Facile Synthesis of CO₂‐Responsive Nano‐Objects: Batch versus Semi‐Batch RAFT Copolymerization

Abstract

Precise polymer architecture and self‐assembled morphological control are attractive due to their promising applications, such as drug delivery, biosensors, tissue engineering and “smart” optical systems. Herein, starting from the same hydrophilic units poly(ethylene glycol) (PEG), using CO2‐sensitive monomer N, N‐diethylaminoethyl methacrylate (DEAEMA) and hydrophobic monomer benzyl methacrylate (BzMA), a series of well‐defined statistical, block, and gradient copolymers is designed and synthesized with similar degree of polymerization but different monomer sequences by batch and semi‐batch RAFT polymerization process and their CO2‐responsive behaviors of these nano‐objects is systematically studied. The gradient copolymers are generated by using semi‐batch methods with programmed monomer feed rate controlled by syringe pumps, achieving precise control over desired gradient copolymer composition distribution. In aqueous solution, the copolymers could self‐assemble into various aggregates before CO2 stimulus. Upon bubbling CO2, the gradient copolymers preferred to form nanosheet‐like structures, while the block and statistical copolymers with similar molar mass could only form larger vesicles with thinner membrane thickness or disassemble. The semi‐batch strategy to precisely control over the desired composition distribution of the gradient segment presents an emerging trend for the fabrication and application of stimuli‐responsive polymers.

Carbon Dioxide Capture by Emerging Innovative Polymers: Status and Perspectives

“…[ 202 ] Guo et al, for example, utilized hydrophilic units of PEG, CO 2 ‐sensitive monomer of N , N ‐diethylaminoethyl methacrylate (DEAEMA), and the hydrophobic monomer of benzyl methacrylate (BzMA) to synthesize a variety of well‐defined statistical, block, and gradient copolymers. [ 203 ] By employing both batch and semibatch RAFT polymerization techniques, this process resulted in CO 2 ‐responsive nano‐objects that self‐assembled with bubbling CO 2 to nanosheet‐like structures for the gradient copolymers and large vesicles with thinner membrane thickness for the block and statistical copolymers. Moreover, Guo and co‐workers reported a facile synthesis for producing well‐defined CO 2 ‐responsive gradient copolymers, denoted as PBzMA‐ b ‐P(DEAEMA‐ grad ‐NVP)‐ b ‐PNVP, using switchable RAFT polymerization.…”

CO2-responsive gels

“…[87][88][89] Similarly, CO 2 -induced self-assembled structures with complex morphologies have been realised including vesicles, 90,91 worm-like micelles, [92][93][94] and nano-objects. [95][96][97] As a subset of CO 2 -responsive polymers, gels (i.e., cross linked polymers) have attracted increased interest over recent years due to advantages provided by their insolubility and the range of particle sizes that they can embody (from nanogels to macrogels). In addition, the use of CO 2 as a gelling stimulus has been used to explore several interesting and practical applications, such as enhanced oil recovery (EOR).…”

“…87–89 Similarly, CO 2 -induced self-assembled structures with complex morphologies have been realised including vesicles, 90,91 worm-like micelles, 92–94 and nano-objects. 95–97…”

Higher Fatty Acid-Based CO2-Controllable Dual-Circulation Approach for Oil Recovery

“…Among many chemical products and processes, stimuliresponsive compounds 1−3 have been of great interest as recyclable reagents. The compounds with stimuli-responsive properties were discovered and synthesized 4 early on, and stimuli-response of the compound was achieved through pH, 5 light, 6 temperature, 7 enzyme, 8 etc. Now, numerous CO 2responsive compounds have been prepared.…”

“…Among many chemical products and processes, stimuli-responsive compounds − have been of great interest as recyclable reagents. The compounds with stimuli-responsive properties were discovered and synthesized early on, and stimuli-response of the compound was achieved through pH, light, temperature, enzyme, etc. Now, numerous CO 2 -responsive compounds have been prepared. , CO 2 is regarded as a new natural and harmless stimulant, which was also relevant to the study of greenhouse gas capture and gas anti-solvent. , The CO 2 -responsive compounds had been diffusely applied into solid–liquid separation, washing oil, biotechnology, extraction, , medicine, and other multi-disciplinary fields in the form of compound solvent, sol–gel, and emulsion …”