Synthesis of poly(phenyleneethynylene)s using calcium carbide

Abstract

Our research focused on the development of the synthesis of poly(phenylene-ethynylene)s (PPEs) from primary chemical feed stock calcium carbide and aryl diiodides via the Pd-catalyst cross coupling reaction. The reaction proceeds smoothly at ambient temperature with all commercially inexpensive reagents to generate the PPEs in satisfactory yields (60-93%) after double precipitation with methanol. Moreover, a number of PPEs which containing various substituent such as butyloxy, octyloxy, ethyhexyloxy, methyl diethoxy and oxypropanol are successfully prepared in excellent yields (71-93%). The GPC data of the resulting PPEs show the narrow polydispersity index (PDI) vary from 2.0 to 2.5 and high degree of polymerization (DP) ranging from 35 to 130. When compare these data with the conventional method, it indicates that our PPE show equal or better properties in term of DP and PDI. Interestingly, NMR characterizations of PPEs indicate that no homocoupling of alkyne in the PPE structure suggesting defect free PPEs is obtained from this method. The photophisical properties of prepared PPEs are also investigated showing high quantum efficiency of the polymers (0.34 - 0.71).