Periodic Polymerization and the Generation of Polymer Giant Vesicles Autonomously Driven by pH Oscillatory Chemistry.

Jinshan Guo,Juan Pérez-Mercader,Eszter Poros-Tarcali

doi:10.3389/fchem.2021.576349

Jinshan Guo, Juan Pérez-Mercader + Show 1 more

Open Access

https://doi.org/10.3389/fchem.2021.576349

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Abstract

Using the radicals generated during pH oscillations, a semibatch pH oscillator is used as the chemical fuel and engine to drive polymerization induced self-assembly (PISA) for the one-pot autonomous synthesis of functional giant vesicles. Vesicles with diameters ranging from sub-micron to ∼5 µm are generated. Radical formation is found to be switched ON/OFF and be autonomously controlled by the pH oscillator itself, inducing a periodic polymerization process. The mechanism underlying these complex processes is studied and compared to conventional (non-oscillatory) initiation by the same redox pair. The pH oscillations along with the continuous increase in salt concentration in the semibatch reactor make the self-assembled objects undergo morphological evolution. This process provides a self-regulated means for the synthesis of soft giant polymersomes and opens the door for new applications of pH oscillators in a variety of contexts, from the exploration of new geochemical scenarios for the origin of life and the autonomous emergence of the necessary free-energy and proton gradients, to the creation of active functional microreactors and programmable release of cargo molecules for pH-responsive materials.

Highlights

Amphiphilic copolymers can self-assemble into various structures, making them increasingly attractive in the design and construction of functional materials (Discher and Eisenberg, 2002)
Scheme 1 illustrates the main processes of the semibatch BrO3−−SO32– pH-oscillator driven polymerization induced self-assembly (PISA), during which the hydroxypropyl methacrylate (HPMA) is polymerized on the poly(ethylene glycol) 4-cyano4(phenylcarbonothoylthio)pentanoate (PEG-CTA) solvophilic calculated by the increase in the area of polymer peak (-CH2-C(COOR)CH3, 0.8–1.0 ppm, black line) or the decrease in the area of monomer peak (CH2, used the one at 6.1–6.2 ppm, blue line); the monomer conversions were determined by 1H-NMR spectra of the reaction mixtures sampled out at different times
Radicals generated in the semibatch BrO3− − SO32– pH oscillator can be used as chemical fuel and engine to drive polymerization induced self-assembly for the autonomous one-pot synthesis of functional giant vesicles

Summary

Introduction

Amphiphilic copolymers can self-assemble into various structures, making them increasingly attractive in the design and construction of functional materials (Discher and Eisenberg, 2002). For example, with some solvophilic macroRAFT agent (or chain transfer agent, CTA), its chain-extension with a solvophobic monomer chain generates living (in the sense of polymer chemistry) amphiphiles This non-equilibrium process brings about the simultaneous self-assembly of the amphiphiles into collective structures such as micelles, “worms” or vesicles controlled by parameters such as concentration or packing parameter (Israelachvili, 2011) of the generated amphiphiles, pH, temperature, salt concentration, etc., The uncomplicated and simple controllability of the PISA process, make PISAgenerated polymersomes excellent candidates for many applications ranging from drug delivery or macro-/nanoreactors, to protocell designs (Cheng and Pérez-Mercader, 2020; Canning et al, 2016; Yeow and Boyer, 2017)

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