Dhiraj K. Garg

Bio: Dhiraj K. Garg is an academic researcher from University of Strasbourg. The author has contributed to research in topics: Microreactor & Radical polymerization. The author has an hindex of 7, co-authored 14 publications receiving 178 citations. Previous affiliations of Dhiraj K. Garg include Shiv Nadar University & Institut Charles Sadron.

Coil Flow Inversion as a Route To Control Polymerization in Microreactors

Abstract: Linear and branched polymers of 2-(dimethylamino)ethyl methacrylate (PDMAEMA) were synthesized in flow by atom transfer radical polymerization (ATRP) and self-condensing vinyl copolymerization adapted to ATRP, respectively, in capillary type stainless steel coiled tube (CT) microreactors. Coil flow inversion (CFI) was introduced to achieve better mixing and narrower residence time distributions during polymerization. This strategy was adopted to improve control over macromolecular characteristics and polymer architecture. Polydispersity index (PDI), as an overall indicator of control over polymerization, was significantly lower for CFI in the case of linear PDMAEMA, 1.39 compared to 1.53 for CT. For branched polymers containing up to 10 mol % of inimer, a reduced PDI was also obtained for CFI microreactor. As for the branching efficiency, it was found to follow the following trend CFI > CT > batch reactor.

Flow Inversion: An Effective Means to Scale‐Up Controlled Radical Polymerization Tubular Microreactors

Abstract: Continuous-flow atom transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate in tubular microreactors of different diameters and geometries is studied. Scale-up of tubular reactors from micro (876 μm ID) to milliscales (1753 and 4083 μm IDs) is investigated. Coil flow inverter (CFI) reactors having 3 and 6 m length (three and seven bends, respectively) are also considered for this study. Positive effects of flow inversion are visible in all three types of reactors expressed by an increase in molecular weight and monomer conversion as well as a decrease in the PDI for the same operating parameters. An increase in reactor diameter results in an increase in the throughput. It is worthy to mention that a CFI reactor having 4083 μm ID and 3 m (three bends) is found to increase the throughput by ten times without significantly increasing the PDI compared to a coiled tube microreactor with 876 μm ID, 6 m and no flow inversion pattern. However, pressure drops are higher (+0.1 bar) in case of larger diameter tubes.

Analytical Solution of Free Radical Polymerization: Derivation and Validation

Abstract: An elegant, simple, and exact analytical solution (AS) was obtained for a large range of elementary steps with practical importance in free radical polymerization. The AS matches excellently with the numerical solution for the four cases of monomer–polymer systems studied ranging from the slowest to the fastest. It works equally well for different initiators, different initiator and monomer concentrations, presence or absence of solvent, various solvent volume fractions, and different temperatures. It also matches quite well with experimental data reported in the literature. This AS is not only in line with previous published solutions but also extends their applicability in a natural way. Overall, the conceptual correctness as well as predictive capabilities of the derived AS are established beyond doubt. This AS has the potential to be used in various practical applications such as model based process control, CFD simulations, and so forth.

Analytical Solution of Free Radical Polymerization: Applications- Implementing Gel Effect Using AK Model

Abstract: In this work, gel/glass/cage effects using the Achillias and Kiparissides (AK) model has been incorporated in the analytical solution (AS) obtained in our previous work. The AK model is based on the Chiu, Carratt, and Soong (CCS) model and free volume theory. The results of AS matched quite well with the numerical solutions as well as with the experimental data for methyl methacrylate (MMA). Various variables like termination kinetic coefficient, initiator efficiency, macroradicals concentration profile matched with the established published results. The work clearly demonstrates that AS is sufficiently flexible to accommodate gel/glass/cage effects explicitly although it was not primarily derived for these conditions. This extends the practical usage of AS for the whole range of conversion under isothermal conditions.

Continuous flow enzyme-catalyzed polymerization in a microreactor | nist

Abstract: Enzymes immobilized on solid supports are increasingly used for greener, more sustainable chemical transformation processes. Here, we used microreactors to study enzyme-catalyzed ring-opening polymerization of ε-caprolactone to polycaprolactone. A novel microreactor design enabled us to perform these heterogeneous reactions in continuous mode, in organic media, and at elevated temperatures. Using microreactors, we achieved faster polymerization and higher molecular mass compared to using batch reactors. While this study focused on polymerization reactions, it is evident that similar microreactor based platforms can readily be extended to other enzyme-based systems, for example, high-throughput screening of new enzymes and to precision measurements of new processes where continuous flow mode is preferred. This is the first reported demonstration of a solid supported enzyme-catalyzed polymerization reaction in continuous mode.