# Conjugated polymers/materials

1. Mar 28, 2015

### Agalev

• Please post this type of questions in HW section using the template. You have to show your attempts at solving the problem to receive help, this is a forum policy.
Hey,

I'm having a problem for some time finding out which of these materials are conjugated polymers and which aren't.

2. Mar 28, 2015

### Staff: Mentor

How are they defined?

3. Mar 28, 2015

### Agalev

This is the only thing I got are the pictures and the defenition of conjugated materials. But I don't know which one's have pi-bonds

4. Mar 28, 2015

### Staff: Mentor

Sole presence of pi bonds is not enough.

But lets start from here. What is a pi bond? Where is it present?

5. Mar 28, 2015

### Agalev

There has to be an alternating single and double bond like in the second molecule. Also in the thirth a double bound can shift to a single

6. Mar 28, 2015

### Staff: Mentor

There are no alternating single and double bonds in the second molecule!

7. Mar 28, 2015

### Agalev

they have to be round molecules? So 3,4 and the last one are the conjugated polymers

8. Mar 28, 2015

### Staff: Mentor

Nope. What does "alternate" mean? Compare

-=-=-=-=-=-

and

---=---=---=---

Which one would you call "alternate"?

9. Mar 29, 2015

### Agalev

Yes the first one is alternating. But how does the alternation work when the molecule is round? Is it like the last molecule?

10. Mar 29, 2015

### Staff: Mentor

It doesn't have to go all the way around, but in general it is the same, you are looking for a path consisting of alternate double/single bonds.

To make things more complicated some of these "round" systems are aromatic, which makes their properties different, but that's another story.

11. Mar 29, 2015

### Agalev

Ok thanks for your help so far! I thought alternating meant that a bound switches from single to double and vicacersa.

So they are all conjugated except for te second one?

Or is something else to be conciderid for the aromatic compounds?

12. Mar 29, 2015

### Staff: Mentor

Fro the polymer to be considered conjugate I don't think it is enough that it contains conjugate bonds - I think the conjugate bond system must extend to the whole molecule (which means it must go through the "main linking chain" of the polymer).

13. Mar 29, 2015

### Agalev

Thanks a lot, you helpt me a great deal