Disorder Transition Temperature Research Articles

Shifting the Order−Disorder Transition Temperature of Block Copolymer Systems with Electric Fields

ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTShifting the Order−Disorder Transition Temperature of Block Copolymer Systems with Electric FieldsHeiko G. Schoberth†, Kristin Schmidt‡, Kerstin A. Schindler†, and Alexander Böker*§View Author Information Lehrstuhl für Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth, Germany; Materials Research Laboratory, University of California, Santa Barbara, California 93106; and Lehrstuhl für Makromolekulare Materialien and Oberflächen and DWI an der RWTH e.V., RWTH Aachen University, D-52056 Aachen, Germany* Corresponding author. E-mail: [email protected]†Universität Bayreuth.‡University of California, Santa Barbara.§RWTH Aachen University.Cite this: Macromolecules 2009, 42, 10, 3433–3436Publication Date (Web):April 22, 2009Publication History Received24 January 2009Revised31 March 2009Published online22 April 2009Published inissue 26 May 2009https://doi.org/10.1021/ma900166wCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1049Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (817 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Copolymers,Electric fields,Microphase,Scattering,Transition temperature Get e-Alerts

Structure and Properties of Hexa- and Undecablock Terpolymers with Hierarchical Molecular Architectures

We report the synthesis, phase behavior, and viscoelastic and mechanical properties of a new type of multiblock copolymer composed of glassy poly(cyclohexylethylene) (C), semicrystalline poly(ethylene) (E), and elastomeric poly(ethylene-alt-propylene) (P). Five nearly monodisperse CECEC−P hexablock terpolymers and one (CECEC)2−P undecablock copolymer were synthesized by sequential anionic polymerization followed by catalytic hydrogenation. These multiblock copolymers, which contain equal volume fractions of P and compositionally symmetric CECEC, microphase separate by two different processes: segregation induced by crystallization of the E blocks and through chemical incompatibility between C, E, and P. These materials contain two different complex morphologies each with two length scales determined by the local (C−E) and overall (C−E−P) order−disorder transition temperatures relative to the glass and crystallization temperatures of the C and E blocks, respectively. Structure was determined by SAXS, TEM, ...

Time-resolved SAXS studies of self-assembling process of palladium nanoparticles in templates of polystyrene- block-polyisoprene melt: Effects of reaction fields on the self-assembly

Nanocomposites composed of palladium (Pd) nanoparticles, (Pd) n, and a symmetric diblock copolymer (dibcp) of poly(styrene)- block-poly(isoprene) (PS- b-PI) were prepared via thermal reduction of palladium acetylacetonate, Pd(acac) 2, by isothermal heat treatments of the as-cast dibcp films containing Pd(acac) 2 by 1 wt%, at temperatures below and above the order–disorder transition temperature ( T ODT) of the dibcp. Effects of the reaction field on the thermal reduction process of Pd(acac) 2 were studied by setting the field either in the disordered state or the ordered state of the dibcp. The reduction process was studied in situ and at real time by time-resolved small-angle X-ray scattering. In the as-cast films, a larger fraction of Pd(acac) 2 is preferentially incorporated in PS lamellar microdomains, seemingly due to stronger interactions of Pd(acac) 2 with PS than with PI. The spatial concentration fluctuations of (Pd) n in the final stage of the reduction reflect the memory of the concentration fluctuations of the dibcp before the reduction, either in the disordered state or in the ordered state. We found that the scaled scattering form factor of (Pd) n is universal with time and temperature of the reduction. This reveals that the reduction mechanism of Pd(acac) 2 and the growth mechanism of (Pd) n do not depend on temperature; they are same below and above T ODT. However, the reduction rate and the growth rate as well as the concentration of (Pd) n in the final stage depend on temperature: the higher the temperature is, the larger are the rate and the concentration.

Theoretical investigation of phase equilibria by the continuous displacement cluster variation method

Abstract By employing the continuous displacement cluster variation method, order – disorder transition behavior of a two-dimensional square lattice is investigated. It is demonstrated that the distribution of displaced atoms around a Bravais lattice point continuously changes with temperature. The additional freedom of atomic displacement contributes to the entropy and thermal lattice expansion is confirmed. Finally, it is shown that the order – disorder transition temperature decreases as compared with the one by the conventional cluster variation method in which no local atomic displacements are allowed.

Random Copolymer Effect in Self-Assembled Hydrogen-Bonded P(S-co-4VP)(PDP) Side-Chain Polymers

Random copolymers of styrene and 4-vinylpyridine P(S1−x-co-4VPx) were synthesized to study the effect of the random copolymer “repulsion” on the self-assembly in hydrogen-bonded complexes with pentadecylphenol (one PDP molecule per 4VP group). The major trends observed as a function of the fraction of styrene monomers 1 − x in the random copolymer are a decrease in order−disorder transition temperature, TODT, and a decrease in the periodic length scale of the ordered lamellar state. The lower TODT results from a partial shielding in the disordered state of the highly unfavorable styrene/4-vinylpyridine interactions by the PDP alkyl tails. The reduced layer thickness in the ordered state is due to the relaxation into a more coil-like conformation of the alkyl tails of the PDP amphiphiles, made possible by the presence of styrene units. The self-assembly properties of P(S1−x-co-4VPx)(PDP)1.0 are compared with those of the lamellar self-assembled homopolymer-based P4VP(PDP)x system, where x denotes the number of PDP molecules per 4VP repeat unit. As in P(S1−x-co-4VPx)(PDP)1.0, in P4VP(PDP)xalso only a fraction x of the total number of monomers of the macromolecule may potentially hydrogen bond with PDP molecules at any given instant. In contrast to P(S1−x-co-4VPx)(PDP)1.0, for P4VP(PDP)x, however, the long period is found to increase for decreasing values of x.

Lamella reorientation in thin films of a symmetric poly(l-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(l-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (TgPLLA), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (Tc), the glass transition temperature of PS (TgPS), the peak melting point of PLLA crystals (TmPLLA), and the end melting point of PLLA crystals (Tm,endPLLA). When annealed at (Tc=) 80°C (Tc<TgPS<TODT, order–disorder transition temperature), 123°C (TgPS<Tc<TmPLLA<TODT), 165°C (TgPS<TmPLLA<Tc<Tm,endPLLA<TODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced. The PLLA crystallization between PS layers was hypothesized to account for the lamella reorientation during annealing. The crystallization, chain conformation, and possible chain folding mechanisms were discussed, based on detailed analysis of the lamellar structure before and after crystallization.

Manipulating ordering transitions in interfacially modified block copolymers

We report a synthetic strategy that allows us to manipulate the interfacial region between blocks and control ordering transitions in poly(isoprene-b-styrene) [P(I-S)] block copolymers. This interfacial modification is accomplished by combining a semi-batch feed with anionic polymerization techniques. Using this approach, we are able to control the segmental composition and molecular interactions in our phase-separated block copolymers, independent of molecular weight and block constituents. A library of copolymers is prepared with various interfacial modifications to examine the effect of interfacial composition on copolymer self-assembly. The morphological characteristics of the self-assembled structures are investigated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). Normal and inverse tapered block copolymers, containing approximately 15–35 vol% tapered material, show a measurable decrease in the order–disorder transition temperature (TODT) relative to the corresponding non-tapered diblock copolymers, with the inverse tapered materials showing the greatest deviation in TODT. Additionally, TODT was inversely related to the volume fraction of the tapered region in both normal and inverse tapered copolymer materials.

The CSA calculation of the bcc Zr-Be phase diagram

In the recent years it has been shown that the fcc-based phase diagram can be calculated from the cluster site approximation (CSA) with remarkable accuracy and great computational simplicity over the cluster variation method (CVM). The basis of this method is briefly recalled in this paper. The CSA approximation is applied to estimate the bcc based order disorder phase diagrams of the Be-Zr system. The input parameters are the cluster interactions which are obtained from first principles calculations published recently. We discuss in detail the relationships between the adjustable parameter in this method and the order disorder transition temperature. Calculations of the formation Gibbs energies are carried out for the ordered and disordered phases and are compared with the ones obtained by the CVM method.

Molecular Architecture Effect on the Self-Assembly Behavior of Comb-Coil Block Copolymers Displaying Lamellae-within-Lamellae Morphology

Supramolecular comb-coil block copolymers formed by the stoichiometric complexation of two amphiphilic surfactants, dodecylbenzenesulfonic acid (DBSA) and 3-pentadecylphenol (PDP), with the poly(4-vinylpyridine) (P4VP) blocks in a linear PS-b-P4VP and a nonlinear AnBn-type heteroarm star PS-P4VP copolymer have been investigated. All linear and heteroarm star systems under study exhibited lamellae-within-lamellae morphology even at high PS volume fraction, at which the previously studied systems showed lamellae-within-cylinder or lamellae-within-sphere morphology. The interlamellar distances of the larger-scale copolymer microdomains were found to be much larger in all heteroarm complexes than those in their linear counterparts. This was attributed to the chain crowding effect coupled with the different types of arrangement of comb blocks forming the smaller-scale lamellar mesophase. Moreover, the order−disorder transition temperatures of both the larger- and smaller-scale structures in the heteroarm star ...

Macroscopically oriented lamellar microdomains created by “cold zone-heating” method involving OOT

The zone-heating method, which involves ordering of materials under moving temperature gradient ∇T, has been widely used as a technique to create macroscopically oriented ordered structures of various kinds of materials. We applied this method to a large molecular weight symmetric polystyrene-block-polyisoprene diblock copolymer (dibcp) at a temperature where the ∇T field exists below its order–disorder transition temperature TODT of the dibcp. In this method we first prepared the solvent-cast bulk films of the dibcp having a nonequilibrium morphology of hexagonally packed cylindrical microdomains (hex-cyl) by using a solvent selectively good for polyisoprene blocks. Then the zone-heating method was applied to the order–order transition process from the nonequilibrium hex-cyl to equilibrium lamellae. The “cold zone-heating” method, “cold” in the sense of the ∇T field existing below TODT, successfully created macroscopically oriented lamellae with their normals preferentially oriented parallel to the ∇T axis and their edges preferentially standing with respect to the bulk film surfaces. It was also found that the initial orientation of the (100) plane of hex-cyl normal to the ∇T axis prefers to that parallel to the ∇T axis for a better macroscopic alignment of lamellae. A possible model for the cold zone-heating-induced lamellar orientation will be discussed in the text.

Atomic ordering and magnetic properties in Ni 2Mn(Ga xAl 1− x) Heusler alloys

The phase stability and magnetic properties of Ni 2Mn(Ga x Al 1− x ) alloys were studied by differential scanning calorimetric and magnetometric measurements, and X-ray diffraction and transmission electronic microscopic observations. The order–disorder transition temperature from the B2 to the L2 1 phase, T t B 2 / L 2 1 , linearly increases with increasing x and the magnetic properties depend on the annealing conditions. Especially in the Ni 2Mn(Ga 0.5Al 0.5) alloy, the condition of the atomic order can be varied from a B2 to an L2 1 structure by the annealing temperature. The magnetic property of the fully ordered L2 1 phase is ferromagnetic with a Curie temperature T C of about 380 K, while that in the B2 phase is antiferromagnetic with the Néel temperature T N of about 300 K.

Preparation of Nanowells on a PS‐b‐PMMA Copolymer Thin Film by CO2 Treatment

AbstractOrdered nanowells with diameters of ca. 40 nm and depth of 1–2 nm were prepared on a poly(methyl methacrylate) (PMMA) spherical domain, which was exposed on the polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) copolymer thin film. The PS‐b‐PMMA film formed spherical PMMA domains after the film was annealed above the order–disorder transition temperature. CO2 was dissolved into the PS‐b‐PMMA thin film at 8.6 MPa and at a temperature of 20 °C. The release of CO2‐pressure at the same temperature created the nanowell on the PMMA domain. The temperature and pressure to create nanowells in the PMMA domain affected the possibility of nanowell's formation.magnified image

Microphase Separation and Morphology of the Real Polymer System by Dynamic Density Functional Theory, Based on the Equation of State

Microphase separation and morphology evolution of polystyrene and polybutadiene blends are quantitatively studied by the dynamic density functional theory that is based on the equation of state (EOS-based DDFT). The structure parameters of coarse-grained beads are regressed from the experimental pressure−volume−temperature data of pure components. The comparisons between simulated and experimental results are presented as illustrations. Notably, in the region near the critical composition, the deviation of the order−disorder transition temperature between simulation and experiment is <10 °C. Considering the fact that EOS-based DDFT is a unique simulation method that can predict the morphologies of blends in the different temperatures and compositions and match the simulated and experimental results in the same time, which is beyond the capabilities of the phase equilibrium theory and other simulation methods, such a deviation is obvious, but definitely acceptable. The factors that affect the accuracy of t...

Self-Assembled Poly(4-vinylpyridine)−Surfactant Systems Using Alkyl and Alkoxy Phenylazophenols

Para-substituted alkyl and alkoxy phenylazophenols (PAP’s) have been synthesized and used as hydrogen-bonded side chains for poly(4-vinylpyridine)-based comb-shaped supramolecules akin to the well-studied poly(4-vinylpyridine)/pentadecylphenol systems. In this paper we report the self-assembly of these new materials as investigated by DSC and simultaneous SAXS/WAXS. The systems exhibit smectic ordering with a periodicity in the range of 3.0−4.2 nm. The periodicity length scale, the order−disorder transition temperature (TODT), and the glass transition temperature Tg of the self-assembled systems all increase with increasing alkyl chain length. The correlation between TODT and Tg observed is argued to be the consequence of the increasing segregation in the self-assembled systems with increasing alkyl tail length of the amphiphiles.

Particle−Particle Interactions and Chain Dynamics of Fluorocarbon and Hydrocarbon Functionalized ZrO2 Nanoparticles

The chain conformation and dynamics of hydrocarbon and perfluorocarbon fatty acids adsorbed on 4 nm ZrO2 particles were characterized by solid-state 13C chemical shift and 19F NMR relaxation measurements, respectively, and compared to those from previous studies on lower surface area fumed metal oxide powders. The interdigitation of chains between neighboring particles, which increases with chain length, can be detected from the splitting of the 13C NMR and 19F NMR signals of the CH3 and CF3 groups, respectively. Similar to the case of alkanethiol self-assembled monolayers (SAMs) on gold nanoparticles, this interdigitation allows for efficient chain packing despite the high surface curvature. The hydrocarbon chains on the ZrO2 nanoparticles are more ordered, and the reversible chain length dependent order-disorder transition temperatures are elevated relative to those of the same fatty acids adsorbed on fumed ZrO2 powder. Likewise, the 19F spin lattice relaxation times of the fluorocarbon chains approach those of the bulk acids with increasing chain length and interdigitation, indicating densely packed chains.

Heat capacities, order–disorder transitions, and thermodynamic properties of rare-earth orthoferrites and rare-earth iron garnets

Rare-earth orthoferrites, RFeO 3, and rare-earth iron garnets (RIGs) R 3Fe 5O 12 ( R=rare-earth elements) were prepared by citrate–nitrate gel combustion method and characterized by X-ray diffraction method. Isobaric molar heat capacities of these oxides were determined by using differential scanning calorimetry from 130 to 860 K. Order–disorder transition temperatures were determined from the heat capacity measurements. The Néel temperatures ( T N) due to antiferromagentic to paramagnetic transitions in orthoferrites and the Curie temperatures ( T C) due to ferrimagnetic to paramagnetic transitions in garnets were determined from the heat capacity data. Both T N and T C systematically decrease with increasing atomic number of R across the series. Lattice, electronic and magnetic contributions to the total heat capacity were calculated. Debye temperatures as a function of absolute temperature were calculated for these compounds. Thermodynamic functions like C p , m o , S m o , H o, G o, ( H T o - H 0 o ) , ( H T o - H 298.15 K o ) , - ( G T o - H 298.15 K o ) / T , Δ f H m o , and Δ f G m o have been generated for the compounds RFeO 3(s) and R 3Fe 5O 12(s) based on the experimental data obtained in this study and the available data in the literature.

Thermal and structural study of Ni–Fe–Ga ferromagnetic shape memory alloys

Abstract Some thermal and structural characteristics of Ni–Fe–Ga alloys were studied by means of differential scanning calorimetry (DSC), thermo mechanical analysis (TMA), and X-ray diffraction techniques. It was observed that martensitic transition temperature rapidly decreases and Curie temperature increases with Fe content. The order–disorder transition temperature from a L21 to A2 structures grows linearly with iron content, as measured by TMA. TMA has been found as a useful tool to perform these characterizations.

Self-Assembly of Poly(diethylhexyloxy-p-phenylenevinylene)-b- poly(4-vinylpyridine) Rod−Coil Block Copolymer Systems

We describe the synthesis, the morphology, and self-assembly behavior of semiconducting poly(4-vinylpyridine-b-diethylhexyloxy-p-phenylenevinylene) (P4VP-b-PPV) rod−coil block copolymer systems. Three different block copolymers with 55%, 80%, and 88% coil volume fraction were synthesized by convergent anionic polymerization in THF using lithium α-methylstyrene as initiator. The morphology of the block copolymers was studied by transmission electron microscopy, small-angle X-ray scattering, and small-angle neutron scattering as a function of the volume fraction of the rod block as well as different annealing conditions. The microphase-separated morphologies in these block copolymers vary from lamellar, to hexagonal, and spherical, when the volume fraction of the rod is progressively reduced. By combining the lattice parameter measured by scattering techniques with the volume fraction of rod domains obtained by nuclear magnetic resonance, it was shown that the block copolymers in the lamellar structure are organized in a smectic C double layer, while in the hexagonal phase they self-organize in a homeotropic arrangement, with the rod blocks forming the dispersed phase. Furthermore, while self-assembly of rod−coil block copolymers in columnar hexagonal phase prevents close rod packing, for the lamellar phase evidence of this configuration among rods is shown by wide-angle X-ray scattering. As a consequence, the morphology and long-range order in the lamellar phase are the result of simultaneous inter-rods liquid crystalline interactions and the tendency to microphase segregation of rod and coil. As a result, depending on temperature, the lamellar phase can exist both with rods oriented in a smectic configuration and with randomly packed rods. We show that annealing the lamellar phase below its order−disorder transition temperature, TODT, but above the maximum affordable temperature for inter-rods liquid crystalline interactions, called smectic-in-lamellar to lamellar order−disorder transition temperature, TSL (with TSL< TODT), leads to highly improved long-range lamellar order, which is then preserved when the system is cooled below TSL, at which temperature rod close packing is fully recovered.

Synthesis and Thermodynamic Properties of Poly(cyclohexylethylene-b-dimethylsiloxane-b-cyclohexylethylene)

Poly(styrene-b-dimethylsiloxane-b-styrene) (PS−PDMS−PS) triblock copolymers were prepared by anionic polymerization and subsequently hydrogenated using a platinum/rhenium catalyst supported on ultrawide pore silica (Pt/Re−SiO2), yielding PCHE−PDMS−PCHE, where PCHE refers to poly(cyclohexylethylene). The hydrogenation reaction resulted in polymer with negligible chain degradation as confirmed by 1H NMR and size exclusion chromatography (SEC). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) experiments revealed a lamellar morphology for all specimens. Thermodynamic properties were inferred from the order−disorder transition temperatures as determined by SAXS and dynamical mechanical spectroscopy (DMS). The resulting segment−segment interaction parameter, χ(T), is assessed in the context of current published approaches to treating the thermodynamics of nonpolar polyolefins, particularly block copolymers.

Orientational Order in Block Copolymer Films Zone Annealed below the Order−Disorder Transition Temperature

We report measurements of rapid ordering and preferential alignment in block copolymer films zone annealed below the order-disorder transition temperature. The orientational correlation lengths measured after approximately 5 h above the glass-transition temperature ( approximately 2 microm) were an order of magnitude greater than that obtained under equivalent static annealing. The ability to rapidly process polymers with inaccessible order-disorder transition temperatures suggests zone annealing as a route toward more robust nanomanufacturing methods based on block copolymer self-assembly.