent of reaction, and it calculates the weight average degree of polymerization.
It is valid for a stepwise polymerization of A-B or of equal amounts of A-A and B-B
When does polydispersity = 1 + extent of reaction?
When dealing with a stepwise polymerization of A-B or equal amounts of A-A and B-B
What are the variables in this equation and what is it used to calculate?
It is used for stepwise star polymerizations of R(A)f with A-B when you want to figure out the probability that a chain selected at random has arm lengths of exactly y1, y2, y3, etc given a star monomer with “f” arms and an extent of reaction of “p.” It is equivalent to the mole fraction of chains of this exact description in the batch.
What are the variables in this equation and what is it used to calculate?
” f “ is the number of arms in a star polymer
“ x “ is degree of polymerization
“ p “ is extent of reaction.
This calculates the mole fraction of chains of length x in a stepwise star polymerization when it is at a specified extent of reaction. It is equivalent to the probability of selecting one of these chains at random from the solution.
What does this formula calculate, and what does f represent?
f is the number of arms in a star polymer. It calculates the limit of the polydispersity of a stepwise star polymerization as it approaches an extent of reaction of 1.
What are the differences in the r values in these equations?
In the blue one, it is the ratio of branched A groups to total A groups.
In the red one it is the ratio of molecules with A groups to molecules with B groups (where A is limiting)
What do the variables in this equation mean, and what does it calculate?
Alpha is a measure of the tendency of a polymerization to gel.
Let “A” be the sort of groups that are on the branched monomer.
r = All A groups no matter where they are / All B groups
Rho = Branched A groups / Total A groups
Pa = The probability that an A group has reacted. This equals extent of reaction when A is limiting.
What do the variables in this equation mean, and what does it calculate?
Alpha is a measure of the tendency of a polymerization to gel.
Let “A” be the sort of groups that are on the branched monomer.
r = All A groups no matter where they are / All B groups
Rho = Branched A groups / Total A groups
Pb = The probability that an B group has reacted. This equals extent of reaction when B is limiting.
What is the difference between the r values in these equations?
In the blue equation
r = Branched TYPE of Groups / Non-Branched type of groups
In the red equation
r = Limiting reagent groups / Non-Limiting reagent groups
What is the difference between the rho values in these equations?
In the red equation, rho is extent of reaction.
In the blue equation, rho is the ratio of branched A groups over total A groups.
Write a symbolic reaction for an initiator dissociating
For an initiator dissociating, what is the rate law for the formation of radicals?
Write a symbolic reaction for monomer activation in a radical addition polymerization
What is the rate law for the formation of activated monomers in a radical addition polymerization?
Write a symbolic reaction for the propagation step in a radical addition polymerization.
Write the rate law for how quickly monomers are being used up during a propagation step of a radical polymerization
Write a symbolic reaction for termination via combination for a radical addition polymerization
Write the rate law for how quickly growing polymer is consumed via termination in a radical addition polymerization.
What is this formula used to calculate, and what are the variables in it?
It calculates the polymerization rate in a radical addition polymerization.
kp = the propagation rate constant.
kd = the dissociation rate constant
kT = the termination rate constant ( = kC + kDP)
[R2]0 = The molarity of initiator initially present
[M] = The current molarity of monomers present
t = time
f = the fraction of radicals which when produced participate in the polymerization
What is this formula used to calculate and what are the variables in it?
It calculates the extent of reaction in a radical addition polymerization.
kp = the propagation rate constant.
kd = the dissociation rate constant
kT = the termination rate constant ( = kC + kDP)
[R2]0 = The molarity of initiator initially present
[M] = The current molarity of monomers present
t = time
f = the fraction of radicals which when produced participate in the polymerization
What is this formula sued to calculate and what do the variables in it represent
It calculates the kinetic chain length.
kp = the propagation rate constant.
kd = the dissociation rate constant
kT = the termination rate constant ( = kC + kDP)
[R2] = The current molarity of initiator present
[M] = The current molarity of monomers present
f = the fraction of radicals which when produced participate in the polymerization
What are the variables in this equation and when do you use it?
It is used to find the expected number average degree of polymerization of a radical addition polymerization.
kp = the propagation rate constant.
kd = the dissociation rate constant
kT = the termination rate constant ( = kC + kDP)
kTr = the deactivation by chain transfer to transfer agent rate constant
[T] = The current molarity of chain transfer agent
[R2] = The current molarity of initiator present
[M] = The current molarity of monomers present
f = the fraction of radicals which when produced participate in the polymerization
Triple squiggle = The number of dead chains formed per termination event
