Effects of the molecular structure of styrene-isoprene block copolymers on the interfacial characteristics of polystyrene/polyisoprene blends

The effects of the molecular structure of the styrene-isoprene block copolymer on the interfacial tension, the morphology and the interfacial adhesion of polystyrene/polyisoprene were investigated. A reduction in interfacial tension is observed with the addition of a small amount of copolymer, followed by a leveling off as the copolymer concentration exceeds the critical micelle concentration. The reduction in interfacial tension between polystyrene and polyisoprene is more significant when the isoprene-rich diblock copolymer is added than the cases when the symmetric or styrene-rich diblock copolymer is added. The interfacial tension data seem to be consistent with the phase morphology and the interfacial adhesion: the lower the interfacial tension, the smaller the domain size of dispersed phase and the better the interfacial adhesion. © 1996 John Wiley & Sons, Inc.     

Estimating the segregation strength of microphase‐separated diblock copolymers from the interfacial width

The ever‐growing catalog of monomers being incorporated into block polymers affords exceptional control over phase behavior and nanoscale structure. The segregation strength, χN, is the fundamental link between the molecular‐level detail and the thermodynamics. However, predicting phase behavior mandates at least one experimental measurement of χN for each pair of blocks. This typically requires access to the disordered state. We describe a method for estimating χN from small‐angle X‐ray scattering measurements of the interfacial width between lamellar microdomains, t_x, in the microphase‐separated melt. The segregation strength is determined by comparing t_x to self‐consistent field theory calculations of the intrinsic interfacial width, t_i, as a function of the mean‐field χN. The method is validated using a series of independent experimental measurements of t_x and χN, measured via the order–disorder transition temperature, T_ODT. The average absolute relative difference between χN calculated from t_x and the value calculated from T_ODT is a modest 11%. Corrections for nonplanarity of the interfaces are investigated but do not improve the agreement between the experiments and theory. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. J. Polym. Sci., Part B: Polym. Phys. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 932–940     

Interfacial behaviors of PMMA-PEO block copolymers at the air/water interface

Amphiphilic block copolymers are attracting con-siderable attention because they exhibit unique self- assembly properties in selective organic solvents[1―4]. Semicrystalline poly(ethylene oxide) (PEO), having many interesting physicochemical properties s…     

Surface mixed adsorption films of 2,4,6- trimethylphenol–2,4,6-trichlorophenol at aqueous solution/air interface

 The results of experimental studies of the adsorption at the solution/air interface from an aqueous mixture: 2,4,6-trimethylphenol–2,4,6-trichlorophenol are presented. The surface properties of the above-mentioned mixture were studied by surface potential and surface tension measurements. These measurements were carried out as a function of the concentration of 2,4,6-trimethylphenol aqueous solution at a constant concentration of 2,4,6-trichlorophenol. Using the results obtained and based on the Gibbs equation, Helmholtz formula and Motomura’s method the relative surface excesses of adsorbed substances, effective dipole moments, surface molar fractions of solutes and miscibility of adsorbed films were determined. Received: 7 November 1997 Accepted: 26 February 1998     

Morphology control and inducing a curvature on the domain interface by increasing the steric bulk of polymethacrylate in POSS‐containing diblock copolymers

Herein, a novel rod‐coil type polyhedral oligomeric silsesquioxane (POSS)‐containing diblock copolymer was designed to enable the self‐assembly of hexagonally packed cylinders of the POSS‐containing domain in a poly(n‐butyl methacrylate) (PnBMA) matrix. When POSS‐containing diblock copolymers were synthesized with polyisoprene or poly(methyl methacrylate), cylindrical structures could not be obtained as POSS‐containing polymers form stretched rigid rods. This makes the formation of cylindrical structures with the POSS‐containing domain entropically unfavorable. Therefore, to obtain the cylindrical structures, we constructed a novel diblock copolymer using PnBMA to increase the steric bulk and segment volume of the flexible coil. Steric crowding of the butyl groups reduces the entropic free stretching energy of the PnBMA chains, which in turn encourages the formation of a POSS‐containing hexagonally packed cylindrical structure within the PnBMA matrix as the system minimizes the total free energy of the thermodynamically stable nanostructure. Small angle X‐ray scattering and transmission electron microscopy analyses indicated that cylinders of the POSS domain had formed. Oxygen plasma etching was then used on the thin film to selectively remove the PnBMA domain to yield line and space structures with a high degree of long‐range order and a 14 nm feature size. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2234–2242     

Synthesis and spectroscopic characterization of symmetrical isoprene–methyl methacrylate diblock copolymers bearing different anthracene derivatives at the junctions

We describe the synthesis and characterization of 1‐(1‐anthryl)‐1‐phenylethylene (1‐An‐E) and 1‐(2‐anthryl)‐1‐phenylethylene (2‐An‐E). These species were used to end cap the living end group of polyisoprene (PI) obtained by anionic polymerization in tetrahydrofuran. The anions generated were used to initiate methyl methacrylate polymerization. In this way, we synthesized two symmetrical PI‐poly(methyl methacrylate) (PMMA) block copolymers each with a single dye at the junction. PI‐An1‐PMMA has an anthracene linked via its 1‐position. PI‐An2‐PMMA has the anthracene linked via its 2‐position. We compare the UV and fluorescence properties of the polymers to model compounds with similar chromophores. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1225–1236, 2003     

Well‐defined PE‐b‐PDMS diblock copolymers via the combination of thiol‐ene click and esterification reactions: Facile synthesis and compatibilization for HDPE/silicone oil blends

Well‐defined diblock copolymers of linear polyethylene (PE) and poly(dimethylsiloxane) (PDMS) have been synthesized through a facile route combining the thiol‐ene click chemistry of vinyl‐terminated polyethylene (PE‐ene) and the sequential esterification reaction. The resulting diblock copolymers are characterized by ¹H NMR, FT‐IR, DSC, TGA, and TEM. In addition, the PE‐b‐PDMS diblock copolymers have been evaluated as compatibilizers in the blends of high‐density polyethylene (HDPE) and silicone oil. The morphological analysis and mechanical properties demonstrate that the compatibilized blends with low loading concentration of PE‐b‐PDMS display significant improvements in modulus of elasticity and elongation at break as compared to the uncompatibilized binary blends. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3205–3212     

On the effect of trace impurities at the air/water- and the mercury/water interface

An aqueous solution of 1 10^–4 Mn-octanoic acid containing 0.005 M hydrochloric acid and 0.1 M sodium chloride was used to demonstrate the influence of surface-active trace impurities on the air/water- and the mercury/water interface. The solution was purified stepwise to obtain states of successively growing surface-chemical purity. The effect of contamination at the air/water- and the mercury/water interface was followed simultaneously by monitoring the dynamic surface tension in the case of ad- and desorption and the differential capacity, respectively, at various stages of purity. The results give evidence that the effect of trace impurities at the air/solution surface is as important as at the mercury/solution interface.     

The surface tension of aqueous polyvinylamine and copolymers with <Emphasis Type="Italic">N</Emphasis>-vinylformamide

 The surface tensions of aqueous poly(N-vinylformamide) (PNVF), polyvinylamine (PVAM), and PNVF–PVAM copolymers were measured as functions of pH. The nonionic PNVF gave a pH-independent surface tension of 68 mN/m. The surface tension of PVAM was pH dependent; at pH 10 it was 56 mN/m, whereas it was 71.5 mN/m at pH 3.5. The transition from higher to lower surface tension values occurred most dramatically between pH 8 and 9, reflecting the dissociation behavior of the amine groups. The copolymers showed intermediate behavior. Received: 20 August 2001 Accepted: 26 September 2001     

Charge reversal at the air/water interface as inferred from the thickness of foam films

Experiments are reported with foam films from aqueous solutions with increasing concentration of a cationic surfactant. A correlation is established between the foam film thickness and the possible variation of diffuse electric layer potential at the air/water interface from a negative value in absence of surfactant to positive values at higher surfactant concentrations. It is concluded that a charge reversal at the air/water interface is expected to occur under increasing concentration of cationic surfactants in aqueous solutions.     

Segmental dynamics of poly(styrene-b-2-vinylpyridine) in bulk and at the surface/air interface

Anionically polymerized poly(α-deuterostyrene) and poly(β-deuterostyrene-b-2-vinylpyridine) (DSVP), selectively deuterated on the styrene backbone, were studied using deuterium wide-line NMR in bulk and adsorbed on silica and alumina. Changes in the segmental dynamics of the bulk and adsorbed polymers were inferred via changes in the NMR line shape with temperature. The DSVP bulk sample, which consisted of micellar aggregrates with a 2-vinylpyridine core, was more rigid than the homopolystyrene of a similar molecular weight. A significant change in mobility occurred at 20°C higher in the DSVP bulk sample than it did in homopolystyrene. The DSVP-adsorbed sample showed more restrictive mobility than bulk DSVP. The spectra of the adsorbed samples contained “rigid” Pake patterns with considerable intensity at temperatures where the collapse of the Pake pattern for the DSVP bulk sample was observed. DSVP bound to the silica surface was found to have a mobility similar to the same copolymer on alumina. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1609–1616, 1998     

A study on the production of PMMA/P(MMA-AAm) composite polymer particles and the effect of acrylamide content on the adsorption behaviors of biomolecules

 A series of poly(methyl methacrylate)/poly(methyl methacrylate-acrylamide) composite polymer particles was prepared with varying proportions of acrylamide in the copolymer shell layer. Adsorption behaviors of some biomolecules and specific activity of adsorbed trypsin were studied. The hydrophobic interaction between the composite polymer particle surfaces and biomolecules decreased with increasing acrylamide content. Received: 7 February 2001 Accepted: 16 May 2001     

Aggregate formation in oil and adsorption at oil/water interface: thermodynamics and its application to the oleyl alcohol system

The thermodynamic equations for examining aggregate formation in an oil phase and adsorption at the oil/water interface of a nonionic solute were derived. The total differentials of chemical potentials of species and the oil/water interfacial tension were expressed as functions of temperature, pressure, and the total concentration of solute in the oil phase after explicit consideration of aggregate formation. The partial derivatives of the chemical potentials and the interfacial tension with respect to the independent variables were found to provide the thermodynamic quantities of aggregate formation and adsorption from oil phase to the interface by introducing the concept of an ideally dilute associated solution. These equations were applied to the cyclohexane solution of oleyl alcohol/water system, and the adsorption and aggregate formation was examined.     

Novel poly(vinyl ether) block copolymers: Synthesis and colloidal stabilization of α-Fe2O3 in water and organic solvents

 Novel poly(vinyl-methylether)-b-poly(vinyloxy-4-butyric acid) diblock copolymers were made for the purpose of colloidal stabilization of particles in liquids. The synthesis via cationic polymerization with HI/I₂ initiation and the characterization of such novel diblock copolymers is described. A set of polymers was prepared including block copolymers with different block length ratios and the two separate homopolymers having the chemical composition of one of the blocks. Colloidal stabilization of α-Fe₂O₃ particles in water could be realized with all polymers except with the (vinylmethylether) homopolymer. One of the block copolymers was used for evaluation of the stabilizing abilities in organic solvents. Stable α-Fe₂O₃ dispersions could be prepared in solvents with very different polarities, ranging from methanol to toluene. In addition, it is shown that particles stabilized with these block copolymers can be easily transferred from water to an organic liquid. Received: 15 May 1997 Accepted: 13 October 1997     

The thickness and contact angle of sodium dodecyl sulfate foam films depending on the concentration of LiCl

 In the present study a detailed investigation of the thickness and contact angles of foam films prepared from sodium dodecyl sulfate as a function of LiCl concentration was carried out. Concentration of LiCl was varied in a wide range from 0.05 to 2.0 M. It was found that in the investigated system Newton black foam films are formed at LiCl concentrations higher than 1.4 M. This observation is proved by contact angle measurements and calculated values for the change of interaction free energy between common and Newton black films. Received: 6 January 1998 Accepted: 11 March 1998     

The interactions of saturated fatty acids at the dodecane/water interface and their sodium salts at the air/water interface

The interfacial tension of lauric, myristic and palmitic acids at the dodecane/water interface and of their sodium salts at the air/water interface were measured using the Du Noüy (ring) method. On the basis of these results the standard free energies of adsorption (ΔG⁰_ad) and of micellization (ΔG⁰_mic) of the above mentioned systems were calculated. According to deviations of the Langmuir isotherm, the corresponding interactions were discussed from the dependence of the standard free energy of adsorption on the interface coverage (Θ).     

Chain diffusion in the melt of an asymmetric diblock copolymer in the disordered and ordered state

 The self-diffusion in a polystyrene-b-polyisoprene diblock copolymer with a strongly asymmetric composition was investigated with dependence on temperature by pulsed field gradient (PFG) NMR. The diblock shows with decreasing temperature a disorder-to-order-transition at T _ODT=393 K from a micellar liquid-like to a bcc ordered state which was recently measured by SAXS [M. Schwab and B. Stühn, Phys. Rev. Lett. (1996) 76: 924]. Two diffusivities were observed, one of the free diblock chains and one of the diblock chains fixed in micelles. The volume fraction of free chains decreases with decreasing temperature. The diffusivity of the free chains must be related to chain stretching. The experiments show that within the time of the NMR experiment (300 ms) there is no exchange between the diblock chains in the free state and those fixed in the core of the micelles. Received: 25 March 1997 Accepted: 25 April 1997     

嵌段共聚物的临界条件液相色谱分离与表征

嵌段共聚物是由两种或两种以上不同性质的聚合物链段通过共价键连接形成的特殊聚合物。它可以结合构成嵌段的不同种类聚合物的性质,得到性能比较优越的功能性聚合物材料,因此越来越受到人们的重视。然而,嵌段共聚物的分离和表征一直都是一项颇具挑战性的工作。临界条件液相色谱（liquid chromatography at the critical condition,LCCC）作为一种新型的液相色谱分离技术,可以使嵌段共聚物中的某种嵌段处于“色谱不可见”（chromatographic invisible）状态,不会影响整个聚合物的保留时间,从而根据嵌段共聚物中其他嵌段长度来分离嵌段共聚物。本文介绍了LCCC分离法的分离原理与实现途径,较为系统地综述了LCCC分离表征嵌段共聚物的近期研究进展,并对该方法目前存在的问题及今后发展前景进行了探讨。     

Investigation of the interactions in emulsions stabilized by a polymeric surfactant and its mixtures with an anionic surfactant

 The interaction of a nonionic polymeric surfactant with an anionic surfactant at the oil–water interface has been studied by its effects on the droplet size, stability and rheology of emulsions. Oil-in-water (o/w) emulsions were prepared using isoparaffinic oil and mixtures of a nonionic polymeric surfactant with an anionic surfactant. The macro-molecular surfactant was a graft copolymer with a backbone of polymethyl methacrylate and grafted polyethylene oxide (a graft copolymer with PEO chains of MW=750). The anionic surfactant was sodium dodecyl sulfate (SDS). The stabiliza-tion of the emulsion droplets was found to be different when using one or the other surfactant. The mechanism of stabilization of emulsion droplets by the macro-molecular surfactant is of the steric type while the stabilization by anionic surfactant is of the electrostatic repulsion type. Emulsions stabilized with mixtures present both types of stabilization. Other effects on the preparation and stabilization of emulsions were found to be dependent on properties associated with the surfactant molecular weight such as the Marangoni effect and Gibbs elasticity. The initial droplet size of the emulsions showed a synergistic effect of the surfactant combination, showing a minimum for the mixtures compared to the pure components. Emulsion stability also shows a synergistic interaction of both surfactants. Rheological measurements allow for the estimation of the interparticle interaction when measured as a function of volume fraction. Most of the effects observed can be attributed to the differences in interfacial tension and droplet radius produced by both surfactants and their mixtures. The elastic moduli are well explained on the basis of droplet deformation. Ionic versus steric stabilization produce little difference in the observed rheology, the only important differences observed concerned the extent of the linear viscoelasticity region. Received: 22 November 1996 Accepted: 24 March 1997     

Influence of temperature on the composition of mixed monolayer formed at the methyl alcohol/acetic acid aqueous solutio–air interface

The influence of temperature on the composition of mixed monolayer formed at the methyl alcohol/acetic acid aqueous solution was examined by surface tension measurements. Surface tension of various two-component solutions was obtained at 10, 20 and 28 °C temperatures in the 0–0.5 M range of bulk concentration of alcohol and acid, respectively. Three independent methods, i.e., the Gibbs adsorption equation (GAE), regular solution approximation (RSA) and Butler adsorption isotherm (BAI) were applied to calculate surface composition of the methyl alcohol/ acetic acid mixed monolayer. It was shown that in the temperature range of 10–28 °C the surface molar fraction of the solutes remained constant for the fixed bulk concentration of alcohol and acid. Additionally, based on the RSA and BAI methods, we showed there were no interactions between solute molecules in the mixed monolayer in the studied range of concentrations. Received: 18 December 1997 Accepted: 8 May 1998