Poly -phenylene alkanedioate s

Almost a mirror image of poly(alkylene terephthalate)s (PAT), these polymers are essentially polyesters formed from aliphatic diacids and hydroquinone (1,4-dihydroxybenzene), giving the general structure  

The P hydrogen atoms necessary for the chain scission via cyclic intermediate much cited for the preceeding classes of polyester are absent. It is therefore thought that thermal degradation will occur selectively by ester exchange to produce high yields of cyclic 

---