Conjugated polymers have elicited the attention of researchers as a promising class of materials in organic electronics for more than two decades. Particularly, poly(3-hexylthiophene) (P3HT) has garnered great interest due to its solution processability, stability, and mechanical flexibility.  However, absolute determination of molecular weight for P3HT has remained ambiguous.  Conventional calibration of size-exclusion chromatography (SEC) has proven effective for many flexible polymers but has been shown to overestimate molecular weight of P3HT by a factor of 1.6-2.0.  Light scattering (LS) can give absolute molecular weights of polymers when the refractive index increment (dn/dc) is known.  It would be advantageous for true molecular weight to be found in a single step.  We endeavored to apply universal calibration (UC) for SEC to P3HT samples.  UC is based on hydrodynamic volume versus retention time rather than molecular weight versus retention time with conventional calibration.  The values obtained from UC were compared with those obtained using LS.  To ensure the highest possible level of certainty in the LS data, dn/dc of every sample was measured.  We observed a poor correlation between light scattering data and UC.  We also discussed the possible reason for such discrepancy. 

Failure of universal calibration to determine molecular weight of poly(3-hexylthiophene)

247th National Meeting (2014)

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