Poly(3-ether substituted thiophene)s: Structures and properties

Poly(3-ether substituted thiophene)s are prepared from chemical oxidation with FeCl3 and have the structures: where (i) X  H; Y  (OC 7 H 15 ) 1 , (O(CH 2 ) 2 OC 4 H 9 ) 2 , (O(CH 2 )O(CH 2 )OCH 3 ) 3 ; (ii) X  CH 3 ; Y  (OC 7 H 15 ) 4 , (O(CH 2 ) 2 OC 4 H 9 ) 5 ; (iii) X  H; Y  (CH 2 OC 6 H 13 ) 6 ; (iv) X  H; Y  ((CH 2 ) 2 OC 5 H 11 ) 7 . The polymers of type (i) are crosslinked; only their oligomers are soluble. The polymer of type (iii) can not be obtained from its monomer by the present chemical method, since its monomer contains an allylic oxygen, which is easy to be attacked. The polymers of type (ii) and (iv) are soluble and have high molecular weight. FeCl3-doped polymer 7 at the doping level 0.04 is soluble and can be cast into flexible free standing film with a conductivity of 10−4S /cm. Those with an oxygen atom in the repeated unit of the side chain (polymers 4 and 7) have lower conjugation length in solution and solid forms in comparison with poly(3-octylthiophene) (P3OT) and have no appreciable thermochromism. The oxidation potential of polymer 7 is 1.0 V/SCE which is comparable with that of P3OT (1.01 V/SCE). Polymer 5, which has two oxygen atoms in the repeated unit, has higher conjugation length (λmax=535 nm) and lower oxidation potential (0.6 V/SCE) compared to P3OT (λmax = 500 nm, 1.01 V/SCE).