Fine structure and phase transition behavior of fluorinated comb copolymers

The fine structure in the solid state and phase transition behavior of newly synthesized comb copolymers having fluorocarbon and hydrocarbon side‐chains were investigated by temperature controlled wide angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). From the WAXD profiles, two kinds of short spacing peaks based on the formation of the subcell for fluorinated and hydrogenated side‐chains were confirmed at 5.0 and 4.1 Å, respectively. Furthermore, two kinds of endothermic peaks, which corresponded to melting peaks of both side‐chain crystals, appeared in heating process of the DSC thermograms. From these experimental findings, the phase separation structure having the independently packed immiscible side‐chain crystalline was formed in the whole polymer crystal. In addition, it was found that these comb polymers formed highly ordered (double) layer structure estimated using WAXD and small angle X‐ray scattering (SAXS). These fluorinated comb copolymers form a monolayer on the water surface and their transferred film with phase‐separated structure at nanometer size on solid. There were hydrogenated domains at 10–20 nm diameter scales in these phase separated surface structure of monolayers. From these experimental results, these copolymer monolayers are expected to be used as a new molecular device such as nanolithography based on the surface patterning of polymer nanomaterials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 416–425, 2006     

Crystallization and chain conformation of semicrystalline and amorphous polymer blends studied by wide‐angle and small‐angle scattering

We examine the crystallization and chain conformation behavior of semicrystalline poly(ethylene oxide) (PEO) and amorphous poly(vinyl acetate) (PVAc) mixtures with wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and small‐angle neutron scattering (SANS) experiments. For blends with PEO weight fractions (wt_PEO) greater than or equal to 0.3, below the melting point of PEO, the WAXD patterns reveal that crystalline PEO belongs to the monoclinic system. The unit‐cell parameters are independent of wt_PEO. However, the bulk crystallinity determined from WAXD decreases as wt_PEO decreases. The scattered intensities from SAXS experiments show that the systems form an ordered crystalline/amorphous lamellar structure. In a combination of WAXD and SAXS analysis, the related morphological parameters are assigned correctly. With the addition of amorphous PVAc, both the average amorphous layer thickness and long spacing increase, whereas the average crystalline layer thickness decreases. We find that a two‐phase analysis of the correlation function from SAXS, in which the scattering invariant is linearly proportional to the volume fraction of lamellar stacks, describes quantitatively the crystallization behavior of PEO in the presence of PVAc. When wt_PEO is close to 1, the samples are fully spaced‐filled with lamellar stacks. As wt_PEO decreases from 1.0 to 0.3, more PVAc chains are excluded from the interlamellar region into the interfibrillar region. The fraction outside the lamellar stacks, which is completely occupied with PVAc chains, increases from 0 to 58%. Because the radius of gyration of PVAc with a random‐coil configuration determined from SANS is smaller than the average amorphous layer thickness from SAXS, we believe that the amorphous PVAc chains still persist with a random‐coil configuration even when the blends form an ordered structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2705–2715, 2001     

Packing manner of graft copolymers with rigid‐rod main chains and amorphous‐crystalline diblock copolymers as side chains

We have investigated the morphology and packing manner of graft copolymers consisting of rigid‐rod‐like poly(γ‐benzyl L ‐glutamate) (PBLG) main chains and grafted diblock copolymers of amorphous poly(propylene glycol) (PPG) and crystalline poly(ethylene glycol) (PEG). The results of differential scanning calorimetry and wide‐angle X‐ray scattering measurements for graft copolymers with higher side‐chain volume fractions suggest that the rodlike main chains and crystallized PEG chains exist in segregated domains. Small‐angle X‐ray scattering profiles for these samples show diffraction intensity maxima accompanied by higher order peaks, the positions of which suggest the formation of an ordered layered structure. From these observations, the graft copolymers are estimated to form repeated layered structure consisting of segregated PBLG, PPG, and PEG layers. A proposed model for molecular packing of the graft copolymers is consistent with the experimental observation that the repeating distance for the layered structure decreases with an increase in the volume fraction of side chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1904–1912, 2002     

Deformation mechanisms in uniaxial‐oriented semi‐crystalline PET‐films as a function of orientation to tensile direction

Poly(ethylene terephthalate) films with oriented lamellar structure were deformed in tensile experiments and investigated in situ using small angle X‐ray scattering. The tensile direction was set parallel, normal and in an angle of 45° relative to the surface normal of the lamellae. Data were interpreted in terms of two‐dimensional autocorrelation functions. The deformation of lattice spacing and lamellar orientation can largely be explained by affine transformations. The sample, where the lamellar surface normal was normal to tensile direction, developed a chequerboard type arrangement of crystalline parts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 159–169     

Control through monomer placement of surface properties and morphology of fluoromethacrylate copolymers

The arrangement of monomers and morphology of fluorinated copolymers of methyl methacrylate (MMA) were found to be important for controlling the surface energy of the materials when formed into thin films. Novel copolymers of MMA and 2,2,3,3,4,4,4‐heptafluorobutyl methacrylate (F3MA) were prepared with different monomer placement, namely statistical and block arrangements of the monomer units. The surface energies decreased with increasing incorporation of F3MA, in a manner consistent with previous reports for similar copolymers; however, the surface energies of the block copolymers were consistently lower than the statistical copolymers. This was interpreted as arising from conformational restriction of presentation of the fluoromonomers to the surface in the statistical copolymers, and formation of phase‐separated domains at the surface of the block copolymers. The morphology of the block copolymers was confirmed by small angle X‐ray scattering measurements, which allowed calculation of a solubility parameter for the fluorinated segments. The results have implications for the design of more environmentally acceptable materials with ultra‐low surface energies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2633–2641     

Microstructural evolution underlying the ternary stages of the elastic behaviors for poly(ether‐b‐amide) copolymer elastomers

Three stages of elastic behavior were observed during cyclic deformations for poly(ether‐b‐amide) (PEBA) segmented copolymers based on crystalline hard segments of polyamide 12 (PA12) and amorphous soft segments of poly(tetramethylene oxide) (PTMO). The underlying microstructural evolution was characterized by a combination of in situ Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS) technologies. The γ–α″ phase transition of crystalline PA12 occurred upon stretching, and the orientation of the α″ phase was less reversible under larger strains. PTMO chain orientation cannot be restored to the initial state, contributing to plastic deformation. Driven by the entropy effect, the strain‐induced crystallization of PTMO can fuse during sample retarding, exerting little influence on the residual strain. For PEBA with a shore D hardness of 35 D, the long period (L) can be restored to the initial L after the sample was unloaded until system fibrillation. The tie molecules between adjacent oriented lamellae can be by drawn out high stress in a PEBA material with a shore D hardness of 40 D, and the relaxation led to a second long period. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 855–864     

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     

Semidilute solution structure of cellulose in an ionic liquid and its mixture with a polar organic co‐solvent studied by small‐angle X‐ray scattering

Structural and thermodynamic properties of cellulose solutions in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EMIMAc) and its binary mixtures with N,N‐dimethyl formamide (DMF) are studied by small‐angle X‐ray scattering (SAXS). These measurements indicate molecular dissolution of the cellulose chains without any significant aggregation. The power–law relationships of the evaluated correlation length and osmotic modulus to concentration exhibit exponents of ?0.76 and 2.06 for EMIMAc and ?0.80 and 2.14 for DMF/EMIMAc solvent mixture, respectively. Thus, these solvents can be considered to be good solvents for cellulose. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 888–894     

Domain size equilibration in sphere‐forming block copolymers

The kinetics of domain size equilibration were studied for asymmetric poly(ethylene‐alt‐propylene)‐b‐poly(dimethyl siloxane) (EPDMS) and polyisoprene‐b‐poly(dimethyl siloxane) (IDMS) block copolymers in the body‐centered cubic ordered phase. Small‐angle X‐ray scattering measurements of the principal peak position (q*) were made as a function of time after temperature jumps within the ordered state. The equilibration times were remarkably long, especially on cooling and for temperatures below 100 °C. For example, after a quench to 40 °C, q* for EPDMS had not fully equilibrated even after several weeks of annealing; IDMS required several days to equilibrate at the same temperature. In contrast, a lamella‐forming EPDMS sample was able to adjust q* within the timescale of the measurements (i.e., minutes) with both heating and cooling over the same temperature range. Measurements of tracer diffusion indicated that chain mobility was not the rate‐limiting step, although differences in mobility did account for the differences between EPDMS and IDMS. Rather, the limiting step was the required reduction in the number density of spheres on cooling; the disappearance of spheres, either by evaporation or by fusion, provided a large kinetic barrier. Lamellae, however, could adjust domain dimensions simply by local displacements of individual chains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 715–724, 2003     

Structure of molten stereoregular polyolefins with different side‐chain sizes: Linear polyethylene,polypropylene, poly(1‐butene), and poly(4‐methyl‐1‐pentene)

The melt structures of linear polyethylene and the isotactic vinyl polymers polypropylene, poly(1‐butene), and poly(4‐methyl‐1‐pentene), along with the corresponding methyl, ethyl, and isobutyl side chains, were studied with wide‐angle X‐ray diffraction. As the size of the side branch increases from zero (polyethylene) to methyl, ethyl, and isobutyl, a prepeak appears below the main diffraction peak in the total structure factor. The prepeaks become stronger and shift to lower scattering vectors with increasing bulkiness of the side chain. There is a strong correlation between the position of the prepeaks in the melt and the average nearest‐neighbor helix–helix packing distance in the crystals, implying similar helical conformations in the melts. © 2000 John Wiley & Sons, Inc.* J Polym Sci B: Polym Phys 38: 2480–2485, 2000     

Equilibrium short‐range order in the isotropic phase of a poly(ester‐imide) with a C22H44 alkane spacer

Small‐angle X‐ray scattering (SAXS) was performed on a sample of poly(4,4′‐ phthaloimidobenzoyldoeicosamethyleneoxycarbonyl) (PEIM‐22) as a function of temperature. Wide‐angle X‐ray diffraction and differential scanning calorimetry were used to follow the isotropization of the crystalline PEIM‐22. The crystals of PEIM‐22 consist of biphasic layers up to the isotropization temperature. A series of SAXS peaks are observed for the crystals between θ = 0.3 and 3.5°. The width of these peaks indicates the formation of a smectic‐like, crystalline layer structure of a coherently scattering domain size of only 3–4 repeating units. In the isotropic phase, a single, broader peak remained at a spacing of ≈2.6 nm, suggesting even at high temperature the existence of equilibrium, short‐range, local order. The SAXS profiles were calculated based on a model of alternating layers of a linear, paracrystalline lattice. The results were discussed together with similar data on model compounds in the literature, and it is suggested that the short‐range order in the isotropic phase is due to a nanometer‐scale separation of the polar, aromatic phthaloimidobenzoyl from the flexible doeicosamethyleneoxycarbonyl. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 611–621, 2000     

Synthesis and self‐assembly of highly incompatible polybutadiene–poly(hexafluoropropylene oxide) diblock copolymers

A versatile coupling reaction for the preparation of polybutadiene–poly‐(hexafluoropropylene oxide) (BF) diblock copolymers is described. Six diblock copolymers with different block lengths were characterized by nuclear magnetic resonance spectroscopy and size exclusion chromatography; all six had total molecular weights below 15,000. Microphase separation of the block copolymers in the bulk state was established by small‐angle X‐ray scattering (SAXS) and differential scanning calorimetry. SAXS data suggest that the diblocks are characterized by an unusually large Flory‐Huggins interaction parameter, χ, on the order of 10. However, extraction of χ from the order–disorder transition gave large (order 1) but significantly different values, thereby suggesting that these copolymers are too small and too strongly interacting to be described by block copolymer mean‐field theory. Dynamic light scattering was used to analyze dilute solutions of the title block copolymers in four selective organic solvents; the sizes of the micelles formed were solvent dependent. The micellar aggregates were large and nonspherical, and this is also attributed to the high degree of incompatibility between the two immiscible blocks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3685–3694, 2005     

Poly(ethylene imine)‐graft‐poly(ethylene oxide) brush‐like copolymers: Preparation,thermal properties,and selective supramolecular inclusion complexation with α‐cyclodextrin

Poly(ethylene imine)‐graft‐poly(ethylene oxide) (PEI‐g‐PEO) copolymers were synthesized via Michael addition reaction between acryl‐terminated poly(ethylene oxide) methyl ether (PEO) and poly(ethylene imine) (PEI). The brush‐like copolymers were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the crystallinity of the PEO side chains in the copolymers remained unaffected by the PEI backbone whereas the crystal structure of PEO side chains was altered to some extent by the PEI backbone. The crystallization behavior of PEO blocks in the copolymers suggests that the bush‐shaped copolymers are microphase‐separated in the molten state. The PEO side chains of the copolymers were selectively complexed with α‐cyclodextrin (α‐CD) to afford hydrophobic side chains (i.e., PEO/α‐CD inclusion complexes). The X‐ray diffraction (XRD) shows that the inclusion complexes (ICs) of the PEO side chains displayed a channel‐type crystalline structure. It is identified that the stoichiometry of the inclusion complexation of the PEI‐g‐PEO with α‐CD is close to that of the control PEO with α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2296–2306, 2008     

Morphology and crystal structure of the poly(ethylene oxide)–hydroquinone molecular complex

The occurrence of a molecular complex between poly(ethylene oxide) (PEO) and p‐dihydroxybenzene (hydroquinone) has been determined using different experimental techniques such as differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and Fourier transform infrared spectroscopy (FTIR). From DSC investigations, an ethylene oxide/hydroquinone molar ratio of 2/1 was deduced. During the heating, the molecular complex undergoes a peritectic reaction and spontaneously transforms into a liquid phase and crystalline hydroquinone (incongruent melting). A triclinic unit cell (a = 1.17 nm, b = 1.20 nm, c = 1.06 nm, α = 78°, β = 64°, γ = 115°), containing eight ethylene oxide (EO) monomers and four hydroquinone molecules, has been determined from the analysis of the X‐ray diffraction fiber patterns of stretched and spherulitic films. The PEO chains adopt a helical conformation with four monomers per turn, which is very similar to the 7₂ helix of the pure polymer. A crystal structure is proposed on the basis of molecular packing considerations and X‐ray diffraction intensities. It consists of a layered structure with an alternation of PEO and small molecules layers, both layers being stabilized by an array of hydrogen bonds. The morphology of PEO–HYD crystals was studied by small angle X‐ray scattering and DSC. As previously shown for the PEO–resorcinol complex, PEO–HYD samples crystallize with a lamellar thickness corresponding to fully extended or integral folded chains. The relative proportion of lamellae with different thicknesses depends on the crystallization temperature and time. Finally, the observed morphologies are discussed in terms of intermolecular interactions and chain mobility. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1197–1208, 1999     

Fluorinated comblike homopolymers: The effect of spacer lengths on surface properties

A series of polyacrylate monomers with F‐alkylalkyl [F(CF₂)_n(CH₂)_n′] side groups were prepared by free‐radical polymerization. The effect of the chemical structure on the surface properties of poly(ethylene terephthalate)s was evaluated by variations in the relative length of the fluorocarbon and hydrocarbon units in the side group. The resulting polymers were quite surface‐active in the solid state. The surface and bulk organization was investigated by X‐ray photoelectron spectroscopy analysis. A strong correlation between the bulk organization and surface properties of the polymers was established. The outmost layer, formed from trifluoromethyl groups and some ester functions, suggests that the side chain is arranged irregularly in the polymer–air interface. The length of the lateral chain governs this organization: long fluorinated chains and short hydrocarbon spacers are essential elements of the molecular design for such low‐surface‐energy materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3737–3747, 2005     

Simultaneous wide‐angle X‐ray diffraction and differential scanning calorimetry analysis of the melting and recrystallization behavior of polyethylene and isotactic polypropylene containing cyclopentane units in the main chain

The melting and crystallization behavior of polyethylene and isotactic polypropylene containing 1,2‐ or 1,3‐disubstituted cyclopentane units in the main chain has been studied with simultaneous wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry. For the ethylene‐based copolymers, the position of a reflection peak in the WAXD patterns shifts to a low angle with the increasing acquired temperature. The temperature dependence on the axial length of the crystal lattice is more marked in the copolymers forming orthorhombic crystals (containing 1,2‐cyclopentane or 5.6 mol % 1,3‐cyclopentane units) than in those forming hexagonal crystals (containing 8.1 mol % 1,3‐cyclopentane units). For the isotactic propylene‐based copolymers, the position of the reflection peaks in the WAXD patterns is independent of the acquired temperature. The proportion of the γ form in the copolymer containing the 1,2‐cyclopentane units is higher than that in the copolymers containing the 1,3‐cyclopentane units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1457–1465, 2004     

Cavitation and morphological changes in polypropylene deformed at elevated temperatures

Polypropylene (PP) thick films were subjected to tensile drawing at various temperatures from the room temperature to 100 °C. Morphological alterations during drawing were followed by wide‐angle X‐ray scattering, small‐angle X‐ray scattering, and scanning electron microscopy (SEM) of sectioned and etched samples, volume strain measurement, and light transparency measurement at various level of strain. The morphological observations were paralleled with stress–strain determination. Samples drawn at 25 and 40 °C undergo severe cavitation contributing to their volume increase up to 90–95%. The volume increase contributes greatly to the engineering strain. PP drawn at 70 and 100 °C does not cavitate. At the strain up to 1.2, a high lamellae orientation is observed in SEM, whereas the 2D WAXS patterns show in contrary circular diffraction rings indicating low orientation of crystals. The rotation of lamellae toward drawing direction is associated with reverse rotation of chains in crystals due to fine chain slips. These two rotations in opposite directions counterbalance resulting in a much weaker crystal orientation than expected from the SEM images. Noncavitating samples retain their translucency up to a high strain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1271–1280, 2010     

Morphology of α‐transcrystalline isotactic polypropylene under tensile stress studied with synchrotron microbeam X‐ray diffraction

The morphology of transcrystalline isotactic polypropylene under tensile stress was studied with wide‐angle synchrotron X‐ray diffraction. The strain was apparently generated predominantly within the amorphous phase because no change in the crystal structure or in the orientation of the lamellae was detected. The results are interpreted in terms of anchoring of the transcrystalline layer to the fiber surface, and the possible consequences of these morphological features on the mechanical properties of the aramid–polypropylene composite as a whole are discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2016–2021, 2001     

Characterization of proton‐conducting organic–inorganic polymeric materials by ASAXS

The distribution of ZrO₂ and phosphotungstic acid (PTA) in a matrix of sulfonated polyether ketone was investigated by anomalous small‐angle X‐ray scattering (ASAXS). Scattering curves were obtained using X‐ray energies near the Zr and W absorption edges, allowing the independent analysis of the distribution of ZrO₂ and PTA in the sample. The interaction between both inorganic components improved their dispersion considerably when compared with films containing just one of the additives. The synergism was correlated to previous investigations concerning proton conductivity and permeability of the membranes developed for direct methanol fuel cell. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2981–2992, 2005     

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