The intensity maxima of lamellar reflections in small-angle scattering patterns from uniaxially oriented polymers such as fibers do not generally fall on a straight layer line or on a circular are. The shape of the reflection can be analyzed by measuring the periodicity L-phi of the lamellar planes as a function of the angle phi between the reflection and z. L-phi is measured parallel to the fiber axis z. The data give a straight line in a plot of L-phi(2) vs tan(2) phi. This shows that the reflection is elliptical and provides a basis for fitting small-angle patterns in an elliptical coordinate system using few parameters. Further analysis of patterns that extend to large values of phi shows that an elliptical fit is not merely a convenience; it is also the best fit. Many possible structures could cause the lamellar reflection to lie on a curve, but few models predict an ellipse. The simplest is affine deformation of the lamellar structure. Recognizing that a single lamellar population will give reflections of an elliptical form allows populations of lamellae to be distinguished even when the reflections overlap strongly, with long spacings L-M different by only 2-8%. This permits a greater understanding of the processes of fiber drawing and annealing.

The use of small-angle scattering (SAS) of x-rays or neutron from oriented semicrystalline polymers to characterize the lamellar structures is discussed. The features of the SAS data that are commonly analyzed are the lamellar spacing L, angle phi between the lamellar reflection and fiber-axis, the widths of the lamellar reflections along (z) and perpendicular (x) to the fiber-axis, and the integrated intensity of the lamellar peak. In addition, we find that the variations with x of the maxima and the longitudinal width of the lamellar reflection are also related to important aspects of the structure. The intensity maxima of the lamellar reflections in small angle scattering patterns from polymer fibers do not fall on a straight layer line, or on a circular are. The shape of this are is analyzed by measuring the periodicity Lm of the lamellar planes measured parallel to z as a function of phi. A straight line fit to a plot of L-phi(2) VS. tan(2)phi shows the elliptical shape of the reflection. This provides a basis for describing the intensity distribution in SAS patterns in an elliptical coordinate system using a minimum number of parameters. It is proposed that a combination of lamellar rotation and shear could cause the lamellar reflection to lie on an ellipse. The increase in the longitudinal width of the lamellar peak with x is attributed to misorientation of the lamellar stacks.

Amorphous orientation in polymers is described in terms of the fraction of the amorphous chain segments which are oriented, and the degree of alignment of the amorphous chain segments. The method for evaluating these two features using two-dimensional x-ray diffraction data is described. Whereas the unoriented amorphous component contributes to an isotropic amorphous halo, the oriented component gives rise to enhanced scattering near the equator. The method is illustrated using the data from PET and nylon 6. The role of amorphous orientation in determining dimensional stability, diffusion behavior and glass transition temperature is discussed.

A surfactant-free emulsion process has been developed for the preparation of copolymers of chlorotrifluoroethylene with vinylacetate or vinylidene fluoride. A redox initiator system, consisting of sodium-meta-bisulfite, t-butylhydroperoxide, and ferrous sulfate heptahydrate, has been found to be effective in preparing self-emulsifying fluoropolymers with a monodisperse particle size distribution, having up to 45% polymer solids in water. Over the range studied in this investigation, the particle number and the ultimate particle size is linearly related to the quantity of initially charged redox catalyst. Under conditions of optimal catalyst concentrations, a greater number of particles is produced in the surfactant-free process than that which can be obtained using conventional fluorosurfactants. Particle number is defined at the earliest stage of polymerization and remains constant throughout the polymerization, unless surfactant is postadded to the surfactant-free latex at a very early stage in the polymerization. The aqueous phases of various latices have been purified by ion-exchange and dialysis, enabling the sulfonic acid-terminated fluoropolymer end groups to be quantified. The highest level of bound sulfonic acid is obtained at elevated temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2211–2225, 1998

The fibrillar and the lamellar structures in a range of poly(ethylene terephthalate) fibers were studied by small-angle X-ray scattering. The intensity maxima in the lamellar peaks lie on a curve that can be described as an ellipse. Therefore, the two-dimensional images were analyzed in elliptical coordinates. The dimensions of the coherently diffracting lamellar stack, the dimensions of the fibrils, the interfibrillar spacing, and the orientation of the lamellar surfaces were measured in addition to the lamellar spacing. The orientation of the lamellar planes and the size of the lamellar stacks had a better correlation with mechanical properties of the fibers than did the lamellar spacing. In particular, longer and wider lamellar stacks reduced fiber shrinkage, as did the closer alignment of the lamellar normal to the fiber axis. These structural features were also associated with lower tenacity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2527–2538, 1998

Two-dimensional small-angle scattering (SAS) data from oriented polymers are parameterized by profile fitting the intensity distribution to a product of two orthogonal functions. Elliptical cylindrical coordinates were found to best describe the observed small-angle scattering data. Each of the essential features of the small-angle X-ray/neutron scattering from uniaxially oriented polymers—the equatorial streak, lamellar reflections and interfibrillar interference peaks—is described completely by a single function in the elliptical coordinates. The parameters of the fit are used to describe the fibrillar and the lamellar structures. The analysis is illustrated with data from nylon 6 fibres, and the results are compared with those from a previous analysis of the same data as a series of one-dimensional scans. The method has enabled us to follow the changes in the weak equatorial scattering attributed to fluid-like organizations of the fibrils. The elliptical coordinates can be used to describe the wide variety of small-angle patterns that have been reported in the literature. The applicability of the elliptical coordinate system to SAS data is shown to be a natural consequence of the scattering object being elongated along the flow or the draw direction. Ellipticity could be used as a quantitative measure of the shape and the orientation distribution of the scattering object.

Two-dimensional wide-angle X-ray scattering data from oriented polymers are profile fitted by describing the intensity distribution as a product of two orthogonal functions in polar cylindrical coordinates. The parameters of the fit are used to describe the structure in terms of amorphous and crystalline orientation, crystallinity and crystallite size. The possibility of using the data to refine the unit cell parameters and the atomic coordinates is discussed. The analysis is illustrated with data from a nylon 6 fibre, and the results are compared with those from a previous analysis of a series of one-dimensional scans. The method is compared to alternative modelling approaches such as Rietveld refinement.

The tendency of linear para-aromatic polyamides to aggregate in DMAc/LiCl solutions is well documented in the literature. In this note it is shown that this tendency is retained even when the polyamides are rendered much more soluble in DMAc/LiCl through the introduction of a nitro group on every third aromatic ring along the stiff chain. When the polyamides are highly branched, they conform with the fractal model. These fractal polyamides agglomerate in several distinct size aggregates; the size of the aggregates and the fraction of the polymer in them are affected by both the solution temperature and the molecular weight of the polymer. With respect to aggregate sizes, the temperature effects are reversible.

The maximum entropy method was used for deconvolving the effect of size broadening in X-ray diffraction (XRD) scans. This technique is used to determine the number of components present in the diffuse halo from amorphous polymers and to sharpen the peaks in poorly crystallized polymers. The results of deconvolution are subsequently used in profile-fitting the data. The method is illustrated using data from poly(ethylene terephthalate) (PET) samples with crystallinities ranging from ca. 0 % to 50 %. Our analysis showed that while one peak is sufficient to describe the amorphous scattering in some polymers (e.g., nylon 6), two or more components are necessary for others (e.g., PET) in the angular range of 5-35-degrees. Our analysis suggests that the amorphous halo in this angular range is, in general, determined by the average interchain distances in the corresponding crystal lattices. The amorphous phase in crystallizable polymers can have a significant amount of medium-range order derived from the local order in the crystalline phase.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe fractal nature of 1-step highly-branched rigid rodlike macromolecules and their gelled-network progeniesS. M. Aharoni, N. S. Murthy, K. Zero, and S. F. EdwardsCite this: Macromolecules 1990, 23, 9, 2533–2549Publication Date (Print):April 1, 1990Publication History Published online1 May 2002Published inissue 1 April 1990https://pubs.acs.org/doi/10.1021/ma00211a022https://doi.org/10.1021/ma00211a022research-articleACS PublicationsRequest reuse permissionsArticle Views280Altmetric-Citations49LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The aim of the present work is to investigate the conformational change of conjugated chains upon doping by small angle neutron scattering. Polymer solutions such as n-butylthiophene (C 4 HS(CH 2 ) 3 CH 3 ) n doped with NOSbF 6 can provide such a goal. For the neutral chains, results show that, at room temperature, even for the lowest polymer concentration studied (c p = 0.1 mg/cc), a positive interchain interaction occurs. At higher temperature (T = 65°C), an isolated chain behavior can be measured allowing to measure the statistical length b = 55 A ̊ and the extension of the lateral groups L t = 12 A ̊ . With a polymer concentrationsas low as c p = 0.5 mg/cc and a dopant concentration equivalent to one dopant molecule per monomer unit, the chain conformation is modeled by a rod structure, b > 850 A ̊ . At the same dopant concentration, but with c p = 2.4 mg/cc, the scattering function show a q −2 behavior. In any case, no correlation hole is observed, which differs markedly from the usual behavior observed in polyelectrolyte solutions.

AbstractPolymer (II) exhibits a surprisingly high, temp.‐dependent (α)D ‐258° (47 °C), ‐367° (25 °C), ‐450° (10 °C), whereas the polymer (IV) has (α)D ‐480° (47 °C), ‐485° (21 °C), and ‐498° (10 °C).

Preparation par amorcage avec NiII de polyisocyanures avec des substituants en α (un est optiquement actif)