In situ grazing incidence small‐angle X‐ray scattering study of solvent vapor annealing in lamellae‐forming block copolymer thin films: Trade‐off of defects in deswelling

Solvent vapor annealing (SVA) is one route to prepare block copolymer (BCP) thin films with long‐range lateral ordering. The lattice defects in the spin‐coated BCP thin film can be effectively and rapidly reduced using SVA. The solvent evaporation after annealing was shown to have a significant impact on the in‐plane ordering of BCP microdomains. However, the effect of solvent evaporation on the out‐of‐plane defects in BCPs has not been considered. Using grazing‐incidence x‐ray scattering, the morphology evolution of lamellae‐forming poly(2‐vinlypyridine)‐b‐polystyrene‐b‐poly(2vinylpyridine) triblock copolymers, having lamellar microdomains oriented normal to substrate surface during SVA, was studied in this work. A micelle to lamellae transformation was observed during solvent uptake. The influence of solvent swelling ratio and solvent removal rate on both the in‐plane and out‐of‐plane defect density was studied. It shows that there is a trade‐off between the in‐plane and out‐of‐plane defect densities during solvent evaporation. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 980–989     

Resonant soft x‐ray scattering and reflectivity study of the phase‐separated structure of thin poly(styrene‐b‐methyl methacrylate) films

Combined soft X‐ray scattering and reflectometry techniques promise analysis of polymer thin film domain structure and composition without resorting to chemical modification or isotopic labeling. This work explores the capabilities of these techniques in polymer films of poly(styrene‐b‐methyl methacrylate) (P(S‐b‐MMA)). The results demonstrate that the techniques give detailed information on the domain structure of thin films using well‐known modeling procedures. Discrepancies were noted between the X‐ray optical parameters that are needed to best fit the reflectivity data to the model and the expected parameters. The sources of these discrepancies are discussed in terms of instrument configuration parameters, sample attributes, and, particularly, anisotropy of the chromophore parameters. The results show that fitting the soft X‐ray reflectivity data is much more sensitive to these X‐ray optical parameters than the soft X‐ray scattering data. Nevertheless, fits to both types of data yield quantitative measures of the polymer film's lamellar morphology that are consistent with each other and with literature values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Self‐assembly of metallo‐supramolecular block copolymers in thin films

The self‐assembly of a metallo‐supramolecular PS‐[Ru]‐PEO block copolymer, where ‐[Ru]‐ is a bis‐2,2′:6′,2″‐terpyridine‐ruthenium(II) complex, in thin films was investigated. Metallo‐supramolecular copolymers exhibit a different behavior as compared to their covalent counterparts. The presence of the charged complex at the junction of the two blocks has a strong impact on the self‐assembly, effecting the orientation of the cylinders and ordering process. Poly(ethylene oxide) cylinders oriented normal to the film surface are obtained directly regardless of the experimental conditions over a wide range of thicknesses. Exposure to polar solvent vapors can be used to improve the lateral ordering of the cylindrical microdomains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4719–4724, 2008     

Radiation damage in polymer films from grazing‐incidence X‐ray scattering measurements

Grazing‐incidence X‐ray scattering (GIXS) is widely used to analyze the crystallinity and nanoscale structure in thin polymer films. However, ionizing radiation will generate free radicals that initiate crosslinking and/or chain scission, and structural damage will impact the ordering kinetics, thermodynamics, and crystallinity in many polymers. We report a simple methodology to screen for beam damage that is based on lithographic principles: films are exposed to patterns of X‐ray radiation, and changes in polymer structure are revealed by immersing the film in a solvent that dissolves the shortest chains. The experiments are implemented with high throughput using the standard beam line instrumentation and a typical GIXS configuration. The extent of damage (at a fixed radiation dose) depends on a range of intrinsic material properties and experimental variables, including the polymer chemistry and molecular weight, exposure environment, film thickness, and angle of incidence. The solubility switch for common polymers is detected within 10–60 s at ambient temperature, and we verified that this first indication of damage corresponds with the onset of network formation in glassy polystyrene and a loss of crystallinity in polyalkylthiophenes. Therefore, grazing‐incidence X‐ray “patterning” offers an efficient approach to determine the appropriate data acquisition times for any GIXS experiment. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1074–1086     

Capillary flow behavior of worm‐like micelles studied by small‐angle X‐ray scattering and small angle light scattering

A novel capillary flow device has been developed and applied to study the orientation of worm‐like micelles, among other systems. Small‐angle X‐ray scattering (SAXS) data from micelles formed by a Pluronic block copolymer in aqueous salt solution provides evidence for the formation of worm‐like micelles, which align under flow. A transition from a rod‐like form factor to a less persistent conformation is observed under flow. Flow alignment of worm‐like micelles formed by the low molar mass amphiphile system cetyl pyridinium chloride+sodium salicylate is studied for comparative purposes. Here, inhomogenous flow at the micron scale is revealed by streaks in the small‐angle light scattering pattern perpendicular to the flow direction. Copyright © 2006 John Wiley & Sons, Ltd.     

Differential scanning calorimetry,small‐angle X‐ray scattering,and wide‐angle X‐ray scattering on homogeneous and heterogeneous ethylene‐α‐copolymers

The objective of this work was to use both X‐ray and differential scanning calorimetry techniques in a comparative study of the lamellar and crystalline structures of heterogeneous and homogeneous ethylene‐α‐copolymers. The samples differed in the comonomer type (1‐butene, 1‐hexene, 1‐octene, and hexadecene), comonomer content, and catalyst used in the polymerizations. Step crystallizations were performed with differential scanning calorimetry, and the crystallinity and lamellar thicknesses of the different crystal populations were determined. Wide‐angle X‐ray scattering was used to determine crystallinities, average sizes of the crystallites, and dimensions of the orthorhombic unit cell. The average thickness, separation of the lamellae, and volume fractions of the crystalline phase were determined by small‐angle X‐ray scattering (SAXS). The results revealed that at densities below 900 kg/m³, polymers were organized as poorly organized crystal bundles. The lamellar distances were smaller and the lamellar thickness distributions were narrower for the homogeneous ethylene copolymers than for the heterogeneous ones. Step‐crystallization experiments by SAXS demonstrated that the long period increased after annealing. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1860–1875, 2001     

Interface development in polycarbonate/poly(methyl methacrylate) bilayer films

We report the effect of annealing over a range of temperatures and times on the mixing, stability, and interfacial width in thin bilayer films of bisphenol A–polycarbonate (PC) on deuterated poly(methyl methacrylate) (dPMMA). These bilayer films were highly stable when annealed at temperatures of up to 438 K, the temperature at which the degradation of the blends of these materials was first detectable by thermogravimetric analysis. At higher temperatures, dewetting of the PC upper layer of the film occurred at an increasing rate. Nuclear reaction analysis showed that the PC and dPMMA layers remained segregated. Neutron reflectometry data showed that the interfacial width between the two polymer layers grew rapidly from 0.5 nm for an unannealed sample to approximately 4.0 nm, the latter value being in good agreement with the predicted value for the interfacial width in the absence of any reaction. Extended annealing at 438 K and lower temperatures had no effect on the interfacial width, whereas at higher temperatures, the interfacial width increased to approximately 5.5 nm before the films became unstable. The broadening of the interface found at higher annealing temperatures was attributed to an increase in the miscibility of the polymers induced by the monomer from the unzipping of the dPMMA chains. There was no evidence of a thermally induced chemical reaction between the two polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2351–2362, 2001     

Online wide‐angle X‐ray diffraction/small‐angle X‐ray scattering measurements for the CO2‐laser‐heated drawing of poly(ethylene terephthalate) fiber

Fiber‐structure‐development in the poly(ethylene terephthalate) fiber drawing process was investigated with online measurements of wide‐angle and small‐angle X‐ray scattering with both a high‐luminance X‐ray source and a CO₂‐laser‐heated drawing system. The intensity profile of the transmitted X‐ray confirmed the location of the neck‐drawing point. The diffraction images had a time resolution of several milliseconds, and this still left much room for improvement. Crystal diffraction appeared in the wide‐angle X‐ray images almost instantaneously about 20 ms after necking, whereas a four‐point small‐angle X‐ray scattering pattern appeared immediately after necking. With the elapse of time after necking, the four‐point scattering pattern changed into a meridional two‐point shape. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1090–1099, 2005     

Microstructure and morphology of self‐assembling multiblock poly(ethylene‐1‐butene)‐n copolymers in solution studied by wide‐Q small‐angle neutron scattering and microscopy

Multiblock ethylene‐1‐butene copolymers (PEB‐n) with graded ethylene content (where n is the number of ethyl branches per 100 backbone carbons) represent efficient cold filter plugging point (CFPP) depressants for crude oils and middle distillates. The aggregation behavior and the interaction with wax molecules of a tetrablock PEB‐2.6/PEB‐6.0/PEB‐10.9/PEB‐13.2 and triblock PEB‐6.5/PEB‐8.9/PEB‐10.1 copolymers in decane solutions were investigated over a wide temperature range by combining different small‐angle neutron scattering techniques and optical microscopy. The experimental results revealed in the decrease of temperature formation and evolution of multisized structural levels showing a hierarchical organization on the length scale from 1 nm up to 10 μm. One‐dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one‐dimensional copolymer structure shows longitudinal density modulation and micellar‐like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. The wax crystallization in board‐like objects of much smaller size than required by the CFPP criterion of oil and refinery industry (filter mesh size of 45 μm) is templated and controlled by the assembling features of the crystalline–amorphous PEB‐n multiblock copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Characterization of multicomponent polymer trilayers with resonant soft X‐ray reflectivity

Resonant soft X‐ray reflectivity (RSoXR) has been used to quantify the layer thicknesses and the interfacial widths of a single, complex thin film with three polymeric layers supported on an inorganic substrate. By adjusting the photon energy, the sensitivity to particular interfaces within the trilayer can be selectively enhanced. The results significantly improve and broaden the capabilities of RSoXR, which has previously only been demonstrated and used for bilayers on silicon substrates. The capability of RSoXR to characterize polymer trilayers was not readily predictable from prior bilayer results, as the RSoXR characterization of bilayers benefits from a strong X‐ray reflection from the substrate that serves as a reference beam with which the reflections from the other interfaces interfere with. The impact of having the capability to investigate trilayers is exemplified by discussing the utility of RSoXR to characterize organic electronic light emitting multilayers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1291–1299, 2009     

Ordering poly(trimethylsilyl styrene‐block‐D,L‐lactide) block copolymers in thin films by solvent annealing using a mixture of domain‐selective solvents

Controlling the morphology, domain orientation, and domain size of block copolymer (BCP) thin films is desirable for many applications in nanotechnology. These properties can be tuned during solvent annealing by varying the solvent choice and degree of swelling which affect the effective miscibility and volume fraction of the BCP domains. In this work, we demonstrate with a bulk lamellae‐forming BCP, poly(4‐trimethylsilylstyrene‐block‐D ,L ‐lactide) (PTMSS‐b‐PLA), that varying the composition of a mixture of solvent vapors containing cyclohexane (PTMSS‐selective) and acetone (PLA‐selective), enables formation of perpendicularly oriented lamellae with sub‐20‐nm pitch lines. The BCP domain periodicity was also observed to increase by 30%, compared to bulk, following solvent annealing. Furthermore, solvent annealing alone is shown to induce a transition from a disordered to an ordered BCP. We rationalize our observations by hypothesizing that the use of a combination of domain selective solvent mixtures serves to increase the effective repulsion between the blocks of the copolymer. We furnish results from self‐consistent field theory calculations to support the proposed mechanism. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52, 36–45     

Time‐resolved crystallization study of absorbable polymers by synchrotron small‐angle X‐ray scattering

Changes in the lamellar morphology that occurred during the quiescent isothermal crystallization of absorbable poly(p‐dioxanone) (PDS) and PDS/poly(glycolide) block copolymer were studied by synchrotron small‐angle X‐ray scattering. Important morphological parameters such as the lamellar long period, the thicknesses of the crystal and amorphous phases, and the scattering invariant were estimated as a function of time, and trends observed over a wide range of experimental conditions are discussed. Thicker but more perfect lamellae were detected at higher crystallization temperatures. The breadth of the normalized semilog Lorentz‐corrected intensity peak systematically decreased with increasing temperature. In addition, the values of the crystallization half‐time and the Avrami exponent (n = 2.5), determined from the real‐time changes in the lamellar development, showed superb agreement with the bulk crystallinity data generated from other experimental techniques, such as calorimetry and dielectric relaxation spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 153–167, 2001     

Ordering in thin films of asymmetric diblock copolymers

The time evolution of the free surface of asymmetric diblock copolymers of polystyrene and poly(methyl methacrylate) on a strongly interacting surface was studied with atomic force microscopy. The surface morphology underwent morphological transitions to satisfy commensurability conditions. These transformations were consistent with recent self‐consistent field arguments predicting the phase transitions of copolymers as a function of thickness (see M. J. Fasolka, P. Banerjee, A. M. Mayes, G. Pickett, & A. C. Balazs, Macromolecules 2000, 33, 5702). © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 663–668, 2001     

Specific recognition of syndiotactic poly(methacrylic acid) in porous isotactic poly(methyl methacrylate) thin films based on the effects of stereoregularity,temperature, and solvent

The effects of stereoregularity, temperature, and solvent on the specific recognition of syndiotactic (st)‐poly(methacrylic acid) (PMAA) in macromolecularly porous isotactic (it)‐poly(methyl methacrylate) films were investigated to give important insights into the regularity and stability of nanospaces in the it‐PMMA films as well as template polymerization. The porous it‐PMMA films were fabricated on quartz crystal microbalance (QCM) substrates via the layer‐by‐layer (LbL) assembly of it‐PMMA/st‐PMAA, plus the st‐PMAA extraction from the assembly. QCM analysis and infrared spectroscopy revealed the first case of stereocomplex formation using st‐PMAA with lower stereoregularity (rr = 73%) in the LbL films, while st‐PMAA obtained with conventional free radical polymerization (rr = 62%) was barely incorporated into the porous it‐PMMA films. The maximum st‐PMAA incorporation increased from 25 to 40 °C, but there were almost no difference between 40 and 55 °C, indicating that the it‐PMMA crystallization would also be accelerated with increasing temperature. The studies on st‐PMAA incorporation with various complexing solvents revealed that the host it‐PMMA in the porous films could only form the original stereocomplex with 2/1 unit‐molar stoichiometry (st‐PMAA/it‐PMMA) in acetonitrile/water or ethanol/water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3651–3657, 2010     

Syntheses and self‐assembly of poly(benzyl ether)‐b‐poly(N‐isopropylacrylamide) dendritic–linear diblock copolymers

This article describes the syntheses and solution behavior of model amphiphilic dendritic–linear diblock copolymers that self‐assemble in aqueous solutions into micelles with thermoresponsive shells. The investigated materials are constructed of poly(benzyl ether) monodendrons of the second generation ([G‐2]) or third generation ([G‐3]) and linear poly(N‐isopropylacrylamide) (PNIPAM). [G‐2]‐PNIPAM and [G‐3]‐PNIPAM dendritic–linear diblock copolymers have been prepared by reversible addition–fragmentation transfer (RAFT) polymerizations of N‐isopropylacrylamide with a [G‐2]‐ or [G‐3]‐based RAFT agent, respectively. The critical micelle concentration (cmc) of [G‐3]‐PNIPAM₂₂₀, determined by surface tensiometry, is 6.3 × 10^?6 g/mL, whereas [G‐2]‐PNIPAM₂₃₅ has a cmc of 1.0 × 10^?5 g/mL. Transmission electron microscopy results indicate the presence of spherical micelles in aqueous solutions. The thermoresponsive conformational changes of PNIPAM chains located at the shell of the dendritic–linear diblock copolymer micelles have been thoroughly investigated with a combination of dynamic and static laser light scattering and excimer fluorescence. The thermoresponsive collapse of the PNIPAM shell is a two‐stage process; the first one occurs gradually in the temperature range of 20–29 °C, which is much lower than the lower critical solution temperature of linear PNIPAM homopolymer, followed by the second process, in which the main collapse of PNIPAM chains takes place in the narrow temperature range of 29–31 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1357–1371, 2006     

Investigation of the deformation of homogeneous poly(ethylene‐co‐1‐octene) by wide‐ and small‐angle X‐ray scattering using synchrotron radiation

The deformation behavior of homogeneous ethylene‐1‐octene copolymers was investigated as a function of the crystallinity and the crystal size and perfection, respectively, by wide‐ and small‐angle X‐ray scattering using synchrotron radiation. The crystallinity and the crystal size and perfection, respectively, are controlled by the copolymer composition and the condition of melt crystallization. The deformation includes rotation of crystals, followed by plastic deformation and complete melting of the initial crystal population, and final formation of microfibrils. The process of rotation, plastic deformation, and melting of crystals of the initial structure is completed at lower strain if the size and perfection of the crystals, respectively, decrease, that is, if crystals thermally melt at lower temperature. The kinetics of the fibrillation of the initial structure seems independent of the crystal symmetry, that is, rotation and melting of pseudohexagonal and orthorhombic polyethylene crystals (as evident in low‐crystalline specimens) are similar. The structure of the microfibrils, before and after stress release, is almost independent of the condition of prior melt crystallization, which supports the notion of complete melting of the initial crystal population. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1919–1930, 2002     

Small‐angle X‐ray scattering from poly(methylmethacrylate) in aqueous solutions of t‐butyl alcohol

Segment‐segment interaction of poly(methylmethacrylate) in t‐butyl alcohol‐water mixtures in poor solvent regime was studied. From the small‐angle X‐ray scattering measurements of semidilute solution range, the binary and ternary cluster integrals of polymer segments were determined from concentration dependence of the correlation length at various temperatures just above the upper critical solution temperature. We have calculated the contributions of the segment–segment interaction to the entropy and enthalpy from the measured temperature dependence of these interaction parameters and found that both quantities are negative and decrease with decreasing t‐butyl alcohol content. FT‐IR absorption peak of carbonyl group of poly(methylmethacrylate) shifts to the lower frequency with increasing water content. The implications of these findings are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2195–2199, 1999     

Pore size distributions in low‐k dielectric thin films from X‐ray porosimetry

X‐ray reflectivity has been used to determine the mass uptake of probe molecules in porous thin films supported on thick silicon wafers. The adsorption occurs by capillary condensation when the films are exposed to probe vapor at controlled partial vapor pressures. The probe solvent partial pressure was varied by mixing saturated air and dry air at constant temperature or by changing sample temperature at a constant vapor concentration. Pore size distribution in the films can be calculated from the probe uptake with typical porosimetric approaches such as the application of the Kelvin equation to convert partial pressure into pore size. For illustration, the pore size distribution of three different nanoporous thin films, the primary candidate of ultra‐low‐k interlevel dielectrics in the next generation of integrated circuit chips, was determined with this technique. These samples represent different generations of low‐k dielectrics developed by industry. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2170–2177, 2002     

Synthesis and self‐assembly of novel amphiphilic copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate)

In this study, a novel type of amphiphilic block copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate) (PLA‐block‐PAAA) with biodegradable poly(lactic acid) as hydrophobic block and poly(ascorbyl acrylate) (PAAA) as hydrophilic block was successfully developed by a combination of ring‐opening polymerization and atom transfer radical polymerization, followed by hydrogenation under normal pressure. The chemical structures of the desired copolymers were characterized by ¹H NMR and gel permeation chromatography. The thermal physical properties and crystallinity were investigated by thermogravimetric analysis, differential scanning calorimetry, and wide angle X‐ray diffraction, respectively. Their self‐assembly behavior was monitored by fluorescence‐probe technique and turbidity change using UV–vis spectrometer, and the morphology and size of the nanocarriers via self‐assembly were detected by cryo‐transmission electron microscopy and dynamic light scattering. These polymeric micelles with PAAA shell extending into the aqueous solution have potential abilities to act as promising nanovehicles for targeting drug delivery. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Well‐defined amphiphilic polymethylene‐b‐poly(acrylic acid) diblock copolymers: New synthetic strategy and their self‐assembly

Well‐defined amphiphilic polymethylene‐b‐poly (acrylicacid) diblock copolymers have been synthesized via a new strategy combining polyhomologation and atom transfer radical polymerization (ATRP). Hydroxyl‐terminated polymethylenes (PM‐OH) with different molecular weights and narrow molecular weight distribution are obtained through the polyhomologation of dimethylsulfoxonium methylides following quantitative oxidation via trimethylamine‐N‐oxide dihydrate. Subsequently, polymethylene‐based macroinitiators (PM‐MIs M_n = 1,300 g mol^?1 [M_w/M_n = 1.11] and M_n = 3,300 g mol^?1 [M_w/M_n = 1.04]) are synthesized by transformation of terminal hydroxyl group of PM‐OH to α‐haloester in ～100% conversion. ATRPs of tert‐butyl acrylate (t‐BuA) are then carried out using PM‐MIs as initiator to construct PM‐b‐P(t‐BuA) diblock copolymers with controllable molecular weight (M_n = 8,800–15,800 g mol^?1 M_w/M_n = 1.04–1.09) and different weight ratio of PM/P(t‐BuA) segment (1:1.7–1:11.2). The amphiphilic PM‐b‐PAA diblock copolymers are finally prepared by hydrolysis of PM‐b‐P(t‐BuA) copolymers and their self‐assembly behavior in water is preliminarily investigated via the determination of critical micelle concentrations, dynamic light scattering, and transmission electron microscope (TEM). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012