Under harsh conditions, the desorption of polyampholytes from bentonite (Bent) can affect the performance of drilling fluids. To study the desorption of polyampholyte from bentonite, partially hydrolyzed copolymers of acrylamide and diallyl dimethyl ammonium chloride (HPAD), containing carboxyl groups, quaternary ammonium groups and amide groups was synthesized via free radical copolymerization followed by hydrolyzation. The molecular structure of HPAD was characterized by 1H NMR and 13C NMR. The adsorption equilibrium of HPAD on Bent in the presence of 10 wt% NaCl was 106 mg·g–1. The adsorption-desorption behavior of HPAD on Bent was studied using a high pressure and high temperature (HPHT) filtration apparatus, to obtain the filtrate liquid and filter cakes. The content of HPAD in the filtration and the filter cakes was determined via UV and element analysis, respectively. As the temperature increased, the desorption of HPAD from Bent accelerated owing to molecular thermal motion and thermal degradation of the adsorptive groups. Notably, the decomposition rate of the amide group was more than twice that of the quaternary ammonium group. The critical temperature for HPAD desorption was 135°C, as the decomposition of the adsorptive groups became predominant over intensified molecular thermal motion at high temperatures.

AbstractThe influence of density of amino groups, nanoparticles dimension and pH on the interaction between end-functionalized polymers and nanoparticles was extensively investigated in this study. PS–NH2 and H2N–PS–NH2 were prepared using reversible addition–fragmentation chain transfer polymerization and atom transfer radical polymerization. Zero-dimensional carbon dots with sulfonate groups, one-dimensional cellulose nanocrystals with sulfate groups and two-dimensional graphene with sulfonate groups in the aqueous phase were added into the toluene phase containing the aminated PS. The results indicate that aminated PS exhibited the strongest interfacial activity after compounding with sulfonated nanoparticles at a pH of 3. PS ended with two amino groups performed better in reducing the water/toluene interfacial tension than PS ended with only one amino group. The dimension of sulfonated nanoparticles also contributed significantly to the reduction in the water/toluene interfacial tension. The minimal interfacial tension was 4.49 mN/m after compounding PS–NH2 with sulfonated zero-dimensional carbon dots.

Nanoparticle (NP)-surfactants formed by the self-assembly of NPs and endfunctionalized polymers at the hydrophilic/hydrophobic interface have a wide range of Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 4 March 2020 applications in many fields. In this study, the influence of density of amino groups, NPs dimension and pH on the interaction between end-functionalized polymers and NPs were extensively investigated. Single amino-terminated polystyrene (PS-NH2, Mw ≈ 0.6k, 2.5k, 3.5k, 3.9k) and diamino-terminated polystyrene (H2N-PS-NH2, Mw ≈ 1.1k, 2.8k) were prepared using reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization. NPs with different dimensions (zero-dimensional carbon dots with sulfonate groups, one-dimensional cellulose nanocrystals with sulfate groups and two-dimensional graphene with sulfonate groups) in the aqueous phase were added into the toluene phase containing the aminated PS. The influence of pH and the molecular weight of amino-terminated PS on the interfacial tension between two phases were investigated. The results indicate that aminated PS exhibited the strongest interfacial activity after compounding with sulfonated NPs at a pH of 3. Terminating PS with amino groups on both ends leads to better performance in in reducing the water/toluene interfacial tension than modifying the molecular structure of PS on a single end. The dimension of sulfonated NPs also contributed significantly to the reduction of the water/toluene interfacial tension. The minimal interfacial tension was 4.49 mN/m after compounding PS-NH2 with sulfonated zero-dimensional carbon dots. Molecular dynamics simulation on the evolution of the water/toluene interface in the presence of sulfonated carbon dots and H2N-PS-NH2 revealed that these opposite charged substances moved towards the interface in an extreme short time and orderly assembled in a thermodynamic equilibrium.A mixture of potassium phthalimide (2.13 g), PS 3a (2.51 g) and DMF (30 mL) was heated at 80 °C for 12 h under argon. Then, the mixture was added to water, and the product 3b was prepared by filtration [17] . Synthesis of H2N-PS-NH2 (3c)Product 3b (1.83 g), hydrazine hydrate (1.05 g) and DMF (25 mL) were added to a three-neck flask. The mixture was stirred at 80 °C for 16 h under argon. The mixture was added to methanol, and the precipitate was washed with deionized water and brine.Then, H2N-PS-NH2 3c was obtained. The chemical structure of 3a, 3b and 3c was characterized by 1 H NMR, and the spectra are shown in Figure 2. Figure 2. 1 H NMR spectra of 3a, 3b and 3c; A: Ar-H, B: Ph-CH-Br, C: phthalimide-CH2. Synthesis of CDs-SO3HCitric acid (8.01 g) was added to deionized water (100 mL). The mixture was sonicated and transferred to a hydrothermal kettle. The reaction was carried out at 200