Free radical polymerization of butyl acrylate in monodispersed droplets: Comparison between two heating strategies

Abstract

Monodispersed droplets could be easily generated in coaxial microdevice, and a reaction based upon these discrete droplets is an attractive approach thanks to isolated reaction units, efficient mixing, and precise residence time control. In this work, free radical polymerization of butyl acrylate was conducted in monodispersed droplets of several hundred microns. Two different heating methodologies, microwave heating and conventional heating with oil bath were adopted to initiate polymerization, respectively. The polymerization under conventional heating could be regarded as an isothermal process, while the polymerization under microwave heating gradually underwent a temperature increase. So the poly (butyl acrylate) obtained by microwave heating has larger average molecular weight and higher polydispersity index. Meanwhile, the conversion of butyl acrylate was significantly improved by microwave heating compared with conventional heating, even though the reaction temperature under microwave heating might be lower than the temperature of the oil bath. This remarkable enhancement was a direct proof of the nonthermal effect of the microwave field for free radical polymerization.

Role of External Field in Polymerization: Mechanism and Kinetics

“…A successful droplet-flow process was employed to FRP of BA under both MWH and CH. 1016 Enhanced polymerization rate and broader molar mass distribution were found for the microwave-assisted polymerization as compared to the CH counterpart. The authors attributed the rate enhancement and the higher dispersity to the promoted decomposition of AIBN and nonisothermal process under MWH, respectively.…”

“…On the other hand, microwave irradiation has also been widely utilized in the heterogeneous systems, such as suspension polymerization, , emulsion polymerization, − and dispersion polymerization. − In comparison with polymerization under conventional heating, microwave-assisted heterogeneous systems showed some advantages in terms of the significant decrease in the reaction time, considerable improvement in yield, and more uniform morphology of the obtained polymer particles. Additionally, microwave irradiation has also been utilized to promote the MOF-based catalytic radical polymerization …”

Direct measurement of the differential pressure during drop formation in a co-flow microfluidic device

“…Co-flow microchannels and similar co-flow junction geometries have been utilized quite extensively by researchers in the field of microfluidics to study important fundamental scientific topics such as dynamic interfacial tension and the formation of monodispersed and complex drop populations and to explore novel methods for the fabrication of functional materials. [16][17][18][19][20][21][22] However, no simple and reliable method for the detection of the inner channel pressure has been developed, thereby limiting the scope to which this co-flow junction's structure may be applied. Herein, we choose such a microchannel structure as an example to show that the CLG could be used in structures where traditional sensors are typically unavailable.…”

Microwave-Induced Grafting of Maleic Anhydride onto the Surface of a Polypropylene Film for High Adhesion to Polyamide 6

“…However, the mechanical properties of the polymer are adversely affected to some degree under irradiation environments, and the cost of irradiation equipment and energy consumption are high. , Compared with these, microwave irradiation is a special case, which can be effectively absorbed by polar substances but has no effect on nonpolar materials like PP . Because the polar molecules of the initiator vibrate sharply with the high-frequency periodic change of the electric field under microwave irradiation, the decomposition rate of the initiator can be accelerated at low temperatures. , As a result, the efficiency of the surface grafting reaction induced by microwave irradiation is high, while the bulk properties of PP are not influenced by surface modification. , …”

“…27 Because the polar molecules of the initiator vibrate sharply with the high-frequency periodic change of the electric field under microwave irradiation, the decomposition rate of the initiator can be accelerated at low temperatures. 28,29 As a result, the efficiency of the surface grafting reaction induced by microwave irradiation is high, while the bulk properties of PP are not influenced by surface modification. 20,30 Presently, several research studies used microwave-induced methods to graft MAH onto PP for the improvement of mechanical properties and wettability.…”