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Successful field trials of surfactant-based Production Enhancement (PROE) technology in different shale plays including Permian Basin, Bakken and Eagle Ford indicate that specially tailored surfactant formulations can improve the unconventional well productivity during flowback and production. One major challenge for the operator is to further optimize the surfactant dosage to maximize the economic return. Analysis of the residual surfactant concentration in the produced water (PW) might provide a new path to optimize the surfactant application in the field. Such quantitative measurements can help understand how much surfactant is consumed in the downhole and how much surfactant is in the flowback, and possibly correlate back to the well performance. Additionally, surfactant partitioning and adsorption behaviors can be studied through residual analysis, which will further provide guidance to develop next generation of surfactant formulations. In this study, a liquid chromatography-mass spectrometry (LC-MS) method was developed to accurately measure the residual surfactant concentration in the produced water. The liquid chromatograph (LC) separates the surfactant from sample matrix and avoids the possible interference, and then the mass spectrometer (MS) detects the separated surfactant, signal correlating to the residual concentration. This analytical method provides unrivalled selectivity and specificity compared to other methods reported in the literature. In addition, a Methyl Orange method was developed and can potentially be used in the field for quicker measurements. Produced water samples collected from a Huff-and-Puff treatment in the Permian Basin were evaluated using both methods. Our results indicate that both methods can successfully capture the trend of residual concentration vs. production time. The deviation between LC-MS and Methyl Orange measurements was due to the presence of ADBAC (alkyldimethylbenzylammonium chloride) in the produced water, which is a cationic amine surfactant typically used as biocide in the well stimulation. It produces positive interference and thus leads to a higher residual detection in the Methyl Orange test. Notably, the residual concentration of surfactant in produced water decreased with time after the well was placed back to production, which is consistent with the concept that more surfactant will adsorb to the rock surface or partition into the oil phase over production time. In summary, we believe the LC-MS and Methyl Orange methods can potentially be used to detect residual concentration for any type of surfactant-based applications in unconventional reservoirs including Huff-and-Puff, completion, frac protect, surfactant flooding and re-frac. The field application of surfactant-based chemistry followed by this type of residual analysis can help understand the underlying mechanisms of the surfactant and provide further guidance for production optimization of shales.

Bottle testing for emulsion breakers (EBs) in steam-assisted gravity drainage (SAGD) operations is a standard practice; however, it has been observed that, in some cases, EBs recommended via bottle tests can fail during field trials as a result of conditions being disparate, such as higher temperatures and pressures in the field that cannot be safely or easily replicated in the lab. To make better EB recommendations, an optimized methodology based on interfacial rheology measurements was developed. Compressibility tests performed at different temperatures (80–120 °C) were used to compare effect of EBs on parameters such as initial compressibility, initial interfacial tension, phase transition ratio, and drop crumpling or detachment ratio (ratio of the compressed surface area to the original surface area at which the interface starts to collapse or at which the drop detaches). Furthermore, the addition of the EB to the oil phase versus aqueous phase was investigated. The effects of EBs at the oil/brine int...

Steam-assisted gravity drainage (SAGD) is one of the unconventional methods used in Canada to extract heavy oil; however, a stable water-in-oil-in-water (W/O/W) emulsion is generated during production. The emulsion is then pumped into a high-temperature separator, after adding a diluent, a reverse emulsion breaker (REB), and an emulsion breaker (EB) to separate the oil and water and comply with the sales oil specifications. This work is focused on understanding the demulsification processes under high-temperature (80–120 °C) and high-pressure (700–900 kPa) conditions. Compressibility, crumpling film or drop detachment ratios, and interfacial tension (IFT) were used to evaluate the demulsifiers. REBs were found to decrease IFT and cause the interfacial film to be reversible. These effects showed a dependency with the temperature, and their magnitude varied with the chemistry of the REB. Effective REBs formed complexes with natural anionic surfactants present in the oil phase, weakening the irreversible fil...

A detailed characterization of a produced emulsion, obtained from Steam Assisted Gravity Drainage (SAGD) operations, as well as synthetic emulsions, prepared after diluting the oil with three different solvents, was carried out. Reference samples were also used for comparison purposes, in which the oil phase was solely composed of diluent. Non-conventional techniques such as Differential Scanning Calorimetry (DSC) and Multiple Light Scattering with near infrared radiation were employed for the studies. DSC was used to determine the type of emulsion and to quantify the amount of free and emulsified water for either synthetic or produced emulsions. The stability of the emulsions was monitored by using multiple light scattering of near infrared radiation and it was correlated with the compositional differences of the diluents (paraffinic vs aromatic nature and surface active compounds) and their potential effects on asphaltene precipitation. A comparison of the results with droplet size and zeta potential values indicated that stability in this type of emulsions results from a balance of the steric and electrostatic mechanisms, the former being the dominating force. Model oils were also prepared by diluting extracted asphaltenes with toluene and mixtures of toluene and heptane. It was demonstrated that asphaltene aggregates can be present even at concentrations as low as 0.005 wt% and they play a key role on SAGD emulsion stabilization.

In steam-assisted gravity drainage (SAGD) operations, the produced fluids are complex water-in-oil-in-water (W/O/W) emulsions. A diluent is often added to reduce the density and viscosity of the heavy crude oil. However, the quality and composition of the diluents may in some cases increase emulsion stability and cause the dehydration of the oil to be more difficult because there are more surface-active agents added to the oil coming from the diluent streams. Thus, this work was aimed at studying the effect of three different diluents on interfacial film formation of a Canadian heavy oil. Interfacial elasticity and compressibility were evaluated, and the results were then correlated with emulsion stability. The wettability of the systems was also studied. The systems studied behaved as if a bidimensional gel near its gelation point had organized at the interface, in which adsorbed amphiphilic materials, such as asphaltenes and resins, self-aggregated at the interface, forming a network that acts as a stab...

Activated (AS) and carboxymethylated (CMS0.24) cassava starch derivatives were studied as corrosion inhibitors for carbon steel XC35 in a 200 mgL-1 NaCl solution. They were characterized by back titration and Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical techniques were used to evaluate the inhibitive properties of starches at room temperature and the chemical composition of the protective films was determined by X-Ray Photoelectron Spectroscopy (XPS). Electrochemical measurements revealed that AS acts as mixed inhibitor, whereas CMS0.24 mainly inhibits the anodic reaction. In both cases, the protection increased with the inhibitor concentration; nevertheless, after 24 hours of immersion, the CMS0.24 loses its properties, while AS molecules still maintains them. XPS analyses show that the inhibitive films are composed of an iron oxide/hydroxide mixture in which starch molecules are incorporated. Results were explained taking into consideration the hydrophilicity and the strength of the ionic interaction of the starches with the metal surface.

Starch complexes were obtained from activated and pregelatinized cassava starch (AS) or carboxymethyl starch (CMS) by using quaternary ammonium salts (QAS). The synthesis of the CMS was carried out by a single or double step carboxymethylation reaction with monochloroacetic acid. Different parameters were assayed to prepare the ionic complexes: CMS or AS as starting materials, anhydroglucose unit/QAS ratio, and length of the alkyl chain of the alkyltrimethylammonium bromide (C n TAB) salt. The products were characterized by FTIR, 1 H and 13 C NMR, and the Kjeldhal method. The results indicated a much more favorable complex formation when using CMS, obtaining the highest degree of substitution or complexation (0.72) and reaction efficiency (0.96) when C 18 TAB was employed. DSC and WAXS experiments evidenced the crystallization of the octadecyl chain introduced in the starch, exhibiting a dependence on sample water content. TGA and TVA analysis showed the stability of the complexes up to ∼150 °C and that degradation takes place in at least two stages with the release of the surfactant moiety in a first stage and the degradation of the starch skeleton in a second stage.

Transuranic radionuclides such as uranium tend to be a pervasive environmental contaminant. It is absorbed through the intestine or a lung, deposited in the tissues, predominantly kidney and bone, and is carcinogenic. A novel nanosensor system has been developed for voltammetric tracing of environmental uranium contamination. The sensor consists of an organophosphorous ligand, (t-butylphenyl)-N,N-di-(isobutyl) carbamoylmethylphosphineoxide (CMPO) functionalized superparamagnetic core–shell magnetic nanoparticles and magnet based electrodes. It exploits the natural affinity of uranium for phosphate molecules to fabricate a highly specific and reproducible sensor. The small dimension along with a dramatically increased contact surface has lead to a faster response and higher sensitivity. The system uses an external magnetic field gradient for preconcentration and removal of the analyte from the surrounding aqueous media. The redox properties of the analyte are exploited for enumeration of variables by electrochemical techniques such as square wave voltammetry. The detection limit of the system is observed to be in parts-per-billion (ppb) of the uranyl concentration.

The physical and chemical modification of cassava starch was carried out to prepare compounds that were evaluated as corrosion inhibitors of carbon steel under alkaline conditions in 200 mg L −1 NaCl solutions. Two species were tested: an activated starch (AS) and a carboxymethylated starch (CMS) with two different degrees of substitution ( DS ). The success of the chemical procedure was confirmed by 13 C NMR. The DS was determined by back titration and products with 0.13 (CMS 0.13 ) and 0.24 (CMS 0.24 ) were obtained. The inhibitive properties were studied by means of electrochemical impedance spectroscopy. It was found that modified starches have corrosion inhibitive properties and that their protection level depends on the type and amount of active groups present in the molecules. AS showed better performance than CMS, whose inhibition ability increases with the degree of substitution. This result was explained by the strong ionic interaction between AS and ferrous cations, which was confirmed by the electrostatic potential mapping of the monomeric units. After the corrosion experiments, the surfaces also were investigated through atomic force microscopy. It was found that a densification of the inhibitive layer was responsible for the higher protection level afforded by AS after 24 h of immersion.

Moisture sorption isotherms of native and ten hydrophobically modified cassava starches were determined at 25 °C using a moisture sorption analyzer in an a w range of 0–0.94. Modified cassava derivates were obtained by modifying native cassava starch (CS) with octenyl succinic anhydride (OSA) and by modifying a carboxymethylated cassava starch (CMCS) with quaternary ammonium salts having different alkyl chain lengths (CnTAB with n = 12, 14, 16, and 18). In comparison to native cassava starch, the results obtained showed that OSA modification yielded a more hydrophobic material for the whole a w range, while the ionic complexes obtained from CMCS and quaternary ammonium salts produced more hydrophobic starches at low a w values and more hydrophilic ones at high a w values. It was found that the experimental data were well represented by the GAB model and that the monolayer water contents decreased with chemical modification. The moisture sorption kinetic parameters showed that water adsorption process became slower in chemically modified starches.

In this work, the compatibilization of a poly(ϵ-caprolactone) with a number-average molecular weight of 120,000 g/mol (PCL120) and maize starch was investigated by the addition of a chemically modified poly(ϵ-caprolactone). Two types of blends were prepared by melt extrusion. In type A blends, low-molecular-weight compatibilizers were used: (1) a poly(ϵ-caprolactone) with a number-average molecular weight of 10,000 g/mol that was reacted with maleic anhydride to obtain chains terminating in carboxylic groups and (2) low-molecular-weight poly(ϵ-caprolactone)s (number-average molecular weights of 600 and 2000 g/mol) with one pendant carboxylic group within the chains. With these groups of blends, tensile testing and scanning electron microscopy demonstrated that the compatibilizers were generally effective in inducing a better dispersion for a 60/40 poly(ϵ-caprolactone)/maize starch blend with a compatibilizer, improving the mechanical properties in comparison with uncompatibilized blends. The blends with 30% starch were not improved by the addition of compatibilizer, and this may be related to the rheology of the blends during preparation. In type B blends, high-molecular-weight compatibilizers were prepared through the grafting of variable amounts of acrylic acid or maleic anhydride to PCL120 chains. The best compatibilizer action was obtained with 0.7 wt % maleic anhydride grafted to PCL120 because both the dispersion and mechanical properties were further improved in comparison with uncompatibilized blends and type A blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Two types of mixtures were prepared by solution blending: high molecular weight polyhydroxybutyrate (PHB)/poly(e-caprolactone) (PCL) and PHB/low molecular weight chemically modified PCLs (mPCL). The morphology, crystallization, and enzymatic degradation of the blends were studied by differential scanning calorimetry, polarized light optical microscopy, scanning electron microscopy, 1 H NMR, and weight loss measurements. In addition, enzymatic degradation studies were performed by an exposure to Aspergillus flavus. High molecular weight PHB/PCL blends were found to be immiscible in the entire composition range. Phenomena such as PCL fractionated crystallization and a decrease in PHB nucleation density were detected. When PHB was blended with mPCLs, the blends were partially miscible; two phases were formed, but the PHB-rich phase exhibited clear signs of miscibility through a depression of both the T m and the Tg of the PHB component (which was stronger with lower molecular weight mPCL), and an increase in the growth rate of PHB spherulites in the blends as compared to neat PHB or to the PHB component in the PHB/PCL blends. The biodegradation by a exposure to A. flavus showed that the blends are synergistically attacked in comparison to the homopolymers. Two factors may influence the improved degradation rate of the blends: the dispersion of the components and their crystallinity that was reduced in view of the fractionated crystallization and impurities transfer. In the case of the PHB/mPCL blends, the increased miscibility between the components caused a reduction in the degradation rate.

The thermal behavior of melt-mixed polypropylene (PP)/poly(ϵ-caprolactone) (PCL) blends was investigated with differential scanning calorimetry, and it was quantitatively related to the morphology observed through scanning electron microscopy. The PP/PCL blends were immiscible in the whole composition range; however, some interesting phenomena were found. Blends with low PP contents crystallized in a fractionated fashion. By applying a self-nucleation procedure, we demonstrated that this occurred because of a lack of highly active heterogeneities within the confined PP domains. On the other hand, PP acted as a nucleating agent for PCL, and when the PP content was reduced, the higher surface/volume ratio increased its nucleating activity. The nucleating effect was improved when the PP was self-nucleated because of the better nucleating effect of PP annealed crystals. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1365–1379, 2007

The effect of blending poly(styrene-co-maleic anhydride) with 14 mol% MA (PSMA14) with poly(ɛ-caprolactone) (PCL) is studied by calorimetry, X-ray diffraction, dielectric techniques, and microscopy. Variations in PCL crystallization, melting temperatures and crystallinity degree were observed. Additionally, the presence of a wide and asymmetric enthalpic step, whose position follows Fox predictions, demonstrates miscibility between the blend components. This is in agreement with the interlamellar location of PSMA14. Thermally stimulated depolarization techniques evidenced two segmental dynamics, with distinct compositional variations due to the local differences in composition perceived by each component as a consequence of chain connectivity. The two effective glass transition temperatures vary with composition, in agreement with the self-concentration model predictions when using the Kuhn's segment length for each component. From isothermal crystallizations a marked depression of the PCL equilibrium melting point ( T m o ) is observed in the blends together with an increase in the half-crystallization times, τ1/2, as the content of PSMA14 grows. PCL-rich blends exhibited ring-banded spherulites, with a ring periodicity that increased with crystallization temperature and with PSMA14 content. Preliminary results of the phase separation process are given from samples that were thermally treated under different conditions.

A first attempt was made to produce novel ABC triblock terpolymers with three potentially crystallisable blocks: polyethylene (PE), poly(ethylene oxide) (PEO), and poly(e-caprolactone) (PCL). Polybutadiene-b-poly(ethylene oxide) diblock copolymers were synthesized by living anionic polymerization. Then, a non-catalyzed thermal polymerization of e-caprolactone from the hydroxyl end group of the PB-b-PEO diblock precursors was performed. Finally, hydrogenation by Wilkinson catalyst produced PE-b-PEO-b-PCL triblock terpolymers. Side reactions were detected that lead to the formation of undesired PCL-b-PEO diblock copolymers, however, these impurities were successfully removed by purification. A range of triblock terpolymers with PCL and PEO minor components were prepared. Topological restrictions on the PEO middle block prevented this block from crystallizing while the complex crystallization behavior of the PE and PCL blocks was documented by DSC and WAXS measurements.

The isothermal crystallisation behaviour of the polyethylene block within polystyrene-b-polyethylene-b-poly(e-caprolactone), SEC, triblock copolymers was studied by differential scanning calorimetry. The morphology was observed by transmission electron microscopy. Melting scans after isothermal crystallisation performed at different times were employed to determine the crystallisation kinetics one step at a time (“isothermal step crystallisation”). Double melting endotherms were observed after isothermal crystallisation and they were interpreted as a result of the melting of two lamellar populations. These arise from the intrinsic short chain branching distribution within the hydrogenated polybutadiene chains that conform the PE blocks and from their location within the copolymer microdomains. The Hoffman–Weeks procedure failed to yield reasonable values for the equilibrium melting point of the PE blocks as a result of the distribution of linear sequences present in these blocks. The results indicate that as the degree of PE confinement increases the Avrami index decreases to values that are even lower than 1, a result that can be explained by the nature of the homogeneous nucleation process that is in between sporadic and instantaneous.

Chain mobility in multiphase polymeric materials is studied by thermally stimulated depolarization currents and dielectric spectroscopy in poly(styrene)-b-poly(butadiene)-b-poly(c-caprolactone) triblock copolymers and poly(carbonate)/poly(c-caprolactone) blends. The variation in the relaxation time distribution of the dielectrically active components and in the number of orientable dipoles in the amorphous phases of these materials is interpreted as the result of the existence of a rigid amorphous phase constrained by the crystalline regions or in the case of the blends by a phase segregation which takes place when the crystallization process of the blend components advances. The mean relaxation times for the secondary and segmental motions are not affected when the phases are segregated.

Dielectric relaxations of polycarbonate (PC) and poly(e-caprolactone) (PCL) blends that were thought to be completely homogeneous in the amorphous phase from many previous calorimetric studies are performed by using the thermally stimulated depolarization currents technique. Samples kept for 18 months at room temperature were compression-molded and then either quenched or slowly cooled. Quenched samples evidenced a phase separation for the 20/80 PC/PCL composition and the existence of continuous concentration fluctuations for other blend compositions. The slowly cooled samples from the melt exhibited an increase of the crystallinity degree for both blend components, together with a segregation of a predominantly rich PCL phase and the appearance of high-temperature relaxations attributed to interfacial polarization. These findings are confirmed by new calorimetric results on the same blends and by transmission electron microscopy. The spherulitic growth rate also points to the coexistence of two phases wh...

The surface patterns resulting from fast crystallization of as-cast and annealed thin films (ca. 100 nm) of two polystyrene- b -polybutadiene- b -poly(e-caprolactone) ABC triblock copolymers is investigated through atomic force microscopy (AFM). Two different substrates are used: silicon and mica. The behaviour is compared with the bulk morphology obtained through transmission electron microscopy (TEM). AFM images of the as-cast films revealed surfaces with lamellar patterns. Based on the observation of T-shaped grain boundaries between lamellae, and on a comparison of the microdomain dimensions obtained by TEM and AFM, the surface pattern is rationalized as being formed by amorphous and crystalline polycaprolactone (PCL), with the PCL/PB block copolymer interfaces located parallel to the susbstrate. The formation of islands and holes in annealed films with a lamellar ‘floor’, depending on the conmensurability between film thickness and long period, is also observed, indicating a parallel orientation of the block copolymer lamellae.

The confinement of crystallizable blocks within AB or ABC microphase-separated block copolymers in the nanoscopic scale can be tailored by adequate choice of composition, molecular weight, and chemical structure. In this work we have examined the crystallization behavior of a series of AB and ABC block copolymers incorporating one or two of the following crystallizable blocks: polyethylene, poly(e-caprolactone), and poly(ethylene oxide). The density of confined microdomain structures (MD) within block copolymers of specific compositions, in cases where the MD are dispersed as spheres, cylinders, or any other isolated morphology, is much higher than the number of heterogeneities available in each crystallizable block. Therefore, fractionated crystallization takes place with one or several crystallization steps at decreasing temperatures. In specific cases, the clear observation of exclusive crystallization from homogeneous nuclei was obtained. The results show that, regardless of the specific morphologica...

In SAGD (Steam Assisted Gravity Drainage) operations the produced fluids are complex water-in-oil-in-water (W/O/W) emulsions. A diluent is often added to reduce the density and viscosity of the heavy crude oil. However, the quality and composition of the diluents may in some cases increase emulsion stability and cause the dehydration of the oil to be more difficult as there are more surface-active agents added to the oil coming from the diluent streams. To simulate temperature and pressure conditions during SAGD operations, this work studied the effect of three diluents on interfacial rheology of a Canadian heavy oil and synthetic brine at 120°C and 130 psi and then correlated with emulsion stability and oil dehydration. When compared to 25°C, all three diluents exhibited higher higher compressibility at 120°C, while the initial interfacial tension, "phase change" area ratio (area ratio at which the phase change from high compressibility region to low compressibility region), and crumpling ratio (ratio of the compressed surface area to the original area at which the interface starts to collapse) exhibited a more complex behavior. The higher interfacial tension and higher compressibility were correlated with the lower emulsion stability at increasing pressure and temperature in the absence of treating chemicals. Increasing ageing of the film from 10 minutes to 1 hour at 120°C had a similar effect on the three diluents, suggesting the formation of a more elastic film as asphaltenes start to cross-link on the interface. The effect of demulsifiers (emulsion breakers-EB and reverse emulsion breakers-REB) on interfacial was also investigated at RT and 90°C. Demulsifiers that produced the minimum interfacial tension (IFT) with changing concentrations demonstrated to be the best demulsifiers in the bottle tests. A synergistic effect in reducing IFT was found when EB and REB when combined.

The preparation of polystyrene-b-poly(ethylene oxide)-b-poly(-caprolactone) triblock co- polymers using three different strategies is described. Experimentally, a method we have called "thermal" is the simplest one of the three employed. However, it presents serious limitations for the preparation of high molecular weight triblock copolymers with low polydispersity. The titration method is a more elegant alternative to prepare the PS-b-PEO-b-PCL triblock copolymers. Nevertheless, the stoichiometric titration of the precursor terminal hydroxyl groups requires much expertise, and it becomes more difficult as the concentration of such terminal groups decreases when the precursor molecular weight increases. Finally, the sequential method may be regarded as the most convenient one. However, the experimental steps involved a solvent exchange during polymerization that must be performed under conditions of strict purity and high vacuum. Several triblock and pentablock copolymers of varying compositions and molecular weights were successfully prepared. The fact that these copolymers contain two crystallizable blocks, i.e., PEO and PCL, makes them very interesting from a structural point of view. The copolymers were found to be phase segregated according to evidence provided by DSC and WAXS. The crystallization and melting behavior of both PEO and PCL blocks is greatly affected by composition. Fractionated crystallization phenomena were detected when either one or both blocks constituted the minor components within the block copolymers.

In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(∈-caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass-transition temperature (T g ) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the T g was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T o m ) by the Hoffman-Weeks extrapolation method. A T o m depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60-70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed.

A new technique to thermally fractionate polymers using DSC has been recently developed in our laboratory. The applications of the novel successive self-nucleation and annealing (SSA) technique to characterize polyolefins with very dissimilar molecular structures are presented as well as the optimum conditions to thermally fractionate any suitable polymer sample with SSA. For ethylene/α-olefin copolymers, the SSA technique can give information on the distribution of short chain branching and lamellar thickness. In the case of functionalized polyolefins, detailed examinations of SSA results can help to establish possible insertion sites of grafted molecules. The application of the technique to characterize crosslinked polyethylene and crystallizable blocks within ABC triblock copolymers is also presented.

The microphase morphology of a polystyrene-block-polybutadiene-block-poly(e-caprolactone) SBC triblock copolymer is studied through transmission electron microscopy. Even though crystallization of the PCL block takes place well below the PS glass transition, lamellar microphases and the formation of well-defined spherulites are observed. The typical long-range order normally obtained for amorphous triblock copolymers is not obtained in the SBC triblock copolymer. The morphology of a polystyrene-block-poly(e-caprolactone) diblock copolymer was also observed and compared with the triblock copolymer. To investigate whether the crystallization temperature (Tc) is a parameter influencing the final morphology, samples of the triblock copolymer were crystallized at 45 and 42 °C. This reduction in Tc results in a morphological transition from a simple lamellar morphology (PS, PB, and PCL form layers), which we call lamellar−lamellar (ll), to a lamellar−cylindrical (lc)-morphology with PS and PCL layers and PB cyl...

The relationship between the microphase morphology and stress−strain behavior of a polystyrene-block-polybutadiene-block-poly(e-caprolactone) SBC triblock copolymer has been investigated with polystyrene as the major component. The semicrystalline PCL block does not change significantly the basic morphology, but it affects the form of the microdomains, so that S57B27C16 shows a “polygonal” core shell morphology in a PS matrix. This morphology seems to be the consequence of crystallization in the inner PCL cylinders inducing deformation of the microdomains, which may create interfacial stresses. These stresses can generate small microcrazes upon external loading which may be responsible for the high elongations at break in this material. Moreover, the long-range order of the microdomains, which can be affected through the preparation conditions, determines the stress−strain behavior. Copolymers with 57 and 51 wt % PS and a corresponding “PS matrix” exhibit elongations at break up to ∼800%.

The hydrogenation of polystyrene-block-polybutadiene-block-poly(£-caprolactone) SBC triblock copolymers was performed in the presence of the Wilkinson catalyst RhCl(P(C 6 H 5 ) 3 ) 3 . Reaction conditions (hydrogen pressure, temperature and reaction time) were varied to ensure quantitative hydrogenation without detectable side reactions. Gel permeation chromatography showed no broadening of the molecular weight distribution during hydrogenation. The efficiency of the catalyst is markedly influenced by the molecular weight of the copolymer. Due to the presence of the polyethylene (PE) block, the resulting polymers exhibit a reduced solubility in comparison to the starting materials. Using differential scanning calorimetry (DSC), preliminary results about the crystallization and melting behavior of the PE-block were obtained. In the triblock copolymers, the PE-block showed a marked depression of the melting point and crystallinity when compared to pure hydrogenated polybutadiene of equivalent molecular weight and microstructure or to a comparable PE-block within a polyethylene-block-poly(e-caprolactone) diblock copolymer. A fractionated crystallization process of the PCL-block was observed when the PCL component in the hydrogenated triblock copolymers was present as a minor phase.

Polystyrene-block-polybutadiene-block-poly(e-caprolactone) SBC triblock copolymers with a PCL matrix exhibit microphase separation into three different phases within the spherulitic superstructures. Mixing of the PS-block can occur upon melting of the PCL-block if the molecular weight is low enough. Even though the crystallization takes place well below the PS-glass transition, a deformation of the amorphous microphases into ellipsoidal core-shell cylindrical microdomains is observed by TEM. These copolymers have mechanical properties which are dominated by the PCL (Poly(e-caprolactone)) matrix with an influence of the amorphous blocks.

During the Steam Assisted Gravity Drainage (SAGD) production process, complex water-in-oil-in-water (W/O/W) emulsions are generated, which need to be treated to promote water-phase separation and recovery of the oil. Due to the similar density of heavy oil and water, dilution is frequently required to improve the separation process, but also to reduce the viscosity of the extracted bitumen to facilitate flow. Although significant research has been carried out to understand the stabilizing and destabilizing factors of both water-in-oil and oil-in-water emulsions, studies related to the characterization of complex W/O/W emulsions containing diluents are still limited. When carrying out this type of analysis, the complex relationship among different variables should be considered, such as the chemistry and concentration of stabilizing agents, water-to-oil ratio and droplet charge. Temperature and shearing methods are process conditions that must be also considered. In this study we combined several techniques to characterize production fluids and synthetic emulsions, using diluents with different composition. Differential Scanning Calorimetry (DSC) was explored as a tool for analyzing the emulsions. Since the oil present in these fluids did not exhibit any thermal transition between -80°C and 30°C, the DSC could be used to quantify the amount of free and emulsified water in one measurement, for either synthetic or produced emulsions. Results demonstrated that this technique has a high potential to characterize emulsified systems with precision, requiring only small amounts of sample and without applying any pre-treatment. The technique can also be used to screen demulsifiers after performing a specific thermal treatment within the equipment. Bottle tests are commonly used in the industry to monitor emulsion behavior. They are easy to perform, but are subject to the judgment of the experimenter, who measures the partitioning of the phases and in some cases their relative opacity. To perform a more quantitative analysis, demulsification was monitored in real-time, using a multiple light scattering device. Phase separation rates were highly influenced by the nature and amount of diluent used and they were correlated with droplet size, interfacial tension and surface pressure measurements. Results were rationalized based on the differences in the asphaltene-resins interfacial film, which will determine the emulsion behavior upon separation in the field when using demulsifiers.

In SAGD (Steam Assisted Gravity Drainage) operations the produced fluids are a complex water-in-oil-in-water (W/O/W) emulsion. A diluent, which is a major operational cost item, is often added to the produced fluid to reduce the density and viscosity of the heavy crude, thereby facilitating oil and water separation. The variable quality of the diluent and various types of diluent can increase the emulsion stability and cause the dehydration of the oil to be more difficult as there are more surface-active agents added to the oil from the diluent stream. In this work, the effect of various diluents on interfacial films was studied by measuring interfacial elasticity and "dynamic" surface pressure isotherms and then correlated with emulsion stability and oil dehydration. Compressibility, crumpling film ratio (ratio of the compressed surface area to the original area at which the interface starts to collapse), and surface pressure were determined from the surface pressure isotherms. When interfacial rheological measurements were conducted on fluids treated with the diluent, the system behaved as if a bidimensional gel near its gelation point had organized at the interface. In other words, adsorbed amphiphilic materials such as asphaltenes and resins had self-aggregated at the interface and formed a network, which presents all the rheological characteristics of a gel, acting as a stabilizing mechanism for produced emulsions. When the interface was aged for 20 hrs, its gel strength was nearly 70% higher than the fresh interface, suggesting an explanation why aged emulsions are more difficult to treat. As the surface area of an oil droplet submersed in water is reduced, asphaltene molecules adsorbed onto the interface are drawn closer together and resist compression. This gives information about how rigid the drop surface becomes. The software of interfacial rheological measurements can be set up to capture drop images during compression measurements, allowing us to observe the formation of rigid interfacial skins at the oil-water interface. The amount of skin formed at a droplet surface increased with increasing asphaltene concentration and varied in different diluents. Unlike elasticity and interfacial tension measurements, this method can predict emulsion stability in different diluents and at various asphaltene concentrations. A correlation exists between the interfacial compressibility, crumpling film ratio, and emulsion stability: the higher the crumpling film ratio and the lower the compressibility, the more stable the emulsion. This new test method gives more insights into mechanisms of emulsion stabilization caused by the diluent and asphaltene and potentially can be employed to study the structure and demulsifying performance relationships of EBs (emulsion breakers) and REBs (reverse emulsion breakers).

The dynamic crystallization and the melting behavior of polystyrene-block-poly(e-caprolactone) (PS-b-PCL, short notation SC), polybutadiene-block-poly(e-caprolactone) (PB-b-PCL, BC) and polystyrene-block-polybutadiene-block-poly(e-caprolactone) (PS-b-PB-b-PCL, SBC) have been studied using differential scanning calorimetry. The copolymers with high molecular weight exhibit microphase separation into microphases consisting of polystyrene, polybutadiene and poly(e-caprolactone) and partial crystallization of the corresponding PCL block. The crystallization occurs at temperatures below the PS glass transition. Depending on the block copolymer composition, crystallization takes place through a combination of heterogeneous and homogeneous nucleation. Isothermal crystallization was studied in order to determine the equilibrium melting point, T m 0 , of the PCL block, which depends on the weight ratio w PB :w PCL . The crystallization kinetics was analyzed in terms of Avrami equation. A general decrease in the overall crystallization rate in the block copolymers relative to the equivalent PCL homopolymer was found. Additionally, the growth rate of the spherulites was followed using polarized optical microscopy. Depending on the composition and flexibility of the block connected to PCL, some copolymers showed ring-banded spherulites.

The sequential anionic polymerization of polystyrene-block-polybutadiene-block-poly(e-caprolactone) (SBC) triblock copolymers as well as polystyrene-block-poly(e-caprolactone) (SC) and polybutadiene-block-poly(e-caprolactone) (BC) diblock copolymers was achieved in benzene. To initiate the polymerization of the highly reactive e-caprolactone, the nucleophilicity of the carbanion has to be reduced. For this purpose 1,1-diphenylethylene (DPE) was used. To avoid inter- and intramolecular transesterification reactions of the growing caprolactone block, the reaction time of this monomer in the block copolymers was strictly controlled. The reaction between polybutadienyl anions and DPE is too slow, and an incomplete reaction results in side reactions when e-caprolactone is added. An alternative method was developed, which consisted in the addition of a small quantity of styrene, after the polymerization of butadiene, to diminish the total reaction time and reduce the probability of chain transfer.

4-Urazoylbenzoic acid groups are attached to the chain ends of polyisobutylene. The cooperative assembling process of these polar groups is studied by DSC and dielectric and dynamic mechanical spectroscopy. The melting of the ordered clusters occurs in the temperature range 380-390 K. Distortions within the U4A clusters (Σ process) are monitored below the melting temperature T m with dielectric spectroscopy. On a larger length scale, these distortions also lead to stress relaxation which can be probed by dynamic mechanical measurements. Near T m , the relaxation ofU4A multiplets (α* relaxation) is detected with dielectric spectroscopy. In this temperature range, dynamic mechanical measurements show a transition from elastic behavior to viscous flow. The results are rationalized with molecular modeling calculations.

A self-assembled 3D hydrogel–nanoparticle composite integrated surface plasmon resonance (SPR) sensor is reported here. The novel assembled substrate was developed by means of a surface mediated radical co-polymerization process to obtain a highly sensitive hydrogel-based thin film that possesses specific binding sites for target analytes. Initially, amino group modified gold nanoparticles (AuNPs) were covalently linked to acrylic acid monomer. Following this, N-isopropylacrylamide (NIPAAm) and AuNPs linked acrylic acid (AAc) monomers were randomly co-polymerized by the “grafting from” method in the presence of initiator and crosslinker onto the sensing surface. Surface charecterization techniques were utilized to evaluate the thickness and composition of the hydrogel-nanoparticle film. The sensing platform was employed to study the binding kinetics and conformational changes of the ArsA ATPase as a consequence of binding trivalent arsenicals under a variety of conditions. ArsA, the catalytic subunit of the ArsAB arsenite (As(III)) translocating ATPase, is one of the five proteins encoded by the arsenical resistance (ars) operon of plasmid R773 in cells of Escherichia coli, that confers resistance to trivalent and pentavalent salts of the metalloid arsenic. SPR measurements indicate that the 3D hydrogel-nanoparticle coated sensors exhibited a higher sensitivity than that of the 2D AuNPs decorated sensors. Binding of As(III) to ArsA is greatly facilitated by the presence of magnesium ion and ATP.

In this work we present an experimental study of shear and apparent elongational behavior of linear low-density (LLDPE) and low-density (LDPE) polyethylene blends by means of capillary rheometry. The characterization of these rheological properties is crucial in the design of a blend that combines the ease of processing of LDPE with the mechanical advantages of the LLDPE. Two different low-density polyethylenes and one common linear low-density polyethylene were used to prepare the blends. The results obtained indicate a strong sensitivity of the rheology of the blend to changes in the molecular weight of the LDPE employed. For the higher molecular weight LDPE, the shear viscosity of the blend was essentially equal to that of the LDPE homopolymer up to a concentration of 25% of LLDPE, whereas the apparent extensional viscosity was appreciably lower. For the lower molecular weight LDPE, the same trend was obtained regarding the shear viscosity, but in this case the apparent extensional viscosity of the blend was somewhat higher than that of the LDPE homopolymer.

The estimated equilibrium melting points of the poly(e-caprolactone) (PCL) fraction in poly(styrene-co-maleic anhydride)/poly(e-caprolactone) blends (PSMA14/PCL), where the PSMA has 14 mol% of maleic anhydride units, were successfully analyzed by means of the Nishi-Wang equation yielding a negative Flory-Huggins interaction parameter ( c = -1.46 ). This result indicates strong interactions between the blend components, whose magnitude do not change with composition. The kinetics of the PCL spherulitic growth was investigated as a function of composition and crystallization temperature by polarized optical microscopy and analyzed using the traditional Lauritzen-Hoffman (LH) secondary nucleation theory, as well as a modified version of it. The composition dependence of nucleation constants, Kg, in crystal growth regime II suggests that crystal fold energy, se, decreases with the addition of PSMA14, but when the concentration of PSMA14 reaches 20% or more, non additional effect is observed, a fact that was attributed to the PCL effective concentration considered in the Lodge and McLeisch model for miscible blends Mediante la ecuación de Nishi-Wang se llevó a cabo en este trabajo un análisis de los puntos de fusión en equilibrio estimados de la fracción de poli(e-caprolactona) (PCL) contenida en mezclas de poli(estireno-co-anhídrido maleico)/poli(e-caprolactona) (PSMA14/PCL), donde el PSMA posee 14% molar de unidades de anhídrido maleico. Como resultado se obtuvo un parámetro de interacción de Flory-Huggins negativo (c = -1.46), resultado que indica la existencia de fuertes interacciones entre los componentes de la mezcla, cuya magnitud no cambia con la composición. La técnica de microscopía óptica de luz polarizada permitió estudiar la cinética de crecimiento esferulítico de la PCL en función de la composición y de la temperatura de cristalización. Posteriormente, se aplicó la tradicional teoría de nucleación secundaria de Lauritzen-Hoffman (LH), así como también una de sus versiones modificadas. La dependencia de las constantes de nucleación, Kg, con la composición en el régimen de crecimiento II sugiere que la energía de pliegue disminuye con la adición de PSMA14. Sin embargo, cuando la concentración de PSMA14 alcanza el 20% o más, no se observa efecto adicional, hecho que se atribuyó a la concentración efectiva de PCL que se considera en el modelo de Lodge y McLeisch para mezclas miscibles

Recent results on the crystallization of block copolymers with more than one crystallizable block are reviewed. The effect that each block has on the nucle- ation, crystallization kinetics and location of thermal transitions of the other blocks has been considered in detail. Depending on the thermodynamic repulsion between the blocks, the initial melt morphology in weakly segregated double crystalline di- block copolymers can be sequentially transformed by the crystallization of the dif- ferent blocks. The crystallization kinetics of each block can be dramatically affected by the presence of the other, and by the crystallization temperature; the magni- tude of the effect is a function of thermodynamic repulsion. Also the morphology has been investigated and peculiar double crystalline spherulites with intercalated semi-crystalline lamellae of each component have been observed in weakly segre- gated diblock copolymers. In the case of ABC triblock copolymers with more than one crystallizable block, many interesting effects have been found; among them, self-nucleation, sequential or coincident crystallization, and fractionated crystalliza- tion can be mentioned. Additionally, the effect of the topological constrains due to the number of free ends has been studied. Factors like chemical structure, molec- ular weight, molecular architecture and number of crystallizable blocks provide a very large number of possibilities to tailor the morphology and properties of these interesting novel materials.

Polypropylene/poly(e-caprolactone) (PP/PCL) blends were prepared by melt mixing. The thermal behaviour of the blends was investigated using differential scanning calorimetry (DSC) and dynamical rheology in the solid state (RSA). Both non-isothermal and isothermal crystallizations were performed. The Avrami equation was applied to the latter case. DSC and RSA results demonstrated in agreement with morphological observations that PP/PCL blends are immiscible in the whole composition range. PP acts as a nucleating agent for PCL, and when PP forms the disperse phase, it crystallizes in a fractionated fashion. When PCL is the disperse phase, it exhibits an unexpected melting point depression after cooling at 10 °C/min. Such depression was not observed after isothermal crystallizations, indicating that under non-isothermal crystallization kinetic problems show up. Thus, global crystallization is governed by a competition between nucleation and diffusion, which depends on crystallization conditions and composition. Introduction Preparation of polymer blends has been extensively used to obtain new materials with useful properties. Usually, polymer blending is performed to reduce costs, to prepare materials with specific properties, to develop products with improved properties or to recycle industrial polymers. Unfortunately, most polymer blends are immiscible. Thus, it is imperative to have a good interfacial adhesion between the components to generate compatibility [1]. Although many commercial polymers are semicrystalline, studies on both crystallization and morphology of immiscible polymer blends containing at least one semicrystalline component are relatively scarce, especially if a polar component is involved [2,3]. The properties of semicrystalline blends depend strongly on their crystallinity, crystalline morphology and degree of dispersion. Several phenomena that influence the crystallization behaviour of the system have been reported. Among these phenomena, the following can be mentioned: nucleation and epitaxial crystallization [4-8], migration of heterogeneities from one phase towards the other [9,10], fractionated crystallization [11,12], rejection, engulfing or deformation of the dispersed phase by the growing superstructures of the matrix [13-15], and induction of crystal modifications [16]. Although crystallizability of the components induces immiscibility in the solid state in most cases, if a good

Thermally stimulated depolarization currents, TSDC, experiments have been performed on a series of poly(styrene)-b-poly(butadiene)-b-poly(epsilon-caprolactone) triblock copolymers SBC with different proportions of the poly(epsilon-caprolactone) crystallizable block, PCL. The morphology of the segregated microphases varies with the PCL content and has been observed by transmission electron microscopy. The crystallinity of the PCL block is estimated by wide angle x-ray scattering, WAXS. The relaxation times distribution is extracted by a numerical decomposition of the TSDC spectra and it is shown that this distribution is not significantly changed on going from the homopolymer to the triblock copolymer with 16 wt % to 77 wt % of PCL in the original samples. Better segregation of the mesophase structure is reached when the samples are annealed at 413 K and important variations in the TSDC and WAXS spectra are observed as a result of the thermal treatment. For the S09B14C77 triblock copolymer the results obtained can be explained by postulating the existence of a rigid amorphous phase in the PCL block. Such rigid amorphous phase is located between the core-shell cylinders formed by the other blocks [with poly(styrene)(PS) as core and poly(butadiene)(PB) as shell] and is constrained by undulated lamellae of crystalline PCL material. In the case of S35B15C50 triblock copolymer, an important amount of diffuse PS-PCL interphase where the homopolymers are mixed must be present before annealing. The results for the material with the less abundant PCL block are explained as a result of the confinement in nanotubes of PCL surrounded by PB embedded in a vitreous PS matrix. Broadband dielectric experiments on these same materials confirm the results obtained by TSDC spectroscopy.

The self-nucleation of branched polyethylene chains of different degrees of chain mobility was studied. The polyethylene block (PE block) within poly(styrene-b-ethylene-b-caprolactone) triblock copolymers (SEC) of varying compositions was studied. Differential scanning caloriometry was used to determine the self-nucleation domains as a function of the self-nucleation temperature (T s ). The self-nucleation behavior of PE chains within SEC block copolymers was found to be anomalous in comparison to the classical self-nucleation behavior exhibited by homopolymers. When the degree of chain constraint is high, as in the the case where the SEC copolymer only contains 15% of PE, domain II (only self-nucleation domain) completely disappears and annealing can take place before self-nucleation occurs. This means that chain constraint complicates the self-nucleation process and this situation persists until, upon decreasing the self-nucleation temperature (T s ), annealing has generated crystals tha are big enough to act a self-nuclei for the less restricted portions of the chain. If the PE content in the copolymer is very low (15%), two crystal populations can be distinguished. This may reflect the differences in diffusion of the PE chain segments close to the interfaces with the other two blocks and those segments that are close to the middle of the PE block. the influence of chain constraint on determining the difficulty of the chains to self-nucleate was further explored using a crosslinked low-density polyethylene (XLDPE). In this case, crosslinking junctions instead of covalent links with other blocks restrict chain mobility. Nevertheless, a similar difficulty in self-nucleation was found as in the case of the PE block within SEC triblock copolymers in contrast to neat LDPE, a polymer that exhibited the classical self-nucleation behavior with the usual three domains.

Polystyrene-block-poly(ethylene-co-butylene)-block-poly(∈-caprolactone triblock copolymers (SEC ) were prepared by hydrogenating polystyrene-block-polybutadiene-block-poly(∈-caprolactone triblock copolymers (SBC) previously prepared by sequential anionic polymerization. The effect of the crystallization of the polyethylene block (PE) upon cooling from a phase-segregated melt on the crystallization process of the adjacent polycaprolactone block (PCL) was investigated by means of differential scanning calorimetry and polarized optical microscopy. It was found that there was no nucleation effect of the PE block on the PCL block under controlled cooling conditions in the DSC. On the contrary, an antinucleation effect was detected when nucleation of the PCL block crystals within the SEC triblock copolymers was attempted. It was demonstrated that such an antinucleation effect was induced by the annealing of the polyethylene block crystals of the SEC copolymers. By the application of the successive self-nucleation and annealing technique (SSA) the possibility of producing a distribution of lamellar thickness within the PCL and the PE blocks of the SEC triblock copolymers was shown. These results, together with the spherulitic morphology displayed by the SEC copolymers with more than 50 wt.-% PCL, are consistent with previous morphological observations in SBC triblock copolymers. Those observations indicate that the chain stems within the lamellar crystals in the PCL blocks could be perpendicular to the interphase of the block copolymer domains, even though the crystallization occurred from a heterogeneous melt.