Role of the Anilinium Ion on the Selective Polymerization of Anilinium 2-Acrylamide-2-methyl-1-propanesulfonate

Effect of Ultra-High Temperature Degradation on the Physical Properties and Chemical Structure of an AMPS-Based Copolymer Oil-Well Cement Additive PADIM in Aqueous Solution

2-acrylamido-2-methylpropane sulfonic acid (AMPS) based copolymer fluid loss agent is a kind of widely utilized additive in oil-well cement. However, when applied in ultra-high temperature (UHT) formation environment, its fluid loss control efficiency is significantly declined due to the thermal degradation behavior, and corresponding mechanism study is still lacking. Regarding the above issue, this work synthesized one representative copolymer fluid loss agent PADIM and investigated its thermal degradation mechanism in UHT aqueous environment, which was polymerized by AMPS, N, N-dimethylacrylamide (DMAA), itaconic acid (IA) and methacryloxyethyltrimethyl ammonium chloride (MTC). The aim of this paper was to provide a theoretical guidance for the futural structural design of the fluid loss agents for oil well cement slurry at UHTs. The copolymer solution was subjected to isothermal aging at 180-240 °C for 1.5 h or 6.0 h (to simulate short-period and long-period aging, respectively), and the aged products were further analyzed. It was found that the thermal decomposition onset temperature of the copolymer solid was 294.6 °C. However, its thermal stability in aqueous solution was significantly lower, with substantial main chain breakage and functional group transformations occurring below 240 °C. As a result, the apparent viscosity and average molecular weight were significantly reduced from 4216 mPa·s and 31,666 Da before aging to 107.4 mPa·s and 8590 Da after aging at 240 °C for 6.0 h. Meanwhile, the side groups (-SO3- and -COO-) were removed and the unsaturated alkenes were produced due to main chain degradation. In terms of application performance, the fluid loss control ability of the aged product diminished gradually from 22 mL to 196 mL as the aging temperature increased from room temperature to 210 °C. This decline was attributed to a reduction in molecular weight and a decrease in product adsorption capacity caused by the removal of side groups.

Silk Fibroin-g-Polyaniline Platform for the Design of Biocompatible-Electroactive Substrate

The structural modification of biopolymers is a current strategy to develop materials with biomedical applications. Silk fibroin is a natural fiber derived from a protein produced by the silkworm (Bombyx mori) with biocompatible characteristics and excellent mechanical properties. This research reports the structural modification of silk fibroin by incorporating polyaniline chain grafts through a one-pot process (esterification reaction/oxidative polymerization). The structural characterization was achieved by ¹H-NMR and FT-IR. The morphology was studied by scanning electron microscopy and complemented with thermogravimetric analysis to understand the effect of the thermal stability at each step of the modification. Different fibroin silk (Fib): polyaniline (PAni) mass ratios were evaluated. From this evaluation, it was found that a Fib to PAni ratio of at least 1 to 0.5 is required to produce electroactive polyaniline, as observed by UV-vis and CV. Notably, all the fibroin-g-PAni systems present low cytotoxicity, making them promising systems for developing biocompatible electrochemical sensors.

Theoretical Study of Vinyl-Sulfonate Monomers and Their Effect as the Dopants of Polyaniline Dimers

Establishing the structure–property relationships of monomers and polymers via theoretical chemistry is vital for designing new polymer structures with a specific application. Developing bifunctional monomers with selective polymerizable sites is one of the strategies employed to obtain complex polymeric systems. In this work, a theoretical study on anilinium 2-acrylamide-2-methyl-1-propanesulfonate (ani-AMPS) and anilinium 4-styrenesulfonate (ani-SS) monomers and their respective doped polyaniline dimer (PAni-d AMPS or PAni-d SS) was performed. The study focused on understanding the susceptibility of the vinyl group to a radical attack and the conformation changes resulting from the coordinated covalent bond between sulfonate and aniliniun. Applying Density Functional Theory with the B3LYP functional and a basis set of 6 − 31 + G(d,p), the structures of the ani-AMPS, ani-SS, PAni-d AMPS, and PAni-d SS were optimized, and the different chemical descriptors were determined. The simulation showed that the reactivity of the vinyl group in the ani-AMPS is slightly higher. The sulfonate group undergoes a conformational change when bonding with PAni-d AMPS or PAni-d SS compared to its respective bifunctional monomer. Additionally, the electronegativity of PAni-d depends on the dopant’s structure. Thus, the bonded spacer between the vinyl and sulfonate groups (dopant) plays a notable role in the final characteristics of ani-AMPS, ani-SS, PAni-d AMPS, and PAni-d SS.

Brush-like Polyaniline with Optical and Electroactive Properties at Neutral pH and High Temperature

In this research, a brush-like polyaniline (poly(2-acrylamide-2-methyl-1-propanesulfonate)-g-polyaniline)-b-poly(N-vinylcarbazole) (BL PAni) was developed as a strategy to overcome the limited processability and dedoping above pH 4 of conventional polyaniline (PAni). For the BL PAni synthesis, RAFT polymerization (homopolymer), RAFT-mediated surfactant-free emulsion polymerization (block copolymer), and interfacial oxidative polymerization were applied to graft the PAni chains. NMR and FT-IR spectroscopies were performed to confirm the structural elucidation of the reaction pathways, while the thermal properties were analyzed by TGA and DSC. Notably, the BL PAni presents absorption throughout the visible region and up to the near-infrared, showing dedoping resistance at up to 80 °C and at a neutral pH. The absorption range of the BL PAni, block copolymer, and homopolymer were studied by UV–Vis spectroscopy in solid-state and dispersion/solution, highlighting BL PAni and poly(anilinium 2-acrylamide-2-methyl-1-propanesulfonate)-b-poly(N-vinylcarbazole) (PAAMP-b-PVK) due to the π-stacking between the anilinium and carbazole groups. The cyclic voltammetry confirmed the persistence of electroactivity at a pH near 7.