What polymer is formed by anionic polymerization of each...

Key Concepts

Chain-Growth Mechanism

The chain-growth mechanism refers to the process where the polymer chain builds up by the sequential addition of monomer units to an active site on the growing polymer. In anionic polymerization, this process is characterized by rapid propagation once an active site is established, leading to polymers with predictable structures.

Living Polymerization

Living polymerization describes a process where the polymer chains continue to grow without significant termination or chain transfer. Anionic polymerization is a prime example of a living polymerization technique, allowing for the synthesis of polymers with low polydispersity and the ability to form block copolymers through the sequential addition of different monomers.

Anionic Polymerization

Anionic polymerization is a form of chain-growth polymerization initiated by an anionic species, typically involving a nucleophilic attack on a monomer's electron-deficient site. This method enables precise control over molecular weight and structure because the active chain ends remain ‘live’ until a terminating agent is added, often resulting in narrow molecular weight distribution.

Monomer Reactivity

Monomer reactivity is a crucial aspect in anionic polymerization, as monomers must be compatible with the anionic initiator and have substituents that stabilize the negative charge during propagation. Only certain monomers, especially those with electron-withdrawing groups, undergo this type of polymerization efficiently.

Transcript

00:01 This is the answer to chapter 3.

00:04 Problem number 12 from the smith organic chemistry textbook.

00:08 And this problem is asking us to draw the results, the product of two anionic polymerizations.

00:17 And so remember, this relates to apocity.

00:22 And the polymer -making bonds that we form are going to be carbon -oxygen bonds rather than carbon -carbon bonds.

00:31 And so we should start by considering the epoxide that we're given.

00:41 And so here is our monomer.

00:46 This is the epoxide that we have for a.

00:49 And we should think about what that's going to look like once it's opened.

00:54 And from there, we can begin to get the answer.

01:01 So the way that a lot of these answers look for these, this type of polymerization, is you just draw the central unit once in brackets with this n notation.

01:17 So the lowercase n.

01:19 And that basically just indicates that it's repeating as many times as you'd like.

01:24 And so having drawn that, we then need to think about what our open -de -opoxide is going to look like.

01:34 And so in this case, it's going to look like, oops, where'd that line go? in this case, it's going to look like this.

01:43 And so it'll be a bond there.

01:48 It will be a bond there.

01:50 And so this central unit here is our open -de -opoxide.

02:00 And again, it's in the end brackets.

02:03 And so this means that it repeats, you know, indefinitely, and number of times.

02:11 And then the only other thing we need to draw is what the two ends of this polymer are going to look like.

02:18 So each of the ends of this polymer is just going to be another open -opoxide.

02:29 But an opened epoxide with another hydroxy on it.

02:35 Because remember hydroxy is going to open the epoxide to begin with to sort of kick this whole process off.

02:44 And so our end pieces are going to have hydroxy functionality on them...

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