Reversible addition-fragmentation chain transfer synthesis of amidine-based, CO2-responsive homo and AB diblock (Co)polymers comprised of histamine and their gas-triggered self-assembly in water

Development and Applications of CO2-Responsive Gels in CO2 Flooding and Geological Storage

Gel systems are widely used as plugging materials in the oil and gas industry. Gas channeling can be mitigated by reducing the heterogeneity of the formation and the mobility ratio of CO2 to crude oil. Cracks and other CO2 leaking pathways can be plugged during the geological storage of CO2 to increase the storage stability. By adding CO2-responsive groups to the classic polymer gel's molecular chain, CO2 responsive gel is able to seal and recognize CO2 in the formation while maintaining the superior performance of traditional polymer gel. The application of CO2 responsive gels in oil and gas production is still in the stage of laboratory testing on the whole. To actually achieve the commercial application of CO2 responsive gels in the oil and gas industry, it is imperative to thoroughly understand the CO2 responsive mechanisms of the various types of CO2 responsive gels, as well as the advantages and drawbacks of the gels and the direction of future development prospects. This work provides an overview of the research progress and response mechanisms of various types of CO2 responsive groups and CO2 responsive gels. Studies of the CO2 responsive gel development, injectivity, and plugging performance are comprehensively reviewed and summarized. The shortcomings of the existing CO2 responsive gels system are discussed and the paths for future CO2 responsive gel development are suggested.

Electrical Response of Poly(N-[3-(dimethylamino)Propyl] Methacrylamide) to CO2 at a Long Exposure Period

Amine-functionalized polymers (AFPs) are able to react with carbon dioxide (CO₂) and are therefore useful in CO₂ capture and sensing. To develop AFP-based CO₂ sensors, it is critical to examine their electrical responses to CO₂ over long periods of time, so that the device can be used consistently for measuring CO₂ concentration. To this end, we synthesized poly(N-[3-(dimethylamino)propyl] methacrylamide) (pDMAPMAm) by free radical polymerization and tested its ability to behave as a CO₂-responsive polymer in a transducer. The electrical response of this polymer to CO₂ upon long exposure times was measured in both the aqueous and solid phases. Direct current resistance measurement tests on pDMAPMAm films printed along with the silver electrodes in the presence of CO₂ at various concentrations reveal a two-region electrical response. Upon continuous exposure to different CO₂ flow rates (at a constant pressure of 0.2 MPa), the resistance first decreased over time, reaching a minimum, followed by a gradual increase with further exposure to CO₂. A similar trend is observed when CO₂ is introduced to an aqueous solution of pDMAPMAm. The in situ monitoring of pH suggests that the change in resistance of pDMAPMAm can be attributed to the protonation of tertiary amine groups in the presence of CO₂. This two-region response of pDMAPMAm is based on a proton-hopping mechanism and a change in the number of free amines when pDMAPMAm is exposed to various levels of CO₂.

Water treatment using stimuli-responsive polymers

Stimuli-responsive polymers are a new category of smart materials used in water treatment via a stimuli-induced purification process and subsequent regeneration processes.

Facile synthesis of well-controlled poly(1-vinyl imidazole) by the RAFT process

Synthesis of well-controlled poly(1-vinyl imidazole).

Degradable vinyl copolymers through thiocarbonyl addition-ring-opening (TARO) polymerization

The radical copolymerization of the thionolactone dibenzo[c,e]oxepane-5-thione with acrylates, acrylonitrile, and N,N-dimethylacrylamide afforded copolymers containing a controllable amount of backbone thioesters which could be selectively cleaved. The process is compatible with RAFT polymerization and promising for the development of advanced degradable polymers.

Controlling CO2 -Responsive Behaviors of Polymersomes Self-Assembled by Coumarin-Containing Star Polymer via Regulating Its Crosslinking Pattern

An oligo(ethylene glycol)-based star polymer of N₂ -(OEG-C)₃ with fluorescent coumarin as hydrophobic end groups and dual tertiary amines as the star center is designed and synthesized. Owing to its amphiphilic nature of N₂ -(OEG-C)₃ , it will self-assemble into hollow vesicles with coumarin groups dispersed in the hydrophobic membrane and exhibits CO₂ -responsive behavior due to the protonation of amine centers with CO₂ . More importantly, coumarin moieties can either form non-crosslinking with γ-cyclodextrin via the 2/1 host-guest inclusion, or covalently photodimerized by 365 nm light, offering a tunable crosslinking pattern in the hydrophobic membrane and thus adjusting its CO₂ -stimulated reorganization and disassembly behaviors of these vesicles in aqueous solution.

Facile Fabrication of CO2-Responsive Nanofibers from Photo-Cross-Linked Poly(pentafluorophenyl acrylate) Nanofibers

CO₂-responsive nanofibers were facilely prepared from photo-cross-linked poly(pentafluorophenyl acrylate) (PPFPA) nanofibers via "amine-active ester" chemical modification. Photo-cross-linked PPFPA nanofibers were modified with histamine under mild conditions to generate cross-linked poly(histamine acrylamide) (PHAAA) nanofibers featuring a CO₂ responsiveness. As expected, the prepared cross-linked PHAAA nanofibers can exhibit a CO₂-responsive behavior to induce a reversible transition from hydrophobic to hydrophilic upon alternating addition and removal of CO₂ on the surface of nanofibrous membranes. Based on this finding, we could demonstrate that cross-linked PHAAA nanofibers can be employed for reversible absorption and release of protein using bovine serum albumin (BSA) as a model.

A synthetic approach toward a pH and sugar-responsive diblock copolymer via post-polymerization modification

A novel pH- and sugar-responsive diblock copolymer containing phenylboronic acid was synthesized by RAFT and a post-polymerization modification strategy.

CO2-Responsive polymer materials

This paper reviews the chemical fundamentals of CO₂-responsive polymers as well as the latest reported “smart” material systems switched by CO₂.

CO2-Responsive graft copolymers: synthesis and characterization

The synthesis and self-assembly study of CO₂-responsive graft copolymers fabricated from a “graft-to” strategy based on pentafluorophenyl esters as grafting sites.

A CO2-switchable amidine monomer: synthesis and characterization

Smart system employed CO2 gas as new trigger has been attracting enormous attention in recent years, but few monomers that are capable of switching their hydrophobicity/hydrophility upon CO2 stimulation have been reported. A novel CO2 responsive monomer, 4-vinylbenzyl amidine, is designed and synthesized in this work with N,N-dimethylacetamide dimethyl acetal and 4-vinylbenzyl amine that is prepared through the Gabriel reaction. In bi-phase solvent of n-hexane and water, the monomer dissolves in n-hexane first and then transforms into water upon the CO2 treatment, indicating a hydrophobic to hydrophilic transition. This transformation is demonstrated as reversible by monitoring the conductivity variation of its wet dimethyl formamide solution during alternate bubbling/removing CO2. The protonation of 4-vinylbenzyl amidine upon CO2 treatment is demonstrated by 1H NMR which also accounts for the dissolubility change. The reversible addition-fragmentation chain-transfer polymerization of this monomer is also performed, finding the reaction only occurs in glacial acetic acid. The reason can be ascribed to the different radical structure produced in different solvent.

CO2-responsive polymeric materials: synthesis, self-assembly, and functional applications

CO2 is an ideal trigger for switchable or stimuli-responsive materials because it is benign, inexpensive, green, abundant, and does not accumulate in the system. Many different CO2-responsive materials including polymers, latexes, solvents, solutes, gels, surfactants, and catalysts have been prepared. This review focuses on the preparation, self-assembly, and functional applications of CO2-responsive polymers. Detailed discussion is provided on the synthesis of CO2-responsive polymers, in particular using reversible deactivation radical polymerization (RDRP), formerly known as controlled/living radical polymerization (CLRP), a powerful technique for the preparation of well-defined (co)polymers with precise control over molecular weight distribution, chain-end functional groups, and polymer architectural design. Self-assembly in aqueous dispersed media is highlighted as well as emerging potential applications.

The use of electrostatic association for rapid RAFT synthesis of histamine polyelectrolyte in aqueous solutions at and below 25 °C

Electrostatic association for rapid and quantitative synthesis of well-defined polyelectrolytes in dilute aqueous solutions at and below 25 °C.

CO2/pH-responsive particles with built-in fluorescence read-out

A novel fluorescent monomer was synthesized to probe the state of CO₂-responsive cross-linked polymer particles.

Synthesis and self-assembly of ABC linear triblock copolymers to target CO2-responsive multicompartment micelles

A series of ABC triblock copolymers were synthesized by tailoring the block length, suggesting polymers in a narrow composition window (0.34 ≤ f_F ≤ 0.38) might transform from spherical micelles to multicompartment micelles upon stimulation of CO₂.

Triply responsive soft matter nanoparticles based on poly[oligo(ethylene glycol) methyl ether methacrylate-block-3-phenylpropyl methacrylate] copolymers

The stimulus-responsive properties of nanoparticles based on poly[oligo(ethylene glycol) methyl ether methacrylate-b-3-phenylpropyl methacrylate] (p(OEGMA-b-PPMA)) copolymers in alcohols are described.

Thiol-reactive functional poly(meth)acrylates: multicomponent monomer synthesis, RAFT (co)polymerization and highly efficient thiol–para-fluoro postpolymerization modification

Novel Passerini-made pentafluorophenyl-functional (meth)acrylate monomers are (co)polymerized by RAFT and modified quantitatively with a variety of functional primary, secondary, and tertiary thiols.

RAFT-prepared α-difunctional poly(2-vinyl-4,4-dimethylazlactone)s and their derivatives: synthesis and effect of end-groups on aqueous inverse temperature solubility

Five R-group di-functional dithiobenzoates have been prepared and used in the reversible addition–fragmentation chain transfer polymerization of 2-vinyl-4,4-dimethylazlactone.

Ethanolic RAFT Dispersion Polymerization of 2-(Naphthalen-2-yloxy)ethyl Methacrylate and 2-Phenoxyethyl Methacrylate with Poly[2-(dimethylamino)ethyl Methacrylate] Macro-Chain Transfer Agents

The ethanolic reversible addition-fragmentation chain transfer dispersion polymerization (RAFTDP), at 21 wt-%, of 2-(naphthalen-2-yloxy)ethyl methacrylate (NOEMA) and 2-phenoxyethyl methacrylate (POEMA) with a poly[2-(dimethylamino)ethyl methacrylate] macro-chain transfer agent (CTA) with an average degree of polymerization of 20 (PDMAEMA20) is described. DMAEMA20-b-NOEMAy (y = 20–125) block copolymers were readily prepared under dispersion conditions in ethanol at 70°C. However, the polymerization of NOEMA was not well controlled, with size exclusion chromatograms being distinctly bi or multimodal with measured dispersities . Though NOEMA copolymerization was not ideal, the resulting series of block copolymers did exhibit the anticipated full spectrum of nanoparticle morphologies (spheres, worms, and vesicles). Interestingly, these morphology transitions occurred over a relatively narrow range of block copolymer compositions. In the case of POEMA, copolymerization was also poorly controlled with 1.50 ≤ ĐM ≤ 1.83 for the series of DMAEMA20-b-POEMAy copolymers. In contrast to the NOEMA-based copolymers, the POEMA series only yielded nanoparticles with a spherical morphology whose size increased with increasing average degrees of polymerization of the POEMA block. Collectively, though both NOEMA and POEMA can be utilized in ethanolic RAFT dispersion polymerization formulations, these preliminary studies suggest that neither appears to be an ideal aryl methacrylate choice as comonomer, especially if the goal is to combine the synthesis of well-defined copolymers with efficient nanoparticle formation.

The use of endogenous gaseous molecules (NO and CO2) to regulate the self-assembly of a dual-responsive triblock copolymer

A nitric oxide (NO) and carbon dioxide (CO₂) dual-responsive block copolymer was self-assembled in aqueous solution upon gas stimuli to form nanostructures.

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

With an additional methyl group in the ion bridge, sulfobutylbetaine (co)polymers show significantly higher UCSTs than their more common sulfopropylbetaine counterparts making them a promising class of smart materials.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

A combination of the Passerini reaction and RAFT polymerization is used to produce novel (co)polymers carrying double bond, protected triple bond, protected alcohol, pentafluorophenyl, and diene side group functionality.

Insights into the relationship between CO₂ switchability and basicity: examples of melamine and its derivatives

Owing to its wide availability, nontoxicity, and low cost, CO2 working as a trigger to reversibly switch material properties, including polarity, ionic strength, hydrophilicity, viscosity, surface charge, and degree of polymerization or cross-linking, has attracted an increasing attention in recent years. However, a quantitative correlation between basicity of these materials and their CO2 switchability has been less documented though it is of great importance for fabricating switchable system. In this work, the "switch-on" and "switch-off" abilities of melamine and its amino-substituted derivatives by introducing and removing CO2 are studied, and then their quantitative relationship with basicity is established, so that performances of other organobases can be quantitatively predicted. These findings are beneficial for forecasting the CO2 stimuli-responsive behavior of other organobases and the design of CO2-switchable materials.

ROMP (co)polymers with pendent alkyne side groups: post-polymerization modification employing thiol–yne and CuAAC coupling chemistries

The synthesis of a series of copolymers via ring-opening metathesis polymerization (ROMP) containing pendent trimethylsilyl-protected alkyne functional groups is described.