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Amorphous samples of polyethylene terephthalate were stretched with different rates and stretching ratios at different temperatures. Afterwards they were crystallized. The arrangement of the crystals and the conformations of the chains in the noncrystalline regions were investigated by means of X-ray wide-angle scattering, X-ray small-angle scattering, birefringence measurements and nuclear magnetic resonance measurements. The influence of the morphological structure on the mechanical strength was determined. The stretching ratio itself generally does not characterize the orientation state. The structure obtained after crystallization depends mainly on the birefringence of the sample after stretching before crystallization. With increasing birefringence one obtains all intermediate structures starting from the well known spherulites composed of twisted lamellae in the unoriented material up to a paracrystalline lattice of lamellae split up into mosaic blocks in the highly oriented state. Also the conformations of the chains in the noncrystalline regions are influenced by the stretching. With increasing orientation the amount of tie molecules with comparatively large end-to-end distances becomes larger. The improvement of the mechanical properties with stretching is caused not only by the increasing orientation of the molecules but also by the increasing amount of taut tie molecules.

Density, heat of fusion and melting temperature data of annealed polyethylene single crystals suggest the existence of a temperature-dependent pseudo-amorphous surface layer which contains chain folds and free chain ends. In the ideal two-phase model, one assumes two such amorphous layers of thickness l/2 each on the two (001) surfaces of the crystalline core of thickness D = L -l, where L is the total thickness of the single crystal. The thickness of such a layer was calculated under the assumption of random length loops and cilia (free chain ends) for the case of adjacent reentry and of a Maxwellian distribution of loop width. The excess energy requirement of the shortest loops with the high concentration of gauche conformations favors longer loops and hence increases the surface layer thickness. The reduction of entropy by the restrictions imposed by finite loop width and the availability of a half space only acts in the opposite direction. The calculated thickness depends on the true supercooling ΔT = Tm° - T if L is kept constant and on relative supercooling ΔTrel = Tm-T, where Tm is the actual melting point of the crystal, if the crystal core thickness D is kept constant. A qualitative agreement between theory and experiment on this basis seems possible by proper consideration of the contribution of loops and cilia.

Investigations of the glass transition and melting of partially crystalline polymers by nuclear magnetic resonance provide valuable information on the nature of noncrystalline regions. The broad line NMR signal was separated into a narrow component and a broad component by using a new method which does not imply the ambiguity usually present. From the intensity of the narrow component the mobile fraction was determined. This fraction was extrapolated to “infinite” temperature. By subtracting the mobile fraction from the noncrystalline fraction, the noncrystalline rigid fraction was obtained. Comparison of the measured second moments of the two components of the NMR line with calculated second moments of chains with fixed ends shows the following: The mobile fraction is formed by chains with either one end fixed or both ends fixed in a comparatively small end-to-end distance (for example, loops with adjacent reentry); the noncrystalline rigid fraction is formed by chains whose ends are fixed in a comparatively large or medium end-to-end distances (for example, tie molecules connecting different crystals). More detailed information on the chains forming the mobile fraction as well as on the structure in the melt was obtained by high resolution NMR. It was shown that near range order in the melt, for example, the formation of bundles of parallel chains, causes deviations from the lorentzian shape of the NMR line. During primary crystallization the chains within the bundles of parallel chains crystallize. During secondary crystallization, extremely mobile chains outside these bundles are incorporated into the crystals.

6 pags., 4 figs., 1 tab., Poly(ethylene terephthalate) (PET) was annealed in vacuum at different temperatures (190-260 °C) for different times (10 min-24 h) in order to examine the mechanical properties (microhardness) of PET samples with a wide range of molecular weights (10000-120000). Short annealing times result in a twofold decrease in mol. wt. due to hydrolytic decomposition. However, long annealing times give rise to a substantial molecular weight increase. It is found that microhardness (H) rises linearly with the degree of crystallinity obtained during up-grading of mol. wt. and its extrapolation leads to H-values of completely crystalline PET, Hc PET = 405 MPa for samples with conventional mol. wt. and of 426 MPa for samples with mol. wt. higher than 30000. It is shown that the increase of mol. wt. for each set of samples with a given range of degree of crystallinity also causes a slight increase of H. The influence of mol. wt. upon hardness is discussed in the light of the changes in the physical structure (crystallinity, crystal thickness) which is formed at given heat treatment conditions. © Steinkopff Verlag 1998., The authors are grateful to DGICYT, Spain (Grant PB94-0049) for the support of this investigation. The partial support of DFG, Germany (Grant DFG-FR 675/21-1) is also highly appreciated. Part of the work is performed in the frame of the Partnership Contract between University of Hamburg and University of Sofia. One of us (S.F.) deeply appreciates the tenure of a sabbatical grant from DGICYT

The miscibility of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) with poly(butylene terephthalate) (PBT) has been studied by 13C CP/MAS NMR complemented with DSC measurements. The blends were prepared by a solution precipitation method. The DSC examination shows that the Tg of the blends is between the Tg of the two homopolymers. The crystalline enthalpy of PEN decreases continuously when the amount of PEN decreases. The Tm and ΔHm of PBT were lowered continuously as the PEN ratio was increased, while that of PEN was lowered as the PBT ratios were increased. These results imply that PEN is compatible with PBT. HT1ρ values for the blend 50 PEN/50 PBT and pure components have been measured. Since single-component NMR relaxation behavior was observed, miscibility was demonstrated for the blend. Intermolecular cross polarization from the protons in PBT to carbons in deuterated PEN was examined by measuring the full decoupling, no decoupling, and delayed decoupling 13C CP/MAS spectra of the blends of deut...

Selectively deuterated poly(ethylene-2,6d-naphthalene dicarboxylate) (PEN) was synthesized, obtaining a material in which either the ethylene groups (PEN-Ed1 or the naphthalene ring (PEN-Nd6) was deuterated. By means of deuteron nuclear magnetic resonance (2H-NMR), the molecular mobility of the deuterated groups was investigated as a function of temperature. The spectra were measured by the solid echo method, applying different waiting times tw The longitudinal relaxation curves were obtained by determination of the maximum intensity of the echo as a function of tw It was found that in the amorphous regions of PEN, the molecular mobility of the ethylene groups is higher than in the amorphous regions of PET. In PEN crystals in the β-modification form, trans-gauche jumps of the ethylene groups with almost equal occupation of the trans and the gauche conformation take place already at 90°C. This is not the case in either PEN crystals in the a-modification form or in PET crystals. The rotational moti...

Two different etching techniques that reveal the semicrystalline morphology of polyesters have been developed and applied to an analysis of the phase structure of copolyesters made by reacting poly(hydroxybenzoic acid) (PHBA), and poly(ethylene naphtha-lene-dicarboxylate) (PEN). One technique is based on oxidation with acidic permanganate solutions and is used to study the macroscopic distribution of different phases. The other is based on sa-ponification with alkaline reagents and reveals more detailed structure within the various phases. Etching and electron microscopic examinations have been carried out for three different PEN-co-PHBA compositions. Three different types of solid phase are revealed: (1) a phase rich in PEN; (2) a phase containing roughly equal proportions of the two components, liquid crystalline at high temperatures; (3) a solid phase of crystalline HBA-rich molecules, which segregate into laminar regions. These observations are consistent with the previously published thermal...

Most polymers crystallize by a nucleation-and-growth mechanism in which spherulites develop as a consequence of the radial growth of branching crystalline lamellae from heterogeneous nuclei. The amorphous component is included within the spherulites. These grow until they impinge and become volume filling. The primary crystallization occurs at the expanding interface of the spherulite with the amorphous polymer. Secondary crystallization may sometimes occur within the spherulite. Spherulite growth kinetic is often followed microscopically. The small-angle light scattering technique developed in our laboratory [1] has proved to be a conveient method for quantitatively following spherulitic crystallization. It can provide information about the number and sizes of spherulites as well as their internal crystallinity.

The high-resolution solid state 13C NMR spectra of the different crystal modifications of poly(4-hydroxybenzoate)s and their copolymers have been obtained by means of high-power proton decoupling, cross-polarization, and magic angle spinning. The resolution was sufficient in order to resolve the resonance lines of all seven differently bonded carbon atoms in the PHBA repeat unit. From the chemical shift splitting of the ortho ring carbon atoms it is deduced that, in crystalline PHBA, the torsional angle between the ester plane and the phenylene ring plane deviates from 90°. The deviation increases in the order modification II > modification III > modification I. The variable-contact-time measurements indicate that the chain packing in crystal modification I is denser than in the crystal modification II.

This paper reports the effect of solid state annealing on the structure of a liquid crystalline polymer composed of 80% 4-hydroxybenzoic acid (HBA) and 20% 2-hydroxy-6-naphthoic acid (HNA) using small-angle X-ray scattering. Two-dimensional diffraction patterns possessing strong meridional reflections were recorded using synchrotron radiation at temperatures of 215, 251 and 269°C. The long period increased with increasing anneal temperature, but was largely unaffected by increasing the length of time spent at the anneal temperature. The intensity of meridional scattering increased with both increasing anneal temperature and time. In order to obtain an estimate for the average crystallite thickness at the anneal temperature, the small-angle meridional scattering was evaluated by means of the interfacial distribution function approach.

9 pags., 11 figs., Amorphous poly(ethylene naphthalene‐2,6‐dicarboxylate) (PEN) films (∼ 220 μm thick), stored in ambient atmosphere for different periods of time and after annealing at different temperatures below T = 123°C, for different times, have been investigated by infrared spectroscopy (FTIR), microhardness, and differential scanning calorimetry (DSC). FTIR spectroscopy and weight measurements reveal the presence of water which is easily removed by annealing of the films. Films again recover their initial weight and absorption bands after 1‐2 days storage in ambient atmosphere. Samples annealed at different temperatures T for different times t show an increasing microhardness for relatively short times of t. The microhardness passes through a maximum at an annealing time depending on T, and it decreases toward values somewhat larger than the initial ones. The changes observed in the microhardness and in the values of the excess enthalpy with storage time of the samples at room temperature depend on the physical aging as well as on the content of water of PEN films. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc.

A study of the phase structure of two linear polyethylene fractions has been carried out by Raman spectroscopy and from the analysis of the interface distribution function from the SAXS intensity data. Very good agreement is obtained for the core crystallite thickness, the liquid-like region, and the thickness of the interface from these two independent techniques. Moreover, the X-ray analysis distinguishes isothermally formed crystals from quenched crystals in cases where the Raman technique is not selective.

10 pags., 5 figs., The 4000–2000 cm infrared spectral region from transmission FTIR spectra of films (≈ 220 μm thick) of amorphous poly (ethylene terephthalate) (PET) and poly(ethylene 2, 6‐naphthalenedicarboxylate) (PEN) was analyzed. In addition to the strong bands for the stretching vibration modes of H‐C bonds, the ester‐overtone band at about 3430 cm and a doublet (3630, 3550 cm) band, related to absorbed water, appear. The spectra for these materials show significant differences in absorptivity and frequency for the ester overtone band. Real time water sorption/desorption in these films was investigated simultaneously by FTIR spectroscopy and by measurement of weight changes. A linear correlation between the integrated absorbance of the water bands and the relative weight variation of the films was found for these two polymers. Results show that the infrared absorptivity of these bands is identical in both materials and that water molecules are weakly bound to ester groups throughout the films. However, it turns out that the water content is higher in the case of PEN which has a larger specific volume. Copyright © 1995 Hüthig & Wepf Verlag

Using synchrotron radiation, one is able to measure the small angle X-ray scattering (SAXS) and the wide angle X-ray scattering (WAXS) of polymers within seconds. Thus one can follow in real time the change of scattering during crystallization, melting, and stretching, as well as during different kinds of processing. We have built up at HASYLAB in Hamburg a beamline dedicated to investigations of phase transitions in polymers. Besides a furnace, a goniometer and a stretching device one can also insert into the beam an extruder for investigating the fiber spinning process. We have performed simultaneous measurements of WAXS and SAXS during crystallization and melting of polymers. Three different mechanisms of secondary crystallization were identified: growth of crystals, formation of new crystals and formation of new lamellar stacks. Interesting results were obtained for the crystallization of highly oriented polymers during melt spinning. Here a SAXS pattern appears before WAXS crystal reflections are visible, indicating that two phases with different densities have been formed before any crystalline order can be detected. By means of SAXS during stretching of blockcopolymers of styrene-butadiene-styrene the dimensions and the increasing orientation of the styrene cylinders were determined.

Through the use of a high intensity synchrotron X-ray source and a specially constructed X-ray transparent flow cell, the feasibility of monitoring phase transformations in situ within the extruder has been demonstrated. Specifically, in the present experiments on polyethylene the emergence of a new, flow-induced phase was noted at around 150°C arising in the capillary portion of the rheometer consistent with the hexagonal crystal form of polyethylene. This ‘mobile’ mesophase would account for the recently discovered rheological melt flow singularity (the ‘extrusion window’) occurring at 150°C in agreement with previous hypotheses.

The microhardness (H) of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) with a wide range of crystallinities, spherulitic morphologies and different lamellar periodicities has been determined. The influence of the temperature and time of crystallization from the glassy state upon the microhardness values has been examined. For structures where primary crystallization is incomplete, it is shown that H increases linearly with the volume fraction of spherulites. For materials where primary crystallization is completed, H depends on the crystallization temperature and appears to be a function of both the crystallinity and the crystal size. The results are discussed in the light of theoretical predictions of hardness.

The melting and recrystallization of yarns of polyamide 6 spun at different take-up velocities ranging from 3 500 to 5 600 m/min was investigated by means of wide-angle X-ray scattering (WAXS) employing synchrotron radiation and by differential scanning calorimetry (DSC). It was shown that the first peak in the double melting peak of the DSC-curves is caused by the melting of the γ-crystals. The melting point is increased by approximately 5°C when the take-up velocity is increased from 3 500 m/min to 5 600 m/min. The addition of calcium stearate to the material has no effect on the thermal stability of the crystals, but seems to have some effect on the crystallization rate.

The scattering behaviour of polyetherester thermoplastic elastomers based on polybutylene terephthalate as hard segments and polyethylene glycol ( Mn = 1000) as soft segments in a ratio 49/51 wt.% is studied under stress. Drawn (λ = 5) bristles are annealed with fixed ends in order to create a standard initial structure. Samples with structure destroyed by additional drawing as well as with structure regenerated by solid-state reactions or chemical crosslinking are prepared. The data from small-angle x-ray scattering (SAXS) taken under or without stress are evaluated using Stribeck's method and the sizes of crystalline (d 1) and amorphous (d 2) regions are directly obtained. A constant value of d 1 ≊ 50 A is found for all samples except for the chemically crosslinked one, for which d 1 changes at deformations higher than 80% due to axial displacement of the crystallites. The size of the amorphous regions d 2 measured under stress (e > 30-50%) rises slightly and reversibly followed by a drop simil...

Samples of poly(ether ether ketone) (PEEK), poly(ether ether ketone ketone) (PEEKK), and poly(ether ketone ether ketone ketone) (PEKEKK) were crystallized at different temperatures by stepwise cooling from the melt to obtain samples which show multiple melting peak in a calorimetric investigation. The melting behavior of these materials was investigated by WAXS and SAXS and by DSC. The change of the degree of crystallinity, of the SAXS power Q, and of the long period was determined as a function of temperature during heating. It was concluded that( the additional meltiong peaks are caused by muelting of some thin crystals within lamellar stacks and not by melting of complete lamellar stacks

Copolyesters of poly(tetramethylene terephthalate) (PTMT) and p-hydroxybenzoic acid (PHB) are obtained by means of transesterification in the molten state using different ratios of the starting reagents. After treatment with trifluoroacetic acid, the total reaction product could be divided into a soluble part and an insoluble one, differing in the tetramethylene terephthalate/oxybenzoate (TMT/OB) units ratio. It was proved by 1H NMR that the fraction of OB units in the soluble part of the copolyester varies from 3 to 12 mol-% for PHB feed contents of 10–80 mol-%. There is no systematic influence of the PHB feed content on the copolyester composition. The maximum OB content was achieved at 20 mol-% PHB in the starting mixture. The results from 13C NMR, DSC, WAXS and crystallization kinetics measurements suggest the presence of blocks of TMT units in the macrochains. The observed thermal properties and crystalline structure are explained in terms of the inhomogeneity of both chemical composition and units sequence in the total reaction products. This leads to the coexistence of at least two phases differing mainly in their content of OB units.

On-line small-angle and wide-angle x-ray scattering experiments were performed during the melt spinning of polyvinylidene fluoride using the DESY synchrotron light source. In these studies, the melt-spinning apparatus consisting of a screw extruder, a metering pump, and a take-up motor system were assembled on two separate stepper-motor-driven platforms. To investigate the structure development during crystallization, the tape location at the desired distance from the die could be positioned at the beam level with synchronous vertical movement of extruder and take-up platforms

The WAXS pattern of the continuous carbon fiber-reinforced laminates can be viewed as a superposition of the scattering patterns arising from the carbon fibers and the polymer matrix. In order to obtain the scattering of the matrix alone, the scattering of the pure reinforcing fibers has been measured at different azimutal angles. A procedure has been developed to substract the scattering of the fibers from that of the complete laminate. From the corrected diagrams, the decree of crystallinity has been determined. Crystallinefractions of 0.46 and 0.34 have been obtained for the PET and the PEEK-based laminates, respectively.

Cross-polarization/magic-angle spinning 13 C nuclear magnetic resonance measurements on blends of poly(ethylene terephthalate) (PET), poly(ethylene naphthalene dicarboxylate) (PEN) and copolyesters of PET and p -hydroxybenzoic acid (PHB) were performed using different dephasing times of the dipolar decoupling. In the case in which the spectra of the two components of the blends are different, information on miscibilities is obtained by measurements with full dipolar decoupling. In the case of similar spectra, however, this method cannot be applied. It is shown that, under this condition, information on phase separation is obtained if the measurements are performed with delayed decoupling and no decoupling. While blends of PEN and copolyesters of PEN are miscible, phase separation is obtained if one component contains PEN and the other one PET.

Semicrystalline poly(ethylene terephthalate) was hydrolysed in water at 180°C under elevated pressure and subsequently treated with ethanol, following the etching process first developed by Miyagi and Wunderlich. The weight loss, the wide-angle X-ray scattering and the molecular weight were measured as a function of etching time. It was found that even at the end of the etching process not all the amorphous material could be removed by the hydrolysis treatment. By comparing the obtained results with those derived from an elaborate small-angle X-ray scattering study and with wide-angle X-ray scattering measurements, it was concluded that only those amorphous regions lying outside of the lamellar stacks were removed. Subsequently, the lamellar stacks themselves were attacked. It was also found that at the very beginning of the hydrolysis process additional crystals were formed in the material.

Samples of poly(acrylonitrile) which were deuterated in the α-position (PAN-α-d 1 ) and in the β-position (PAN-β,β-d 2 ) were heated from room temperature to 180°C. The longitudinal relaxation curves and the NMR spectra of the deuterons were measured as a function of temperature. It was found that the longitudinal relaxation curve could be separated into two exponential curves. The traction of the component showing the larger relaxation time T 1 decreased with increasing temperature. The shape of the NMR spectra changes from a Pake spectrum at room temperature to a spectrum typical for rapid crankshaft motion at 180°C

Oriented liquid-crystalline solutions of the rigid heteroaromatic polymers poly( p -phenylene benzobisthiazole) and poly( p -phenylene benzobisoxazole) in polyphosphoric acid were transformed into crystalline phases by absorption of moisture. At moderate moisture levels crystal-solvate phases are formed by co-crystallization of the polymer and its solvent, whereas at high water content the crystalline polymer phase is formed by deprotonation of the polymer. Two crystal-solvate forms have been identified, as the moisture content increases up to about 10% (w/w), denoted form I and form II. Transitions between the different phases, as a function of temperature and time, were studied by X-ray diffraction using the high-intensity synchrotron source. The intensity of the crystalline reflections from the form I state decrease gradually with increasing temperature up to final melting at about 70°C. The orientation of the crystalline phase is maintained up to its melting. Recrystallization is observed upon quenching, showing the reversibility of this transition. The behaviour of the form II phase differs markedly. As the temperature is increased, a gradual crystal-crystal transition occurs in the temperature range of 250–300°C from the form II state to the crystalline polymer state. This transformation is irreversible. A novel recrystallization phenomenon is observed when the liquid-crystalline phase is heated to about 250°C. Crystalline reflections appear at spacings close to those of the crystalline polymer state. These reflections disappear upon cooling. These transformations are discussed in terms of the state of protonation of the polymer in its solution in polyphosphoric acid. Form I is considered a complex of the protonated polymer and the acid anions, which dissolves at moderate temperatures. Recrystallization at elevated temperature is suggested to result from deprotonation of the polymer. The state of protonation of the polymer in the form II state is still not understood.

The molecular orientation in poly(ethylene terephthalate) (PET) drawn by necking was studied before and after crystallization by 2 H nuclear magnetic resonance (n.m.r.) and by wide-angle X-ray scattering (WAXS) pole figures. In order to determine separately the orientation of the benzene ring and of the ethylene groups, the n.m.r. investigations were performed on samples in which only the benzene ring was deuterated as well as on samples in which only the ethylene groups were deuterated. By applying different ‘waiting times’ in the n.m.r. measurements, it was also possible to determine separately the orientation of chains of different mobilities. Thus, more detailed and more complete information on molecular orientation is obtained by n.m.r. than by WAXS. As far as a comparison was possible, agreement between n.m.r. and WAXS was obtained. In addition, the n.m.r. results show that, for example, a parallelization of the planes of the benzene rings occurs not only in the crystals but also in the amorphous regions, and that the ethylene groups are oriented to a smaller degree in the draw direction than the benzene ring parts of the chain.

Blends of deuterated and nondeuterated copolyesters of poly(ethylene terephthalate) (PET) and poly(p-hydroxybenzoic acid) (PHB) were studied, the PET content varying between 80 and 60 mol% and the sample containing 60 mol% being liquid crystalline. The molecules contained deuterated and nondeuterated blocks of various lengths. The average degree of polymerization and radius of gyration of these blocks were measured and the length of the statistical element b was calculated as a function of composition. It was concluded that, in the nematic state, the molecules are not elongated

Highly oriented linear polyethylene was prepared by elongational flow injection molding. The changes in crystal orientation were investigated as a function of temperature by real-time wide-angle X-ray diffraction. Additionally, the influence of molecular weight upon the microstructure and the changes in orientation, during heating near the melting point, and after cooling have been examined. A shish-kebab structure is inferred for the high molecular weight samples (Mw≥105) from SAXS observations, while for samples with Mw

Solvent-induced crystallization (SINC) was observed in a polyetherimide (PEI), a thermoplastic used as a matrix in carbon fiber composites. This observation was made using wide angle X-ray scattering (WAXS), differential scanning calorimery (DSC), and optical microscopy. It was discovered that methylene chloride induces crystallization in the PEI by penetrating the surface and swelling the bulk polymer

The mechanical properties of copolyesters of p-hydroxybenzoic acid (PHB) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) and of PHB and poly(ethylene terephthalate) (PET) were investigated over a wide range of compositions using the microhardness technique. The mechanical behaviour has been interpreted in terms of an aggregate model of additive units of structure. On this basis the changes in microhardness with composition can be related to the following factors: degree of crystallinity, crystal thickness and polymorphic crystal forms. In the case of the amorphous materials the increase of the microhardness with increasing number of flexible chain sequences (PET, PEN) has been discussed in terms of a simple additive behaviour of single components PET/PHB and PEN/PHB. In the case of the crystallized materials it is shown that the hardness of the PET and PEN crystals is an increasing function of the crystallite dimensions (flexible chain domains).

Magic angle spinning nuclear magnetic resonance spectroscopic investigations were performed on solid state high density polyethylene (HDPE) and low density polyethylene (LDPE) crosslinked by γ-irradiation using doses up to 40 Mrad. The free induction decay was measured at various spinning frequencies in order to obtain information on the influence of crosslinks and branches on molecular mobility in the amorphous regions of the semicrystalline material. The anisotropy of motion caused by crosslinks and entanglements is characterized by the anisotropy parameter, a , and the correlation time of anisotropy fluctuations τ ca . It was found that in HDPE the values of a are larger and those of τ ca are smaller than in LDPE. In HDPE crosslinking leads to a shift of the spectrum of a to larger values whereas in LDPE no change is observed upon irradiation. However, if the material is molten, upon irradiation the molecular mobility is markedly decreased in both HDPE and LDPE. The results are discussed comparing densities of crosslinks and entanglements.

It is investigated by computer simulation whether space problems prevent a closing packing of chain molecules if the chain molecules are randomly coiled. Chains consisting of 100 beads were introduced into a primitive cubic lattice in such a way that each lattice point is occupied by not more than one bead. It was possible to occupy up to 88% of the lattice points. The average square end-to-end distance of the chains in the concentrated system is the same as for a single chain. Neither perfect chain bundles nor imperfect chain bundles occur in a considerable amount. This shows that it is possible to pack closely randomly coiled chains.

Beim Aufschmelzen von Polyathylenterephthalat findet zunachst eine Abnahme des Molekulargewichtes statt, die vermutlich durch Spuren von Wasser bedingt ist, und anschliesend eine Zunahme als Folge eines Fortschreitens der Polykondensation. Die Halbwertszeiten der Kristallisation verringern sich mit abnehmendem Molekulargewicht; bei der Zunahme des Molekulargewichtes wachsen sie wieder bis uber den ursprunglichen Wert an. Geringe Mengen von Feuchtigkeit, wie sie z.B. beim Kontakt mit Quecksilber oder Silikonol auftreten, fuhren bereits dazu, das die Polykondensation in einen Abbau ubergeht.

The structure and phase transitions of block copolymers of PBT and PEO having different composition were investigated by DSC, SAXS, and WAXS. Two different glass transitions and two melting points were observed. The increase of the integral SAXS intensity with temperature was much smaller than in the case of homopolymers, which is explained by a broad melting range. The long period strongly increases with temperature, which is attributed to growth of domains.

X‐ray investigations were carried out on well‐oriented liquid‐crystal side‐chain polymers of two series: (1) a polyacrylate‐methylacrylate copolymer series with polar –CN end group and (2) the polyacrylate or polymethylacrylate with –OCH3 end group. To explain the diffraction phenomena a new fan‐shaped model is suggested. Using this model the packings in the SmA phase were discussed and the correlation function G(r) was determined from the inner reflections. The order parameters were calculated on the basis of the intensity simulation of the outer reflections.

The microhardness of films of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) blends prepared by co-precipitation from solution followed by melt-pressing and quenching was determined. The miscibility, transesterification and crystallization properties of these blended films were reported previously [1]. The PET/PEN compositions chosen were 10/90, 30/70, 44/56, 60/40, 70/30 and 90/10. The microhardness of films was notably affected by the composition. It is shown that the deviation of microhardness from the additivity law of the single components depends on the time for which the blend was melt-pressed before quenching in ice water. The results are discussed in light of changes occurring from the initial two-phase structure of the single components through the one-phase structure up to the PET-co-PEN obtained by transesterification of the two components.

This article starts with a short introductory chapter on the generation and properties of synchrotron radiation. Afterwards instrumentation available for research on polymers are discussed and finally the results obtained up to now in polymer science.

The dielectric constant and dielectric loss values for random copolyesters of poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalenedicarboxylate) (PEN), and poly(p-hydroxybenzoic acid) (PHB) have been determined in the 103-106 Hz frequency range. The variation of the dielectric properties with temperature has been related mainly to two processes: (1) The α relaxation, which is associated to the glass transition and which has been shown to be dependent on the molecular order of the systems. Copolymers with liquid crystalline order exhibit an α relaxation process occurring at lower temperatures than the amorphous ones. (2) The β process which has been assigned to a local motion of the ester groups attached to both sides of the aromatic rings. The β process also depends on the molecular order. The existence of a liquid crystalline state increases the dipolar correlation of both the β and the β relaxation processes., DGICYT (Grant PB94-0049), Spain

6 pags., 3 figs., The complex dielectric permittivity has been measured in the 10−10 Hz frequency range for selected random copolyesters of poly(ethylene terephthalate). The variation of the dielectric properties with temperature has been qualitatively related mainly to two processes. The α relaxation, which is associated with the glass transition, has been shown to be dependent on the molecular order of the systems. The β relaxation process has been assigned to local motions of the ester groups attached to both sides of the aromatic rings. The β process is also shown to exhibit a dependence on molecular order. © 1995 Hüthig & Wepf Verlag, Zug

Structure and properties of ferroelectric copolymers of poly(vinylidene fluoride).- Packing of chain segments: A method for describing X-ray patterns of crystalline, liquid crystalline and non-crystalline polymers.- PVA-Iodine complexes: Formation, structure, and properties.

4 pags. 2 figs., The microhardness, H, of random copolymers of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene-2,6-dicarboxilate) (PEN) was determined over a wide range of compositions. It is shown that microhardness of the materials is strongly affected by the composition. The mechanical property, H, of the quenched amorphous copolyester films is discussed in terms of a simple model given by the additivity values of the single components Ha PET and Ha PEN. In materials containing up to 30% PEN, crystals of PET are found after annealing at temperatures 10 °C below their melting points. In materials containing ∼ 80% PEN, after annealing at about 20 °C below the melting point, crystals of PEN are formed. The observed deviation of H for the crystallized films from the additive behaviour of the single components can be quantitatively related to two factors: the changes occurring in the crystallinity value and in the thickness of PET and PEN crystals. © 1992 Chapman & Hall.

6 pags., 7 figs., The microhardness (H) of poly(ethylene terephthalate) (PET) containing catalysts, as well as of PET without catalysts has been investigated. Two types of morphologies have been examined: (a) structures where spherulitic growth is incomplete, resulting from a primary crystallization from the glassy state and (b) samples in which spherulitic crystallization is completed. It is shown that for the former materials, H is an increasing linear function of the volume of the spherulites and depends on annealing time and catalyst content. For the latter materials, H is nearly constant with increasing annealing temperature (TA). Results are discussed in the light of three principal structural factors which determine the microhardness behavior: (1) the volume content of spherulites within the material; (2) the value of crystallinity within the stacks of the lamella, which turns out to be a constant; (3) the average thickness of the crystals, which increases slightly with TA after crystallization is completed. An expression which takes into account the above parameters and offers a description of the H of polyethylene terephthalate is proposed.

A small-angle X-ray scattering study on styrene-butadiene-styrene block copolymers during stretching is reported. Measurements have been performed at the Hamburg Synchrotron Radiation Laboratory at DESY using a two-dimensional position-sensitive detector. A pattern of layer lines perpendicular to the stretching direction with ellipsoidal envelope is obtained. This indicates a good orientation of cylindrical polystyrene domains along the stretching direction. The diameter-to-length ratio of the cylinders was found to be 0.6, the length being approximately 39 nm. The long period of the undrawn sample is about 47 nm. Upon stretching, initially this value increases almost affinely, while for γ >3 it tends to reach a constant value. The extension at which the curve bends coincides with the inflection point in the stress-strain curve; at higher values of extension, most of the polybutadiene chains are probably completely stretched and further extension is achieved partly by disruption of the polybutadiene matrix.

Mise au point d'un goniometre pour mesurer les figures de pole de diffusion RX centrale par rayonnement synchrotron et avec des detecteurs de positionnement. Etirage uniaxial homogene et par striction et biaxial homogene d'echantillons de PET et etude de l'influence des conditions d'etirage sur l'orientation des lamelles cristallines; comparaison avec les figures de pole obtenues par diffusion. Diffusion centrale tres influencee par la taille limitee et l'arrangement irregulier des cristaux

Die Zug-Dehnungsdiagramme von unverstrecktem sowie verstrecktem Polyathylenterephthalat wurden sowohl bei Raumtemperatur als auch oberhalb der Einfriertemperatur untersucht. Die unverstreckten Proben waren zuvor bei verschiedenen Temperaturen kristallisiert worden. Die verstreckten Proben waren zuvor im unverstreckten Zustand kristallisiert, dann bei verschiedenen Temperaturen verstreckt und anschliesend erneut kristallisiert worden. Von besonderem Interesse war der Einflus der Kristallisations-sowie der Verstreckungs-temperatur auf den Elastizitatsmodul, die Bruchspannung und die Bruchdehnung. Die bei Raumtemperatur gemessene Bruchdehnung geht als Funktion der Kristallisationstemperatur durch ein Minimum. Dieses Minimum tritt bei Messungen oberhalb der Einfrier-temperatur nicht mehr auf. Der Elastizitatsmodul und die Bruchspannung liegen im allgemeinen um so hoher, je groser die Orientierung der Probe ist. Eine Kristallisation der unverstreckten Proben verandert diese Grosen daher kaum. Eine Verstreckung der Probe fuhrt aber zu einer wesentlichen Erhohung, die noch groser wird, wenn man die Probe nach dem Verstrecken kristallisiert. Eine Kristallisation vor der Verstrekkung der Probe wirkt sich dagegen nachteilig auf die Bruchspannung und den Elastizitats-modul aus, da sie offenbar die Ausbildung einer guten Orientierung beim Verstrecken hemmt. Ebenso wirkt sich auch eine Erhohung der Verstrecktemperatur uber die Einfrier-temperatur ungunstig aus. The stress-strain diagrams of undrawn and drawn polyethylene terephthalate were measured at room temperature and above the glass transition temperature. Before the stress-strain measurements the undrawn samples had been crystallized at various temperatures, whereas the drawn samples had been crystallized in the undrawn state, then were drawn at various temperatures and finally were crystallized again. The influence of the temperature of crystallization and the temperature of drawing on the Young's modulus, the tensile strength, and the fracture strain were of special interest. The fracture strain as a function of the crystallization temperature shows a minimum at room temperature. This minimum disappears above the glass transition temperature. Young's modulus and tensile strength generally are found the higher, the higher the degree of orientation in the sample. Crystallization of the undrawn samples therefore does not change these values significantly. But a drawing of the samples leads to a significant increase which is still more pronounced if the sample is crystallized after the drawing. Crystallization before drawing of a sample leads to a decrease of Young's modulus and tensile strength because in this case apparently the formation of a sufficient orientation during the drawing cannot take place. An increase of the drawing temperature above the glass transition temperature also leads to a decrease in the mentioned values.

The thermomechanical curves of monoaxially drawn PA-12 films are recorded. The films were previously subjected to annealing at different temperatures from 40°C to 170°C. The values of Tg and Tm derived from the thermomechanical curves show non-linear dependence on the applied tension stress. The intensity of the IR absorption bands assigned to the folded conformation of the macromolecules increases with the rise of annealing temperature. In the IR spectrum of the film annealed at 170°C and subjected to additional drawing the intensity of these bands decreased as the degree of drawing increased. These results are interpreted as an indication for crystallization with folding of the macromolecules upon annealing and defolding under the conditions of recording of the thermomechanical curves. WAXS patterns suggest the presence of γ crystalline modification in PA-12 under the conditions applied. Von einachsig gereckten PA-12-Filmen wurden die thermomechanischen Kurven aufgenommen. Die Filme wurden zuvor bei verschiedenen Temperaturen zwischen 40 und 170°C getempert. Die den thermomechanischen Kurven entnommenen Werte fur Tg und Tm weisen eine nicht-lineare Abhangigkeit von der angewendeten Zugspannung auf. Die Intensitat der fur die Faltungskonformation der Makromolekule charakteristischen Infrarotbanden nimmt bei steigender Tempertemperatur zu. Im IR-Spektrum des bei 170°C getemperten und danach zusatzlich gereckten Films nimmt die Intensitat dieser Banden mit dem Reckgrad ab. Die Ergebnisse werden als Hinweis auf die Faltungskristallisation der Makromolekule beim Tempern und auf die Entfaltung beim Registrieren der thermomechanischen Kurven interpretiert. Durch Rontgenweitwinkelstreuung wird die Anwesenheit der kristallinen γ-Modifikation im PA-12 unter den Untersuchungsbedingungen nachgewiesen.