Microdomain morphology of lamella‐forming diblock copolymer confined in a thin film

We report the self‐consistent field theory (SCFT) of the morphology of lamella‐forming diblock copolymer thin films confined in two horizontal symmetrical/asymmetrical surfaces. The morphological dependences of thin films on the polymer‐surface interactions and confinement, such as film thickness and confinement spatial structure, have been systematically investigated. Mechanisms of the morphological transitions can be understood mainly through the polymer‐surface interactions and confinement entropy, in which the plat confinement surface provides a surface‐induced effect. The confinement is expressed in the form of the ratio D/L₀, here D is film thickness, and L₀ is the period of bulk lamellar‐structure. Much richer morphologies and multiple surface‐induced morphological transitions for the lamella‐forming diblock copolymer thin films are observed, which have not been reported before. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1–10, 2009     

Interfacial properties of diblock copolymers at penetrable interfaces: Density profile,stretching, and interfacial tension

The interfacial properties of diblock (AB) copolymers near an interface between two solvents are studied by using the exact Green's function of a Gaussian copolymer chain at an attractive penetrable interface. We have studied the mean‐square end‐to‐end distance of the copolymer, 〈R²(z)〉, as a function of the distance of the joint point of the copolymer to the interface, z, the segment density distribution ρ(z), and the reduction of the interfacial tension Δγ_c due to the presence of the diblock copolymer. The density profile and the stretching of the copolymer chain are in agreement with both experimental results and simulations. The reduction in the interfacial tension is found to decrease with the increase in the degree of polymerization of the copolymer chain.     

MOLECULAR AND SUPRAMOLECULAR ORDERING IN CONFINED ENVIRONMENTS

Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c相似文献   

Monodispersed PEG‐b‐PSt nanoparticles prepared by atom transfer radical emulsion polymerization under microwave irradiation

Atom transfer radical emulsion polymerization of styrene using PEG‐Cl as macroinitiator under microwave irradiation was successfully conducted and monodispersed nanoparticles were prepared. The PEG‐Cl macroinitiator was synthesized, and confirmed by FTIR spectrum. The structure of the PEG‐b‐PSt diblock copolymer was characterized by ¹H‐NMR and the number of styrene unit in the diblock copolymer was calculated. The morphology, size, and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and photon correlation spectroscopy (PCS). The effects of the ratio of macroinitiator and monomer, the ratio of catalyst and macroinitiator on the size and size distribution of nanoparticles were investigated. It was found that the diameters of PEG‐b‐PSt nanoparticles prepared under microwave irradiation were smaller (<50 nm) and more monodispersed than those prepared with conventional heating. Moreover, with the increasing of the ratio of St/PEG‐Cl, the hydrodynamic diameters (D_h) of the nanoparticles increased and the poly index decreased, both D_h and poly index of the nanoparticles prepared under microwave irradiation were smaller then those prepared with conventional heating; as the concentration of catalyst increased, the D_h of the nanoparticles decreased and the poly index of the nanoparticles increased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 481–488, 2008     

Effect of Film Thickness on the Columnar Packing Structures of Discotic Supramolecules in Thin Films

The effects of film thickness on the columnar packing structure of discotic supramolecules in a thin supported film have been investigated by grazing‐incidence small‐angle X‐ray scattering technique using magnetically aligned cobalt octa(n‐decylthio)porphyrazine (CoS10) films on octadecyltrichlorosilane (OTS)‐functionalized substrates as model systems. Magnetically aligned CoS10 films with a range of film thicknesses (49–845 nm) form uniaxially oriented ‘edge‐on’ columnar superstructures with their columnar directors perpendicular to the applied magnetic field. However, the orientational ordering of the columnar packing in the plane perpendicular to the applied magnetic field is strongly dependent on the film thickness. While being damped by the elasticity of the side chains of CoS10, the strong interfacial interaction at the film‐substrate interface propagates up to 50–100 nm from the substrate, maintaining the orientation of columnar packing in the plane perpendicular to the applied magnetic field. When the distance from the film‐substrate interface becomes larger than about 100 nm, symmetric tilting of columnar layer orientation, which saturates at 11.5°, occurs due to longitudinal edge dislocations induced by accumulated elastic deformation.     

Continuous Thermodynamic Integration in Field‐Theoretic Simulations of Structured Polymers

This work explores the use of continuous thermodynamic integration in field‐theoretic simulations of a symmetric diblock copolymer melt. Free energies of the lamellar and disorder phases are evaluated by thermodynamic integration from a reference state (an Einstein crystal, λ = 0) to a diblock copolymer (λ = 1). This is followed by integration over the interaction parameter, χ_b , to locate the order–disorder transition (ODT). Then the equilibrium lamellar spacing and free energy cost of stretching and compressing lamellae are examined. The ODT, lamellar spacing, and compression modulus are consistent with previous calculations, though found faster and more precisely. The above quantities do not depend on simulation box size, suggesting that finite‐size effects are small and simulating two lamellar periods is sufficient to accurately evaluate bulk behavior. Furthermore, the statistical uncertainty in the ODT increases quickly with system size, suggesting that small systems may lead to more precise results.     

Surfactant-Water Systems with Small Layer Rigidity Phase Stability,Defects Models and Defects Mobility in Polyoxyethylene Surfactant with Water

Abstract

Starting from recent experiments in non-ionic surfactants, we discuss various topics characteristic of low rigidity K ₁ materials. (1) The stability of the lamellar and cubic phases is studied in a simple model involving K ₂ the saddle-splay constant K ₂, and entropy terms due to the chains. We expect the lamellar phase to have a large range of existence, and the cubic phase to be of small extent. (2) We compare to cubic phases stability in large K ₁ materials. We discuss the mobility of edge dislocations on the basis of a new model of the core which involves stretching of the core layers in one dimension, and easy nucleation of pores in this region. The core extension is a characteristic length of low K ₁ materials which is much larger than de Gennes' length for microemulsions with a similar low K ₁.     

Complex Macrophase‐Separated Nanostructure Induced by Microphase Separation in Binary Blends of Lamellar Diblock Copolymer Thin Films

The nanostructures of thin films spin‐coated from binary blends of compositionally symmetric polystyrene‐b‐polybutadiene (PS‐b‐PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing‐incidence small‐angle X‐ray scattering (GISAXS) after spin‐coating and after subsequent solvent vapor annealing (SVA). In thin films of the pure diblock copolymers having high or low molar mass, the lamellae are perpendicular or parallel to the substrate, respectively. The as‐prepared binary blend thin films feature mainly perpendicular lamellae in a one‐phase state, indicating that the higher molar mass diblock copolymer dominates the lamellar orientation. The lamellar thickness decreases linearly with increasing volume fraction of the low molar mass diblock copolymer. After SVA, well‐defined macrophase‐separated nanostructures appear, which feature parallel lamellae near the film surface and perpendicular ones in the bulk.

     

The pH induced vesicle to micelle morphology transition of a THP‐protected polymer

A diblock copolymer consisting of tetrahydropyranyl acrylate (THPA) as a pH‐deprotectable block, and a permanently hydrophobic block, methyl acrylate, was synthesized by RAFT polymerization using a quaternary amine functionalized, hydrophilic, RAFT chain transfer agent. The polymer self‐assembled in water to form vesicles with D_h = 130 nm, as determined by DLS and cryogenic transmission electron microscopy. Acid catalyzed deprotection of the THPA units to yield acrylic acid resulted in a vesicle to micelle morphology transition, as evidenced by the decrease in hydrodynamic diameter to D_h = 19 nm and the observation of micelles by dry state transmission electron microscopy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3026–3031     

Effect of ionic impurities on the electric field alignment of diblock copolymer thin films

In Forschung hast Du immer zu mir gesagt, Schaffe etwas!. Mein Chef, ich habe immer versucht Deinen Befehlen zu folgen. Ich widme Dir diese Veröffentlichung. Mensch, mit fünf und siebzig bist Du noch jung, schön Geburtstag!The effect of ionic impurities on the electric field alignment of lamellar microdomains in polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films was studied using transmission electron microscopy (TEM) and atomic force microscopy (AFM). At lithium ion concentrations greater than ~210 ppm, the microdomain morphology in block copolymers could be aligned in the direction of an applied electric field, regardless of the strength of interfacial interactions. Complete alignment of the copolymer microdomains, even those adjacent to the polymer/substrate interface, occurred by a pathway where the applied electric field enhanced fluctuations at the interfaces of the microdomains with a wavelength comparable to L_o, the equilibrium period of the copolymer. This enhancement in the fluctuations led to a disruption of the lamellar microdomains into smaller microdomains ~L_o in size, that, in time, reconnected to form microdomains oriented in the direction of the applied field.     

Phase‐Field Simulation of Long‐Wavelength Line Edge Roughness in Diblock Copolymer Resists

We examine stochastic computer simulations of the Leibler‐Ohta‐Kawasaki (LOK) phase‐field model 1 , 2 and demonstrate that long‐wavelength line edge roughness (LER) and line width roughness (LWR) in a lamellar diblock copolymer resist depend monotonically on quench depth and noise strength, and that the LER and LWR spectra both exhibit a peak at k₀–the characteristic wavenumber of mesophase separation in diblock copolymers. For k ⪅ k₀, we find that the LER spectrum approximately scales like k^−1.6. These observations are consistent with previous theoretical, computational, and experimental examinations LER and LWR in diblock copolymer melts, and thus the LOK phase‐field model should be considered a capable and appropriate framework for future examination of long‐wavelength LER and LWR in block copolymer resist systems.

     

Interface Orientation and Chain Conformation in Simulated Symmetric Diblock Copolymer Lamellar Systems

Summary: We describe the results of Monte Carlo simulations, based on the cooperative motion algorithm, of the lamellar structure generated at finite temperature by a symmetric diblock copolymer. The (70 × 70 × 70) simulation box in which the polymer chains were embedded for each simulation was rotated, based on the interface orientation, to bring the interfacial planes of the simulated structure into parallel. We found that the interface thickness, as defined by the distribution of the junction points, became narrower at lower temperature, and that the interface plane was characterized by a waviness with a maximum peak‐to‐valley distance of 20–30 lattice bonds. Compared with the isotropic state (T/N = ∞), chains at lower temperatures were stretched in the direction perpendicular to the interface; but only modestly compressed in the direction parallel to the interface. Individual block chains within the lamellar domains still behave like random coils. The block copolymer molecules exhibit only a modest tendency to orient themselves with their end‐to‐end vector perpendicular to the plane of the lamellar interface. Considered as an ensemble average, the results we obtained are similar to those reported from small angle neutron scattering measurements for the mean conformation of the PSd blocks of symmetrical PSd‐PVP diblock copolymers.

2‐D projections onto the X‐Z plane of the end beads for the A‐ and B‐chains (gray) and the junction points J (black) at T/N = 0.2. The interface plane is oriented parallel to the Y‐Z plane by rotating the simulation box. The distribution profiles of junction points and the end beads across the system in the direction of interface normal are shown in the lower part of the figure.     

Monte Carlo simulation of AB diblock copolymer between surface and substrate and comparison of experimental results

The morphologies of AB diblock copolymer film between the substrate and surface were investigated via Monte Carlo simulations on simple cubic lattices. The morphological dependence of the diblock copolymer thin film on the thickness, as well as the composition and interactive intensity has been mainly studied. With the increase of A‐segments fraction, various microdomain morphologies including regular parallel stripe‐like, mesh‐like, and normal lamella near the region of the surface were generated in this work. The morphology of thin films of asymmetric diblock copolymer was found to form cylinders in a bulk system when L_z was equal to 30. The morphologies of PS‐b‐PDMS diblock copolymer films have been studied via atomic force microscopy (AFM) and transition electron microscopy (TEM) measurements. The surface morphology of the PS‐b‐PDMS copolymer thin film shows a mesh‐like microphase separated structure, and PDMS continuous phase protruded on the PS dispersed phase. The surface composition of PS‐b‐PDMS copolymer thin films was measured by means of X‐ray photoelectron spectroscopy (XPS) and ATR‐IR. The comparison results show that the experimental observations are in good agreement with the simulation results. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1835–1845, 2006     

Polymeric catalyst with polymerization-enhanced Lewis acidity for CO2-based copolymers

Ring-opening copolymerization of CO₂ and epoxides is a promising way to manufacture high value-added materials. Despite a variety of catalyst systems have been reported, the reaction is still limited by low activity and polymer selectivity. Herein, a strategy of polymerization-enhanced Lewis acidity is reported to construct a series of highly efficient polymeric aluminum porphyrin catalysts (PAPCs). The characterization of the coordination equilibrium constant (K_eq) showed significantly enhanced Lewis acidity of PAPC (K_eq = 18.2 L/mol) compared to the monomeric counterpart (K_eq = 6.4 L/mol), accompanied with increased turnover frequency (TOF) from 136 h⁻¹ to 5500 h⁻¹. Through detailed regulation of Lewis acidity, the highly Lewis acidic PAPC-OTs displayed a record high TOF of 30,200 h⁻¹ with polymer selectivity of up to 99%.     

Compositionally symmetric diblock copolymer blends of moderate polydispersity

Recent experimental evidence and theoretical predictions indicate that binary blends of relatively monodisperse diblock copolymers remain miscible if the molecular weight disparity of the constituent copolymers is not too great. In this work, we examine the effect of moderate copolymer polydispersity on both the microstructural characteristics and phase behavior of blends prepared from four compositionally symmetric poly(styrene-b-isoprene) (SI) diblock copolymers ranging in polydispersity (M̄_w/M̄_n) from 1.02 to 1.30. Blend periodicities, measured by small-angle X-ray scattering, compare favorably with predictions from a strong segregation theory proposed for lamellar diblock copolymer blends composed of monomolecular copolymers. Transmission electron microscopy, employed to ascertain the real-space morphological characteristics of these blends, reveals that a lamellar → cylindrical transition occurs in macrophase-separated blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2653–2658, 1997     

Morphology of Symmetric Diblock Copolymers Confined Between Two Stripe‐Patterned Surfaces – Tilted Lamellae and More

Summary: We report the first Monte Carlo simulations on the thin‐film morphology of symmetric diblock copolymers confined between either symmetrically or antisymmetrically stripe‐patterned surfaces. Under suitable surface configurations (where the lamellae can comply with the surface patterns and can have a period close to the bulk lamellar period L₀), tilted lamellae are observed for film thicknesses D ≥ 2L₀; the checkerboard morphology is obtained for smaller film thicknesses. The A‐B interfaces in the tilted lamellae are basically perpendicular to the surfaces in their immediate vicinity, and exhibit undulations away from them. In some cases, the severe frustration imposed by the two patterned surfaces leads to irregular or unexpected morphologies, which represent locally stable states. The efficient sampling of our expanded grand‐canonical Monte Carlo technique enables us to observe more than one locally stable morphologies and the flipping between them during a single simulation run.

Tilted lamellae between symmetrically patterned surfaces (perpendicular to z) with a surface pattern period of 1.5L₀ and a film thickness of 2.67L₀. L₀ is the bulk lamellar period and the black curves mark the A‐B interfaces.     

Properties of polystyrene-poly(methylmethacrylate) random and diblock copolymers in dilute and semidilute solutions

Solution properties for random and diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) have been measured by dynamic and total intensity light scattering in solvents of differing quality. The results are compared with the corresponding properties for PS and PMMA homopolymers of similar molecular weight, in order to determine if interactions between unlike monomers are significant. The hydrodynamic radius (R_h) and diffusion second virial coefficient (k_d) for the random copolymer are found to be larger than the corresponding values for the homopolymers in a solvent which is near-theta for the two homopolymers, whereas no such effect is observed for the block copolymer. This suggests that most intrachain interactions occur a relatively short distance along the chain backbone. In a mutual good solvent R_h and k_d of the random copolymer are comparable to the average of the values for the homopolymers, indicating that in a good solvent monomer/solvent interactions dominate over monomer/monomer interactions. For an isolated diblock copolymer in a mutual good solvent, there is no evidence that interactions between unlike monomers lead to additional expansion of the entire molecule, as measured by R_h, nor expansion of the individual blocks as probed by light scattering with one block optically masked. However, at low but finite concentration there is evidence (the coefficients of the binary interaction terms in the viscosity and the mutual diffusion coefficient, and the second and third virial coefficients) that a weak ordering effect may exist in block copolymer solutions, far from the conditions where microphase separation occurs. Finally, measurements of ternary polymer-polymer-solvent solutions show no dependence on monomer composition or monomer distribution for the tracer diffusion of probe PS-PMMA copolymers in a PMMA/toluene matrix. This indicate that the frictional interaction is largely unaffected by interactions between unlike monomers. However, there is evidence that the thermodynamic interaction is more unfavorable between a random copolymer and the homopolymer matrix than between a diblock and the matrix. © 1994 John Wiley & Sons, Inc.     

A study of the surface analysis of some water‐soluble polymers by inverse gas chromatography

The surface characterization of 2‐(dimethylamino)ethylmethacrylate (DMA) and 2‐(N‐morpholino)ethylmethacrylate (MEMA) homopolymers and DMA–MEMA diblock copolymer was studied using inverse‐gas chromatography (IGC). The analyzed surface properties of (co)polymers were the dispersive component of the surface energy ( ) and the acid–base characters of (co)polymer surfaces. The specific free energy (ΔG^sp), enthalpy (ΔH^sp), and entropy (ΔS^sp) of adsorption of polar probes on (co)polymers were calculated. The values of ΔH^sp were correlated with both the donor and the modified acceptor numbers (AN) of the probes to quantify the acidic K_A and the basic K_D parameters of (co)polymer surfaces. The values obtained for the K_A and K_D parameters indicated basic characters for the surface of (co)polymers. The dispersive component values of the surface energy and the acid–base surface parameters of the DMA–MEMA diblock copolymer surface were found to be between those homopolymers as expected. Copyright © 2008 John Wiley & Sons, Ltd.     

Organized polymerization of functional diblock copolymers possessing central isoprene groups

Functional diblock copolymers possessing central isoprene groups were synthesized by anionic addition in a three-stage process using styrene, isoprene, and 2-vinylpyridine monomers. These diblock copolymers formed microphase-separated structure in the solid state. Where the central isoprene groups are organized regularly at the domain interface of the microphase-separated structure, this is due to the functional groups being located at the block junction position. Addition-condensation of diblock copolymer film with sulfur monochloride formed A_nB_n star block copolymers by organization effects. © 1993 John Wiley & Sons, Inc.     

Non‐equilibrium phase behavior of diblock copolymer melts and binary blends in the intermediate segregation regime

The phase behavior of intermediately segregated (χN = 45) poly(ethylene)‐poly(ethylethylene) (PE–PEE) diblock copolymers and PE–PEE binary blends are characterized using transmission electron microscopy and small‐angle X‐ray scattering. Surprisingly, the preparation‐dependent, nonequilibrium phase behavior can be overwhelming even at this degree of segregation. A pure diblock with a poly(ethylene) volume fraction of f_PE = 0.46 exhibited coexisting lamellae and perforated layers when prepared using a precipitation technique, but contained only the lamellar morphology when solvent cast. This preparation dependence was more dramatic in binary diblock copolymer blends with average compositions of 〈f_PE〉 = 0.44, 0.46, and 0.48. Precipitated blends exhibited a microphase separated structure that was disordered and bicontinuous; however, solvent cast samples exhibited either a cylindrical, coexisting cylindrical and lamellar, or lamellar morphology. This nonequilibrium behavior is attributed to the high degree of segregation and the proximity to the cylinder/lamellae phase boundary. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2229–2238, 1999