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Biopolymer films with a thickness of 100@mm are prepared using spin coating technique with solutions consisting of 25wt.% polycaprolactone or poly-l-lactide in dichloromethane. SU-8 stamps are fabricated using three photolithography steps. The stamps are used to emboss 3D microstructures in the biopolymer films. It is found that the best pattern transfer for the polycaprolactone films is achieved just below the melting point at 60^oC. For the poly-l-lactide films the best pattern transfer is achieved at 120^oC.

The development of epitaxial technology for the fabrication of quantum dot (QD) gain material operating in the 1.55 μm wavelength range is a key requirement for the evolvement of telecommunication. High performance QD material demonstrated on GaAs only covers the wavelength region 1-1.35 μm. In order to extract the QD benefits for the longer telecommunication wavelength range the technology of QD fabrication should be developed for InP based materials. In our work, we take advantage of both QD fabrication methods Stranski-Krastanow (SK) and selective area growth (SAG) employing block copolymer lithography. Due to the lower lattice mismatch of InAs/InP compared to InAs/GaAs, InP based QDs have a larger diameter and are shallower compared to GaAs based dots. This shape causes low carrier localization and small energy level separation which leads to a high threshold current, high temperature dependence, and low laser quantum efficiency. Here, we demonstrate that with tailored growth conditions, which suppress surface migration of adatoms during the SK QD formation, much smaller base diameter (13.6nm versus 23nm) and an improved aspect ratio are achieved. In order to gain advantage of non-strain dependent QD formation, we have developed SAG, for which the growth occurs only in the nano-openings of a mask covering the wafer surface. In this case, a wide range of QD composition can be chosen. This method yields high purity material and provides significant freedom for reducing the aspect ratio of QDs with the possibility to approach an ideal QD shape.

Electret charge stability has been related to the size of the spherulites in polypropylene. As the size of the spherulites is decreased the stability is increased. This is seen for isothermal conditions at 90 °C and 120 °C as well as for 90 % relative humidity at 50 °C. The charge release temperature is also increased in thermally stimulated voltage discharge experiments as the size of the spherulites is decreased. The size of the spherulites is controlled though the cooling rate from polypropylenes liquid state.

Spin coated thin films (∼400 A) of poly(styrene)–poly(dimethylsiloxane) (PS–PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which ranged in molecular weight from 7 kg/mol to 500 kg/mol. The films were annealed above and below the highest glass transition temperature of the two polymer blocks but below the order–disorder transition temperature. Information concerning the chemical in-depth distribution of the films was extracted by use of peak shape analysis of the X-ray Photoelectron Spectra via the Tougaard Method. The amount of dimethylsiloxane in the uppermost part of the films was quantified as a function of annealing time and temperature. For annealing above the PS glass transition temperature, surface segregation of the dimethylsiloxane chain-ends occurs for all the studied PS–PDMS diblock copolymers. At room temperature, surface segregation takes place only when the amount of dimethylsiloxane in the diblock copolymers is small.

The morphology evolution of polycarbonate–polystyrene (PC/PS) blends during the compounding process in three blending methods of industrial relevance, namely melt blending, re-melt blending in a twin-screw extruder and tri-melt blending in an injection-moulding machine, was investigated using scanning electron microscopy (SEM) to examine nine blend compositions. Blends were prepared at compositions where phase inversion was expected to occur according to model predictions. The experimental results were compared to the values of the point of phase inversion calculated with the semi-empirical model. The results show that the formation of co-continuous morphology strongly depends on blend composition and melt blending method, whereas the model prediction for phase inversion deviates from the experimental values. Further, we found that the initial mechanism of morphology evolution involves the formation of blades or stratifications in the continuous phase. These blades or stratifications became unstable due to the effects of flow and interfacial forces. We also found that fibre formation in the dispersed phase was favoured by higher shear rate.

The non-linear rheology of the lamellar phase of a polystyrene–polyisoprene diblock copolymer is studied by oscillatory shear experiments. The relaxation of the shear modulus, G(t, γ) is studied as a function of strain amplitude, γ, up to large amplitude strains, γ=100%. The decay of G(t, γ) is analysed using the model-independent CONTIN inverse Laplace transform algorithm to obtain a series of relaxation times, which reveals multiple relaxation processes. The timescale for the fastest relaxation processes is compared to those previously observed for diblock copolymer melts via dynamic light scattering experiments. The slowest relaxation process may be related to the shear-induced orientation of the lamellae. It is shown that time-strain separability G(t, γ)=G(t)h(γ) can be applied, and the damping function h(γ) is consistent with a strongly strain-softening system exhibiting plastic flow at large strains.

In this paper we present an experimentally determined phase diagram of binary blends of the diblock copolymers poly(styrene)-poly(isoprene) and poly(isoprene)-poly(ethylene oxide). At high temperatures, the blends form an isotropic mixture. Upon lowering the temperature, the blend macro-phase separates before micro-phase separation occurs. The observed phase diagram is compared to theoretical predictions based on experimental parameters. In the low-temperature phase the crystallisation of the poly(ethylene oxide) block influences the spacing of the ordered phase.

Both polymer blends and diblock copolymers have been investigated with small-angle neutron scattering (SANS) in varying temperature and pressure fields. Four samples were studied: a polymer blend of near critical composition and the corresponding symmetric diblock copolymer of poly(ethylethylene) (PEE) and poly(dimethylsiloxane) (PDMS) and two further symmetric diblock copolymers of poly(ethylenepropylene) (PEP) and PDMS differing in their molecular mass. From the SANS results the phase transition temperatures, the Flory-Huggins interaction parameter, the Ginzburg number, and the sizes of the chain were determined. As the transition temperature and the Flory-Huggins parameter are independently determined from the SANS data, the Clausius-Clapeyron equation offers a cross-check of the theoretical background used for SANS analysis. The resulting parameters showed for all samples qualitatively similar behavior. In particular, a quite unusual decrease of the phase boundaries in low increasing pressure regimes was observed. Analysis based on the Clausius-Clapeyron equation shows that the reason for this pressure-induced decrease of the phase boundary is a dominating increase of the entropic Flory-Huggins parameter. The Ginzburg parameter was found constant with pressure. The size of the diblock copolymer chains changes-with temperature and pressure. Beyond the chain stretching observed near the ordering temperatures (T-ODT) for both decreasing temperature and applied pressure, a discontinuous decrease of the chain size was consistently found at the TODT The chain size vs temperature was found to follow a scaling behavior with slightly different exponents in the disordered and the ordered regimes consistent with former simulation calculations.

A new bicomponent conetwork, poly(ethyl acrylate)-linked-polyisobutylene (PEtA-l-PIB), was synthesized by radical copolymerization of equal amounts of telechelic α,ω-dimethacrylic PIB (MA−PIB−MA, Mn/(kg/mol) = 11.2, Mw/Mn = 1.12, and MA/chain = 2.0) obtained via quasi-living carbocationic polymerization and ethyl acrylate in 10% solution for each component in a common solvent, tetrahydrofuran, followed by extraction and drying. Low amounts of extractables (2.5% in acetone and 4.6% in hexane) and nearly theoretical composition (51% PEtA and 49% PIB) of the resulting conetwork indicate efficient network formation; i.e., this new conetwork is composed of PIB chains connected at each end to two PEtA chains. DSC experiments gave close to literature value Tg's (−68 °C for PIB and −22 °C for PEtA), indicating a segregated morphology in this conetwork. In contrast to reported results for similar conetworks containing PIB and other polymers with polar groups, surface analysis with XPS found no significant differen...

We report about self-diffusion experiments on a compositionally asymmetric poly(ethylene-co-propylene)-block-poly(dimethylsiloxane) diblock copolymer exhibiting the lamellar and the gyroid morphology. The echo attenuation curves were analyzed by fitting a logarithmic normal distribution function. The self-diffusion coefficients were broadly distributed compared to the distribution caused by the polydispersity alone. This is attributed to the onset of anisotropic diffusion in the lamellar morphology and to unavoidable traces of homopolymers. The most probable self-diffusion coefficients and the values calculated for a hypothetical disordered diblock copolymer melt are lower than the self-diffusion coefficients of the constituent homopolymers having the same molar mass. This is explained by entanglements of the majority block which hinder single-chain diffusion parallel to the interfaces formed due to the microphase separation of the different blocks.

Using a fully oriented sample of a diblock copolymer, poly(dimethylsiloxane)-block-poly(ethylene-co-propylene), we have observed, by dynamic light scattering, the undulation mode of the block copol...

We have studied phase boundaries and critical scattering on equivalent systems of homopolymer blends and diblock copolymers with different end groups terminating the polymer chains. The aim is to investigate the effect of end groups relative to the effect of the covalent junction in diblock copolymers. Either effect intuitively causes corrections with a V-1 dependence on the molar volume V. Besides the experimental phase boundaries, the Flory−Huggins interaction parameter has been determined and is discussed. The polymer systems studied is based on poly(styrene), PS, and poly(ethylene oxide), PEO, where the latter polymer chain is terminated by either a hydroxy or a methoxy group. The change from hydroxy to methoxy end groups caused a change in the phase boundary of 90K and 45K for homopolymer blends (V = 1970 cm3/mol) and diblock copolymers (V = 17 700 cm3/mol), respectively.

Conifer fibers were used to reinforce polypropylene (PP). To improve the compatibility between the conifer fibers and the PP matrix, the fibers were either grafted with maleated PP (MAPP), treated by adding MAPP, or mixed with ethylene/propylene/diene terpolymer (EPDM). The treatments resulted in improved processing, as well as improvements in the thermal and mechanical properties of the resultant composites compared with the composites filled with untreated conifer fibers. Moreover, MAPP grafting and MAPP treating displayed more obvious benefits than EPDM treating in terms of thermal properties, processing flowability, and tensile strength improvements. EPDM treating also produced more significant benefits than either MAPP grafting or MAPP treating in terms of impact strength and tensile elongation improvements. These improvements were attributed to surface coating of the fibers when EPDM was used. In addition, the effect of the concentration of the conifer fibers on the properties of the composites and the difference between MAPP grafting and MAPP treating were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2833–2841, 2001

A polystyrene/polyethyleneoxide PS/PEO homopolymer blend and a diblock copolymer were investigated by small angle neutron scattering experiments. The measured susceptibilities could be described by theories which take strong fluctuations into account. The yielded Flory-Huggins interaction parameter Γ is different between the blend and the diblock copolymer, in accordance to previous experiments [1, 2, 3]. This important difference of Γ could make the predictability of the phase boundaries worse than 50 K. When comparing the PS/PEO samples to other systems, a systematology seems to be missing.

We have used dynamic light scattering to study the dynamics of ternary polymer blends consisting of poly(dimethylsiloxane) (PDMS) and poly(ethylethylene) (PEE) homopolymers and a PDMS-PEE diblock copolymer nearly symmetric in composition. The intensity autocorrelation functions for the binary blend are single-exponential, and the associated correlation length ξ scales with reduced temperature ϵ in accordance with the Ising universality class (i.e., ξ ∼ ϵ−ν, with ν = 0.63). An addition of copolymer depresses the critical temperature, but also increases the magnitude of ν. For compositions within the microemulsion channel, ξ exhibits a distinct maximum with decreasing temperature, near the Lifshitz line obtained from the static structure factor. For a particular composition, there is a “re-entrant” microemulsion, as the system passes into and then out of the phase-separated region upon cooling.

The self-diffusion of an asymmetric poly(ethylene-co-propylene)-b-poly(dimethylsiloxane) diblock copolymer in the hexagonally ordered state is investigated using pulsed field gradient NMR. The order-to-disorder transition (ODT) occurs at TODT = 192 °C. A marked nonexponentiality of the echo attenuations is found, and coming from high temperatures, an increase of this nonexponentiality is observed. This is caused by the onset of anisotropic diffusion along the cylinder axes within the hexagonal order whose orientations are randomly (isotropically) distributed in the sample. The echo attenuation curves are fitted by assuming isotropically oriented grains of parallel cylinders with preferentially longitudinal diffusion along the cylinders and slow molecular propagation from cylinder to cylinder, perpendicular to the cylinder axes. The ratio of diffusivities parallel and perpendicular to the cylinders is of the order of 50 at room temperature, decreasing notably with increasing temperatures. The magnitude and...

We have identified a channel of bicontinuous microemulsion in three chemically distinct hompolymer/hompolymer/block copolymer (A/B/A−B) ternary bends. Experiments were conducted along the isopleth, defined by equal volumes of homopolymer and varying amounts of block copolymer, as a function of temperature. A symmetric condition was achieved through the use of homopolymers with matched degrees of polymerization (NA ≈ NB = NH) and compositionally symmetric diblock copolymers (f ≈ 0.5) where α ≡ NAB/NH ≈ 0.2. We explored PE−PEP/PE/PEP (EP), PEE−PDMS/PEE/PDMS (EED), and PE−PEO/PE/PEO (EO) ternary systems differing in molecular weight by nearly 2 orders of magnitude. Using a combination of small-angle neutron scattering (SANS), rheology, and cloud point measurements, we mapped the phase diagram along the isopleth for each of these systems. On the block-copolymer-rich side of the phase diagrams, a line of lamellar-disorder transitions was observed. On the homopolymer-rich side of the phase diagrams a line of tr...

The lubricating effect of styrene-dimethylsiloxane block copolymer films spin cast on Si wafers was found to increase with increasing size of the poly(dimethylsiloxane) (PDMS) block. Friction properties of symmetrical and close-to-symmetrical block copolymers were evaluated in contact with bromobutyl rubber in a plate-on-plate configuration. X-ray photoelectron spectroscopy showed that the copolymer films were all covered by an at least a 10 nm thick layer of PDMS. The lubricating effect remained constant down to a film thickness comparable to the chain dimensions of the copolymer, R-0, after which it decreased progressively. At thicknesses below R-0, the copolymer dewetted the wafer and formed discrete domains with sizes comparable to R-0. The copolymer could further be blended with up to 70 wt % polystyrene without detecting a decrease in the lubricating effect. A mechanism is proposed for the observed frictional behavior where microflakes are abraded from lamellar copolymer surfaces and stick to the contacting rubber surface, whereafter lubrication may result from sliding of PDMS brushes against each other. (Less)

We report on temperature-dependent self-diffusion measurements of compositionally different and non-entangled poly(ethylene-co-propylene)-b-poly(dimethylsiloxane) PEP-PDMS diblock copolymers in the melt above and below the order-to-disorder transition temperature. Depending on the dimensionality of the structures (lamellar: two-dimensional, hexagonal: one-dimensional, spherical: zero-dimensional) characteristic diffusion mechanisms are observed: in the two- and one-dimensional cases anisotropic single-chain diffusion proceeds along the geometries, i.e. parallel and perpendicular to the interfaces. The shape of the echo attenuations provides information on the anisotropy of motion. Motion perpendicular to the interfaces is markedly suppressed. In the spherical morphology composed of micelle-like structures, however, the diblock copolymers are locally confined to the micelles, and only the collective diffusion of clusters of micelles is observed. In none of the cases is a dramatic change of the self-diffusivity observed at the order-to-disorder transition temperature. The self-diffusion in the disordered state is influenced by concentration fluctuations over a broad temperature range.

Simultaneous small-angle scattering and in situ dynamic mechanical measurements offer an excellent opportunity to relate the macroscopic dynamical mechanical response of block copolymers and their ...

The effect of shear on the orientation of cubic micellar phases formed by a poly(oxyethylene)–poly(oxybutylene) diblock copolymer in aqueous solution has been investigated using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS was performed on samples oriented in a Couette cell using steady shear, and SANS was performed on samples subject to oscillatory shear in situ in a rheometer with a shear sandwich configuration. A body-centered-cubic (bcc) phase observed for gels with concentrations greater than 30 wt % copolymer was found to orient into a polydomain structure, with the close-packed {110} planes both parallel and perpendicular to the shear plane. For gels with 30 wt % copolymer or less, a face-centered-cubic (fcc) phase was observed, and this was also observed on heating the more concentrated gels that formed a bcc phase at room temperature. The fcc phase could be oriented to form a highly twinned structure, with a significant deviation from the ABCABC… stacking sequence of the ideal structure due to random sequences resulting from slip of {111} hexagonal-close-packed planes. For the lower concentration gels, a transition from hard to soft gel on increasing temperature was found to be characterized by a change in the susceptibility of the sample to macroscopic shear orientation, as probed using SAXS. The hard gel could be oriented by shear into a twinned fcc structure, whereas the soft gel comprised a fcc phase with a small grain size, which could not be sheared to form a macroscopically oriented domain. Shear only homogenized the sample, producing a powder SAXS pattern from a fcc structure.

A pressure-sensitive adhesive (PSA) was prepared by mixing low- and high-molecular-weight polyisobutylenes (PIB). Peeling of the adhesive from polycarbonate was observed from the side and from below at three peel rates. A correlation between the peel force and a characteristic dimension of the peel front was obtained. According to the observations, the deformation of adhesive across the peel front is dominated by uniaxial extension. From model stretch experiments simulating the observed stretch history of adhesive, theoretical peel force values were obtained which agree well with the measured peel force values.

Most theoretical treatments of polymer–polymer phase behavior assume that homopolymer mixtures and block copolymer melts are controlled by a common segment–segment interaction parameter knows as χ. This publication describes the results of small-angle neutron scattering (SANS) experiments conducted as a function of temperature and composition from homogeneous mixtures of poly(ethylene) (PE) and poly(ethylenepropylene) (PEP) of equal molecular weight. Analysis of these SANS measurements based on the random phase approximation indicates that χPE/PEP is independent of composition and linear in T−1. The associated symmetric phase diagram calculated with Flory–Huggins theory contains a stability curve that is consistent with the divergence in single phase susceptibility obtained by SANS. This function χPE/PEP(T) is compared with functions for χPE–PEP(T) associated with the homologous PE–PEP diblock copolymers, extracted both from the temperature dependence of the disordered state scattering structure factor, and from the N dependence of the order–disorder transition (ODT) temperature TODT, where N is the degree-of-polymerization. Analysis of these data using mean-field and fluctuation theories leads to four distinct expressions for χPE–PEP(T), none of which is consistent with χPE/PEP(T). We attribute this disparity to the effects of polarization and stretching of diblock molecules in the vicinity of the ODT. A simple model calculation that corrects the prediction for (χN)ODT based on the experimentally determined shift in the SANS peak location corroborates this deduction. We conclude that current theories cannot account for block copolymer and homopolymer phase behavior based on a single function for χ, and suggest that this deficiency may be rectified with a more sophisticated block copolymer theory that properly accounts for chain stretching.

We describe microstructural aspects of phase transitions between the lamellar (L), perforated layer (PL), and gyroid (G) morphologies in diblock copolymer melts. Using small-angle scattering, dynamic mechanical spectroscopy, and transmission electron microscopy, we show that these transformations proceed through the nucleation and growth of the final phase, in contrast to recent calculations that assume evolution from a thermodynamically unstable initial state. Direct L → G transitions are suppressed by the high surface tension associated with L−G grain boundaries; the formation of the metastable PL structure under such conditions reflects the ease with which the L → PL transition can occur, compared to L → G. Similar effects dominate the G → L transition. Mismatches in spacings between epitaxially related lattice planes also influence relaxation kinetics; the P → LG transition rate depends strongly on the relative spacings of the PL [10] and G [211] planes, and the considerable discrepancy between the G ...

Disorder-to-order transitions, in which an isotropic system acquires a spatially periodic structure, are common to a number of phenomena in materials science. Here, we employ small-angle neutron scattering to probe the effects of reciprocating shear on the isotropic-to-lamellar transition of a triblock copolymer composed of poly(ethylene-co-propylene) (PEP) and poly(ethylethylene) (PEE). Prior work has shown that the transition temperature decreases with increasing shear rate, implying that the isotropic state can be produced at low temperatures through application of a flow field [T. Tepe et al., J. Rheol. 41, 1147 (1987)]. Removing this field results in a “jump” to conditions under which the lamellar phase is stable with a time scale set by the relaxation of concentration fluctuations. We describe the ordering process which results, concentrating on the possible existence of a stability limit for the initial (isotropic) state.

Thermal composition fluctuations in a homogeneous binary polymer blend and in a diblock copolymer were measured by small-angle neutron scattering as a function of temperature and pressure. The experimental data were analyzed with theoretical expressions, including the important effect of thermal fluctuations. Phase boundaries, the Flory–Huggins interaction parameter and the Ginzburg number were obtained. The packing of the molecules changes with pressure. Therefore, the degree of thermal fluctuation as a function of packing and temperature was studied. While in polymer blends packing leads, in some respects, to a universal behaviour, such behaviour is not found in diblock copolymers. It is shown that the Ginzburg number decreases with pressure sensitively in blends, while it is constant in diblock copolymers. The Ginzburg number is an estimation of the transition between the universality classes of the `mean-field' approximation and the three-dimensional Ising model. The phase boundaries in blends increase with pressure, while the phase boundary of the studied block copolymer shows an unusual shape: with increasing pressure it first decreases and then increases. Its origin is an increase of the entropic and of the enthalpic parts, respectively, of the Flory–Huggins interaction parameter.

The effects of a large strain (600%) reciprocating steady shear on the lamellar orientation and the order–disorder transition of a nearly symmetric poly(ethylene propylene)–poly(ethylethylene)–poly(ethylene propylene) (PEP–PEE–PEP) triblock copolymer have been studied using small-angle neutron scattering and rheological measurements. Shearing in the ordered state produced parallel lamellae under all steady-state conditions investigated, and the lamellar-to-disorder transition temperature decreased dramatically with increasing shear rate. Both phenomena are qualitatively different from the documented behavior of PEP–PEE diblock copolymers. However, cooling the disordered material while shearing at a relatively low deformation rate initially induces perpendicular lamellae, analogous to the diblock response. These observations are considered in the context of theory and other experimental studies.

High molecular weight block copolymers can be viewed as macromolecular surfactants when blended with thermodynamically incompatible homopolymers. This Letter describes the formation of polymeric bicontinuous microemulsions in mixtures containing a model diblock copolymer and two homopolymers. Although we attribute development of this equilibrium morphology to the effects of fluctuations, mean-field theory provides a quantitative strategy for preparing the bicontinuous state at blend compositions near an isotropic Lifshitz point.

Dynamic light scattering measurements on a symmetric poly(ethylenepropylene-b-dimethylsiloxane) block copolymer reveal three polarized (VV) and one depolarized (VH) modes. The VV modes correspond to cluster diffusion, the heterogeneity mode and a diffusive mode that is tentatively ascribed to adventitious homopolymer. The VH mode is attributed to the reorientational dynamics of the pretransitional composition fluctuations. Furthermore, it is shown that in the ordered state the copolymer is a sufficiently depolarizing medium that VH-inactive modes can appear clearly in the VH scattering geometry

We reexamine the stability of hexagonally modulated layer (HML) and hexagonally perforated layer (HPL) morphologies in a number of block copolymer systems of low to moderate molecular weight. Using small-angle X-ray scattering and dynamic mechanical spectroscopy, we show that these structures are long-lived nonequilibrium states which convert to the bicontinuous gyroid (G) morphology upon isothermal annealing. Comparison of phase transition kinetics across chemically distinct systems spanning a wide range of molecular weights and monomeric friction coefficients reveals a composition dependence to these dynamics. This suggests effects associated with the mobility of individual chains are of lesser importance in explaining the apparent metastability of the HML and HPL structures; instead, the composition dependence of the transition mechanism appears to dominate the observed behavior. The revised phase behavior for these materials is in excellent agreement with mean-field predictions for diblock copolymer m...

The melt-state phase behavior of isotactic polypropylene (i-PP) blended with a series of poly(ethylene/ethylethylene) random copolymers has been investigated using small-angle neutron scattering (SANS). These PEExx copolymers, where xx is the percentage of ethylethylene (EE) units, were prepared by hydrogenation of anionically polymerized polybutadienes with controlled amounts of 1,2 addition. Random phase approximation (RPA) fits to the scattering data for blends of i-PP with a deuterated, low molecular weight PEE90 at 180 °C indicate a statistical segment length for i-PP that is 10% less than that reported previously. Scattering from blends of i-PP with higher molecular weight PEE90 and PEE73 at 180 °C can be quantitatively fit using the RPA theory with χ as the only adjustable parameter, indicating melt miscibility. PEE46 and PEE62 are strongly and marginally immiscible, respectively, with i-PP at 180 °C. These results establish a “window” in EE content in which these random copolymers can form single ...

Samples of compositionally (highly) asymmetric diblock copolymers and, also, mixtures of diblock and triblock copolymers (the latter obtained as end-coupling products of two diblock molecules of the mixture), composed of (a) monodisperse majority block(s) of poly(styrene) (PS) and a polydisperse minority block of poly(methacrylic acid) (PMAA), microphase separate into spherical PMAA microdomains, either in disordered liquid-like state or body-centered-cubic (BCC) arrangement, at various annealing temperatures T, in the strong segregation regime SSR. We found that (i) the microphase separated state is favored over an anticipated molecularly homogenous state, (ii) the spherical microdomain morphology (with BCC symmetry) is favored over an anticipated hexagonally packed cylindrical morphology, (iii) the extent of the dissolution of short PMAA blocks in the PS material can be quantified, (iv) the spherical microdomains are dilated, and (v) despite molecular-weight (and architectural) polydispersity, well-ordered BCC structures can be obtained. (c) 2013 Wiley Periodicals, Inc.

This communication describes dynamic light scattering measurements on three low molar mass symmetric polystyrene–polybutadiene diblock copolymer melts. Above but close to the order–disorder transition, four modes contribute to the time‐dependent correlation function. In the depolarized geometry there is a very fast, broad relaxation typifying the segmental reorientational dynamics and a slower, single‐exponential mode related to chain orientation and stretching. In the polarized experiments two additional processes are seen: the heterogeneity mode related to the self‐diffusion of individual copolymer molecules and a slow mode representing the translational diffusion of large (≂100 nm) clusters. Just below the order–disorder transition (ODT), the slowest mode is shifted to very long times. The heterogeneity mode gives rise to depolarized scattering below the ODT because of the anisotropy induced by the lamellar structure. With the lowest molar mass copolymer above the ODT, it could be seen that the amplitu...

We characterize the phase behavior of a series of polystyrene−poly(2-vinylpyridine) diblock copolymers (Mw ∼ 20 000 g/mol) using dynamic mechanical spectroscopy, transmission electron microscopy, small-angle neutron scattering, and small-angle X-ray scattering. Measurements on symmetric diblocks (fPS = 0.5) permit us to estimate the Flory−Huggins interaction parameter (χ) for this system, which we use to place our findings on a diagram. Four ordered morphologies (lamellae, hexagonally perforated layers, bicontinuous cubic/gyroid, and hexagonally packed cylinders) are found at compositions ranging from 35 to 70 vol % polystyrene. An order−order transition separates the hexagonally perforated layer and Ia3d/gyroid phases at 38 vol % styrene. Studies of shear-oriented material indicate that the cubic microstructure does not appear to grow with a preferred orientation from the layered phase, in contrast to recent findings in other diblock systems. The occurrence of complex phases at compositions between thos...

We have determined the phase behavior of a series of model poly(ethylene)−poly(ethylethylene) (PE−PEE) diblock copolymers with poly(ethylene) block volume fractions (fPE) ranging from 0.25 to 0.46. Four ordered microstructures make contact with the ODT: spheres arranged on a body-centered cubic lattice (Im3m space group), cylinders packed on a hexagonal lattice, a bicontinuous structure of space group Ia3d, and lamellae. A fifth ordered phase, tentatively identified as hexagonally perforated layers (HPL), separates the cylindrical and lamellar morphologies at moderate or greater degrees of segregation. Binary blends of fPE = 0.37 and 0.46 diblocks were used to investigate the bicontinuous cubic phase region in greater detail; these experiments indicate that this phase extends as much as 100 °C below the ODT for 〈fPE〉 values in the blend from 0.385 to 0.420.

Four block copolymer meltstwo poly(isoprene-block-dimethylsiloxane) (PI−PDMS) and two poly(ethylene-alt-propylene-block-dimethylsiloxane) (PEP−PDMS)have been investigated through rheological measurements, SANS, and SAXS. In both systems, lamellar to disorder and Ia3d bicontinuous to disorder transitions have been observed. Upon heating, the sequence of phases lamellae, modified layers, bicontinuous Ia3d, disorder is observed in the f = 0.65 PEP−PDMS sample. Composition fluctuations dominate the disordered state properties over an unprecedented wide temperature window in the f = 0.49 PEP−PDMS sample. The fluctuations are evident both in SANS measurements and through the temperature dependence of the viscosity. The phase behavior of these relatively low molar mass block copolymer melts, which range from 6 to 10 kg/mol, is qualitatively anticipated by the trends reported earlier for progressively lower molar mass diblock copolymers.

The phase behavior of ten polyisoprene-polystyrene (PI-PS) diblock copolymers, spanning the composition range from 0.24 to 0.82 polyisoprene volume fraction (f PI ), has been studied near the order-disorder transition (ODT). Dynamic mechanical spectroscopy, transmission electron microscopy, and neutron and X-ray scattering have been used to characterize phase transition temperatures and ordered state symmetries. Five distinct microstructures were observed for this chemical system : spheres, hexagonally packed cylinders (HEX), lamellae (LAM), hexagonally perforated layers (HPL), and a bicontinuous cubic phase having an Ia3d space group symmetry. The bicontinuous Ia3d phase only occurs in the vicinity of the ODT between the HEX and LAM states at compositions of 0.65 ≤ f pI ≤ 0.68 and 0.36 ≤ f pI ≤ 0.39 (prior report). Farther from the ODT, within these composition ranges, the HPL phase occurs. We did not find the ordered bicontinuous double diamond (OBDD) morphology at any composition or temperature studied, and the overall phase diagram is qualitatively different from those reported previously for PI-PS block copolymers.

Small angle neutron scattering in combination with dynamic and static light scattering has been used to evaluate the association behavior of the styryl- and dienyllithium head groups in benzene. Both types of lipophobic active centers were found to aggregate as dimers which in turn can self-assemble to yield large scale structures. For the dienyllithium systems no evidence for the presence oftetrameric aggregates was found. The assay of the large scale structures revealed them to be prolate ellipsoids. Thus, these model ionomer systems exhibit diblock copolymer and surfactant style behavior in their capacity to generate cylindrical micelles.

Two types of E-glass fibres, a conventional and a high modulus where the last one in the following will be denoted as ECR-glass fibre, were investigated regarding density, diameter, stiffness and strength. The fibres were analysed as pristine and after sizing removal treatments. The sizing was removed by either burning at 565◦C or soxhlet extraction with acetone. It was found that the density and the stiffness increased after removing the sizing by the two removal treatments whereas the diameter did not change significantly. The strength of the fibres decreased after burning as the sizing, protecting against water and fibre-fibre damage, had been removed. The strength of the fibres after extraction was not significantly different from the strength of the pristine fibres despite removing the sizing. This indicates that the bonded part of sizing is still protecting the glass fibre surface.

‘‘Living’’ anionic polymerization offers a readily feasible preparation of very well‐controlled homo‐ or copolymers in a wide range of molar masses and chemical structures. Such samples are vital in experimental polymer physics and the technique presented here offers self‐sufficiency with such samples. The technique of anionic polymerization performed under inert atmosphere is presented here. The components of the setup are described in detail. Purification procedures for glassware and chemicals for specific polymerizations are given. Illustrative examples and results are presented.

Optical nanoparticle pH sensors designed for ratiometric measurements have previously been synthesized using post-functionalization approaches to introduce sensor molecules and to modify nanoparticle surface chemistry. This strategy often results in low control of the nanoparticle surface chemistry and is prone to batch-to-batch variations, which is undesirable for succeeding sensor calibrations and cellular measurements. Here we provide a new synthetic approach for preparing nanoparticle pH sensors based on self-organization principles, which in comparison to earlier strategies offers a much higher design flexibility and high control of particle size, morphology and surface chemistry.

Poly(vinyl pyrrolidone) (PVP) is an important synthetic polymer which has a wide variety of applications in the biomedical field because of its film forming properties including adhesion, excellent physiological compatibility, low toxicity, and reasonable solubility in water and most organic solvents [1]. Recently some studies have been published [2, 3] using micromechanical sensors to characterize thin polymer coatings under various conditions. With the final aim to deposit thin PVP film on cantilevers we studied the process optimization of PVP by spray coating on microscope glass slides. Here, we present a study of the parameters determining the quality of the deposited film. Spray Coating was done in an Exacta Coat Ultrasonic Spraying System (Sonotek, USA) .The main components are illustrated in fig. 1. The tip of the ultrasonic atomizer nozzle was actuated at a frequency of 120 kHz. Nitrogen gas was connected to the inlet of the air focusing shroud. The nitrogen pressure was monitored by a pressure sensor and regulated by a valve. The gas flow and the position of the air focusing shroud allowed the control of the diameter and shape of the spray-coating beam. The movement of the nozzle was controlled by an x-y-z stage. A shadow mask was put on a glass slide before deposition to cover some area from spraying. The masked areas acted as a baseline for characterizing the final coating by a surface profilometer (Veeco Dektak8) from where the thickness and roughness value were calculated as shown schematically in fig. 2. The surface texture was observed with an Optical Microscope (Zeiss). A 0.5 wt. % solution of PVP in water was prepared and introduced in the central column of the nozzle using a syringe pump. Each slide was coated 10times with a flow rate of 0.1ml/min and nitrogen pressure of 0.03Bar which was kept constant for all the experiments. The parameters varied are speed of the moving nozzle while spraying (nozzle path shown schematically in fig.2), temperature of the substrate and distance between nozzle and substrate. Surface morphology of the films is governed mainly by the rate of drying of the spray on the substrate. The depositions can be broadly classified into a dry state, a wet state and an optimized condition in between. The profilometer scan in fig. 3 and the microscope images in fig.4 show the surface for a distance between the nozzle and the substrate of (a) 100mm, (b) 70mm and (c) 90mm respectively. The further the nozzle is away from the substrate the faster the deposited polymer film dries. Spraying with a distance of 100mm gives rise to the dry state (fig. 3a) with avg. roughness (Ra) 158nm. When the distance between nozzle and substrate decreases to 70mm i.e., at the wet state, Ra reduces to 22nm. The disadvantage of the wet condition is that as the polymer remains wet for a longer time it accumulates at the edge of the deposition to form peaks of few microns in height (fig.3b). The optimized condition (fig.3c) lies in between at a distance of 90mm where we get a compromise between the dry and the wet state where Ra is 76nm but there are no edge peaks as shown before. With an increase in temperature (fig. 5a, b and c) the deposition moves from the wet to dry state were roughness increases due to rapid drying of the sprayed drops. Same dry state is observed for coating with an aqueous solution at 60°C (fig.5c) and when a low boiling solvent like dichloromethane (fig. 5d) is used for deposition at room temperature. The speed of the spraying nozzle influences both the final thickness and roughness of the film. The roughness becomes significant when the nozzle is very fast and the amount of polymer sprayed is not enough to coalesce and form a continuous film. This study shows the inter-correlation of different parameters for uniform film formation by spray coating. The findings will be used for coating of cantilevers and for studies of material characteristics of thin polymer films used for example drug delivery.

Structures of poly(ethylene propylene)–poly(ethylene oxide) (PEP–PEO) block copolymer micelles were determined from small-angle X-ray scattering and static light scattering and compared to predictions from a thermodynamic model. Both the corona block length and the solvent water–ethanol ratio were changed, leading to a thorough test of this model. With increasing ethanol fraction, the PEP core–solvent interfacial tension decreases, and the solvent quality for PEO changes. The weight-average block masses were 5.0 kDa for PEP and 2.8–49 kDa for PEO. For the lowest PEO molar mass and samples in pure water (except for the highest PEO molar mass), the micelles were cylindrical; for other conditions they were spherical. The structural parameters can be reasonably well described by the thermodynamic model by Zhulina et al. [Macromolecules2005, 38 (12), 5330–5351]; however, they have a stronger dependence on solvent composition and PEO molar mass than predicted.

The phase behavior of diblock copolymers near the order-disorder transition is studied using transmission electron microscopy, small-angle neutron scattering (SANS) and dynamical mechanical spectroscopy. For a series of polyolefin diblocks with volume fraction, f1, of the block with the larger segment length in the range f1 = 0.63 - 0.75, we find that the transition from lamellae to hexagonally packed cylinder phases occurs via intermediate layered phases that are always characterized by in-plane hexagonal order. One class of diblock forms a hexagonally modulated lamellar (HML) phase, then a hexagonally perforated layer (HPL) phase upon heating from lamellae, while another class forms a modulated hexagonally packed cylinder phase from the HML phase. We attempt to rationalize this based on the differences in inter-layer ordering in the HML phase evidenced by SANS patterns. Detailed phase diagrams for the diblocks depend on molecular weight, and a conformational asymmetry parameter, which is discussed. These results are similar to those found in certain smectic liquid crystal polymorphs, suggesting an analogy between thermotropic liquid crystalline behavior and the intermediate layered phases of diblock copolymer melts.

Two poly(ethylenepropylene)–poly(ethylethylene) (PEP‐PEE) diblock copolymer melts, containing 25% and 83% by volume PEP, were investigated using small‐angle neutron scattering (SANS) and rheological measurements. The SANS measurements were performed with the aid of an in situ shearing device operated directly in the neutron beam. Each sample was observed to possess three equilibrium phases: two ordered phases at low temperature and a disordered phase at elevated temperatures. The low and high temperature ordered phases have been evaluated to be hexagonally packed (hex) cylinders and body centered cubic (bcc) spheres, respectively. Application of a large amplitude dynamic shear deformation to the hex phase leads to well‐aligned cylinders, with a specific crystallographic orientation relative to the shear plane. Upon heating through the cylinder‐to‐sphere transition, the bcc phase grows epitaxially, with the [111] direction coincident with the original cylinder axis, leading to a well‐defined twinned micros...

A homologous series of nine symmetric poly(styrene)-block-poly(butadieme) diblock copolymers was synthesized and characterized. The scaling of the lamellar thickness,D, with the chain lengthN(DαN δ ) was investigated with small-angle X-ray scattering. Different sample preparation methods were used: annealing, solvent-casting and shear alignment. We find that the lamellar thickness and thus the value of the exponent δ depends on the preparation method used,i.e. care must be taken to ensure that the samples investigated are in thermodynamic equilibrium.