Thickness Of Crystalline Lamellae Research Articles

Supramolecular structure and physiochemical properties of annealed maize starches: Effect of starch granule-associated surface and channel proteins

To investigate the effect of starch granule-associated surface and channel proteins (GSCP) on starch during annealing, normal maize starch (NMS) and waxy maize starch (WMS) were subjected to protease treatment then annealing for 0–36 h to study changes in structural and physicochemical properties. The removal of GSCP accelerated the rate of increase in granule size of NMS during annealing. XRD results showed that annealing initially decreases the crystalline order of starch granules, but with prolonged annealing, the relative crystallinity increases. Also, GSCP removal decreases the rate of reduction in relative crystallinity during annealing. The lamellar structure of starch becomes compact in the initial state of annealing. With extended annealing time, the rearrangement of the microcrystalline structure may result in a decrease in compactness. The dual treatment increased the thickness of crystalline lamellae (dc), and the removal of GSCP advanced the change of lamellar structure during annealing. From pasting results, the rigidity of swollen starch was reduced after GSCP removal, while it increased with annealing time for NMS. This study adopted a GSCP removal method that had minimal impact on the structure of starch granules, providing novel information about the role of GSCP in the annealing of maize starch.

Deciphering multi-scale structures and pasting properties of wheat starch in frozen dough following different freezing rates

Starch is the main composition of frozen dough. How the freezing rate of frozen dough affected multi-scale structures and functionalities of starch in the frozen dough and the underlying mechanism are not systematically discussed yet. Both rapid and slow freezing treatment (0.20–1.50 ℃/min) increased the content of amylose, helical structures, crystalline structures, and short-range ordered structures and the thickness of crystalline lamellae and semi-crystalline lamellae, and thus increased swelling power, solubility, peak viscosity, breakdown viscosity, final viscosity, and setback viscosity of starch during heating. A slow freezing treatment (0.20 ℃/min) contributed to the formation of large ice crystals, and in turn, resulted in great changes in starch structures and functionalities. The corrosion of starch granules and the leach of amylose and small amylopectin during the thawing of ice crystals may be responsible for the changes in structures, swelling power, solubility, and pasting properties of starch in the frozen dough.

Consequences of Radiothermal Ageing on the Crystalline Morphology of Additive-Free Silane-Crosslinked Polyethylene.

The radiothermal ageing of silane-crosslinked low-density PE (Si-XLPE) films was studied in the air under three different dose rates (8.5, 77.8, and 400 Gy·h−1) at a low temperature close to ambient (47, 47, and 21 °C, respectively). Changes in crystalline morphology were investigated using a multi-technique approach based on differential scanning calorimetry (DSC), wide- (WAXS) and small-angle X-ray scattering (SAXS), and density measurements. In particular, the changes in four structural variables were accurately monitored during radiothermal ageing: crystallinity ratio (), crystalline lamellae thickness (), long period (), and interlamellar spacing (). Concerning the changes in , a perfect agreement was found between DSC and WAXS experiments. Successive sequences of self-nucleation and annealing (SSA) were also performed on aged Si-XLPE samples in the DSC chamber in order to assess the thickness distribution of crystalline lamellae. This method allowed the thermally splitting of the melting domain of Si-XLPE into a series of elementary melting peaks, with each one characterised by a distinct thickness of crystalline lamellae. DSC (used with the SSA method) showed a slight increase in during the oxidation of Si-XLPE, while SAXS confirmed a catastrophic decrease in . The critical value of the interlamellar spacing characterising the ductile/brittle transition of Si-XLPE was found to be of the same order of magnitude as that for linear polyethylene ( nm). This structural end-of-life criterion can now be used for predicting the lifetime of Si-XLPE in a nuclear environment.

Formation and structure evolution of starch nanoplatelets by deep eutectic solvent of choline chloride/oxalic acid dihydrate treatment

In this study, we report a top-down approach to fabricate starch nanoplatelets (SNPs) based on a deep eutectic solvent (DES) comprised of choline chloride and oxalic acid dihydrate. When subjecting waxy maize starch (WMS) to 2 h of DES treatment, the SNPs of oxalate half-ester were successfully fabricated. The formation mechanism of SNPs was studied by monitoring the changes in nanoplatelet morphology, amylopectin chain distribution, long-range crystallinity, and semi-crystalline lamellar structure of the DES-treated WMS at various treatment times. During the DES treatment, relative crystallinity values of WMS gradually decreased from 28.7 to 25.2%. With increasing DES treatment time from 0 to 1.5 h, the thickness of crystalline lamellae decreased from 6.38 to 5.57 nm, whereas the opposite trend was observed for the thickness of amorphous lamellae. The method developed in this work offers a green and efficient route to prepare non-toxic starch nanomaterials.

Differences in starch multi-layer structure, pasting, and rice eating quality between fresh rice and 7 years stored rice

With the continuous improvement of rice production capacity and the accumulation of reserves year by year, rice sometimes has to be stored for a long time. However, long-term storage of rice has poor sensory properties, which may be related to the structural changes of starch. Different from the previous studies on short-term storage of rice (often 3–12 months), the focus of this study was to understand the differences in starch multi-layer structure, pasting, and rice eating quality between 7 years stored rice and fresh rice. Our research indicated that 7 years stored rice showed higher hardness and lower stickiness compared to fresh rice, which ultimately led to poorer eating quality. These bad changes were related to differences in starch multi-layer structure. The 7 years stored rice had lower amylose content, a lower thickness of crystalline lamellae and short-range ordered structure of starch, and more large starch granules. In particular, the volume mean diameter of 7 years starch was more than 4 times that of fresh starch. 7 years stored rice had more large granular starch and unstable crystal structure, which led to the increase of pasting temperature and the decrease of gelatinization enthalpy during starch gelatinization, and ultimately reduced the eating quality of the rice.

Coaxial μSAXS/POM simultaneous measurement for microstructural characterization of one-dimensional and two-dimensional crystalline polymer

The microfocus beam small-angle X-ray scattering (μSAXS) provides a high spatial resolution ability, and the μSAXS/POM simultaneous measurement facilitates the acquisition of the micro-structural variations in the heterogeneous samples. Herein, at the SSRF BL19U2 beamline, a coaxial μSAXS/POM simultaneous measurement system has been established, comprising of the compound refractive lenses and an in-situ polarizing microscope. The SAXS beam size of 5.43 μm × 6.52 μm with a flux of 2.52 × 1011 photons/s has been employed. In order to obtain realistic microstructural information, the visible light path of the polarizing microscope has been set coaxially with the X-ray to eliminate the field of view deviation. The microstructure of the ringed spherulites of the polyoxymethylene/polybutylenesuccinate blends and high-density polyethene (HDPE) fibers has been simultaneously characterized. The differences in the structural information at different positions inside the banded spherulites have been evaluated. The crystallinity of the HDPE fibers increases from the skin to core, whereas the average crystalline lamellae thickness of the HDPE fibers decreases from skin to core, and the long spacing remains almost unchanged in the fibers.

Relationships between supramolecular organization and amylopectin fine structure of quinoa starch

The molecular and granular structure of 9 quinoa starches were investigated and correlated with each other. The molecular structure of quinoa amylopectin and β-limit dextrins studied by high performance anion exchange chromatography suggested that quinoa amylopectin contained a high amount of short chains. The average external chain length (ECL) and average internal chain length (ICL) of the nine quinoa starch studied were 10.7 and 4.90 glucosyl residues, respectively. Small-angle X-ray scattering (SAXS) was applied to study the lamellar structure of quinoa starches. The average thickness of crystalline lamellae (dc) and amorphous lamellae (da) were 6.07 and 2.60 nm, respectively. Correlation analysis suggested that the amounts of short amylopectin chains were positively correlated with dc and they induced heterogeneity in the crystalline lamellae. The amount of long internal chains was positively correlated with da and they could stabilize the double helices in the crystalline lamellae. The correlation analysis based on individual chains suggested that current chain classification might lack a strong structural basis for the supramolecular organization of the granules. The correlations obtained in current research could be explained using the building block backbone model.

Relationship between molecular structure and lamellar and crystalline structure of rice starch

The relationship between molecular structure and crystalline and lamellar structures of fifteen types of rice starches was studied. GPC and HPAEC were used for the molecular chain analysis and WAXS, SAXS, and CP/MAS 13C NMR were employed for aggregation structural analysis. The amylopectin content and the average lengths of fb1-chains (the degree of polymerization (DP) 13–24) were positively correlated with the amount of double helices (r2 = 0.92 and 0.57, respectively). In contrast, amylose content was positively correlated with the amounts of amorphous materials in starch (r2 = 0.77). The amount of double helices, which constitute a major part of the crystalline matrix, was positively correlated with the lamellar ordering (r2 = 0.81), and negatively correlated with the thickness of crystalline lamellae (r2 = 0.90) and lamellar repeat distance (r2 = 0.84). Conversely, the amount of the amorphous matrix was correlated with these parameters in the opposite way (r2 = 0.50, 0.75, and 0.75, respectively).

In situ synchrotron small angle X-ray scattering investigation of structural formation of polyethylene upon micro-injection molding

A customized micro-injection molding apparatus with a pair of diamond windows in the filling cavity was specifically designed to simulate the extreme processing conditions inherent in the practical micro-molding process. This setup combined with synchrotron radiation allows real-time investigation of multi-scale structural development during the manufacturing process, which enables evaluation of flow-induced crystallization features for a range of polymeric materials. In this study, the structural evolution of high density polyethylene at the nanoscale was investigated by in situ synchrotron small angle X-ray scattering technique under injection molding. The respective structural parameters of kebab lamellae (including the long period, and the average thickness of crystalline lamellae and amorphous phase) and shish formation (such as the radius of gyration, length, and misorientation of the shish) were extensively analyzed from the resulting data. The growth of kebab crystals was found to exhibit a two-step behavior: melting of thin crystallites followed by a recrystallization process occur at the onset of molding whereas an annealing-induced perfectioning of the lamellae is activated at a later stage. In spite of the initial decrease of the shish length and radius, there is an overall increase in the length and misorientation of the shish structure at later times, which can be attributed to a crystallization of partially oriented chains onto the longitudinal surface of the existing shish. The results acquired by the unique combination of this apparatus and synchrotron radiation can provide an effective means to predict the structural formation and modulate the morphology of final products in practical micro-injection molding process of polymers.

Asymmetric Co-unit Inclusion in Statistical Copolyesters

The biodegradation of isodimorphic random butanediol-succinate/adipate copolymers (PBSAs) can be affected by a change in the semicrystalline morphology. A crucial point for the final semicrystalline structure is the incorporation of monomers of the minority component into the crystals of the majority component. We use proton time-domain NMR and wide-angle X-ray scattering to characterize the copolymers across their complete composition range and analyze the possible inclusion of minority comonomers in the PBA-rich 20/80 and the PBS-rich 60/40 composition by applying different solid-state 13C NMR experiments. For the PBA-rich copolymers, we find a nearly constant volumetric crystallinity of 50% up to the 50/50 composition combined with an increase of the crystalline lamella thickness. NMR has detected the BS units incorporated into the BA crystalline structure, where on average every tenth monomer is a BS comonomer. In PBS-rich crystals, the crystallinity and crystallite thickness decrease from neat PBS to PBSA 60/40 by 37% and ∼20%, respectively. We also find evidence that the BA units are excluded from the bulk crystal but accumulate at the crystallite surface. The amount of BA units in these pocket-like structures can be estimated to be 7–9% of the BA comonomer content.

Structural characterization and functionality of starches from different high-amylose maize hybrids

Structures and functionality of two groups of high-amylose maize hybrids starches (HAMHSs) with the same maternal parent but different paternal parent were investigated. H1 and H2 (Group 1) and H3 and H4 (Group 2) had the same maternal parents within the groups, respectively. Paternal parent affected the molecular size of amylopectin components of HAMHS as deduced by gel-permeation chromatography (GPC) analysis of native samples. GPC analysis of debranched samples and further amylose fitting analysis showed the paternal parent effect on the average chain lengths of amylose and long amylopectin (DP > 36). WAXS and SAXS data showed paternal parent only affected the thickness of crystalline lamellae and the amorphous lamellae, but had no effect on polymorph type, crystallinity, lamellar ordering, and long periodic distance of HAMHS. In addition, water solubility and contents of rapidly digestible starch, slowly digestible starch, and resistant starch were all affected by the paternal parent. In summary, we report some significant differences of HAMHS with the same maternal parent but different paternal parent.

Crystallization kinetics, structure, and rheological behavior of poly(ethylene terephthalate)/multilayer graphene oxide nanocomposites

AbstractThis work aims to produce poly(ethylene terephthalate)/multilayer graphene oxide (mGO) nanocomposites via continuous melt mixing in twin‐screw extrusion, and to study the changes in crystallization and melt flow behavior. Three mGO contents (0.05, 0.1, and 0.3 wt%) were used. Differential scanning calorimetry analyses showed that at 0.1 wt%, mGO acted best as nucleating agent, increasing the crystallization kinetics as well as the melt crystallization temperature (Tmc) by more than 20%. It was also observed that mGO increases the crystals perfection. The nucleating behavior was confirmed by X‐ray diffraction and small angle X‐ray scattering analyses, which showed a decrease in the composites' crystalline lamella thickness (lc) and long period. X‐ray microtomography data confirms that this behavior is significantly affected by the mGO agglomerates distribution and specific surface area inside the polymer matrix. The rheological behavior was studied under two different conditions. It was noticed that under lower shear stresses the mGO particles hinder the polymer flow, increasing the composites viscosity and the pseudo‐solid character. However, under higher shear stresses, for example, when flowing through a die, the nanomaterial enters its “superlubricity state,” acting as a lubricant to the flow. This is industrially interesting, because it may allow the use of less severe processing parameters to produce the nanocomposites.

Polyamide-6 structuration induced by a chemical reaction with a polyether triamine in the molten state

Polyamide-6 was modified by reactive extrusion using a triamine as a structuring agent. To scrutinize the reactive medium after the chemical modification and to characterize the new structures obtained, the coupling of several physico-chemical analyses was necessary and applied to either model molecules or polyamide chain. By correlation of liquid NMR, matrix assisted laser desorption ionisation/time of flight mass spectrometry (MALDI-ToF MS), and size-exclusion chromatography (SEC) analyses, it was possible to observe both grafting and polyamide chain scissions that led to randomly branched and linear molecules. One of the most noticeable modifications regarding the properties was a decrease in the amorphous phase mobility with a very small amount of triamine (0.7 wt%). A comprehensive study by X-ray scattering techniques (small and wide angle X-ray scattering, SAXS and WAXS, respectively) allowed us to highlight the noticeable size evolution of the crystalline and amorphous parts at the lamellar scale. In conclusion, these multi-scale experiments demonstrate the possibility of modifying the amorphous phase mobility by controlling the nanostructure morphology of the material, particularly the crystalline lamellae thickness and the rigid amorphous fraction (RAF) content. Thus, an increase in the RAF content of around 6 % induced more restricted mobility in the amorphous phase as the glass transition temperature (Tg) shifted to higher temperature (≈ + 7 °C).

Mechanical Properties and Morphology of Propene–Pentene Isotactic Copolymers

The mechanical behavior of propylene–pentene isotactic copolymers synthesized with a single-center organometallic catalyst in a broad interval of pentene (Pe) concentration, from 3 to 50 mol %, is analyzed. All copolymers show flexible behavior with very high deformation at breaking. The presence and entrance of Pe counits in α and δ forms of isotactic polypropylene (iPP) transform a strong and fragile iPP homopolymer into ductile and flexible materials. The stress at yield decreases as the Pe content increases, but a different behavior has been observed for samples in the α form or in the δ form. In samples in the α form, from 3 to 8.8 mol % of Pe, the stress at yield increases as the thickness of crystalline lamellae increases, while in samples in the δ form containing higher Pe counits, it decreases as the thickness of lamellae increases and Pe content increases. Phase transition of the α form in the mesophase and crystallization of the δ form, in samples with 8–11 mol % of Pe, occur upon deformation a...

Relationships among lamellar morphology parameters, structure and thermal behavior of isotactic propene-pentene copolymers: The role of incorporation of comonomeric units in the crystals

The correlations between the thermal behavior and the crystal morphology of isotactic propene-pentene copolymers were studied through wide-angle (WAXS) and small-angle (SAXS) X-ray diffraction. Copolymers with pentene concentration lower than 11 mol% crystallize in the α form of isotactic polypropylene (iPP) and a concomitant decrease of melting temperature and of the thickness of crystalline lamellae with increasing pentene concentration has been observed. At higher pentene concentrations the trigonal form of iPP crystallizes and a neat increase crystalline lamellar thickness and of the long period, with a slower decrease of melting temperature and crystallinity have been observed. These results have been treated in the general framework of copolymer crystallization theories, using a method proposed by Crist and correlated with the different level of inclusion of pentene co-units in the crystals of α and trigonal forms. For copolymers with pentene concentration lower than 11 mol% pentene co-units are in part incorporated in the crystals of α form. For higher pentene concentrations the decrease of melting temperature coupled with the increase of lamellae thickness with increasing comonomer content is the hallmark of the almost total inclusion of pentene co-units in the crystals of the trigonal form.

In situ study of the tensile deformation micro-mechanisms of semi-crystalline poly(ethylene terephthalate) films using synchrotron radiation X-ray scattering

Wide - and small-angle X-ray scattering are used to perform in situ experiments with synchrotron radiation. The high X-ray intensity enabled the study of the deformation mechanisms of poly(ethylene terephthalate) semi-crystalline films under tension. Microstructural parameters such as crystallinity ratio, macromolecular orientation, long period, length, width and thickness of crystalline lamellae are measured. A new method to follow macromolecular orientation is detailed. In the elastic-viscoelastic region, lamellae rotate along the tensile axis without increase of orientation parameters. The plastic strain is initiated by crystallographic processes: crystal slip with (010)[001] and (010)[010] systems, flexural breaking of the longitudinal lamellae and separation of (010) planes in transverse lamellae. The plastic flow is the continuation of these processes and the strengthening of the macromolecular orientation in both crystalline and amorphous phases. The shear forces applied to transverse lamellae rotating to a longitudinal orientation make them adopt a tilted shape.

Polyethylene containing aliphatic ring and aromatic ring defects in the main chain: Synthesis via ADMET and comparisons of thermal properties and crystalline structure

Three polyethylene containing different non-planar aliphatic ring ether units (1,4-cyclohexylenedioxy, 4,4′-bicyclohexylenedioxy and 4,4′-isopropylidenedicyclohexylenedioxy) were synthesized via acyclic diene metathesis polymerization (ADMET) and subsequent hydrogenation. They were compared with their counterpart polymers containing aromatic ring defects in aspects of chain structural, thermal properties and crystalline structure by investigations with 1H NMR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). Regardless of the trans/cis isomers of cyclohexane moieties in these polymers, the results demonstrated that polyethylene containing non-planar aliphatic ring units showed decreased thermal stability as compared with the corresponding PE containing aromatic ring defects. Moreover, study on crystallization behaviors indicated that in contrast to their aromatic counterparts, introduction of the non-planar aliphatic defects perturbed the corresponding crystal structure more intensively, and larger space is needed to include these defects in the solid phase. As a result, their WAXD reflections shifted to lower scattering angles that correspond to increased d-spacing, and the polymers exhibited lower melting points. SAXS results proved that non-planar aliphatic ring defects result in increased dimension of amorphous region. Calculated by melting points and enthalpy, these polymers had smaller crystalline lamella thickness and lower crystallinity than their aromatic counterparts.

Lamellar structure change of waxy corn starch during gelatinization by time-resolved synchrotron SAXS

In situ experiment of synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) was used to study the lamellar structure change of starch during gelatinization. Waxy corn starch was used as a model material to exclude the effect of amylose. The thicknesses of crystalline (dc), amorphous (da) regions of the lamella and the long period distance (dac) were obtained based on a 1D linear correlation function. The SAXS and WAXS results reveal the multi-stage of gelatinization. Firstly, a preferable increase in the thickness of crystalline lamellae occurs because of the water penetration into the crystalline region. Then, the thickness of amorphous lamellae has a significant increase while that of crystalline lamellae decreases. Next, the thickness of amorphous lamellae starts to decrease probably due to the out-phasing of starch molecules from the lamellae. Finally, the thickness of amorphous lamellae decreases rapidly, with the formation of fractal gel on a larger scale (than that of the lamellae), which gradually decreases as the temperature further increases and is related to the concentration of starch molecular chains. This work system reveals the gelatinization mechanism of waxy corn starch and would be useful in starch amorphous materials processing.

Thermodynamic and structural properties of tuber starches from transgenic potato plants grown in vitro and in vivo

Potato plants harboring Phytochrome B (PHYB) gene from Arabidopsis thaliana or rol genes from Agrobacterium rhizogenes were used to study the effect of transgene expression on structure and properties of starch in tubers. Thermodynamic characteristics of starch (melting temperature, enthalpy of melting, thickness of crystalline lamellae) were shown to be variable depending on the transgene expression and plant culturing mode: in vitro or in soil. The expression of rolB or rolC genes in in vitro cultured plants evoked opposite effects on starch melting temperature and crystalline lamellae thickness. AtPHYB or rolB expression in the soil-grown potato led to the formation of more defective or more ordered starch structures, respectively, in comparison with starches of the same lines grown in vitro. On the whole, our study revealed genotype-dependent differences between starches extracted from tubers of in vitro or in vivo grown plants.

Structure of Arabidopsis leaf starch is markedly altered following nocturnal degradation.

Little is known about the thermal properties and internal molecular structure of transitory starch. In this study, granule morphology, thermal properties, and the cluster structure of Arabidopsis leaf starch at beginning and end of the light period were explored. The structural properties of building blocks and clusters were evaluated by using diverse chromatographic techniques. On the granular level, starch from end of day had larger granule size, thinner crystalline lamellae thickness, lower free surface energy of crystals, and lower tendency to retrograde than that from end of night. On the molecular level, the starch had lower amylose content, larger cluster size, and higher number of blocks per cluster at the end of day than at end of night. It is concluded that the core of the granules contains a more permanent molecular and less-ordered physical structure different from the transitory layers laid down around the core at daytime.