Concentration Of Carboxylic Acid Groups Research Articles

Polymeric surfactants with high acid values for emulsion type pressure-sensitive adhesives

Low molecular weight polymers with hydrophobic-carboxyl groups have been usually used as anionic surfactants in emulsion polymerization for coatings. However, such polymeric surfactants usually have low acid values below 200, because it is difficult to make high acid-value polymeric surfactants using a normal batch reactor. In this work, we polymerized high acid value polymeric surfactant having high acid values successfully up to 380 using CSTR (continuous stirring tank reactor). The synthesized polymeric surfactant was a random copolymer of P(BA-AA) and we applied them as anionic surfactants in making emulsion-type acrylic PSAs (Pressure-Sensitive Adhesives) to investigate the effects of high acid value on the adhesive properties. This CSTR enabled effective control of the polymerization reaction because it could control the composition and molecular weight of polymeric surfactants through varying monomer ratios, retention time, and initiator concentration. The surface tension analysis and emulsion stability test indicated that the polymeric surfactants exhibited a similar level of critical micelle concentration (CMC) and emulsion stability with other conventional anionic surfactants. Also, the adhesion property analysis showed that the PSA used a high acid value polymeric surfactant resulting in superior adhesive properties and heat resistance than the PSA used both low acid value polymeric surfactant and conventional low molecular weight surfactant. It was very notable that polymeric surfactants having unusually high acid values above 300 because of their high contents of carboxylic acid groups could result in superior adhesive properties and heat resistance.

Synthesis and characterization of aqueous base developable negative-tone poly(imide-amic acid) copolymers by the effect of the imidization ratio

Negative-tone photosensitive poly(imide-amic acid) (PIA) copolymers were synthesized from a chemical imidization process using poly(amic acid) that was prepared from a polycondensation reaction of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 4,4′-oxydianiline (ODA), and di[2-(methacryloyloxy)ethyl]-5-aminoisophthalate (Di-HEMA-AP) with photoreactive acrylate groups. The imidization ratio was controlled by the reaction time, and the synthesized PIA copolymers were investigated using spectroscopic methods. The photolithographic behaviors of the formulations composed of PAA and PIA copolymers, Michler’s Ketone (MK), and crosslinker were evaluated using a 2.38 wt. % tetramethylammonium hydroxide (TMAH) solution. The solubility decreased with increasing imidization ratio in an alkaline base solution because of the reducing content of carboxylic acid groups in the polymer main chain. The formulations from PIA copolymers gave clear patterns without distortion by UV light i-line irradiation and followed 2.38 wt. % TMAH solution development.

TEMPO-oxidized cellulose beads for cationic dye adsorption

Toxic organic dyes present in wastewater should be removed before discharge. In this study, TEMPO-oxidized, regenerated cellulose beads were prepared using a simple falling ball technique for cationic methylene blue (MB) removal. The obtained cellulose beads were characterized using various analytical techniques. The results indicated that TEMPO-oxidized cellulose beads displayed porous structures with high content of carboxylic acid groups. Thus, the negatively charged cellulose beads can effectively adsorb cationic MB with an adsorption capacity of 495 mg/g at a starting concentration of 100 mg/L. This simple one-step adsorption process achieved near-complete MB removal at pH 7, indicating strong electrostatic interactions between cationic MB and negatively charged oxidized cellulose beads. The experimental data can be well described by the Langmuir isotherm model and the Pseudo-second-order model. The fabricated cellulose beads exhibit great potential for practical application in dye removal from wastewater.

Pseudo Polyampholytes with Sensitively Ion-Responsive Conformational Transition Based on Positively Charged Host-Guest Complexes.

Biological polyampholytes are ubiquitous in living organisms with primary functions including serving as transporters for moving chemical molecular species across the cell membranes. Synthetic amphoteric macromolecules that can change their phase states depending on the environment to simulate some properties of natural polyampholytes are of great interest. Here, the implementation of synthetic pseudo polymeric ampholytes is explored with ion-recognition-triggered conformational change. The phase transition behaviors of the ion-recognition-creative polyampholytes that contain deprotonated carboxylic acid groups as negative charges and 18-crown-6 units for forming positively charged host-guest complexes are systematically investigated. The ion-recognition-triggered phase transition behaviors of pseudo polyampholytes significantly depend on cation species and concentrations. Only those specific ions such as K+ , Ba2+ , Sr2+ and Pb2+ ions that can form 1:1 host-guest complexes with 18-crown-6 units in polymers enable control over conformational change like that of traditional pH-dependent polyampholytes. By regulating the content of carboxylic acid groups to match the content of ion-recognized positive charges provided by the host-guest complexes, the pseudo polyampholytes are more sensitive to the recognizable cations. Such ion-recognition-triggered amphoteric characteristics make the pseudo polyampholytes act like biological proteins, nucleic acids, and enzymes as molecular transporters, genetic code storage, and biocatalysts in artificial systems.

Research on electromagnetic wave absorption properties of zinc-based acrylate resins for marine antifouling coating

Here, we report on the marine antifouling performance and electromagnetic wave absorption (EMWA) properties of multifunctional zinc-based acrylate resins (ARZn-x). Their controlled hydrolysis with varying contents of carboxylic acid groups and ZnO led to formation of new surfaces that contributed to excellent antibacterial activity (>90%) and reductions in algal adhesion (optimal: 92.5%). Marine field tests demonstrated ideal antifouling performance during immersion in seawater for 4 months, and the coatings inhibited the adhesion and growth of biofouling species in marine. Furthermore, the ARZn-x resin coatings exhibited remarkable EMWA performance, with an RLmin of − 40.18 dB at 1.5 mm and 30.55 GHz, and full absorption of frequencies ranging from 18 to 40 GHz was achieved with thicknesses ranging from 1.0 to 5.5 mm. These resins provide new approaches to the development of multifunctional materials demonstrating marine antifouling performance and EMWA properties.

Oxidative depolymerization of lignin using nitric acid under ambient conditions

In this work, we demonstrated an innovative and cost-effective strategy to produce high- value depolymerized kraft lignin (DKL) from softwood kraft lignin (SKL) and hardwood kraft lignin (HKL). The depolymerization of kraft lignin was successfully achieved by an oxidative approach using nitric acid under ambient conditions (room temperature and pressure). This novel approach has the following features: ambient process conditions, no heat required, absence of catalysts or organic solvents, and no further purification process being required. The obtained DKL products were characterized extensively by gel permeation chromatography with ultraviolet detector (GPC-UV), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS), potentiometric titration and elemental analysis. Treatment of SKL or HKL at a KL/nitric acid (HNO3) mass ratio of 1:4 (w/w) at room temperature for 84 h resulted in DKL products with a weight-average molecular weight (Mw) of 1350 Da, much lower than that of the original lignins. In addition, the DKL products displayed a significant increase in carboxylic acid group content, a high solubility in water at low pH and, significantly lower decomposition temperatures compared to the original lignins. It was confirmed that nitration of the lignin structure occurred during nitric acid-oxidative depolymerization, as evidenced by the presence of 5% nitrogen (N) content in the DKL products.

Long-term surface modification of PEEK polymer using plasma and PEG silane treatment

Despite the several advantages of the Polyetheretherketone (PEEK) polymer, its wide application is limited due to its hydrophobic nature and poor surface adhesion performance. The plasma treatment can effectively transform the hydrophobic surface to hydrophilic. However, their effects are for a short duration, and the modified surfaces gradually lose their wetting and surface adhesion properties. In this work, we have reported a combined effect of plasma and PEG Silane treatment for permanent hydrophilic modification and improved adhesion strength of PEEK surfaces. The time-dependent changes in the contact angles, XPS, and ATR-FTIR spectra results were carefully recorded to investigate the surface properties of the modified surfaces. It was observed that the functional groups and polar component of surface energy played a pivotal role in long-term modification of PEEK surfaces. The Plasma and PEG Silane treated PEEK surface retained a very low contact angle and high content of hydroxide, carboxylic acid, and peroxide groups as compared to the plasma-treated PEEK surfaces. The lap shear test confirms the long-term effects of Plasma and PEG Silane treatment on adhesion properties with high bonding strength after 48 days of sample storage, which was dropped for Plasma treated surface just after 7 days of storage.

Carboxylic acid-modified polysilsesquioxane aerogels for the selective and reversible complexation of heavy metals and organic molecules

Abstract Organofunctional porous methyltrimethoxysilane (MTMS)-based aerogels are attractive for various adsorption purposes due to the combination of their unique properties such as low densities and high specific surface areas with tunable and accessible functional groups that can coordinate to, e.g., heavy metals and/or organic dye molecules in polar and non-polar solutions. Furthermore, the MTMS backbone gives these aerogels mechanical strength, the ability to be dried under ambient conditions and ensures their non-degradability in aqueous media and recyclability. Herein, we report the preparation of carboxylic acid-modified polysilsesquioxane aerogels via a simple and straightforward acid-base catalyzed sol-gel approach by using MTMS and the novel and stable 5-(trimethoxysilyl)pentanoic acid. In this surfactant assisted co-condensation approach, all parameters (concentration, pH, and temperature) have been carefully designed to yield porous (porosities between 82% and 53% and specific surface areas between 345 m2.g−1 and 36 m2.g−1), light (bulk densities between 1.38 g.cm−3 and 1.16 g.cm−3), and hydrophobic aerogels with accessible and reactive functional carboxylic acid groups (-COOH) (accessible surface loading up to 0.19 mmol.g−1) for the adsorption of heavy metals ions (Zn2+ and Cu2+) and cationic dyes (methylene blue and rhodamine B). The maximum adsorption capacities obtained from Langmuir isotherms were 154 mg.g−1, 106 mg.g−1, 111 mg.g−1, and 78 mg.g−1 for RhB, MB, Zn2+, and Cu2+, respectively. An increasing content of carboxylic acid groups influences the morphology, specific surface area and adsorption behavior of the synthesized aerogels. Optimized functionalized aerogels can be dried ambiently and show high and reversible adsorption abilities of 87% over several cycles towards cationic dyes in aqueous media. Moreover, these carboxylic acid-modified aerogels demonstrate excellent adsorption selectivity by adsorbing only positively charged molecules from mixed dye solutions, making them ideal candidates for diverse adsorption processes in polar and non-polar solutions.

PH-Responsive Properties of Asymmetric Nanopapers of Nanofibrillated Cellulose.

Inspired by plant movements driven by the arrangement of cellulose, we have fabricated nanopapers of nanofibrillated cellulose (NFC) showing actuation under pH changes. Bending was achieved by a concentration gradient of charged groups along the film thickness. Hence, the resulting nanopapers contained higher concentration of charged groups on one side of the film than on the opposite side, so that pH changes resulted in charge-dependent asymmetric deprotonation of the two layers. Electrostatic repulsions separate the nanofibers in the nanopaper, thus facilitating an asymmetric swelling and the subsequent expanding that results in bending. Nanofibrillated cellulose was modified by 2,2,6,6-tetramethylpiperidin-1-yloxyl radical (TEMPO) oxidation at two reaction times to get different surface concentrations of carboxylic acid groups. TEMPO-oxidized NFC was further chemically transformed into amine-modified NFC by amidation. The formation of graded nanopapers was accomplished by successive filtration of NFC dispersions with varying charge nature and/or concentration. The extent of bending was controlled by the charge concentration and the nanopaper thickness. The direction of bending was tuned by the layer composition (carboxylic acid or amine groups). In all cases, a steady-state was achieved within less than 25 s. This work opens new routes for the use of cellulosic materials as actuators.

Sustainable Process for the Depolymerization/Oxidation of Softwood and Hardwood Kraft Lignins Using Hydrogen Peroxide under Ambient Conditions.

The present study demonstrated a sustainable and cost-effective approach to depolymerize/oxidize softwood (SW) and hardwood (HW) kraft lignins using concentrated hydrogen peroxide at temperatures ranging from 25 to 35 °C, in the absence of catalysts or organic solvents. The degree of lignin depolymerization could be simply controlled by reaction time, and no further separation process was needed at the completion of the treatment. The obtained depolymerized lignin products were comprehensively characterized by GPC–UV, FTIR, 31P-NMR, TGA, Py-GC/MS and elemental analysis. The weight-average molecular weights (Mw) of the depolymerized lignins obtained from SW or HW lignin at a lignin/H2O2 mass ratio of 1:1 after treatment for 120 h at room temperature (≈25 °C) were approximately 1420 Da. The contents of carboxylic acid groups in the obtained depolymerized lignins were found to significantly increase compared with those of the untreated raw lignins. Moreover, the depolymerized lignin products had lower thermal decomposition temperatures than those of the raw lignins, as expected, owing to the greatly reduced Mw. These findings represent a novel solution to lignin depolymerization for the production of chemicals that can be utilized as a bio-substitute for petroleum-based polyols in polyurethane production.

Chemical characterization of mountain forest soils: impact of long-term atmospheric deposition loadings (Czech-Polish-German border region).

The composition of lipids in soil offers clues to soil degradation processes due their persistency and selectivity in soil, and close relation to long-term processes in the ecosystem, thanks to their role in cell membranes of organisms. Organic solvent-extractable compounds were recovered from soils collected at two sites differing in the degree of forest damage. Gas chromatography/mass spectroscopy and Fourier transform infrared spectroscopy were applied in order to characterize solvent-extractable lipids. Raman spectroscopy was also applied as it provides distinct advantages for determining the structural order of carbonaceous materials. The organic matter measurement techniques were combined with an established simultaneous multi-element measurement technique. Variations in individual soil horizons from the sites were reflected in the crystallinity of epicuticular waxes, presence of long-chain aliphatic hydrocarbons, concentrations of n-alkanes, saturated and unsaturated fatty acids, dicarboxylic acids, and in the content of aromatic structures, hydroxyl, ester, and carboxylic acid groups. The results are explained by differently transformed organic matter. The concentrations of elements in the soils were also affected by atmospheric depositions, including higher accumulations of arsenic and antimony, and lower contents of natural nutrients. These data have potential to be used as sensitive biogenic indicators of ecosystem damage by long-term atmospheric depositions.

A novel environmentally friendly process for depolymerization of hydrolysis lignin using Kraft cooking liquor: chemicals recoverable by the Kraft recovery cycle

AbstractHydrolysis lignin (HL) refers to a lignin‐rich residue obtained after the enzymatic hydrolysis of biomass. It is recalcitrant, heterogeneous, insoluble in most common solvents, and less reactive than other lignins. To enhance the reactivity of HL, a novel environmentally friendly depolymerization approach was demonstrated to produce depolymerized hydrolysis lignin (DHL) using Kraft cooking liquor, white liquor (WL) – recoverable by the Kraft recovery cycle. The effects of various process parameters such as reaction time, WL/HL ratio, and reaction temperature on lignin depolymerization were investigated using a 2 L Parr reactor under N2. The DHLs obtained were then characterized by Gel permeation chromatography (GPC)‐Ultraviolet Detector (GPC‐UV), 31P Nuclear Magnetic Resonance (NMR) spectroscopy, and ultraviolet visible (UV–visible) spectroscopy, while the filtrates were characterized by high‐performance liquid chromatography (HPLC) for saccharinic acids. The DHL yield reached 45–70% from the treatments at 150–190 °C for 1 h at a WL/HL mass ratio of 1:4 ~ 2:1. The weight‐average molecular weight (Mw) value of the DHL obtained at 190 °C after treatment for 1 h at a WL/HL ratio of 2:1 (w/w) was 2600 Da. Moreover, a significant increase in non‐condensed phenolic hydroxyl and carboxylic acid group content was observed with decreasing Mw. Compared with various existing lignin modification approaches, the approach reported here is less expensive and more environmentally friendly if integrated into Kraft pulp mill operations with the residual WL from the lignin depolymerization process being recycled to the mill chemical recovery cycle. Process scale‐up was also demonstrated using a 20 L circulating reactor. In this case, the Mw of the DHL produced after treatment at 170 °C for 2 h was 2400 Da. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

The concentration and origins of carboxylic acid groups in oil paint.

Although the concentration of carboxylic acid (COOH) groups is crucial to understand oil paint chemistry, analytical challenges hindered COOH quantification in complex polymerised oil samples thus far. The concentration of COOH groups is important in understanding oil paint degradation because it drives the breakdown of reactive inorganic pigments to dissolve in the oil network and form metal carboxylates. The metal ions in such an ionomeric polymer network can exchange with saturated fatty acids to form crystalline metal soaps (metal complexes of saturated fatty acids), leading to serious problems in many paintings worldwide. We developed two methods based on ATR-FTIR spectroscopy to accurately estimate the COOH concentration in artificially aged oil paint models. Using tailored model systems composed of linseed oil, ZnO and inert filler pigments, these dried oil paints were found to contain one COOH group per triacylglycerol unit. Model systems based on a mixture of long chain alcohols showed that the calculated COOH concentration originates from side chain autoxidation at low relative humidity (RH). The influence of increasing RH and ZnO concentration on COOH formation was studied and high relative humidity conditions were shown to promote the formation of COOH groups. No significant ester hydrolysis was found under the conditions studied. Our results show the potential of quantitative analysis of oil paint model systems for aiding careful (re)evaluation of conservation strategies.

Papermaking potential of Pennisetum hybridum fiber after fertilizing treatment with municipal sewage sludge

This study uses municipal sewage sludge (MSS) as a fertilizer for cultivating Pennisetum hybridum (hybrid Giant Napier grass). The effects of the MSS treatment on the chemical composition of Pennisetum hybridum and on the properties of paper made from its pulp were investigated. The study found that the holocellulose content of Pennisetum hybridum exceeded 72% and the fiber length reached 0.83 mm for one-year-old MSS treated plants. The tensile index of paper made from Napier grass fiber increased by 194% after beating. SEM observation revealed that the Pennisetum hybridum fiber bonded more tightly after beating. The content of carboxylic acid groups was similar in the fibers of 3-month-old and 1-year-old hybrid Giant Napier plants, and higher than that for 1.5-year-old plants. The present research demonstrates that Pennisetum hybridum fiber is suitable for pulping and paper-making after fertilizing treatment of the plants with MSS, which provides new ways for MSS utilization.

Effect of carboxylic group on the compatibility with retarder and the retarding side effect of the fluid loss control additive used in oil well cement.

The retarding side effect and the compatibility with other additives are the main problems that limit the field application of the synthesized fluid loss control additive (FLCA). The effect of the type and content of carboxylic acid groups on the retarding side effect of FLCA and the compatibility between FLCA and the retarder AMPS-IA synthesized using 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and itaconic acid (IA) was studied in this paper. The type and content of carboxylic acid group have a great influence on the fluid loss control ability, the compatibility with retarder and the retarding side effect of FLCA. FLCA containing IA or maleic acid (MA) shows better compatibility with retarder than FLCA containing acrylic acid, but the retarding side effect of FLCA containing MA is weaker than that of FLCA containing IA. Thus, MA is the most suitable monomer for synthesizing FLCA having good compatibility with retarder AMPS-IA.

Quantifying Carboxylic Acid Concentration in Model Polyamide Desalination Membranes via Fourier Transform Infrared Spectroscopy.

Carboxylic acid groups impart hydrophilicity and ionizable moieties to polyamide membranes for desalination, hence influencing water and ion transport through the material. Model polyamide films were synthesized via molecular layer-by-layer deposition on planar substrates to study the formation process of these materials and overcome the chemical and topological inhomogeneity inherent to conventional interfacially polymerized polyamide membranes. The carboxylic acid content in these model films was characterized using Fourier transform infrared (FTIR) spectroscopy by quantifying the C=O band at 1718 cm-1. The concentration of carboxylic acid groups decreased as the thickness of the membrane increased, suggestive of an increase in crosslink density as the polyamide network develops. For the thinnest molecular layer-by-layer (mLbL) samples, the carboxylic acid concentration for films on gold was 0.35 mmol g-1, whereas analogous films on silicon had an acid content of 0.56 mmol g-1, indicating a clear influence of the substrate on the initial network formation. As the thickness of the membrane increased, the influence of the substrate and initial layer growth became less significant as the carboxylic acid concentration on both substrates reached a value of 0.12 mmol g-1. We demonstrate that FTIR spectroscopy is a practical and accessible way to quantify the carboxylic acid content in these types of extremely thin polyamide membranes to help quantify network formation in these materials.

Tuning the Gas Selectivity of Tröger's Base Polyimide Membranes by Using Carboxylic Acid and Tertiary Base Interactions.

Polyimide-based materials provide attractive chemistries for the development of gas-separation membranes. Modification of inter- and intra-chain interactions is a route to improve the separation performance. In this work, copolyimides with Tröger's base (TB) monomers are designed and synthesized. In particular, a series of copolyimides is synthesized with different contents of carboxylic acid groups (0-50 wt %) to alter the inter- and intra-chain interactions and enhance the basicity of the TB-polyimides. A detailed thermal and structural analysis is provided for the new copolyimides. Gas permeation data reveal a tunable trend in separation performance with increasing carboxylic acid group content. Importantly, this is one of the few examples of copolyimide membranes materials that show enhanced plasticization resistance to high-pressure gas feeds through physical cross-linking.

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 °C for 60 min and 120 °C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids.

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 °C for 60 min and 120 °C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Asphaltene fractionation based on adsorption onto calcium carbonate: Part 2. Self-association and aggregation properties

The self-association and aggregation properties of asphaltene sub-fractions obtained by adsorption onto CaCO3 (doi:http://dx.doi.org/10.1016/j.colsurfa.2016.02.011) were investigated using a combination of near infrared spectroscopy, isothermal titration calorimetry (ITC) and diffusion-ordered 2D NMR spectroscopy (DOSY). Three asphaltenes sub-fractions were prepared: the bulk fraction that stayed in the bulk solution (i.e., did not adsorb on CaCO3), the adsorbed fraction that was obtained by desorption of asphaltenes adsorbed on CaCO3 using tetrahydrofuran, and the irreversibly-adsorbed fraction that was obtained after dissolution of CaCO3. The irreversibly-adsorbed asphaltene sub-fraction, which contained a higher content of carbonyl, carboxylic acid or derivative groups was found to have a significantly higher tendency to self-associate and to form larger aggregates than other fractions. In addition, the properties of above asphaltene fractions were compared with fractions obtained by stepwise precipitation using various n-hexane/crude oil ratios to study the influence of fractionation procedure. The irreversibly-adsorbed asphaltenes exhibited several similarities in properties with the fraction precipitating first from stepwise precipitation procedure (named as asphaltene 3.5V) including lower flocculation onset, higher tendency to self-associate (based on ITC) and a greater ability to adsorb onto stainless steel (based in QCM-D measurements). However, the size of aggregates determined by NMR differed, with the irreversibly-adsorbed asphaltenes forming aggregates of larger aggregate size (11.3Å) than compared to asphaltene 3.5V fractions (7.2Å). In conclusion, our investigations indicate that the asphaltene precipitation tendency depends on both the aromaticity and polarity of asphaltene fractions, and some of the asphaltene sub-fractions present different properties than the whole (or unfractionated) asphaltene fraction.