Improved Mechanistic Insights into Radical Sulfinyl Precursor MDMO-PPV Synthesis by Combining Microflow Technology and Computer Simulations

Abstract

A kinetic model using Predici is developed and applied to obtain an improved mechanistic understanding of the radical sulfinyl precursor polymerization route for poly(2-methoxy-5-(3′-7′-dimethyloctyloxy-4-((octylsulfinyl)methyl))-1,4-phenylenevinylene) (MDMO-PPV) synthesis. In this route, the premonomer1-(chloromethyl)-5-((3,7-dimethyloctyl)oxy)-2-methoxy-4-((octylsulfinyl)methyl) benzene (MDMO)is subjected to a base-induced elimination reaction using NatBuO as base and s-BuOH as solvent. Microreactors are used to ensure rapid mixing of reaction components and sharp quenching at precisely determined time points. Systematic kinetic data that follows the very fast precursor polymerizations with reaction time have in this way become available for the first time. Via the applied kinetic model, the presence of a chain transfer reaction is unambiguously confirmed and kinetic rate coefficients have been deduced, which fall within the typical expectations of radical chain reactions. Two models were further compared, one including chain reinitiation (noninhibition model) and one excluding reinitiation (inhibition model) of the by chain transfer-generated radical species. Investigation of trend lines suggest a preference of the reinitiation model, thereby implying that MDMO-PPV synthesis follows mostly a conventional free radical polymerization mechanism that only differs with respect to its initiation mode and the biradical nature of the propagation step.

Gilch Synthesis of Poly(ortho -Phenylene Vinylenes): A Powerful Access to High-Molecular-Weight Blue-Emitting Polymers

“…In particular, we analyze the significance of competitive Diels–Alder reactions of ortho ‐quinodimethane monomers depending on the substitution pattern. We correlate the findings with latest mechanistic insights into the Gilch synthesis and validate the potential of the reported method with related approaches such as cyclopolymerization of 1,7‐octadiynes …”

An Update on the Pivotal Role of Kinetic Modeling for the Mechanistic Understanding and Design of Bulk and Solution RAFT Polymerization

“…Hence, it is not surprising that deterministic methods for the full CLD calculation have been developed to a limited extent only . The most popular deterministic full CLD method is the discretized Galerkin h‐ p ‐method (dGhp), as explored by Wulkow et al and applicable via the commercial package PREDICI . For RAFT polymerization, one of the earliest PREDICI contributions paid attention to the influence of RAFT specific kinetic parameters on the temporal evolution of the CLD and monomer conversion.…”

Going Beyond the Carothers, Flory and Stockmayer Equation by Including Cyclization Reactions and Mobility Constraints

“…In linear step-growth polymerizations, intramolecular reactions are rarely considered in modeling studies, as they are rather unlikely to happen, although small rings have been mentioned [ 57 , 58 , 59 , 60 ], causing deviations from Equation (5) (and Equation (1)). The same holds for free radical polymerization (FRP) systems, where the occurrence of cyclization reactions has been confirmed for a limited number of cases, including, for instance, short-chain biradicals [ 61 , 62 ]. The situation is different if one uses multifunctional instead of bifunctional monomers in step-growth polymerization, where it is expected that intramolecular reactions play a more important role, as many FG combinations for intramolecular reactions can be identified, especially close to the “gel point”.…”