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The physicochemical investigations on the associative, micellar, and thermodynamic properties of a diblock (PEO)62-b-(PBO)33copolymer in aqueous medium and its interaction with ionic surfactants were carried out by using surface tensiometry, laser light scattering, and steady-state fluorescence spectroscopy. Surface tension and fluorescence measurements were used to find out the critical micelle concentration (CMC) and related thermodynamic parameters of micellization copolymer at various temperatures. The data from dynamic light scattering (DLS) were helpful to obtain the values of hydrodynamic radii (Rh), volume (υh), and hydrodynamic expansion parameter (δh) of the copolymer micelle. Likewise, the measurements from static light scattering (SLS) were employed to determine weight-average molar (Mw), association number (Nw), thermodynamic radius (Rt), thermodynamic volume (υt), anhydrous volume (υa), and thermodynamic expansion parameter (δt) of the copolymer micelles in the temperature range of 20–50°C. Similarly, the interactions between (PEO)62-b-(PBO)33and two ionic surfactants, sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB), have also been investigated by fluorescence spectroscopy and DLS at 30°C. Similarly, the interactions between (PEO)62-b-(PBO)33and two ionic surfactants, sodium dodecyl sulfate and hexadecyl trimethylammonium bromide, have also been investigated by fluorescence spectroscopy and DLS in detail. [ABSTRACT FROM PUBLISHER]

Recent development in dispersion science and technology demands block copolymers with a variable block length and composition. To highlight that purpose, the surface active, associative, colloidal, and thermodynamic behavior of three diblock copolymers having different hydrophilic to hydrophobic ratio is reported here. Using surface tension and light scattering measurements, the micellization and adsorption behavior of polyoxyethylene and polyoxybutylene diblock copolymers of the typeEmBnhave been analyzed. Critical micelle concentration (CMC) and related thermodynamic parameters like free energy (ΔGmic), enthalpy (ΔHmic), and entropy (ΔSmic) of micellization were calculated from CMC value using the closed association model. Likewise, the surface active parameters, like surface excess concentration (Γ2), area per molecule (A2), and thermodynamic parameters such as free energy (ΔGads), enthalpy (ΔHads), and entropy (ΔSads) of adsorption of polymer at the air/water interface, were also calculated at various temperatures. Static and dynamic light scattering techniques were employed for the determination of the weight-average molar (Mw), association number (Nw), polymer–water interaction (A2), and micellar size in terms of hydrodynamic radii (Rh) of copolymer micelles. The effect of block length and solution temperature on the surface and micellar properties of these copolymers was also investigated. [ABSTRACT FROM AUTHOR]

Amphiphilic block copolymer of two triblock copolymer B17E122B17 and B24E450B24, B denoting OCH2CH(C2H5), E denoting OCH2CH2, and the subscripts denoting number-average chain lengths were investigated in solution and characterized through surface tension, viscosity, and dynamic light scattering. Critical micelle concentration, (CMC) determined from the surface tension data was found to decrease with the increase of temperature as well as with the increase in hydrophobic block length for both the copolymers investigated. Standard free energy of micellization (ΔGmic) value was found to decrease in the range (-18 to -23KJmol-1) with the increase of temperature. Standard entropy factor of micellization (TΔSmic) also increased in the range (51.04 to 56.33 KJmol-1) with the rise in temperature, while enthalpy (ΔHmic) is temperature independent. Viscosity and Dynamic light scattering were used to determine intermicellar interactions and to characterize the micelles in dilute solutions respectively. The data obtained demonstrated the formation of compact micelles at low temperatures and of elongated at higher temperatures. [ABSTRACT FROM AUTHOR]

The aqueous solutions of three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type EmB10Emhave been analyzed by surface tension measurements. Surface activity of these triblock copolymers was studied by measuring surface parameters, like surface excess concentration, Γ2, area per molecule of polymer and standard Gibb's free energy of adsorption, ΔoGads, at various temperatures in the range of 20 to 50°C. The Effect of block length of hydrophilic portion of triblock copolymers on surface activity was investigated in this work. Miceller behavior of these triblock copolymers was also investigated using above technique. Critical micelle concentration (CMC) was determined from the plot of surface tension versus log of concentration in the range of temperature of 20–50°C. Thermodynamic parameters, standard free energy of micellization, ΔoGmic, standard enthalpy of micellization, ΔoHmic, and standard entropy of micellization, ΔoSmicwere calculated from CMC value using closed association model in this range of temperature. Self assembly behavior of triblock copolymer E20B10E20was compared with E30B10E30and E48B10E48triblock copolymer. Effect of temperature on surface and miceller properties of the triblock copolymers was also studied. [ABSTRACT FROM AUTHOR]

Some novel ferrocene-containing polyamide-based block copolymer materials with telechelic polydimethylsiloxane oligomer and their organic analogues were prepared by solution-phase polycondensation of ferrocene-based organometallic and terephthaloyl- as well as isophthaloyl-based organic acyl chlorides with a series of semi-aromatic diamines having ether linkages together with variable aliphatic character. The corresponding polyamides of the synthesized materials, without polydimethylsiloxane segment, were also prepared for comparison of physicochemical properties. None of the synthesized organometallic and organic block copolymers along with their respective polyamides melted below 300 °C and their structural features were confirmed by their physical properties and spectroscopic studies. The weight-average molecular weights and molecular parameters of all these materials were determined by the static laser light scattering technique. The materials were soluble in sulfuric acid and partially soluble in common organic solvents, and yet became readily soluble upon N-trifluoroacetylation. The synthesized materials were further characterized by their water absorption characteristics, X-ray diffraction studies and surface morphology (SEM and AFM) and thermal (DSC and TG) analyses, and their structure-property relationships were elucidated from these studies. The energies of pyrolysis for these materials were calculated by the Horowitz and Metzger method. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The associative properties of Me2N (CH2)2OE58B7 and I−Me3N+(CH2)2OE58B7 in aqueous solution in the temperature range of 20-50°C have been investigated by dynamic and static laser light scattering. Here E represents an oxyethylene unit and B an oxybutylene unit. The results obtained were compared with results for E mB n analog. Our result shows that for micelles of dimethylamino-tipped, the hydrodynamic radius, was large as compared with the thermodynamic radius r t, suggesting a 'soft' micelle. For the trimethylammonium-tipped copolymer, r h decreases and r t increase with the increase in temperature. Also the values of association number, N w, were low but increase with increase in temperature, indicating a change from soft micelle at low temperature to small, less swollen micelles at high temperature. The high values of thermodynamic volume per molecule, rt/Nw, for a polymer with charged tip could be attributed to intermicellar charge effect. The effect of salt on various micellar parameters has also been discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

The interactions of triblock copolymers (TBP) with ionic surfactants were studied employing surface tensiometry, electrical conductivity, steady-state fluorescence (SSF), and dynamic light scattering (DLS) techniques. An increasing trend in the critical micelle concentration (CMC) of SDS/CTAB in the presence of triblock copolymers was observed especially at higher polymer to surfactant ratio. The delay in the CMC of surfactants was more pronounced in the presence of E48B10E48 possibly due to its less hydrophobic nature. The negative values of free energy of micellization (ΔGm) both in case of SDS and CTAB confirmed the spontaneity of the processes. The aggregation number (Nagg) and hydrodynamic radius (Rh) of polymer/surfactant mixed systems were determined by SSF and DLS. The suppression of the surfactant micelle size in the presence of TBP was confirmed by SSF and DLS studies. [ABSTRACT FROM PUBLISHER]

The adsorption of poly(ethylene oxide)-b-poly(butylene oxide) diblock copolymers at the solid–liquid interface was studied using a quartz crystal microbalance with dissipation monitoring (QCM-D). The effect of modifying the end group of the hydrophilic block was investigated by comparing the behaviour of trimethylammonium- and dimethylamino-tipped copolymers, designated as TE mB n and DE mB n, respectively. For adsorption from aqueous solution onto a gold surface, results for DE49B22 were similar to those of the T-analogue, but for DE80B34 adsorbed amounts were substantially higher, and for DE27B25 enormously higher, than for the T-analogue. It is suggested that very high levels of adsorption are associated with the formation of a multilayer structure. [ABSTRACT FROM AUTHOR]