can maleic anhydride dimerize or in other words react with itslef?

Answer 1

yes, with photoreactions, or with Molybdenum complexes. These reactions are well documented (see your friend google)>

Answer 2

I cnat find anything in hte enternet and I mean not like photoreaction just at room temperature will it react?

Answer 3

The reaction will occur at room temps, but elevated favors the reverse reaction.