Side Reactions in Aqueous Phase Polymerization of N‐Vinyl‐Pyrrolidone as Possible Source for Fouling

Abstract

A first intense investigation in the kinetics of radical polymerization of NVP was done by Senogles et. al. [7] They revealed a variation of the activation energy for the propagation step Radical PolymerizationAn improved kinetic model for the radical polymerization of N-vinyl-pyrrolidone (NVP) in aqueous medium is developed. Quantum chemical simulations reveal that the transfer to polymer is of minor importance whereas the transfer to monomer by hydrogen abstraction in 3-position of the pyrrolidone ring leads to a radical with a double bond which initiates a new chain bearing a terminal double bond (TDB). The resulting dead chains with one, two, or more TDB are the main source for a strong increase of molar mass in batch reactors at high conversion due to long chain branching and crosslinking. This can be a source for gel formation and fouling in continuous reactors. www.advancedsciencenews.com www.mre-journal.de

Modeling Strategies for the Propagation of Terminal Double Bonds During the Polymerization of N‐Vinylpyrrolidone and Experimental Validation

“…The reaction scheme we assume in this article was identified and discussed in detail in ref. [9]. Initiation, propagation of monomer M and termination are the main reactions in the radical polymerization of NVP in aqueous solution and lead to linear polymer chains.…”

“…Since the complexity of the model would increase even further, we will not consider this here and restrict the model to species with either zero or one radical center as in ref. [9]. We refer to these as the dead species P and living species R respectively.…”

“…[ 8 ] Recently, another mechanism has been suggested in which creation of terminal double bonds (TDBs) by transfer to monomer and subsequent propagation of TDBs is the reason for long chain branching. [ 9 ] The suggestion was motivated by calculations from density functional theory (DFT) and validated by batch experiments.…”

“…Since these objectives are contradictory, multiple models with different levels of detail need to be developed and the informational content must be transferred consistently between levels. For this purpose, we apply two modeling approaches, the classes [ 10,11 ] and the pseudodistribution approach, [ 10,12–14 ] to handle the multidimensional property distributions that result from the reaction mechanism described by Deglmann et al [ 9 ] We condense the detailed information gained from simulations using these models and use it to develop much simpler models with significantly lower computational effort. To refine the kinetic coefficients from ref.…”

“…To refine the kinetic coefficients from ref. [9] and to test the predictive capability of the models, we compare simulation results with experimental results for monomer conversion, molecular weight averages and molecular weight distributions from CSTR experiments.…”