Time-resolved X-ray diffraction studies of structural transitions in organic polymers using synchrotron radiation (original) (raw)
Related papers
Synchrotron studies of polymers at high spatial and temporal resolution
Developments in X-ray synchrotron radiation sources and electronic area detectors have allowed the development of new X-ray diffraction techniques to investigate polymeric materials at high temporal and spatial resolution. These developments are illustrated by studies of poly(ethylene terephthalate) (PET). The fabrication of films and containers of PET typically involves mechanical deformation at elevated temperatures close to its T g . Such processing can have major effects on the degree of polymer orientation and crystallinity and hence on the physical properties of the material. This paper describes the time-resolved X-ray diffraction technique developed to investigate the strain-induced crystallisation in PET under industrial processing conditions with 40 milliseconds time resolution. The investigation of the structural variation in orientation and crystallinity across the wall of a container fabricated from PET using an X-ray beam as small as 2 µm diameter is also described. The potential for more general application of these techniques in the study of other polymer materials is indicated.
Journal of Polymer Science Part B: Polymer Physics, 2010
The mechanical behavior of polymer materials is strongly dependent on polymer structure and morphology of the material. The latter is determined mainly by processing and thermal history. Temperature-dependent on-line X-ray scattering during deformation enables the investigation of deformation processes, fatigue and failure of polymers. As an example, investigations on polypropylene are presented. By on-line X-ray scattering with synchrotron radiation, a time resolution in the order of seconds and a spatial resolution in the order of microns can be achieved. The characterization of the crystalline and amorphous phases as well as the study of cavitation processes were performed by simultaneous SAXS and WAXS. The results of scattering experiments are complemented by DSC measurements and SEM investigations.
Review of Scientific Instruments, 1992
A purpose-desigaed ;;,-ray fiber diffraction camera has been constructed in the Keele University Physics Department to be used at the SERCJaresbury !~aboratory Synchrotron Radia,;oT' Source. '-'he camera allows ti;ne-Tesolvec' studies of the change in both the high-and !ow-angle diffraction patterns during drawing and a!l[leaibg of polymer films to be recordec. Dra";-"ing of the films is achieved by two opposed stepper mo~ors which allow films to be drawn uniaxially in both directioils '?he temperature of the sample ep.vironmen! can be controlleC: to within I °C by a tadio spares proportional, integral, and c 1 erivative (PID) cOI:tro:Ier. Diffrac~ion paUerns can be recorded on the Emaf-Nonius TV :?AST detector or on JhotogI'lphic fi::n. E;;.posu~e t;!!les ilsing t:1e 'RA3T detector are~ypicaliy S 3, represe'1ti;Jg a gain of approximately P. factor of 5 over photographic film.. The FAST detector has a further advan~age over pno!og:-aphic film in that essentially an unlimiteC: number of diffraction patterns can be recorded end-to-end while a structural transition is being followed. A video camera is incorporated to allow the variation in the gross appearance of the specimen to be recorded during drawing and annealing and to be related to the variation in the diffraction pattern. The application of the camera in the study of drawing and annealing of poly (aryl-ether-ether-ketone) (PEEK) is described.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
Exploring the macro and micro-structure development associated with crystallization in polymer materials such as polyethylene and polypropylene can be achieved using Small-and Wide-Angle X-ray Scattering techniques (SAXS/WAXS). Here, SAXS probes the long range ordering or macrostructure and WAXS gives information on the atomic level of ordering (microstructure). Following structure development and hence the crystallization process in polymers, is particularly important as it leads to the stabilisation of the final product.
Macromolecular Research, 2004
The structural changes occurring in the isothermal crystallization processes of polyethylene (PE), polyoxymethylene (POM), and vinylidene fluoridetrifluoroethylene (VDFTrFE) copolymer have been reviewed on the basis of our recent experimental data collected by the time-resolved measurements of synchrotron-sourced wide-angle (WAXS) and small-angle X-ray scatterings (SAXS) and infrared spectra. The temperature jump from the melt to a crystallization temperature could be measured at a cooling rate of 600–1,000°C/min, during which we collected the WAXS, SAXS, and infrared spectral data successfully at time intervals of ca. 10 sec. In the case of PE, the infrared spectral data clarified the generation of chain segments of partially disordered trans conformations immediately after the jump. These segments then became transformed into more-regular all-trans-zigzag forms, followed by the formation of an orthorhombic crystal lattice. At this stage, the generation of a stacked lamellar structure having an 800-Å-long period was detected in the SAXS data. This structure was found to transfer successively to a more densely packed lamellar structure having a 400-Å-long period as a result of the secondary crystallization of the amorphous region in-between the original lamellae. As for POM, the formation process of a stacked lamellar structure was essentially the same as that mentioned above for PE, as evidenced from the analysis of SAXS and WAXS data. The observation of morphology-sensitive infrared bands revealed the evolution of fully extended helical chains after the generation of lamellae having folded chain structures. We speculate that these extended chains exist as taut tie chains passing continuously through the neighboring lamellae. In the isothermal crystallization of VDFTrFE copolymer from the melt, a paraelectric high-temperature phase was detected at first and then it transferred into the ferroelectric low-temperature phase at a later stage. By analyzing the reflection profile of the WAXS data, the structural ordering in the high-temperature phase and the ferroelectric phase transition to the low-temperature phase of the multidomain structure were traced successfully.
Review of Scientific Instruments, 1999
A fully integrated system has been developed which allows the study of the deformation of synthetic polymers by simultaneous small-and wide-angle x-ray scattering ͑SAXS/WAXS͒ and stress-strain techniques at synchrotron radiation sources. Two-dimensional x-ray data collection is achieved via two charge coupled device based area detectors which provide video signal outputs. A video extensometer provides sample strain and cross-section data during deformation. All three video signals are processed by a powerful Synoptics i860 processor based video framegrabber, with no loss of data. With this data collection strategy a temporal resolution of 40 ms is possible. In order to study the mechanical yield of the sample, a bridge-type strain gauge is used which reveals the sample loading. An electronic trigger mechanism provides accurate synchronization of the x-ray data, sample video data, sample loading information and controls the onset of deformation. Two experiments are highlighted showing the drawing of polyethylene at an overall rate of Ϸ10 s Ϫ1 . By analysis of the sample video data it is possible to correlate the SAXS and WAXS data with specific points upon the true stress-strain curve. This novel system is shown to be a useful tool for the investigation of the deformation of polymers at rates that are relevant to industrial processing.
Picosecond X-Ray Diffraction Probed Transient Structural Changes in Organic Solids
Physical Review Letters, 2001
In this Letter, we report on the experimental characterization of the geometry of short-lived electronically excited states in organic solids by time-resolved x-ray diffraction. Here, the structure factor of the organic crystal is measured as a function of time. Since this technique gives complete structural information, it is a very useful tool for learning more about atom motions on the excited-state energy surface -"beyond" the broad band typical of conventional spectroscopy. Although we used molecular crystals rather than free molecules, the compounds show detectable transient structural changes on the ps to ns time scale in our study.
2011
The paper gives general information about the advantages of using synchrotron radiation in investigation of polymer liquid crystals. Examples are given with thermotropic polymer liquid crystal Poly(heptane-1,7-dyil-4,4’biphenyldicarboxylate). The melt formation of smectic liquid crystal phase and consequent crystallization at decreasing temperature is depicted. Detailed description of different structural parameters, derivable from appropriate analysis of the experimental results, is given. With the aim of all those parameters an overall hierarchical structuring during phase transitions could be revealed. Since some basic terms about liquid crystals and polymer liquid crystals are given, the paper would serve as an introductory reading in the field.
X-Ray Fibre Diffraction of the High Performance Polymer Poly(Aryl-Ether-Ether-Ketone)
The high brilliance of the Daresbury Synchrotron Radiation Source has been exploited in x-ray fibre diffraction studies of poly(aryl-ether-ether-ketone) (PEEK). These have allowed ";;leak features in the high and low angle diffraction of PEEK associated with super-lattice structure to be investigated and time-resolved studies to be made of changes in specimen orientation and crystallinity during drawing and annealing.