Showing papers on "Crystallization published in 2004"
TL;DR: It is demonstrated that in both model systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters, which is relevant for nucleation processes during protein crystallization, protein or DNA self-assembly.
Abstract: Controlling interparticle interactions, aggregation and cluster formation is of central importance in a number of areas, ranging from cluster formation in various disease processes to protein crystallography and the production of photonic crystals. Recent developments in the description of the interaction of colloidal particles with short-range attractive potentials have led to interesting findings including metastable liquid-liquid phase separation and the formation of dynamically arrested states (such as the existence of attractive and repulsive glasses, and transient gels). The emerging glass paradigm has been successfully applied to complex soft-matter systems, such as colloid-polymer systems and concentrated protein solutions. However, intriguing problems like the frequent occurrence of cluster phases remain. Here we report small-angle scattering and confocal microscopy investigations of two model systems: protein solutions and colloid-polymer mixtures. We demonstrate that in both systems, a combination of short-range attraction and long-range repulsion results in the formation of small equilibrium clusters. We discuss the relevance of this finding for nucleation processes during protein crystallization, protein or DNA self-assembly and the previously observed formation of cluster and gel phases in colloidal suspensions.
967 citations
TL;DR: The surface potential difference and surface tension at an air-salt solution interface are used to generate a simple model for how ions affect protein stability and solubility through indirect interactions at the protein-solution interface.
965 citations
TL;DR: In this article, the authors investigated a range of solvents with higher boiling points and found that 1,2,4-trichlorobenzene with good solubility and a high boiling point significantly improves the field-effect mobilities up to 0.12 cm2/(V s) with on:off ratios of 106.
Abstract: Chloroform is a general solvent for poly(3-hexylthiophene) (P3HT) active layers in field-effect transistors. However, its low boiling point and rapid evaporation limit the time for crystallization during the spin-coating process, and field-effect mobilities achieved for P3HT films spin-coated from chloroform are typically on the order of 0.01 cm2/(V s). Here we investigate a range of solvents with higher boiling points. We find that 1,2,4-trichlorobenzene with good solubility and a high boiling point significantly improves the field-effect mobilities up to 0.12 cm2/(V s) with on:off ratios of 106. By controlling the microstructure through the choice of solvent while keeping the molecular weight fixed, we observe a clear correlation between the field-effect mobility and the degree of microcrystalline order as measured by X-ray diffraction, as well as the strength of polaronic relaxation of charge carriers in the accumulation layer as measured by optical spectroscopy of field-induced charge.
902 citations
TL;DR: In this paper, the thermodynamic and kinetic factors influencing crystallization pressure are reviewed for cases including capillary rise and evaporation, cyclic wetting and drying, and hydration of cement.
714 citations
TL;DR: A simple spin-coating technique for rapidly fabricating three types of technologically important materials--colloidal crystal, macroporous polymer, and polymeric nanocomposite, each with high crystalline qualities and wafer-scale sizes is reported.
Abstract: This paper reports a simple spin-coating technique for rapidly fabricating three types of technologically important materials--colloidal crystal, macroporous polymer, and polymeric nanocomposite, each with high crystalline qualities and wafer-scale sizes. Dispersion of monodisperse silica colloids in triacrylate monomers is spin-coated onto a variety of substrates. Shear-induced ordering and subsequent polymerization lead to the formation of three-dimensionally (3D) ordered colloidal crystals trapped inside a polymer matrix. The thickness of as-synthesized colloidal crystal-polymer nanocomposite is highly uniform and can be controlled simply by changing the spin speed and time. Selective removal of the polymer matrix and silica spheres lead to the formation of large-area colloidal crystals and macroporous polymers, respectively. The wafer-scale process is compatible with standard semiconductor microfabrication, as multiple micrometer-sized patterns can be created simultaneously for potential device applications. Normal-incidence transmission spectra in the visible and near-infrared regions show distinct peaks due to Bragg diffraction from 3D ordered structures. The spin-coating process opens a new route to the fundamental studies of shear-induced crystallization, melting and relaxation.
659 citations
TL;DR: In this paper, a review relates to the models describing the structural evolution of calcium silicate hydrate (C-S-H) at the crystal-chemical level as a function of composition in terms of calcium to silicon ratio.
481 citations
TL;DR: Schwartz et al. as mentioned in this paper reviewed various chemical aspects of different approaches, including sol-gel, hybrid, and metallo-organic decomposition (MOD) routes, which all have been successfully applied for the deposition of this class of materials.
445 citations
TL;DR: In this article, an extension of this technique to a pilot study of the hydration of a typical Portland cement was described. But the results were compared with independent measures of the same materials by the analysis of backscattered electron images (BSE/IA) and thermogravimetric analysis.
441 citations
TL;DR: This work has found that E. coli, when incubated with cadmium chloride and sodium sulfide, have the capacity to synthesize intracellular Cadmium sulfide nanocrystals, which are composed of a wurtzite crystal phase with a size distribution of 2-5 nm.
398 citations
TL;DR: It is found that to be effective crystallization promoters, the seed particles need to exceed a well-defined minimum size, just above which they act as crystallization ‘catalysts’ as newly formed crystallites detach from the seed.
Abstract: The addition of small 'seed' particles to a supersaturated solution can greatly increase the rate at which crystals nucleate. This process is understood, at least qualitatively, when the seed has the same structure as the crystal that it spawns. However, the microscopic mechanism of seeding by a 'foreign' substance is not well understood. Here we report numerical simulations of colloidal crystallization seeded by foreign objects. We perform Monte Carlo simulations to study how smooth spherical seeds of various sizes affect crystallization in a suspension of hard colloidal particles. We compute the free-energy barrier associated with crystal nucleation. A low barrier implies that nucleation is easy. We find that to be effective crystallization promoters, the seed particles need to exceed a well-defined minimum size. Just above this size, seed particles act as crystallization 'catalysts' as newly formed crystallites detach from the seed. In contrast, larger seed particles remain covered by the crystallites that they spawn. This phenomenon should be experimentally observable and can have important consequences for the control of the resulting crystal size distribution.
390 citations
TL;DR: In this article, a rigid cellulosic network within a poly(oxyethylene) matrix and a stable aqueous suspension of cellulose nanocrystals extracted from tunicate as the reinforcing phase were obtained by casting and evaporating the preparations, using scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis.
TL;DR: A method for creating droplet pairs by generating alternating droplets, of two sets of aqueous solutions in a flow of immiscible carrier fluid within PDMS and glass microfluidic channels is characterized.
Abstract: For screening the conditions for a reaction by using droplets (or plugs) as microreactors, the composition of the droplets must be indexed Indexing here refers to measuring the concentration of a solute by addition of a marker, either internal or external Indexing may be performed by forming droplet pairs, where in each pair the first droplet is used to conduct the reaction, and the second droplet is used to index the composition of the first droplet This paper characterizes a method for creating droplet pairs by generating alternating droplets, of two sets of aqueous solutions in a flow of immiscible carrier fluid within PDMS and glass microfluidic channels The paper also demonstrates that the technique can be used to index the composition of the droplets, and this application is illustrated by screening conditions of protein crystallization The fluid properties required to form the steady flow of the alternating droplets in a microchannel were characterized as a function of the capillary number Ca and water fraction Four regimes were observed At the lowest values of Ca, the droplets of the two streams coalesced; at intermediate values of Ca the alternating droplets formed reliably At even higher values of Ca, shear forces dominated and caused formation of droplets that were smaller than the cross-sectional dimension of the channel; at the highest values of Ca, coflowing laminar streams of the two immiscible fluids formed In addition to screening of protein crystallization conditions, understanding of the fluid flow in this system may extend this indexing approach to other chemical and biological assays performed on a microfluidic chip
TL;DR: In this paper, the melting and crystallization behavior of poly(L-lactic acid) (PLLA; weight-average molecular weight = 3 × 105) was studied with differential scanning calorimetry (DSC).
Abstract: The melting and crystallization behavior of poly(L-lactic acid) (PLLA; weight-average molecular weight = 3 × 105) was studied with differential scanning calorimetry (DSC). DSC curves for PLLA samples were obtained at various cooling rates (CRs) from the melt (210 °C). The peak crystallization temperature and the exothermic heat of crystallization determined from the DSC curve decreased almost linearly with increasing log(CR). DSC melting curves for the melt-crystallized samples were obtained at various heating rates (HRs). The double-melting behavior was confirmed by the double endothermic peaks, a high-temperature peak (H) and a low-temperature peak (L), that appeared in the DSC curves at slow HRs for the samples prepared with a slow CR. Peak L increased with increasing HR, whereas peak H decreased. The peak melting temperatures of L and H [Tm(L) and Tm(H)] decreased linearly with log(HR). The appearance region of the double-melting peaks (L and H) was illustrated in a CR–HR map. Peak L decreased with increasing CR, whereas peak H increased. Tm(L) and Tm(H) decreased almost linearly with log(CR). The characteristics of the crystallization and double-melting behavior were explained by the slow rates of crystallization and recrystallization, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 25–32, 2004
TL;DR: In this paper, the supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films was studied through changing crystallization conditions in two solvents of different structures and polarities.
Abstract: The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution-cast films is studied through changing crystallization conditions in two solvents of different structures and polarities. The crystalline-state chain conformations of isothermally solution-crystallized PVDF in N, N-dimethylacetamide (DMAc), and cyclohexanone are studied through the specific FTIR absorption bands of α, β, and γ phase crystals. There are no changes in the FTIR spectra of cyclohexanone solution-crystallized films in the temperature range of 50–120 °C. In the case of DMAc solution-crystallized films, low temperature crystallization mainly results in formation of trans states (β and γ phases), whereas at higher temperatures gauche states become more populated (α phase). This is due to the variations in solvent polarity and ability to induce a specific conformation in PVDF chains, through the changes in chain coil dimensions. This indicates that in spite of cyclohexanone solutions, the intermolecular interactions between PVDF and DMAc are temperature-sensitive and more important in stabilizing conformations of PVDF in crystalline phase than temperature dependence of PVDF chain end-to-end distance . The high-resolution 19F NMR spectroscopy also showed little displacement in PVDF characteristic chemical shifts probably due to changes in PVDF chain conformation resulting from temperature variations. Upon uniaxial stretching of the prepared films under certain conditions, contribution of trans state becomes more prominent, especially for the originally higher α phase-containing films. Due to formation of some kink bands during film stretching and phase transformation, α phase absorption bands are still present in infrared spectra. Besides, uniaxial stretching greatly enhances piezoelectric properties of the films, maybe due to formation of oriented β phase crystals, which are of more uniform distribution of dipole moments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3487–3495, 2004
TL;DR: In this article, the influence of CaCO 3 nanoparticles on the crystallization of polypropylene (PP) was studied by wide angle X-ray diffraction and polarized optical microscopy.
TL;DR: In this paper, wide-angle X-ray diffraction (WAXD) was used to investigate the effects of shear on the crystallization behavior of polypropylene (PP) with β-nucleating agent.
Abstract: Wide-angle X-ray diffraction (WAXD) was used to investigate the effects of shear on the crystallization behavior of polypropylene (PP) with β-nucleating agent. The melt was subjected to shear at the shear rate from 0.5 to 60 s-1 for 5 s with a CSS450 shear stage. For the PP with low content of the additive, the formation mechanism of the β crystals is almost the same as that of pure isotactic polypropylene (iPP), viz., shear induces. Otherwise, for the samples with high content of the additive, the formation mechanism of the β form are nucleating agent induces. The results clearly show that shear restrains the formation of high β phase for the melt with additive.
TL;DR: In this paper, the role of water and fO2 on phase relations and differentiation trends in mid-ocean ridge basalt (MORB) systems was investigated at 200MPa in the temperature range 1150-950 C at oxygen fugacities corresponding to the quartz-fayalite-magnetite (QFM) and MnO-Mn3O4 buffers.
Abstract: Crystallization experiments were performed at 200MPa in the temperature range 1150–950 C at oxygen fugacities corresponding to the quartz–fayalite–magnetite (QFM) and MnO–Mn3O4 buffers to assess the role of water and fO2 on phase relations and differentiation trends in mid-ocean ridge basalt (MORB) systems. Starting from a primitive (MgO 9 8 wt %) and an evolved MORB (MgO 6 49 wt %), crystallization paths with four different water contents (0 35–4 7 wt % H2O) have been investigated. In primitive MORB, olivine is the liquidus phase followed by plagioclase þ clinopyroxene. Amphibole is present only at water-saturated conditions below 1000 C, but not all fluid-saturated runs contain amphibole. Magnetite and orthopyroxene are not stable at low fO2 (QFM buffer). Residual liquids obtained at low fO2 show a tholeiitic differentiation trend. The crystallization of magnetite at high fO2 (MnO–Mn3O4 buffer) results in a decrease of melt FeO */ MgO ratio, causing a calc-alkaline differentiation trend. Because the magnetite crystallization temperature is nearly independent of the H2O content, in contrast to silicate minerals, the calc-alkaline differentiation trend is more pronounced at high water contents. Residual melts at 950 C in a primitive MORB system have compositions approaching those of oceanic plagiogranites in terms of SiO2 and K2O, but have Ca/Na ratios and FeO * contents that are too high compared with the natural rocks, implying that fractionation processes are necessary to reach typical compositions of natural oceanic plagiogranites.
TL;DR: In this article, a mesoporous anatase films exhibiting favorable properties for photocatalysis and photovoltaic applications were fabricated by the hydrolysis/condensation of TiCl4 in the presence of PHB−PEO block copolymer templates.
Abstract: A strategy is shown to fabricate highly organized mesoporous anatase films exhibiting favorable properties for photocatalysis and photovoltaic applications by the hydrolysis/condensation of TiCl4 in the presence of PHB−PEO block copolymer templates. Dipcoating for evaporation-induced-self-assembly followed by a straight thermal treatment was employed. The evaporation/structuration process and the thermal treatment were mechanistically followed by in situ GISAXS/WAXS measurements, and the final product was carefully analyzed by spectroscopic ellipsometry and transmission electron microscopy to reveal the consequences of crystallization onto the micro-, the meso-, and the macroscale.
TL;DR: In this paper, the effects of stirring rate, contents of emulsifier and contents of cyclohexane on diameters, morphology, phase change properties and thermal stabilities of the capsules were studied by using FT-IR, SEM, DSC and TG.
TL;DR: In this article, a charge coupling device (CCD) camera was installed at the die exit to carefully monitor the shape of extruded polypropylene (PP) foams, and the CCD images were analyzed to illustrate both mechanisms, gas loss and crystallization, during foaming at various temperatures.
Abstract: This article describes the fundamental foaming mechanisms that governed the volume expansion behavior of extruded polypropylene (PP) foams. A careful analysis of extended experimental results indicated that the final volume expansion ratio of the extruded PP foams blown with butane was governed by either the loss of the blowing agent or the crystallization of the polymer matrix. A charge coupling device (CCD) camera was installed at the die exit to carefully monitor the shape of the extruded PP foams. The CCD images were analyzed to illustrate both mechanisms, gas loss and crystallization, during foaming at various temperatures, and the maximum expansion ratio was achieved when the governing mechanism was changed from one to the other. In general, the gas loss mode was dominant at high temperatures and the crystallization mode was dominant at low temperatures. When the gas loss mode was dominant, the volume expansion ratio increased with decreasing temperature because of the reduced amount of gas lost. By contrast, when the crystallization mode was dominant, the expansion ratio increased with increasing temperature because of the delayed solidification of the polymer. The processing window variation with the butane concentration, the change in the temperature ranges for the two governing modes, and the sensitivity of melt temperature variations to the volume expansion ratio are discussed in detail on the basis of the obtained experimental results for both branched and linear PP materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2661–2668, 2004
TL;DR: Recent studies show that targeted mutagenesis of surface patches containing residues with large flexible side chains and their replacement with smaller amino acids lead to effective preparation of X-ray quality crystals of proteins otherwise recalcitrant to crystallization.
TL;DR: Methods to determine the phase diagram of an aqueous solution of a globular protein are described, focusing on the solid (crystal) and condensed liquid states.
TL;DR: The phase transformation and growth of mullite (3Al 2 O 3 ·2SiO 2 ) in kaolin ceramics have been investigated using X-ray diffractometer, transmission electron microscope, select area electron diffractometers, energy dispersion spectrometer and differential thermal analysis as mentioned in this paper.
Abstract: The phase transformation and growth of mullite (3Al 2 O 3 ·2SiO 2 ) in kaolin ceramics have been investigated using X-ray diffractometer, transmission electron microscope, select area electron diffractometer, energy dispersion spectrometer and differential thermal analysis. The mullite which was transformed from kaolin appears at 1050 °C by XRD and tallies with DTA. The initial mullite crystal showed a plate-like morphology. The Al 2 O 3 content in mullite crystal increased from 49.57 to 71.37 wt.% but the lattice parameters of a , b and c axes decreased from 8.085, 8.106 and 3.215 A to 7.882, 7.974 and 2.946 A, respectively, with the grain width increasing from 20 to 70 nm when the kaolin was sintered at 1300 °C for 30 min. The nonisothermal activation energy of mullite crystallization in kaolin ceramics was 1182.3 kJ mol −1 . The growth morphology parameters n and m were both about 2.0, indicating that the bulk nucleation was dominant in mullitization and the crystal growth was controlled by diffusion. Seemingly, this study has been attempted to provide an integrative presentation of the thermal–structural characterization together with detailed kinetic and mechanistic interpretations.
TL;DR: In this article, the onset strain of crystallization was almost independent of the volume of the unit cell, and the deformation of crystal lattice with nominal stress was detected, and strain-induced crystallites were found to be responsible for the increased modulus upon elongation.
Abstract: Strain-induced crystallization of natural rubber samples with various network-chain densities, ν, was investigated by synchrotron X-ray diffraction measurements. It was found that the onset strain of crystallization was almost independent of ν. Lateral crystallite size and degree of orientational fluctuations of crystallites were also evaluated. These results indicated that stretched molecular chains acted as nuclei while surrounding chains could also contribute to the crystal growth. Deformation of crystal lattice with nominal stress was detected, and the strain-induced crystallites were found to be responsible for the increased modulus upon elongation. The unit cell volume decreased almost linearly with nominal stress. By assuming the deformation mechanism of the rubber network as a pantograph, the reinforcement effect of the crystallites is thought to be brought out not directly by crystallites connected in series but indirectly through the surrounding network chains.
TL;DR: In this article, the structural evolution and crystallization dynamics of poly(l-lactide) (PLLA) during isothermal cold-crystallization process are studied by infrared (IR) spectroscopy and two-dimensional correlation analysis.
Abstract: The structural evolution and crystallization dynamics of poly(l-lactide) (PLLA) during isothermal cold-crystallization process are studied by infrared (IR) spectroscopy and two-dimensional correlation analysis. In the CO stretching region, the band shift to a higher wavenumber taking place during the crystallization of PLLA is attributed to the dipole−dipole interaction between the CO groups. A detailed analysis is performed for the range of 1500−1000 cm-1 where bands are highly overlapped. It was found that the 1458 cm-1 band reflects the structural order of the CH3 group, and the band at 1109 cm-1 is related to the C−O−C trans conformation in the crystalline phase of PLLA. The band at 1193 cm-1 is sensitive not only to the structural adjustment of the C−O−C backbone but also to the structural order of CH3 group in crystalline phase. From the analysis of the difference spectra and 2D correlation spectra in the 1500−1000 cm-1 region, it is shown that the structural adjustment of the CH3 group unambiguousl...
TL;DR: In this paper, the effect of organically modified montmorillonite clay addition on crystallization of a polymer matrix has been studied, and two types of commercially available organoclays with different extent of miscibility with a polyester matrix were employed, leading to fully exfoliated and intercalated (low miscibility) morphologies.
Abstract: The effect of organically modified montmorillonite clay addition on crystallization of a polymer matrix has been studied. Two types of commercially available organoclays with different extent of miscibility with a polymer matrix were employed, leading to fully exfoliated (high miscibility) and intercalated (low miscibility) nanocomposite morphologies. The nanocomposites were fabricated via the exfoliation−adsorption technique with the biodegradable polyester matrix polymer poly(l-lactic acid) (PLLA). As-cast nanocomposite films were melted and isothermally crystallized at different temperatures. Bulk kinetics studies and radial spherulite growth rates indicate that when a high degree of filler−polymer matrix miscibility is present, nucleation properties of the organoclay are low relative to the less miscible organoclay. Therefore, the overall bulk crystallization rate was increased in the intercalated system and somewhat retarded in the exfoliated system. Surprisingly, spherulite growth rates were signifi...
TL;DR: A survey of bio-inspired approaches to artificial crystallization can be found in this paper, where the use of organized organic surfaces patterned with specific initiation domains on a submicrometer-scale to control patterned crystal growth is discussed.
Abstract: Nature produces a wide variety of exquite highly functional mineralized tissues using simple inorganic salts. Biomineralization occurs within specific microenvironments, and is finely tuned by cells and specialized biomacromolecules. This article surveys bio-inspired approches to artificial crystallization based on the above concept: that is, the use of organized organic surfaces patterned with specific initiation domains on a submicrometer-scale to control patterned crystal growth. Specially tailored self-assesbled monolayers (SAMs) of w-terminated alkanethils were micropatterned on metal films using soft lithography and applied as organic templates for the nucleation of calcium carbonate. Crystallization results in the formation of large-area, high-resolution inorganic replicas of the underlying crystallization process, including the precise localization of particles, nucleation density, crystal sizes, crystallographic orientation, morphology, polymorph, stability, and architecture. The ability to construct periodic arrays of uniform oriented single crystals, large single crystals with controlled microporosity, or films presenting patterns of crystals offers a potent methodology to materials engineering.
TL;DR: Observations suggest that nucleation and polymorph selectivity is governed by critical size constraints imposed by the ultrasmall pores, promising a new approach to controlling polymorphism and searching for unknown polymorphs.
Abstract: Polymorph selectivity has been achieved during crystallization of anthranilic acid (AA) and 5-methyl-2-[(2-nitrophyenyl)amino]-3-thiophenecarbonitrile (ROY), both considered benchmarks of polymorphic behavior, within nanoporous glass beads and polymer monoliths. Whereas polymorph III of AA crystallizes from the melt on nonporous glass beads or within larger pores, the metastable polymorph II crystallizes in pores with diameters <23 nm, with the selectivity toward this form increasing with decreasing pore size. Of the six ROY polymorphs characterized by single-crystal X-ray diffraction, the yellow form (Y) crystallizes during evaporation of pyridine solutions imbibed by the 30-nm cylindrical pores of porous polycyclohexylethylene (p-PCHE) monoliths. Although both R and ON grow from the melt on the external surfaces of PCHE, only the red form (R) crystallizes in the pores. Amorphous ROY also forms in p-PCHE pores during evaporation from pyridine solutions, subsequently crystallizing to the R nanocrystals upon heating. Although heterogeneous nucleation on the pore walls may play a role, these observations suggest that nucleation and polymorph selectivity is governed by critical size constraints imposed by the ultrasmall pores. The ability to achieve polymorph selectivity in both glass and polymer matrices suggests wide-ranging compatibility with various organic crystalline solids, promising a new approach to controlling polymorphism and searching for unknown polymorphs.
TL;DR: In this paper, the influence of crystallinity and lamellar thickness on the intrinsic deformation behavior of a number of semicrystalline polymers is studied: a poly(ethylene terephthalate) and two different molecular weight grades of polyethylene and polypropylene.
Abstract: The influence of crystallinity and lamellar thickness on the intrinsic deformation behavior of a number of semicrystalline polymers is studied: a poly(ethylene terephthalate) and two different molecular weight grades of polyethylene and polypropylene. The crystallinity and lamellar thickness are altered by varying the rate of crystallization from the melt and by cold crystallization (annealing) at elevated temperatures above Tg but below the melting point. Crystallinity and lamellar thickness are determined by wide-angle X-ray diffraction and small-angle X-ray scattering measurements. Uniaxial compression tests are performed to obtain the large strain intrinsic deformation behavior, e.g., yield stress, strain softening, and strain hardening modulus. The yield stress is found to be proportional to lamellar thickness, whereas the strain hardening modulus is shown not to depend on crystallinity or lamellar thickness. Over the strain range experimentally covered, the strain hardening modulus appears to be well described by a simple neo-Hookean relation and appears to be related to the chain entanglement density. An affirmation for this relation arises from the observation that slowly melt crystallized samples exhibit a lower strain hardening, resulting from a lower chain entanglement density, which is expected to be caused by reeling in of the molecular chains in such a slow crystallization process. The similarity in the results observed on all polymers tested supports the conclusion that the crystalline phase does not contribute to strain hardening, which is primary controlled by the chain entanglement density.