# Can you have addition polymerisation with monomers other than alkenes?

Every example of addition polymerisation I have seen so far has used alkenes as the monomers. I was wondering if it is possible to have some other molecule. I don't think the following molecule can exist due to stability reasons, but as an example could you not use something like

$$\ce{H-N=N-H}\,?$$

Surely all you need is the presence of a double bond?

You're right, the monomer needn't be an alkene. Non-alkenes with double bonds can also form addition polymers. In fact, the monomer needn't always have a double bond either! Surprised? Take a look at this:

(Image source: chemwiki.ucdavis.edu)

• the linked reaction is a condensation polymerisation not an addition polymerisation – bon Jan 5 '15 at 18:06
• What molecule is removed in this "condensation" reaction? Thought so ... this is an addition! – Oscar Lanzi May 18 at 1:50

$$\ce{N2H2}$$ is a very unstable molecule, prone to disproportionation into hydrazine and nitrogen. $$\ce{N-N}$$ bonds except one in $$\ce{N2}$$ molecule are unstable and generally unfavorable. So, no there are no polymers with nitrogen as a sole component of the main chain.

Several classes of compounds of 3-row elements demonstrate tendency for oligomerization, namely $$\ce{(HP)_{n}}$$ derivatives usually exist as a ring. It is possible to obtain metastable at room temperature plastic sulfur, containing linear sulfur chains terminated by free radicals.

However, generally when in search of easily polymerizing molecule that produce main chain containing elements other than carbon, one usually have to look into compounds producing chains with two elements. The most common and known one is formaldehyde $$\ce{CH2=O}$$, producing $$\ce{HO-(CH2-O)_{n}-H}$$ chains. A less known, but interesting example is hexachlorotriphosphazene, the source material for production of Polyphosphazenes.

In general, metastable double bonds are rare for elements other than carbon (sometimes with nitrogen or oxygen partners), so usually reactions intended to produce such bonds, say, $$\ce{Si=Si}$$ usually end with olygomer instead, typically of ring structure. Moreover, single homoelemental bonds are usually much weaker for elements other than CHNOB, so typically when a chains containing other elements is occurred, it is usually hetero-atomic chain, produced by means other than olygomerization of double-bond containing monomer. For example, an extremely wide-used family of polymers (polysiloxanes, or silicones) is produce by hydrolisys of dialkyldicholorsilanes $$\ce{R2SiCl2}$$.

To my knowledge, diazene (diimine, $\ce{N2H2}$) does not polymerize but simply decomposes (to hydrazine and nitrogen). Even in the polymerization azobenzene-substituted vinylethers (consider azobenzene as diazene in with both hydrogen atoms are replaced by phenyl rings), the $\ce{N=N}$ double bond does not participate in the polymerization.

But you are right, a lot of copolymers consists of monomers in which the polymerization does not take place at $\ce{C=C}$ bonds.

Think in the reaction of $\ce{\alpha,\omega}$-diols

• with phosgene ($\ce{COCl2}$) to polycarbonates
• with diisocyanates to polyurethanes

or the reaction of dianhydrides with diamines to polyimides.