Adsorption Of Polymer Molecules Research Articles

Approximate Corona Phase Hamiltonian for Individual Cylindrical Nanoparticle-Polymer Interactions.

Nanoparticle surfaces, such as cylindrical nanowires and carbon nanotubes, are commonly coated with adsorbed polymer corona phases to impart solution stabilization and to control molecular interactions. These adsorbed polymer molecules (biological or otherwise), also known as the corona phase, are critical to engineering particle and molecular interactions. However, the prediction of its structure and the corresponding properties remains an unresolved problem in polymer physics. In this work, we construct a Hamiltonian describing the adsorption of an otherwise linear polymer to the surface of a cylindrical nanorod in the form of an integral equation summing up the energetic contributions corresponding to polymer bending, confinement, solvation, and electrostatics. We introduce an approximate functional that allows for the solution of the minimum energy configuration in the strongly bound limit. The functional is shown to predict the pitch and surface area of observed helical corona phases in the literature based on the surface binding energy and persistence length alone. This approximate functional also predicts and quantitatively describes the recently observed ionic strength-mediated phase transitions of charged polymer corona at carbon nanotube surfaces. The Hamiltonian and the approximate functional provide the first theoretical link between the polymer's mechanical and chemical properties and the resulting adsorbed phase configuration and therefore should find widespread utility in predicting corona phase structures around anisotropic nanoparticles.

Towards enhanced oil recovery: Effects of ionic valency and pH on the adsorption of hydrolyzed polyacrylamide at model surfaces using QCM-D

Adding polymers to the injection water in water-flooding oil recovery increases the viscosity and thereby enhances recovery factor. However, the beneficial effects are often counteracted by adsorption of polymer to the ambient mineral surface. In here, we used Quartz Crystal Microbalance with Dissipation (QCM-D) measurements to study the adsorption of the frequently used hydrolyzed polyacrylamide (HPAM), a weak polyelectrolyte, to silica and alumina model surfaces representing sandstone reservoirs. At pH 6 and 8 and concentrations from 1 mM to 100 mM of NaCl and CaCl2, we find that negatively charged HPAM molecules generally adsorb more strongly to positively charged alumina surfaces. For silica surfaces, the presence of Ca2+ ions, which form strong complexes with the carboxyl groups on the polymer, as evidenced by titration measurements, strongly enhances HPAM adsorption. This effect is attributed to the formation of Ca2+-mediated ion bridges with the substrate. Kinetic measurements suggest a two-step adsorption process consisting of a primary polymer adsorption onto the surface followed – in most cases – by a slower secondary process, which involves rearrangements of previously adsorbed polymer molecules, including polymer-on-polymer adsorption.

Oil recovery by low-salinity polymer flooding in carbonate oil reservoirs

Low-salinity polymer flooding (LSPF) is a promising enhanced oil recovery (EOR) method with a synergetic effect of combining the polymer injection and low-salinity water injection methods. To maximize EOR efficiency, it is essential to design the compositions of low-salinity water appropriately while considering polymer properties. The goal of this study was to investigate the effects of pH and potential determining ions (PDI; SO42− and Ca2+) in low-salinity polymer solution used as injection water on oil production when applying LSPF to a carbonate oil reservoir. From the experimental results, the SO42− ions interfered with polymer adsorption in the neutral SO42--containing polymer solution, while the adsorption was greatly promoted in the acidic conditions, reducing the permeability. In the Ca2+-containing polymer solution, the adsorption trend was different from the SO42− case. In examining the wettability alteration, the change in residual oil saturation between after-LSWF and after-LSPF (ΔSor) was greater with higher SO42− concentration under the neutral state. This means that the end-point of the relative permeability-saturation curves shifted to the right, indicating that wettability was altered to a more water-wet state. Under acidic conditions, ΔSor was smaller compared to the neutral state due to greater polymer adsorption. A small ΔSor was observed when Ca2+ ions were contained in the neutral polymer solution, causing less wettability alteration. This is because Ca2+ ions are involved in precipitation as well as adsorption, thus reducing the permeability more than SO42--containing case. We confirmed these changes also in the contact angle analysis. In conclusion, since SO42− ions interfered with adsorption of polymer molecules and adsorption occurred less in the neutral state, a neutral polymer solution with high SO42− ion concentration as an injection water provided the highest enhancement in the EOR efficiency.

Packing structures and formation of cracks in particulate films obtained by drying colloid–polymer suspensions

We investigated the effects of polymer addition on crack formation in particulate films of colloidal silica. Two types of polyvinyl alcohol (PVA) with different degrees of saponification were compared. Partially saponified PVA (PVA-1) suppressed crack formation. In contrast, weaker suppression was observed when we used fully saponified PVA (PVA-2). Centrifugation experiments of colloid–polymer suspensions revealed that PVA-1 adsorbed on particles well whereas PVA-2 was not adsorbed effectively, suggesting that the polymer–particle interactions strongly depended on the content of polymer functional groups. In addition, we observed segregation of PVA-2 between packed particles, which contributed to a sparse packing structure. We did not observe such segregation of PVA-1 and particles were packed more tightly than for PVA-2. These results clearly showed that the affinity between polymer molecules and suspended particles affected both crack formation and packing structures. We also found that adsorption of polymer molecules did not necessarily suppress crack formation. When we added polyvinyl pyrrolidone (PVP) to silica suspensions, we observed much more cracks than in the sample without polymer even though PVP molecules adsorbed on the silica particles. We conclude that adsorption of polymer molecules on suspended particles is preferable, but does not necessarily suppress crack formation. Miscibility between polymer molecules and particles would be a key issue in crack formation and packing structure of colloid-polymer films.

Atomically thin, large area aluminosilicate nanosheets fabricated from layered clay minerals

Abstract Two-dimensional (2-D) nanosheets, which have dimensions of atomically thin thickness with extremely high aspect ratio, have gathered great attentions due to their interesting properties and potential applications. Especially, some ceramic nanosheets including borides, carbides and sulfides became epitomes of novel functional nanomaterials since they exhibited unique electrical and surface properties distinguished from their bulk forms. In this study, atomically thin nanosheets of aluminosilicate oxides were fabricated via exfoliation of layered clay mineral, mica (muscovite; KAl3Si3O10(OH)2). To overcome the difficulties in exfoliations of large area nanosheets from mica, which has relatively strong interlayer bonding originated from layer charge, polymer assisted wet chemical method were applied. Amphiphilic polymer molecules were successfully intercalated into the ion exchanged muscovite particles to separate each layer. The resulting product possesses nanosheets with micrometer scale lateral sizes. The measured thicknesses of the nanosheets were mainly fell in two groups (1.2–1.7 nm and 2.2–2.7 nm) which correspond to the mono- and di-layer thichnesses of the muscovite with polymer adsorbates, respectively. The FT-IR and Raman results indicated that the adsorption of polymer molecules on the both surfaces of the aluminosilicate nanosheets significantly weaken or even break the interlayer bonding. Contrary to the highly insulating nature of bulk muscovites, the exfoliated nanosheets showed reduced bandgap energy which corresponds to semiconductor regime. The measured optical bandgap of the aluminosilicate ceramic nanosheets was 4.13 eV, which makes this ceramic nanosheet material a potential candidate for various electronic and electro-optic applications including wide bandgap semiconductors and photocatalysts.

A model-based decision analysis comparing water and polymer flooding in the development of a heavy oil field

Polymer flooding is an effective means to recover oil although the method creates conditions absent in traditional water flooding, mainly due to the physical phenomena related to this technique, such as adsorption of polymer molecules and non-Newtonian behavior. This work aims to guide the selection, through a decision analysis methodology, of the best strategy option using comparisons between water and polymer flooding projects in a heavy oil field development, under uncertainty, through a risk-return analysis.The methodology is based on a complete risk evaluation and decision analysis process presented by Schiozer et al. (2015), including the generation of uncertain scenarios, selection of representative models (RM), production strategy optimization for the RM, combination of the strategies in all scenarios, risk-return and risk curves analysis and the selection of the best strategy. The case study is representative of a heavy oil and high heterogeneous reservoir. We combined geological, economic and polymer uncertainties. We use Expected Monetary Value (EMV) as the objective function to measure economic return and Net Present Value (NPV) semi-deviation to measure risk.The results show that simplified comparisons between these two recovery methods, by only changing the injection fluid may lead to ill-informed decisions, and therefore, pre-planning is needed to realize the advantages from additional polymer costs to choose an optimal strategy. Furthermore, the results suggest that polymer flooding may be a viable alternative in the heavy oil field studied in this work.

The Performance of Polymer Flooding in Heterogeneous Type II Reservoirs—An Experimental and Field Investigation

The polymer flooding process has already been applied to the medium permeability type II reservoirs of the Daqing Oilfield (China) to enhance oil recovery. However, this process faces a number of challenges, such as the flooding efficiency, high injection pressure, formation blockage and damage, unbalanced absorption ratio, and economical justification. In this study, single-phase and two-phase flow experiments are performed to investigate polymer injection adaptability with natural cores of type II reservoirs. The enhanced oil recovery (EOR) effects of the polymer are studied by physical simulation experiments, and the results of application in an actual field are also presented. The results indicate that the flow characteristics and injection capability are dominated by the reservoir permeability in polymer flooding. Moreover, the adsorption of polymer molecules and the injection pressure gradient, which reflect formation damage, are affected more significantly by the concentration than by the molecular weight in type II reservoirs. Using the matching relationship, the injection-production process is stable, and additional oil recoveries of 10%–15% can be obtained in heterogeneous type II reservoirs with a high water saturation. This work is significant in that it further accelerates the application of polymer flooding EOR in medium permeability heterogeneous oilfields with high water saturation.

An Investigation of Polymer Adsorption in Porous Media Using Pore Network Modelling

Polymer injection in hydrocarbon reservoirs has been of great interest in petroleum engineering as an enhanced oil recovery method. In order to have a reliable injection plan, an accurate estimation of polymer behaviour is required to control the fluid flow in porous media. However, it is difficult to calculate the flow properties of polymer solutions—known as non-Newtonian fluids—in porous media, due to variable viscosity at different shear rates. Adsorption of polymer molecules onto the rock surface decreases the available cross-sectional area of polymer solution, therefore at a constant rate, the shear rate increases. As a result, it is important to investigate how polymer adsorption can affect the polymer solution flow behaviour in porous media. Moreover, prior to any polymer injection plan, the amount of adsorbed polymer should be calculated, due to the high cost of polymers. In the present study, pore network modelling was used to investigate the effect of polymer adsorption on flow behaviour of polymer solutions in porous media. To achieve this goal, a simple pore was constructed to adequately represent the real structure of the porous medium. It was then validated by simulation of Newtonian fluid flow in the network and comparison of the calculated flow properties with the experimental data. After validation, the pore network was used for simulation of non-Newtonian fluid flow in porous media. The experimental apparent viscosity of non-Newtonian fluid was used for verification of the procedure and the developed network. The apparent viscosity of non-Newtonian was calculated successfully using macroscopic properties of the rock sample and measured bulk properties of non-Newtonian fluid. The effect of polymer adsorption on calculation of non-Newtonian fluid apparent viscosity was then investigated. It was shown that the polymer adsorption process plays an important role in calculation of polymer solution apparent viscosity. The results reveal that polymer adsorption cannot be neglected, especially in near well-bore areas where the adsorption is high. Finally, the effect of wettability in calculating the total amount of adsorbed polymer volume was studied. The results suggest that neglecting the rock’s wettability can result in an overestimation or underestimation of the amount of adsorbed polymer.

Microfluidic Studies of Polymer Adsorption in Flow

Adsorption of polymer molecules under flow conditions governs a broad range of desired or undesired phenomena and has a broad range of applications. Microfluidic platforms integrated with analytical instrumentation offer the capability to study polymer adsorption in flow in a time‐ and labour‐efficient manner. Precise control of the microchannel dimensions and flow parameters enables accurate control of shear forces imposed on polymer solutions and on the molecules deposited on the surface, along with high sensitivity, enhanced reliability, and low reagent consumption. This review highlights recent advances in theoretical and experimental microfluidic studies of polymer immobilization under flow conditions in three area, namely, biosensing, biofouling, and studies of thrombosis and hemostasis. image

Synthesis of bridged β-cyclodextrin–polyethylene glycol and evaluation of its inhibition performance in oilfield wastewater

The bridged β-cyclodextrin–polyethylene glycol (β-CD–PEG) is synthesized through reaction of β-CD with PEG, which has been characterized by Fourier transform infrared spectroscope. The inhibition efficiency of bridged β-CD–PEG on corrosion of Q235 carbon steel in 0.5 M HCl solution has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and weight loss measurements. The results show that β-CD–PEG acted as a mixed-type inhibitor and performed excellent inhibiting effect for the corrosion of the Q235 carbon steel. The steel surface morphologies are analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and then an adsorption mechanism model is proposed. The high inhibitory efficiency of β-CD–PEG is related with the adsorption of polymer molecules at the steel surface and a protective film formation. Finally, these results present a novel corrosion inhibitor works in oil-gas field.

Effect of Concentration on HPAM Retention in Porous Media

Summary This paper investigates the effect of hydrolyzed polyacrylamide (HPAM) polymer concentration on retention in porous media by use of both static and dynamic measurements. Consistent results by use of these two methods show that different polymer-retention behaviors exist in dilute, semidilute, and concentrated regions. In both the dilute and concentrated regions, polymer retention has little dependence on concentration. In contrast, in the semidilute region, polymer retention is concentration dependent. If a porous medium is first contacted sufficiently with dilute polymer solution to satisfy the retention, no significant additional retention occurs during exposure to higher HPAM concentrations. On the basis of the experimental results, a concentration-related retention mechanism is proposed that considers the orientation of the adsorbed polymer molecules and the interaction between molecular coils in solution. By use of this model, we explain why polymer retention does not show much dependence on concentration in the dilute and concentrated regimes. Further, in the semidilute region, we explain how moderate coil interactions lead to mixed adsorbed-polymer orientation and magnitude on rock surfaces, and retention becomes concentration dependent. In field applications of polymer and chemical floods, reduced polymer retention may be achieved by first injecting a low-concentration polymer bank.

A new dye‐modified poly(ethylene oxide)–poly(propylene oxide) polymer used as a dispersant for CI Disperse Red 60

A new dye‐modified poly(ethylene oxide)–poly(propylene oxide) polymer, in which the dye molecule (CI Disperse Red 60) is bonded onto polyether monoamine via a triazine ring, was synthesised for the preparation of dye aqueous dispersions and was characterised by Fourier Transform‐infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy and elemental analysis. This polymer exhibits unique dispersing performance for CI Disperse Red 60. The mechanism behind the improved performance is briefly discussed with the help of adsorption isotherms. The results indicated that the hydrophobic dye group of this polymer can strongly adsorb onto the dye particle surface through π–π interaction while its long hydrophilic poly(ethylene oxide) chains allow the formation of a thick layer around the dye particles. It was speculated that the adsorbed polymer molecule on the dye surface would form a brush‐like monolayer conformation. The dyeing performance of the prepared dye dispersions on polyester fabrics was also investigated. It was found that this polymer can effectively increase the apparent solubility of disperse dye. The dyed fabrics showed very good to excellent fastness to washing and rubbing, while the dyeing effluent was colourless.

The role of hydration degree of cations and anions on the adsorption of high-molecular-weight nonionic polyacrylamide on glass surfaces

This study investigates the effect of two alkali metal cations (Li+, K+) on the adsorption of high-molecular-weight, nonionic polyacrylamide on glass surfaces using a colloidal force probe. The effect of two different anions (Cl−, NO3−) on polymer adsorption is also presented. There is a general consensus that hydrogen bonding is the main mechanism by which nonionic polyacrylamides adsorb to silica and glass surfaces. In the current study, the adsorption of the polymer is found to result in repulsion on approach as early as 20min of incubation in polymer solutions using both 0.27M lithium and potassium chlorides. On the other hand, adhesion on retraction occurs in both solutions but with higher magnitudes for the polymer solution prepared in potassium chloride. Adhesion on retraction in potassium chloride solutions occurs even after 24h of incubation, whilst the adhesion disappears in lithium chloride after 24h of incubation. The force at hard contact measured in the potassium chloride solution is generally one order of magnitude lower than those measured in lithium chloride. This indicates that the adsorbed polymer molecules in potassium chloride solutions attain flatter conformation than the ones in lithium chloride. This is attributed to the higher ability of the potassium cation to increase the adsorption energy of the polymer to the glass surface. This higher adsorption energy results in the adsorbed amount of the polymer in KCl being higher than in LiCl. Because of their lower hydration and larger size compared to lithium, potassium cations decrease the hydration of the glass surface and they have the ability to bind with the oxygen atoms in the polymer molecule to the negatively-charged sites on the glass surface. With potassium nitrate, the approach–retraction measurements indicate different adsorption kinetics of polyacrylamide compared to potassium chloride. The nitrate enhances the extension of the adsorbed polymer molecules away from the surface, reflected by the longer ranged steric repulsion in the approach measurements conducted during 24h of incubation. This is probably attributed to the large size of the nitrate anion, its lower hydration and different chemical structure, which allow it to form H-bonds with the polymer. Hence, the polymer is prohibited from forming H-bonds with the surface allowing it to extend away from the surface. This also negatively affects the adsorbed amount, which is found to be lower than in LiCl.

Synthesis and Properties of an Amphoteric Superplasticizer Compatible with Sulphoaluminate Cement

A novel amphoteric polycarboxylic acid-based superplasticizer (APC) was prepared by solution copolymerization from maleic anhydride (MA), allyl polyethylene glycol (APEG) and dimethyl diallyl ammonium chloride(DADMAC). The cationic monomer DADMAC was introduced for improving the performances of sulphoaluminate cement (SAC) with APC. The condition on preparation of APC was determined by the orthogonal experiment. The flow of paste and mortar were alao assessed. Results indicated that APC could improve the fluidity of paste and motar with APC. Zeta potential measurements indicate steric repulsion between the cement particles carrying adsorbed polymer molecules is the main mechanism for dispersion.

Characterization of the adsorption of high molecular weight non-ionic and cationic polyacrylamide on glass from aqueous solutions using modified atomic force microscopy

High molecular weight, anionic, non-ionic and cationic polyacrylamide are used extensively in the oil industry in applications such as drilling, water shut-off, and enhanced oil recovery. They are also used as flocculants in water treatment processes. This study presents AFM measurements of the adsorption of high molecular weight, MW, non-ionic and cationic polyacrylamide from aqueous solvents on glass. The adsorption of the non-ionic polyacrylamide from 0.01 M NaCl solvent on glass was found to be weak and it took more than three days to attain full-surface coverage. In spite of the very high MW, weak adsorption and slow kinetics; the adsorbed layer thickness indicated a flat conformation of the adsorbed macromolecules, suggesting a low level of adsorption. The increase of the salt content of the solvent to 0.34 M NaCl resulted in faster kinetics and thinner layers, mainly due to the screening of the electrical double layer on the negatively charged glass surface. The adsorption of cationic polyacrylamide from both solvents was almost instantaneous due to the strong electrostatic attraction between the positively charged polymer and the negatively charged glass surface. Despite this strong attraction coupled with the MW being one third of the non-ionic polyacrylamide, the adsorbed layer thickness of the cationic polymer from both solvents were more than those formed using the non-ionic polymer. The increase in the salt content in the case of the cationic polyacrylamide adsorption on glass resulted in thicker adsorbed layer due to the charges of both the polymer and the surface being screened and hence more extended tails and loops of the adsorbed polymer molecules.

Inhibiting the anodic dissolution of a steel with polydiallyldimethylammonium chloride and acrylamide copolymers with trimethylammoniumethylacrylate chloride and sodium acrylate

Polydiallyldimethylammonium chloride, as well as acrylamide copolymers with trimethylammoniumethylacrylate, which are industrial flocculants, are tested as corrosion inhibitors on St45 steel. The inhibitor properties are manifested by polydiallyldimethylammonium chloride and acrylamide copolymer with trimethylammoniumethylacrylate chloride. These are determined by the adsorption of polymer molecules on the metal surface. The protective effect of inhibitors is estimated. A mechanism of the adsorption of the surface-active substances on an iron electrode surface is proposed.

Synergic Effects of Polymeric Additives on Dissolution and Crystallization of Acetaminophen

To study how polymeric additives interact with the crystal surface of acetaminophen, and why they have different effects on drug crystallization and dissolution. The effects of different polymers on the etching patterns, crystallization and intrinsic dissolution rate (IDR) of acetaminophen have been studied. Some polymers have shown clear consistency in their effects on the etching patterns, crystallization and IDR of acetaminophen. For example, hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), not only changed the etching patterns of the acetaminophen (010) face, but also inhibited acetaminophen crystallization significantly. Some polymers, like 2-hydroxyethyl cellulose (HEC), poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) only had limited effects on the IDR and etching patterns, and no significant inhibitory effects on crystallization. Even though some polymeric additives have no structural similarity to acetaminophen, they still can affect dissolution and crystallization of acetaminophen due to the synergic effects of their neighboring subunits during surface adsorption. The effects of polymeric additives on crystallization and dissolution of acetaminophen are affected not only by the specific interactions between adsorbed polymer molecules and crystal surface, but also by the mobility of the functional groups involved in the specific interactions.

Triblock Copolymer Lubricant Films under Shear: Effect of Molecular Cross-Linking

The normal interaction and the behavior under shear of mica surfaces covered by a triblock copolymer of poly(L-lysine)-b-polydimethysiloxane-b-poly(L-lysine) (Plys40-b-PDMS40-b-Plys40) before and after cross-linking reaction with two dicarboxylic acids were studied, combining the capabilities of the surface forces apparatus and atomic force microscopy (AFM). At low pH values, this copolymer spontaneously adsorbed on the negatively charged mica surfaces from aqueous solutions as a consequence of the positive charge of the polylysine moieties, forming an extremely smooth boundary layer. This smooth layer displays a very small resistance to shear under small loads, exhibiting outstanding lubrication properties. Nevertheless, the fusion of two contacting layers can be induced by compression at a certain pressure, a process that causes a marked increase in the friction forces. Cross-linking of the adsorbed polymer molecules by covalent bond formation with dicarboxylic acids increases the mechanical stability of the adsorbed layers and hinders the fusion of the boundary layers under pressure but impairs its lubrication properties to a certain extent.

Surface forces in a confined polymer melt: Self-consistent field analysis of full and restricted equilibrium cases

In full equilibrium the self-consistent field theory for a homopolymer melt confined between two surfaces predicts pronounced oscillatory interaction forces on the monomer length scale. However, when not all the polymer molecules can reversibly equilibrate with the bulk, the trapped molecules may be squeezed, adding a repulsive contribution to the interaction energy. The classical constrained or restricted equilibrium approach by Scheutjens and Fleer two decades ago to deal with this for polymers adsorbed from dilute solutions, breaks down in semidilute and concentrated polymer solutions. We present a generalized restricted equilibrium ansatz applicable also for concentrated polymer solutions. The key idea is that only the adsorbed polymer molecules, i.e., molecules that touch the surface at least once, are forced to remain inside the gap, whereas the nonadsorbing chains are free to move out of the gap when the surfaces approach each other. As in dilute solutions, the forces found in confined melt with trapped adsorbed chains become repulsive. We analyse the dependence of the interaction forces both in full as well as in restricted equilibrium cases as a function of the chain length and the interactions with the surface for a compressible polymer melt.

Hydrogen bonding interactions between adsorbed polymer molecules and crystal surface of acetaminophen

The objective of this work was to investigate whether or not the hydrogen bonding interaction between polymer and crystal surface can be detected by the etching pattern changes in the presence of polymers. The (010) face of acetaminophen single crystal was used as a model solid surface. The etching patterns on the (010) face of acetaminophen crystal by water are in the directions of a- and c-axes, which are the same as the directions of the dominant attachment energies on the (010) face. In the presence of polymer, the hydrogen bonding interactions between adsorbed polymer and crystal surface can affect surface diffusion of acetaminophen molecules and change the etching patterns in the direction of a-axis, i.e., the direction of one hydrogen bond chain. Studies with 2-hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC) and poly(vinyl alcohol) (PVA) showed that polymers, which can form hydrogen bonds with acetaminophen crystal surface, can change etching patterns in the direction of a-axis. Study with Dextran suggested that if a polymer cannot form hydrogen bonds with crystal surface due to steric repulsion, it will not change the etching pattern in the direction of a-axis. Studies with poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) further confirmed that only if a polymer can form hydrogen bonds with acetaminophen on crystal surface, the etching patterns in the direction of a-axis will be affected. The study results suggest that in the presence of polymers, the etching pattern change in the direction of hydrogen bond chain, the a-axis of acetaminophen crystals, can be used to indicate the existence of the hydrogen bonding interactions between adsorbed polymers and acetaminophen crystal surface.