Molecular Weight Characterization of Conjugated Polymers Through Gel Permeation Chromatography and Static Light Scattering

Abstract

Molecular weight is a key parameter of any polymer. Characterizing the molecular weight of conjugated polymers is often nontrivial due to their semiflexible backbones and poor solubilities. Perhaps the most used technique for measuring the molecular weight is gel permeation chromatography (GPC), and results are often calibrated relative to flexible polymer standards. This mismatch between chain flexibilities of samples and standards, combined with poor sample solubility in the mobile phase, leads to inaccuracies in many GPC measurements of conjugated polymers. In this work, we use a universal calibration combined with in-line concentration measurements to yield reliably accurate results for polymers of various stiffnesses. Accuracy of results is verified with absolute molecular weights obtained from static light scattering. We show that measuring the refractive index increment is key to confirm full recovery of the polymer and ensure accurate values of the absolute molecular weight from GPC.

Chain Stiffness of Donor–Acceptor Conjugated Polymers in Solution

“…Chloroform with 0.25% triethylamine at 25 °C was used as the mobile phase with a flow rate of 1 mL/min. A refractive index detector (Wyatt Optilab rEX), photodiode array detector (Waters 2996 PDA), viscometer (Wyatt ViscoStar), and low-angle light scattering detector (Wyatt DAWN HELEOS II, 663.1 nm laser) were used to access the absolute molecular weight and molecular-weight distribution of the polymers . The number-average molecular weight M n and dispersity Đ are reported in Table .…”

“…A refractive index detector (Wyatt Optilab rEX), photodiode array detector (Waters 2996 PDA), viscometer (Wyatt ViscoStar), and low-angle light scattering detector (Wyatt DAWN HELEOS II, 663.1 nm laser) were used to access the absolute molecular weight and molecular-weight distribution of the polymers. 40 The number-average molecular weight M n and dispersity Đ are reported in Table 1. Full dissolution and the absence of large aggregates were confirmed by dynamic light scattering with a DynaPro NanoStar using a laser power of 100 mW and a wavelength of 662 nm.…”

Accurate Quantitation of the Phenyl Group in Methylphenylsilicone Oils by GPC-UV

“…[14][15][16] The common detector in classical GPC instruments is differential refractive index detectors, which also have low sensitivity and narrow linear range in quantitative analysis . [17][18][19] The UV absorption detector, however, is an ideal detector with relatively high sensitivity, superior stability, wide detection range and good selectivity . [20,21] Combination of UV with GPC has been used for quantifying substances and for locating the location of certain groups in polymers .…”

Conjugated Polymers in Solution: A Physical Perspective

“…28 Static light scattering (SLS) can obtain the molecular weight and mean-square radius of gyration (R g ) of polymers. 29 However, because the solution of conjugated polymers would absorb a certain amount of incident light and diminish the signal intensity, the intensity should be corrected. In recent years, transmission electron microscopy (TEM) and other related advanced techniques (such as cryo-TEM, tomography, etc.)…”

“…Dynamic light scattering (DLS) is concerned with the dynamic behavior of polymer chains in solution, probing the translational motion of single chains in dilute solution . Static light scattering (SLS) can obtain the molecular weight and mean-square radius of gyration ( R g ) of polymers . However, because the solution of conjugated polymers would absorb a certain amount of incident light and diminish the signal intensity, the intensity should be corrected.…”