Hydrophobic Association Research Articles

Design of salt-responsive low-viscosity and high-elasticity hydrophobic association polymers and study of association structure changes under high-salt conditions

A hydrophobic associative water-soluble polymer, SRHV, was designed and synthesized in this study. The CAC of SRHV was 0.072 wt% and 0.2 wt%. The scanning electron microscopy tests showed that the polymer demonstrated a multilayer network structure. Rheological tests revealed that polymer solution exhibited low-viscosity and high-elasticity rheological behaviors under high-salinity conditions and this salt-responsive behavior persists at high temperatures. Fluorescent probe tests confirmed that salt addition promoted the formation of hydrophobic association networks. Through molecular dynamics simulation, various parameters, such as mean square displacement (MSD), radius of gyration (Rg), and radial distribution function (RDF), were analyzed to further explain the salt-tolerance mechanism of SRHV and the effect of salt ions on the hydrophobic association structure. The results showed that the viscosity and elasticity of polymers were not necessarily correlated. In addition, elasticity dominated when the positive effect of salt-promoted association exceeded the negative effect of salt-coiled molecular chains and polymer relies on elasticity to achieve an excellent sand-carrying effect at this time. In general, SRHV exhibits great potential for application in oil fields with high salt environment, which could effectively reduce the waste of freshwater resources. Furthermore, this work provides some support for suspending sand relying on elastic.

A Repeatable Dual‐Encryption Platform from Recyclable Thermosets with Self‐Healing Ability and Shape Memory Effect

AbstractRepeatable dual‐encryption platforms, coupled with a strong protective capacity for stored information, are highly desirable for current data security but still a challenge to be realized. Herein, a new type of thermoset‐based repeatable dual‐encryption platform is designed to fulfill the challenge. Through introducing dynamic boroxine bonds and hydrogen bonds within the thermoset, self‐healing, recyclability, and shape‐memory properties can be achieved. Given the shape memory behavior of this thermoset, encryption data within complex 3D structures can be realized. Thus, shape recovery is inevitable for the decryption, providing strong protection for encrypted data. Furthermore, the encrypted data can be protected by showing misleading information before true information during the decryption process, which is caused by the different analogous “LEGO” assembly sequences of thermosets that induces different hydrophobic association interactions. The decrypted information can be erased by heating, realizing the repeatable encryption/decryption. Additionally, the thermosets can be efficiently recycled. This strategy opens up a smart prospect for high level dual‐encryption platform.

Preparation of Cellulose-Based Flocculant and Its Application in the Enrichment of Vitamin K2 in Fermentation Supernatant.

Nutritional food supplements and pharmaceutical products produced with vitamin K2 as raw materials a very promising market in the global scope. The main production method of vitamin K2 is microbial fermentation, but approximately 50% of vitamin K2 synthesized by the main production strain Bacillus subtilis natto exists in extracellular form, which is not easy to separate and extract. In order to solve this problem, in this study, we synthesized a novel cellulose flocculant, MCC-g-LMA, by grafting reaction using microcrystalline cellulose (MCC) and lauryl methacrylate (LMA) as monomers, and ammonium persulfate as an initiator to flocculate VK2 from the fermentation supernatant. The flocculant was characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis, and scanning electron microscopy (SEM), and the grafting reaction was successful. When the flocculant dosage was 48.0 mg/L and pH was 5.0, the flocculation rate of the MCC-g-LMA on the fermentation supernatant reached 85.3%, and the enrichment rate of VK2 reached 90.0%. Furthermore, we explored the flocculation mechanism of VK2 by the MCC-g-LMA and speculated that the flocculation mechanism mainly included adsorption bridging, hydrophobic association and net trapping and sweep effect. In this study, the extraction method for trace high-value biological products in the fermentation supernatant was improved, which provided a method and theoretical basis for the efficient separation and purification of VK2 and other terpenoids.

Nanocarrier-Loaded Imidaclothiz Promotes Plant Uptake and Decreases Pesticide Residue.

There is a great demand for improving the effective utilization of pesticides and reducing their application for sustainable agriculture, and polymeric nanoparticles have provided strong technical support for the efficient delivery of pesticides. To this context, we tried to construct a relatively safe imidaclothiz nano-delivery system for enhanced plant uptake, reduced pesticide residue and improved bioactivity toward green peach aphids. The imidaclothiz could be assembled with the hydrophobic core of SPc through hydrophobic association, which led to the self-assembly of nanoscale imidaclothiz/SPc complex consisting of nearly spherical particles. The SPc decreased the contact angle of imidaclothiz drops and remarkably increased the plant uptake. Furthermore, the bioactivity and control efficacy of imidaclothiz were significantly improved with the help of SPc in both laboratory and field. Excitingly, the residue of imidaclothiz decreased with the help of SPc 7 d after the treatment due to the faster degradation of nanoscale imidaclothiz/SPc complex, which exhibited no negative effects on agronomic traits of tobacco plants. The current study successfully constructed a nano-delivery system for imidaclothiz, which can not only increase the effective utilization of pesticides, but also decrease the pesticide residue.

Super-Stretchable and Self-Healing hydrogel with a Three-Dimensional silver nanowires network structure for wearable sensor and electromagnetic interference shielding

With the rapid development of the electronics industry, smart wearable electronics and electromagnetic interference (EMI) shielding materials have attracted tremendous interest. However, it is still a great challenge to maintain stable performance after damage. Herein, we prepare a super-stretchable and self-healing hydrogel composite with exceptional EMI shielding performance by the in situ polymerization of the acrylamide (AAm) and N-acryloyl-11-aminoundecanoic acid (A-11) in the silver nanowires (AgNWs) aerogel with a cellular structure. Benefiting the continuous three-dimensional AgNWs network, the hydrogel composite has high electrical conductivity (83 S/cm), outstanding resistance-strain response of more than 800% tensile strain, and exceptional EMI effectiveness (SE) of 66 dB in X-band, capable of monitoring human motions as a wearable sensor. Moreover, the reversible hydrophobic association and hydrogen bonding interactions endow the hydrogel composite with excellent self-healing capability (EMI SE healing efficiency of 90%). The healed hydrogel composite can still serve as a sensor to respond rapidly and steadily to human motions. The super-stretchable and self-healing hydrogel composite holds great promise for smart wearable electronics and EMI shielding.

Synthesis and solution properties of hydrophobically associating water-soluble copolymer with dynamic covalent bond

The hydrophobically associating water-soluble terpolymer was synthesized by free-radical copolymerization of acrylamide (AM), diacetone acrylamide (DAAM), and cetyl dimethylallyl ammonium chloride (ACD), and then was crosslinked by acyl hydrazone bonds. The viscosity properties, surface activity, interfacial activity, and the emulsifying ability of the copolymer solution were characterized by the rotational viscometer, tensiometer, interface rheometer, optical microscope, and Formulaction Turbiscan Expert Lab optical analyzer. The dynamism, salt resistance, shear tolerance, and temperature resistance were investigated by viscosity analysis and rheometer measurements. The results showed that the copolymer solution combined chemical with physical cross-linking had high viscosity maintained at high salinity and shear rate. This understanding of the contribution of dynamic covalent bonds and hydrophobic association to the viscosity properties should be informative for the design of oil agents.

Application and Optimization of the Rheological Model for a Hydrophobically Associating Dendrimer Polymer.

Polymer flooding is one of the most important enhancing oil recovery (EOR) technologies in the world. With the optimization of polymer synthesis, the performance of polymer solutions has been greatly improved, which can adapt to more complex oil and gas reservoirs. However, with the continuous improvement of the properties of polymer solutions, the elastic property of polymer solutions is significantly improved, and the rheological law has also changed. This series of changes affects the application of polymer flooding reservoir numerical simulation technology. Therefore, constructing an accurate description model and precise limitation conditions is particularly important. The rheological curve with a wide shear range (0.1~10,000 s−1) and the viscoelasticity of the two polymers (partially hydrolysed polyacrylamide (HPAM) and dendritic hydrophobic association polymer (DHAP)) were analyzed and tested by a rotating rheometer. The results showed that under the experimental conditions, the rheological curve of both polymers can be described by the Carreau rheological model. Meanwhile, the structural viscosity of the hydrophobically associating polymer solution (DHAP) greatly improved the elasticity of the solution and led to the change of elastic modulus. Considering the influence of elastic characteristics on the rheological curve, the relaxation time spectrum derived from small vibration experimental data was used to limit the characteristic relaxation time, that is, the value range of λ. It was observed that the experimental data were highly matched with the nonlinear regression fitting curve of the Carreau rheological model. Therefore, the relationship between different test parameters should be fully considered while studying the rheological constitutive equation of viscoelastic fluid, so as to optimize and improve the equation of it.

Evaluation of temperature resistance of non chemical crosslinked double-tailed hydrophobically associating polymer fracturing fluid

The global spread of COVID-19 continues, industrial raw material production is being tested, and the fracturing cost of oil and gas fields continues to rise, posing new challenges to polymer fracturing fluids. A new hydrophobic association polymer PDMA1 with a double tailed monomer structure was synthesized inside this study. Fourier infrared spectroscopy, Electron microscope scanning, Fluorescence spectroscopy, and polymer viscoelasticity were used to investigate the polymer's basic properties. Finally, using molecular dynamics simulation tools, the network structure of PDMA1 was discovered to be more temperature resistant than that of HPAM. PDMA1 has larger hydrodynamic dimensions than HPAM at the same temperature, its radius of gyration is more than HPAM, and its viscosity is greater than HPAM under the same conditions. This provides an additional avenue of investigation for temperature-resistant hydrophobically associating polymers.

A laboratory study of self-healing hydrophobic association gels used as lost circulation material

Polymer gels, composed of preformed particle gels and in-situ gels, have generated broad interest in lost circulation control for decades. However, there are some drawbacks to them. The sealing layer formed by preformed particle gels was easily eroded by cyclic drilling fluid. The size of them needs match that of pores or fractures. In-situ gels, forming the expected pill in the correct location is challenging due to short gelation time, poor resident ability, and gel strength. Due to their unique recovery properties after damage, self-healing gels have been extensively researched and applied in the biomedicine field. Their prospect application in oil and gas drilling and development engineering has been investigated. In this article, we used self-healing hydrophobic association gels prepared in our previous paper to study their performance in lost circulation control, which aimed to integrate advantages of preformed particle gels and in-situ gels and abandon their disadvantages. The chemical structure and thermal stability of self-healing hydrophobic association gels were measured by FTIR and TGA, respectively, indicating good thermal stability. The swelling experiments at different temperatures suggested that they could absorb more water with the rise of temperature. The healing performance of self-healing gel particles at different temperatures and pressures showed that they could heal into a whole gel with good strength at 1–6 MPa and 25–80 ℃. Their healing properties were prone to temperature, followed by healing time. Their plugging performance was tested by a high temperature and pressure filter, meaning that the breakthrough pressure of 3% self-healing gel plugging agent was 3.5 MPa at 80 ℃, using a steel model with a fracture width of 1 mm to imitate fracture formation. The microscopic visualization device saw gel particles' plugging and healing process, indicating that they entered the lost circulation channels, formed a sealing layer like preformed particle gels, and healed into gel pill like in-situ gels. Self-healing gels could provide a new approach to controlling lost circulation and have a promising application prospect.

Efficient polymer-mediated delivery system for thiocyclam: Nanometerization remarkably improves the bioactivity toward green peach aphids.

The unscientific application of synthetic pesticides has brought various negative effects on the environment, hindering the sustainable development of agriculture. Nanoparticles can be applied as carriers to improve pesticide delivery, showing great potential in the development of pesticide formulation in recent years. Herein, a star polymer (SPc) was constructed as an efficient pesticide nanocarrier/adjuvant that could spontaneously assemble with thiocyclam or monosultap into a complex, through hydrophobic association and hydrogen bonding, respectively, with the pesticide-loading contents of 42.54% and 19.3%. This complexation reduced the particle sizes of thiocyclam from 543.54 to 52.74 nm for pure thiocyclam, and 3814.16 to 1185.89 nm for commercial preparation (cp) of thiocyclam. Interestingly, the introduction of SPc decreased the contact angles of both pure and cp thiocyclam on plant leaves, and increased the plant uptake of cp thiocyclam to 2.4-1.9 times of that without SPc. Meanwhile, the SPc could promote the bioactivity of pure/cp thiocyclam against green peach aphids through leaf dipping method and root application. For leaf dipping method, the 50% lethal concentration decreased from 0.532 to 0.221g/L after the complexation of pure thiocyclam with SPc, and that decreased from 0.390 to 0.251g/L for cp thiocyclam. SPc seems a promising adjuvant for nanometerization of both pure and cp insecticides, which is beneficial for improving the delivery efficiency and utilization rate of pesticides.

Bioinspired wet-resistant organogel for highly sensitive mechanical perception

Smart flexible electronics with underwater motion detection have become a promising research aspect in intelligent perception. Inspired by the strong adaptability of marine creatures to complex underwater environments, conventional biocompatible hydrogels are worth developing into organogels with preferred underwater adhesive properties, hydrophobic and antiswelling performance, and motion perception ability. Herein, a highly sensitive organogel sensor exhibiting good hydrophobicity, electromechanical properties, and adhesion properties was prepared for underwater utilization by regulating the chemical components and internal interactions. The synergistic effect of massive reversible non-covalent bonds ensures the organogel’s excellent underwater adhesion to multifarious substrates. Meanwhile, the interactions of hydrophobic conductive fillers and the dynamic hydrophobic associations in the organogel endow it with satisfactory hydrophobic performance (contact angle of 111.8°) and antiswelling property (equilibrium swelling ratio of −31% after 15-day immersion). The fabricated flexible organogel strain sensor exhibits high sensitivity (gauge factor of 1.96), ultrafast response rate (79.1 ms), low limit of detection (0.45 Pa), and excellent cyclic stability (1044 tensile cycles followed by 3981 compressive cycles). Results demonstrate the proposed organogel’s precise perception of sophisticated human motions in air and underwater, which expands its application scenarios.

Physically cross-linked starch/hydrophobically-associated poly(acrylamide) self-healing mechanically strong hydrogel

Mechanically tough self-healing hydrogels have attracted tremendous attraction in recent years owing to their flexibility and excellent deformation-resistance. Herein, we synthesized a bio-based self-healing hydrogel by incorporating starch onto a hydrophobically associated (HA) domain. The inclusion of physically cross-linked starch onto the HA-poly(acrylamide) (PAM) chain enhanced the mechanical strength of the hydrogel and this enhancement depends on dose level of starch. The ductile and tough HA-PAM network could bear stress and recombine the damage zones within a short time, and hence exhibit noteworthy self-healing ability. Moreover, the introduction of the reversible and physically cross-linked starch network was unable to eliminate self-healing attribute of the HA-PAM network completely. Most importantly, synthesized hydrogel was dimensionally stable after swelling and exhibited noteworthy mechanical strength under such conditions. Thus, this work provides a novel starch incorporated mechanically tough, self-healing hydrogel that can hopefully enrich the current hydrogel research and expand its practical application spectrum.

Influences of charge properties and hydrophobicity on the coagulation of inorganic and organic matters from water associated with starch-based coagulants

In this work, two series of binary graft cationic starch-based coagulants (CS-DMCs and CS-DMLs) with different hydrophobicities and charge densities (CDs) were prepared by graft copolymerization of acrylamide with 2-(methacryloyloxy)-N,N,N- trimethylethanaminium chloride and acryloyloxyethyl dimethyl benzyl ammonium chloride, respectively, on the starch (St) backbone. Kaolin particles, sodium humate (NaHA), and bovine serum albumin (BSA) were used as the simulated sources of inorganic colloidal particles and different organic pollutants in the micropolluted turbid surface water. The influences of the CD and hydrophobicity associated with the St-based coagulants on the removal of kaolin particles, NaHA, and BSA from single, binary, and ternary pollutant aqueous systems were investigated systematically. On the basis of the apparent coagulation performance, the floc characteristics, and the zeta potentials of the supernatants after coagulation, the coagulation mechanisms associated with the structural features of the St-based coagulants and the pollutants treated were explored and discussed in detail. The St-based coagulants with a higher CD and a stronger hydrophobicity showed better coagulation performance due to the synergistic effects of charge neutralization and hydrophobic association. The maximum efficiencies of the optimized St-based coagulant in removal of Kaolin, NaHA and BSA were 93.85%, 100% and 97.52% in their respective single pollutant systems. In addition to these simulated water samples, a real micropolluted turbid surface water tested and compared, further confirming the superiority of the hydrophobically modified cationic St-based coagulants, especially in the purification of organic pollutants in water.

Polymer flooding and its effects on enhanced oil recovery special reference to Upper Assam Basin

Chemical Enhance oil Recovery (CEOR) technology is getting more attention since energy crises are getting worse and frightened. Successful application of polymer flooding depends on the evaluation of rheological and solution properties of injected slug at reservoir conditions, which is function of polymer concentration, salinity, temperature and shear rate. Poly acryl amide (PAM) is commonly used polymer in polymer flooding technique. However, comparative study with other polymers such as xanthan gum (XG) is required while selection of appropriate polymer for CEOR. In present study, the recovery efficiency of PAM and XG as a polymer has been evaluated for application as chemical EOR agent for tertiary phase polymer flooding in Upper Assam basin. The comparative study between PAM and XG has been done in terms of rheological properties. Core flooding experiment of polymer flooding has also been tested to determine the recovery efficiency of the PAM and XG polymer solutions. The results showed that these polymers exhibit favorable salt tolerance, temperature resistance, and recoverable viscosity after shearing, reasonable thickening behavior and improved viscosity enhancement properties due to presence of hydrophobic association in the polymer main chains. Core flooding experiment of polymer flooding has also been tested to determine the recovery efficiency of the PAM and XG polymer solutions. Results show that macroscopic sweep efficiency is the dominant factor during recovery. While an injection of hydrogel polymer to the reservoir is to increase a viscosity of fluid containing water so that the fluid is more difficult to flow than the oil, and as a result, the oil production increases. Shear thinning behavior was observed in case of PAM indicating predominance of the frontal advance theory. As PAM seems to be following both piston like movement and frontal advance theory it can be efficiently enhancing the macroscopic sweep efficiency as well as microscopic displacement efficiency. The overall recovery efficiency of 53% of OOIP was determined for PAM flooding. The overall recovery efficiency by XG polymer flooding was found to be 45%, signifying its lesser efficiency in comparison to PAM. Success of the projects also depends on cost analysis. Simulation by Computer Modelling Group (CMG) study has also been carried out to validate the experimental findings.

Functional characteristics and dominant enhanced oil recovery mechanism of polymeric surfactant

There are more than 40% remaining oil trapped in the reservoir in the mature oilfield even after second and tertiary recovery processes. High performance chemical agent was required for the trapped oil further mobilization. Polymeric surfactant was synthesized by grafting the active ground into the polymer skeleton. It has the advantages of surfactant polymer (SP) flooding and overcome the chromatographic separation during SP flooding. However, it is still unclear how the supramolecular molecular structure of polymeric surfactant affects its properties. Two kinds of polymeric surfactants named HB and HD with different molecular structures were characterized in this paper. Their molecular structure, static properties and enhanced oil recovery (EOR) efficiency were examined and compared via a series of experiments. The results showed that HD was dominated by amide group with hydrophobic association structure, and exhibited the supramolecular characteristics of space network; while HB mainly consisted by ring groups, showing a straight chain structure. HD featured with a better thickening, shear-resistance and salt-resistance ability, while HB can easily emulsify oil. In the microfluidic and three parallel core flooding experiments, HD both presented a higher recovery factor due to its good mobility control performance. Cluster remaining oil obviously declined and film-liked remaining oil slightly increased during HB and HD flooding stage. The incremental oil recovery of HD after water flooding was 26.6%, which was 5.5% higher than that of HB. This work indicates the molecular structure of spatial network is preferred in the design of polymer molecular structure towards EOR in the heterogeneous reservoir.

Butyl rubber-based interpenetrating polymer networks with side chain crystallinity: Self-healing and shape-memory polymers with tunable thermal and mechanical properties

A self-healing and shape-memory interpenetrating polymer network (IPN) is produced by UV polymerization of n-octadecyl acrylate (C18A) monomer in a toluene solution of butyl rubber (isobutylene-isoprene rubber, IIR) using Irgacure 2959 photoinitiator at ambient temperature. IPNs containing 20–80 wt% IIR have crystalline domains formed by side-by-side packed octadecyl side chains aligned perpendicular to the poly(C18A) (PC18A) backbone. TEM images reveal that the morphology of IPNs consists of crystalline domains dispersed in a continuous amorphous matrix where the size of the dispersed phase could be adjusted between µm and nm level by changing the amount of IIR. Calculations indicate that the effective cross-link density of IPNs is mainly determined by their crystalline domains followed by hydrophobic associations while the chemical cross-links between IIR and PC18A components are negligible. We also show that the crystalline domains acting as sacrificial bonds dissipate energy under strain leading to a significant toughness improvement. IPNs exhibit tunable melting temperature (46–50 °C), crystallinity (1.5–25%), Young’s modulus (0.6–35 MPa), toughness (1.3–12 MPa), and a stretchability of up to 1200% by varying the amount of IIR component. What is more, they also exhibit temperature induced healing behavior with 59–77% efficiency, and an effective shape-memory function. The strategy presented here is applicable for the preparation of IPNs based on various rubbers and poly(n-alkyl(meth)acrylates) with long alkyl side chains.

Self-assembly of hydrophobically associating amphiphilic polymer with surfactant and its effect on nanoemulsion

A new scheme for controlling the rheological properties and stability of oil-in-water nanoemulsions is presented based on the polymer-surfactant self-assembly in solution. Specifically, amphiphilic property, hydrophobic association and thermo-responsive behavior is imparted to the polymer by using surfactant as a main function monomer to introduce hydrophilic and hydrophobic groups on the polymer. The polymer can cooperate with the surfactant to form oil-water interfacial film without compromising nanoemulsion formation based on its self-assembly properties. And there can be a moderate increase of the association between the hydrophobic groups on different polymers with increasing temperature based on their hydrophobicity. These behaviors will affect the rheological properties and stability of the nanoemulsion. The thermo-association mechanism of polymer, interaction between polymer and surfactant, and the effects of the polymer on nanoemulsions were analyzed. Test results show that, the thermo-association occurs when the polymer concentration is greater than 0.2%, and the association begins to be obvious when the temperature is higher than 50 °C, which would increase the viscosity of solution. The thermo-association may be attributed to the fact that the curled side chains of the polymer stretch and the hydrophobically association is intensified under higher temperature. The self-assembly of polymer and surfactant increase the interface film dilational modulus of the emulsions, which is conducive to the stability of nanoemulsion droplets. This polymer and the thermo-association mechanism could be applied in the study of smart emulsion and temperature-resistant emulsion.

A microcalorimetric and microscopic strategy to assess the interaction between dietary fibers and small molecules

The interaction between small molecules and neutral soluble dietary fiber is one of the proposed mechanisms determining the bioavailability of these components in the small intestine. However, the weak nature of these interactions makes it difficult to find an analytical method sensitive enough to detect them. Here, we probed the molecular interaction between galactomannan, arabinoxylan, and β-glucan with gallic acid, cinnamic acid, acetylsalicylic acid, and acetaminophen, using advanced analytical methods, namely isothermal titration calorimetry (ITC) and in the form of gold-nanoparticles, transmission electron microscopy (TEM). The results obtained from ITC analysis were fully consistent with the results obtained from TEM. In short, the interaction of these fibers and small molecules was mainly entropically driven, hence involving hydrophobic type association and possible conformational changes of the polysaccharide. However, the enthalpy contribution (hydrogen interaction) is also significant, especially regarding interactions with the acetylsalicylic acid molecule.

Stereostructure Dependence Phenomenon on the Self-Assembly of Ala-Ala-Ala Lipotripeptides.

A series of lipotripeptide stereoisomers based on alanine were synthesized, and their self-assembling behaviors were studied by means of circular dichroism spectra, ATR-IR, temperature-dependent 1H NMR, and X-ray diffraction patterns. In the mixed solvent of hexafluoroisopropanol/H2O (1/9, v/v), eight lipotripeptides were able to self-assembled into nanoflakes or nanoribbons driven by the hydrophobic association of alkyl chains, intermolecular hydrogen bonding among carboxyl groups at C-terminal and amide groups of alanine moieties in the peptide segment. It was found that the stacking chirality of carbonyl groups was determined by the chirality of alanine residue at C-terminal (i.e., "C-terminal determination" rule). Moreover, our research also highlighted the intermolecular hydrogen bonding on amide groups of each alanine residue, terminal carboxyl as well as the molecular packing structures can be subtly manipulated by changing the stereochemical sequence of peptide segment.

Influence of DOM characteristics on the flocculation removal of trace pharmaceuticals in surface water by the successive dosing of alum and moderately hydrophobic chitosan

Hydrophobically-modified chitosan (HC) has emerged as a promising flocculant for trace pharmaceutical removal from surface water. However, the variation in the characteristics of dissolved organic matter (DOM) in different water sources influences the efficacy of HC in removing pharmaceutical compounds. In this work, the flocculation performance of sequentially dosing alum and HC (alum+HC) for the treatment of five water types (three synthetic waters, and samples of two real waters collected from the Yangtze River and the Thames River), having different DOM and five representative pharmaceuticals (initial concentration: 100 ng/L), was assessed by bench-scale jar tests. The DOM characteristics were correlated quantitatively with the removal efficiencies (REs) of the pharmaceuticals. Density functional theory computations were performed to illuminate the interfacial interactions in the flocculation. Alum+HC exhibited a remarkably higher RE of all five pharmaceuticals (maximum RE: 73%-95%) from all waters compared to a conventional coagulant or flocculant (alum or polyacrylamide, respectively). In contrast to using HC alone, alum+HC also achieved a higher RE of pharmaceuticals with nearly half the HC dosage, thereby enhancing the cost-effectiveness of the alum+HC dosing system. Among the different key DOM characteristics, the surface charge and molecular weight of DOM had no evident correlation with RE(pharmaceutical), but the hydrophobic/hydrophilic nature and functional group composition of organic carbon of DOM were strongly correlated: Strongly hydrophobic fractions, with C-C & C=C functional groups (binding pharmaceuticals via hydrophobic association), were beneficial, while hydrophilic fractions with C-OH groups were less effective, for pharmaceutical removal. This work showed the enhanced performance of the alum+HC dosing combination in the removal of different pharmaceutical compounds from different waters, and filled the knowledge gap regarding the performance of hydrophobically-modified flocculants in the treatment of different surface water sources.