Determination of the Molecular Weight of Conjugated Polymers with Diffusion-Ordered NMR Spectroscopy

Kaichen Gu, Jonathan Onorato, Steven Shuyong Xiao, Christine K. Luscombe, Yueh Lin Loo

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Size exclusion chromatography (SEC) is not well suited for characterizing the molecular weight (MW) and MW distribution of conjugated polymers, especially those that absorb strongly at the detection wavelengths, or those that interact with and adsorb on the walls of SEC columns. We demonstrate diffusion-ordered NMR spectroscopy (DOSY) as a complementary method for characterizing the size and size distribution of conjugated polymers. Starting with four batches of poly(3-hexylthiophene), whose distinct and narrow MW distributions had been fully characterized, as a model system, we establish a power-law relationship between the weight-average MW and the diffusion coefficient measured through DOSY. We extend this approach to characterizing poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine], whose absorption properties preclude its characterization with light scattering based techniques, including SEC. By applying the same power law on the diffusion coefficients obtained by DOSY measurements, we extracted P3HT-equivalent MWs and MW distributions for six different batches of PCDTPT. By circumventing the practical issues in SEC measurements, DOSY shows promise as a versatile complement for determining polymer size.

Original languageEnglish (US)
Pages (from-to)570-576
Number of pages7
JournalChemistry of Materials
Issue number3
StatePublished - Feb 13 2018

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry


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