Polymer Molecular Weight Analysis by ¹H NMR Spectroscopy

Abstract

The measurement and analysis of molecular weight and molecular weight distribution remain matters of fundamental importance for the characterization and physical properties of polymers. Gel permeation chromatography (GPC) is the most routinely used method for the molecular weight determination of polymers whereas matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a fast-emerging absolute, and therefore accurate, technique. Although NMR spectroscopy is one of the most powerful tools available for polymer microstructure characterization, among others, its utility in the molecular weight analysis of polymers is somewhat underappreciated. It is a reliable and more readily available teaching tool in comparison to other known techniques, such as GPC and MALDI-TOF MS, for the molecular weight determination of polymers. Demonstrated herein are the simplicity, reproducibility, and convenience of 1H NMR spectroscopy in the analysis of polymer number-average molecular weight (M n), using α-methoxy-ω-aminopolyethylene glycol (MPEG-NH2) and α-methoxy-polyethylene glycol-block-poly-ε-(benzyloxycarbonyl)-l-lysine (MPEG-b-PLL(Z)) as model homopolymer and block copolymer, respectively. The molecular weight data from 1H NMR analysis are compared to those from GPC and MALDI-TOF MS.

Multi-responsive fluorescence of amphiphilic diblock copolymer containing carboxylate azobenzene and N-isopropylacrylamide

“…2 reflects an obvious shift of elution time between the macro-RAFT agent PNIPAm-CPDB and the block copolymer PNIPAm-b-PM6AzCOONa, which further indicates the formation of the azobenzene-containing block copolymer. The difference between M n (GPC) and M n ( 1 H NMR) values was likely due to the differences in hydrodynamic volumes of PM6AzCOONa block and polystyrene standards [47,48]. In addition, the welldefined molecular structure of block copolymer was also confirmed by comparison of its 1 H NMR spectra in different solvents, which were provided in supporting information (Fig.…”

1H NMR Spectroscopy as an Effective Method for Predicting Molecular Weight of Polyaminoamine Dendrimers and Their Derivatives

“…In addition, it has been used as a qualitative and quantitative method for evaluating reaction progress in organic synthesis, [1] molecular weight of polymers in polymerization or condensation, [2][3][4][5] degree of functionalization, [6] composition of organic molecules, [7,8] and metabolization in pharmacological assays. [9] In comparison with gas chromatography (GC), gel permeation chromatography (GPC).…”

Synthesis and Characterization of Lignin-Based Polyurethane as a Potential Compatibilizer

“…To confirm the structure of molecules and reactions, lignin-based polyurethane was characterized by [14]. Sessile drop was used to calculate surface tension using Zisman equation [15]:…”