Microwave‐assisted nitroxide‐mediated polymerization for water‐soluble homopolymers and block copolymers synthesis in homogeneous aqueous solution

Abstract

We performed a critical reinvestigation of microwave enhancement of nitroxide-mediated polymerization (NMP) of acrylamide (AM) in aqueous media in the dynamic (DYN) mode with a combination of a conventional hydrosoluble radical initiator and a b-phosphonylated nitroxide (SG1). Based on the results of our previous work, a complementary series of polymerization reactions was carried out between 130 and 160 C using only the DYN mode to ascertain the existence of a microwave effect. The polymer conversion (p), molar masses, polydispersity index, and viscosity of each sample were measured. The temperature was monitored inside and outside of the vessel using an optical fiber sensor and an IR sensor, respectively. Microwave enhancement of polymerization, temperature control and viscosity of the reaction media were closely related. We also furthered the field of hydrophilic AB diblock copolymer synthesis using a tertiary SG1-based macroalkoxyamine and directly synthesized both poly(acrylamide-b-sodium 2-acrylamido-2-methylpropanesulfonate), a neutral-b-anionic diblock copolymer, and poly(acrylamide-b-3-dimethyl(methacrylamidopropyl)ammonium propanesulfonate), a neutral-b-zwitterionic diblock copolymer, in homogeneous aqueous media. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [5775][5776][5777][5778][5779][5780][5781][5782] 2010

Green Polymer Synthesis: An Overview on Use of Microwave‐Irradiation

“…The ATRP of acrylonitrile with FeBr 2 /isophthalic acid/2-bromopropionitrile under MW conditions showed much higher polymerization rate as compared to the rate obtained under conventional refluxing with tetrachloromethane [98]. MW-assisted nitroxide-mediated radical polymerization of acrylamide in aqueous solution was reported by Rigolini et al [99]. Facile RAFT precipitation polymerization for the microwave-assisted synthesis of well-defined, double hydrophilic block copolymers and nanostructured hydrogels was also reported [100].…”

Synthesis of Glycopolymer Architectures by Reversible-Deactivation Radical Polymerization

“…To date, NMP has been extended to almost all monomers with the exception of vinyl esters and vinyl chloride. Also, SG1 and SG1-derived initiators (essentially BlocBuilder MA) have been applied to the polymerization of acrylamide- [234][235][236], styrenic- [234], acrylate- [234] and methacrylate-monomers [233,237], directly in homogeneous aqueous solution. Nevertheless, the use of a small fraction of comonomer (typically 8% of acrylonitrile for methacrylates, or sodium 4-styrenesulfonate for methacrylic acid) proved essential for the system to work at T < 100 °C and even then the dispersity index was systematically higher than 1.20.…”

A Critical Investigation on the Occurrence of Microwave Effects in Emulsion Polymerizations

“…While infrared sensors (IR sensors) are the most common and cheapest solution for temperature measurement, they are only reliable if they are carefully calibrated and systems of low viscosity are studied . In polymer synthesis, low‐viscosity reaction mixtures tend to be the exception rather than the rule, therefore the combination of an IR sensor and an internal fiber optical probe (FO) has been shown to be the preferred choice of temperature measurement for most accurate and reliable representations of the temperature profile in microwave‐assisted polymerization processes . For the investigation of specific or nonthermal microwave effects, it is important to carefully replicate the microwave‐heated experiments under conventional conditions, paying particular attention to the temperature profiles, including heating and cooling ramps .…”