Coupling of NMR to ACOMP for Terpolymerization Monitoring and Control

Abstract

Monitoring and control of free radical copolymerization using automatic continuous online monitoring of polymerization reactions (ACOMP) with UV detection has been recently achieved. It is difficult, however, to achieve spectral separation of similar monomers with UV alone. Here, nuclear magnetic resonance (NMR) is coupled to ACOMP for the first time and terpolymerization reactions involving acrylamide (Am), sodium acrylate (Ac), and styrene sulfonate (SS) are monitored, and a first attempt at active composition control is made. The NMR resolves the concentrations of Am and Ac, while the UV resolves SS and the sum of Am and Ac. NMR analysis is performed in water, using signal suppression, to eliminate the need for deuterated solvents. From this, instantaneous fractions of each comonomer in the terpolymer are continuously known, along with weight average molecular weight and intrinsic viscosity, IV. Am and Ac have similar reactivities, whereas the reactivity ratio of SS is much larger. Hence, there is high composition drift in batch polymerization and SS is rapidly consumed, leaving a final copolymer of Am and SS to form. Maintaining constant terpolymer composition is taken as a first step toward active control.

Enabling technologies in polymer synthesis: accessing a new design space for advanced polymer materials

“…182 Adapted with permission from Brotherton et al 179 While each of these analyses can be used in isolation to monitor a polymerisation in some fashion, a comprehensive monitoring option is offered by Reed and co-workers in the form of their automatic continuous online monitoring of polymerisations (ACOMP) technology, which is extensively documented. 138,[183][184][185][186] A range of analyses are integrated into a single platform including light scattering, viscometry, 187 refractometry, 183 UV/Vis, 183,188 IR/NIR, 189 light scattering 187,190 and (more recently) NMR 191 spectroscopy which automatically samples from a reaction mixture and performs a series of measurements. Data is then processed according to the appropriate calculations, and detailed information regarding conversion and molecular weight is outputted.…”

“…Step-growth, 144 SET-LRP, 31 free radical [147][148][149] (and emulsion 151,152 Free radical solution, 183,185,[188][189][190] NMP, 184 step-growth, 187 controlled radical 191…”

Observation and Modeling of a Sharp Oxygen Threshold in Aqueous Free Radical and RAFT Polymerization

“…Fundamental information about the reaction and the product can be obtained through a variety of detectorsmonomer conversion and copolymer composition (cumulative and instantaneous) from ultraviolet (UV) absorption spectroscopy, cumulative and instantaneous reduced and intrinsic viscosity (RV and IV, respectively) from capillary viscometry, and weight-average molecular weight ( M w ) (cumulative and instantaneous) from multi-angle static light scattering (MALS). The detection module can be customized to include other instruments, such as a Fourier transform infrared spectrometer, a refractive index (RI) detector, dynamic light scattering, conductivity, polarimetry, and online nuclear magnetic resonance . The model-free data gathered with ACOMP is what makes it such an invaluable tool for both tracking and modeling reaction kinetics, as well as controlling specific parameters of these reactions.…”

Continuous Monitoring and Characterization of Copolymerization Reactions of Acrylate Monomers with Indistinguishable Ultraviolet Spectra Using Infrared Spectroscopy

“…Recently, the terpolymerization of acrylamide (Am), sodium styrene sulfonate (SS), and sodium acetate (NaAc) was monitored and controlled by coupling the ACOMP system with a nuclear magnetic resonance (NMR) instrument. [ 16 ] Among multi‐monomer systems such as Am–SS–NaSS, it is known that calculating comonomer concentration is specifically challenging when monitoring most acrylate monomers, as their UV spectra are essentially identical. The development of accurate new methods that overcome this issue is of high interest, given that production of polyacrylates is a $2.2B market in the United States alone, and is expected to reach $4B globally by 2027.…”