Co-reporter:Yingying Sun, Lianlian Fu, Zhonghua Wu, and Yongfeng Men
Macromolecules 2013 Volume 46(Issue 3) pp:971-976
Publication Date(Web):February 1, 2013
DOI:10.1021/ma3020933
Structural evolution of two ethylene–octene copolymers with different octene content during tensile deformation and recovery was investigated using the in-situ synchrotron small-angle X-ray scattering technique. Sample containing 4 mol % octene shows similar deformation mechanism as observed previously that the whole process of deformation can be regarded as a stretching of two interpenetrating networks of crystalline rigid network and entangled amorphous phase. A transition from a crystalline rigid network dominating behavior at small deformations to a stretching-induced crystalline block disaggregation–recrystallization process occurs at a critical strain where stress generated by the stretched amorphous network reaches a critical value leading to the destruction of crystalline blocks. In sample containing 8 mol % octene, this critical strain is much larger than observed in the other sample. Such a phenomenon is attributed to the fact that only crystalline lamellar stacks and bundle-like crystals with much weakened coupling can be developed in the sample. The weakened coupling between crystalline lamellar stacks is due to the existence of interstack amorphous phase which also leads to an inhomogeneous strain distribution in the system.
Co-reporter:Yaotao Wang, Zhiyong Jiang, Zhonghua Wu, and Yongfeng Men
Macromolecules 2013 Volume 46(Issue 2) pp:518-522
Publication Date(Web):December 31, 2012
DOI:10.1021/ma302389j
Stretching-induced structural changes in polybutene-1 with stable crystalline modification of form I at elevated temperature was investigated by means of the in-situ synchrotron wide-angle X-ray diffraction technique. It was found that oriented metastable form II crystallites with the polymer chain aligned along the stretching direction gradually appear during tensile deformation. Based on the fact that a solid state I to II phase transition cannot take place due to the restriction in chain conformations and lattice dimensions in both phases, the observed occurrence of transition from form I to form II must proceed via a two-step process. First, those form I crystallites with their polymer chain direction tilted with respect to the stretching direction undergo a stress-induced melting process because they experience larger shear stress than the rest. Second, the freed polymer chain segments which have lost their conformational memory in stable form I recrystallize into metastable form II crystallites with their chain direction preferentially aligned along the stretching direction. This result is considered to provide a direct evidence for the stress-induced melting–recrystallization mechanism during tensile deformation of semicrystalline polymers.
Co-reporter:Jia-xue Liu;Yong-feng Men 门永锋
Chinese Journal of Polymer Science 2013 Volume 31( Issue 9) pp:1218-1224
Publication Date(Web):2013 September
DOI:10.1007/s10118-013-1308-6
Demixing and colloidal crystallization in the mixture of charge stabilized colloidal poly(methyl methacrylate) particles and soluble poly(ethylene oxide) were investigated by means of synchrotron small-angle X-ray scattering (SAXS) technique. Phase diagram of the mixture was obtained based on visual inspection and SAXS results. The phase behavior is determined as a function of the concentration of the polymer as well as the volume fraction of the colloidal particles. The system shows a one phase region when the concentration of the polymer is low, whereas a two-phase region is present when the concentration of the polymer is larger than a critical concentration at certain volume fraction of the colloids. Interestingly, a face centered cubic colloidal crystalline structure was formed under certain conditions, which has been rarely observed in experiments of colloid-polymer mixtures with competing interactions.
Co-reporter:Xuelian Chen, Volodymyr Boyko, Jens Rieger, Frank Reinhold, Bernd Reck, Jan Perlich, Rainer Gehrke and Yongfeng Men
Soft Matter 2012 vol. 8(Issue 48) pp:12093-12098
Publication Date(Web):12 Oct 2012
DOI:10.1039/C2SM26580J
The structural evolution in the center of a droplet of a dialyzed styrene–n-butyl acrylate copolymer latex dispersion on a solid surface during drying was studied by means of an in situ synchrotron ultra small-angle X-ray scattering technique. During water evaporation, as the droplet shrinks the shell yields and thickens, as evidenced by the appearance of diffraction peaks at the early stage combined with TGA measurement. As the droplet dried further, colloidal crystalline structure transformation is identified. The transition is attributed to the collapse of the thin shell made of densely packed particles at the surface of the droplet caused by capillary forces that drive the deformation of the shell. As there is a small amount of water remaining beneath the surface layer, charged particles are able to explore new configurations to reestablish a stable structure after leaving the initially formed face-centered cubic structure. Finally, a torus-shaped solid film with a central flat thin film is produced.
Co-reporter:Yingying Sun;Stefan Fischer;Zhiyong Jiang;Tao Tang;Sérgio S. Funari;Rainer Gehrke
Macromolecular Symposia 2012 Volume 312( Issue 1) pp:51-62
Publication Date(Web):
DOI:10.1002/masy.201100010
Abstract
Summary: The crystalline structure and phase morphology of linear, branched polyethylenes and their blends during crystallization and subsequent melting were investigated, using a combination of differential scanning calorimetry (DSC), and synchrotron small angle X-ray scattering (SAXS). A linear polyethylene (PE1) with weight-average molecular weight (Mw) of 114 000 g/mol, and two branched polyethylene copolymers, containing 4.8 mol% (PE4) and 15.3 mol% (PE10) hexane, with molecular weights of 93 000 g/mol and 46 000 g/mol were used as pure samples. Two blends, PE1-4 and PE1-10, each with a weight ratio of 50/50, were prepared by solution blending. Our results indicate that in PE4 a phase separation within the branched component itself occurred, forming a broad distribution of lamellar thicknesses during the crystallization process. PE10 on the other hand did hardly crystallize because of the high degree of branching. Co-crystallization of both components took place in blend PE1-4 and liquid-liquid phase separation occurred in the melt of PE1-10. Morphological parameters were determined by using Bragg's law and the correlation function, respectively. The detected semicrystalline morphology can be well described by the lamellar insertion mode where thin lamellae develop between thicker primary lamellae. During subsequent heating, lamellae melted in the reversed sequence of their formation. The evolution of the structural parameters as a function of temperature revealed that surface melting began at first, and then the complete melting of stacks occurred until the final melting temperature was reached.
Co-reporter:Stefan Fischer, Zhiyong Jiang, and Yongfeng Men
The Journal of Physical Chemistry B 2011 Volume 115(Issue 47) pp:13803-13808
Publication Date(Web):October 25, 2011
DOI:10.1021/jp204998p
Small-angle X-ray scattering data of melt-drawn high-density polyethylene (HDPE) have been analyzed by direct model fitting to projections on the drawing direction. On the basis of the assumption of an infinite paracrystalline lattice as proposed by Hosemann and a rectangular density profile, several additional assumptions have been tested. It turned out that to achieve good fits we have to introduce a finiteness of the lattice for the used samples. Transition zones between crystalline and amorphous regions also improve the model but are of less importance. The most suitable model has been tested on data from an annealing and subsequent cooling process. We show that the additional parameters gained in the modeling approach compared to peak analysis or correlation function analysis lead to a better understanding of the structures and processes in the samples.
Co-reporter:Xuelian Chen, Stefan Fischer, and Yongfeng Men
Langmuir 2011 Volume 27(Issue 21) pp:12807-12814
Publication Date(Web):September 26, 2011
DOI:10.1021/la202300p
Thermogravimetric analysis and a synchrotron small-angle X-ray scattering technique were employed to characterize the structural evolution of a polymeric latex dispersion during the first three stages of film formation at different temperatures and relative humidities. Three intermediate stages were identified: (1) stage I*, (2) stage I**, and (3) stage II*. Stage I* is intermediate to the conventionally defined stages I and II, where latex particles began to crystallization. The change of drying temperature affects the location of the onset of ordering, whereas relative humidity does not. Stage I** is where the latex particles with their diffuse shell of counterions in the fcc structure are in contact with each other. The overlapping of these layers results in an acceleration of the lattice shrinkage due to a decrease of effective charges. Stage II* is where the latex particles, dried well above their Tg, are deformed and packed only partially during film formation due to incomplete evaporation of water in the latex film. This is because of a rapid deformation of the soft latex particles at the liquid/air interface so that a certain amount of water is unable to evaporate from the latex film effectively. For a latex dispersion dried at a temperature close to its minimum film formation temperature, the transition between stages II and III can be continuous because the latex particles deform at a much slower rate, providing sufficient surface area for water evaporation.
Co-reporter:Jianqi Zhang, Zhiyong Yi, Qiao Wang, Zhenyu Liu, Jan Perlich, Rainer Gehrke, and Yongfeng Men
Langmuir 2011 Volume 27(Issue 19) pp:12197-12200
Publication Date(Web):August 29, 2011
DOI:10.1021/la2026939
The influence of solvent annealing on microscopic deformational behavior of a styrene/n-butyl acrylate copolymer latex film subjected to uniaxial tensile deformation was studied by small-angle X-ray scattering. It was demonstrated that the microscopic deformation mechanism of the latex films transformed from a nonaffine deformation behavior to an affine deformation behavior after solvent annealing. This was attributed to the interdiffusion of polymeric chains between adjacent swollen latex particles in the film. It turns out that solvent annealing is much more efficient than thermal annealing due to a much slow evaporation process after solvent annealing.
Co-reporter:Xuelian Chen, Stefan Fischer, Zhiyong Yi, Volodymyr Boyko, Alexandre Terrenoire, Frank Reinhold, Jens Rieger, Xiuhong Li, and Yongfeng Men
Langmuir 2011 Volume 27(Issue 13) pp:8458-8463
Publication Date(Web):May 31, 2011
DOI:10.1021/la201084j
Structural rearrangement in a latex powder during dry sintering at temperatures higher than the minimum film formation temperature was investigated by means of synchrotron small-angle X-ray scattering. Two major effects were identified: (1) Deformation of latex particles leads to a closure of voids between them and an extensive perfectioning of the face centered cubic colloidal crystalline ordering. Such an improvement of the colloidal crystalline structure involves preferential crystal growth along certain crystallographic directions as was evidenced by the measured unmatched relative diffraction intensity distribution of the crystallographic (111) and (220) planes. (2) Interdiffusion of polymeric chains between adjacent particles promotes a nanometer sized aggregation of nonpolymeric materials previously located in the interstices between particles. Size and size distribution of the aggregates at different dry sintering conditions were evaluated by using a model considering spheres dispersed in the system.
Co-reporter:Xuelian Chen;Jianqi Zhang;Zhiyong Yi
Journal of Coatings Technology and Research 2011 Volume 8( Issue 4) pp:489-496
Publication Date(Web):2011/07/01
DOI:10.1007/s11998-010-9314-x
The structural information of commercial styrene-co-butyl acrylate latex particles along radial direction was observed via the contrast-variation technique using synchrotron small-angle X-ray scattering (SAXS). By manipulating the electron density of the dispersion medium, the microstructural parameters of the latex dispersion were evaluated based on quantitative discussion of the scattering intensity distribution profiles. Four isoscattering points could be identified in the contrast-variation measurements, located at the scattering vectors corresponding to the position of the sharp minima of the scattering curve of homogenous spheres. This suggests that the shape and structure of particles were not affected by adding a certain amount of sucrose and salt. This phenomenon was attributed to the existence of the thin surface layers around particle core in the system. The data indicate that the latex particles exhibit a core–shell structure, and the average thickness of the shell is about 2 nm.
Co-reporter:Zhiyong Jiang, Yujing Tang, Jens Rieger, Hans-Friedrich Enderle, Dieter Lilge, Stephan V. Roth, Rainer Gehrke, Zhonghua Wu, Zhihong Li, Xiuhong Li, Yongfeng Men
European Polymer Journal 2010 Volume 46(Issue 9) pp:1866-1877
Publication Date(Web):September 2010
DOI:10.1016/j.eurpolymj.2010.06.004
The morphological development of melt-drawn transparent high-density polyethylene during heating was investigated employing in-situ synchrotron small-angle X-ray scattering (SAXS) technique. The results confirm that at lower temperatures only meridional scattering peaks aligned perpendicular to the extensional flow direction can be observed, indicating a highly oriented lamellar crystallite structure; whereas at higher temperatures an equatorial streak additional to the layer-like meridional scattering pattern develops, reflecting the presence of shish-kebab-like objects in the specimen under investigation. Upon heating, the average thickness of the kebab crystals remains essentially unaffected below 110 °C, and subsequently the selective melting of the less stable kebabs proceeds yielding thicker layered lamellar crystals. When the temperature is raised to 131 °C, the shish-like formation and the thermally stable kebab crystals melt simultaneously. In addition, the microstructure of the melt-drawn specimen subjected to annealing at elevated temperatures was probed at room temperature. As opposed to the SAXS patterns registered at high temperatures, the SAXS diagram measured after annealing shows no equatorial streak, suggesting that the cylindrical structures could be re-formed. This observation can be explained by assuming that the plate-like kebab crystals with their normal parallel to the stretching direction grow and impinge during cooling to room temperature due to secondary crystallization, which can be verified by in-situ SAXS experiments during annealing and subsequent cooling.
Co-reporter:Yu-jing Tang;Zhi-yong Jiang;Hans-Friedrich Enderle
Chinese Journal of Polymer Science 2010 Volume 28( Issue 2) pp:165-170
Publication Date(Web):2010 March
DOI:10.1007/s10118-010-8243-6
The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.
Co-reporter:Zhiyong Jiang, Yingying Sun, Yujing Tang, Yuqing Lai, Sérgio S. Funari, Rainer Gehrke and Yongfeng Men
The Journal of Physical Chemistry B 2010 Volume 114(Issue 18) pp:6001-6005
Publication Date(Web):April 20, 2010
DOI:10.1021/jp101017n
The phase transformation of form III isotactic poly(1-butene) was investigated as a function of temperature. The polymer was isothermally precipitated from a dilute solution in iso-amyl acetate and observed with real-time synchrotron small- and wide-angle X-ray scattering techniques. The results confirmed that the polymorphic transition of form III was strongly dependent on temperature. The phase transformation from form III to form I′ proceeded at a temperature of ca. 80 °C. This was accompanied by the presence of two distinctly different lamellar periodicities arising from form III and I′ crystals, respectively. The coexistence of form III and I′ crystals can persist up to 103 °C, followed by melting and recrystallizing into form II crystals. Finally, the reflections resulting from form II crystals disappeared at 118 °C.
Co-reporter:Zhiyong Jiang, Yujing Tang, Jens Rieger, Hans-Friedrich Enderle, Dieter Lilge, Stephan V. Roth, Rainer Gehrke, Walter Heckmann and Yongfeng Men
Macromolecules 2010 Volume 43(Issue 10) pp:4727-4732
Publication Date(Web):April 27, 2010
DOI:10.1021/ma100303d
The structural evolution of tensile-deformed high-density polyethylene (HDPE) at the lamellar level was investigated as a function of strain using a scanning synchrotron small-angle X-ray scattering technique. Intralamellar crystalline block slips were activated at small deformations, whereas stress-induced fragmentation and recrystallization process proceeded at a larger strain, yielding lamellae with polymeric chains preferentially oriented along the stretching direction. The critical strains marking the onset of the destruction of original crystallites and the fibril formation for isothermally crystallized HDPE were at about 0.4 and 1.2, respectively. In the case of a quenched sample, the critical strain was 0.4. In the isothermally crystallized sample two critical values were observed that could be traced back to the existence of two populations of lamellar stacks with significantly different interlamellar amorphous phase thicknesses. This resulted in distinct mobilities of the amorphous domains and, therefore, different moduli of the entangled amorphous networks. Consequently, the strain required to produce the critical network stress, which gave rise to a fragmentation of the crystalline blocks, was different for each stack of crystalline lamellae.
Co-reporter:Shanshan Hu, Jens Rieger, Zhiyong Yi, Jianqi Zhang, Xuelian Chen, Stephan V. Roth, Rainer Gehrke and Yongfeng Men
Langmuir 2010 Volume 26(Issue 16) pp:13216-13220
Publication Date(Web):July 16, 2010
DOI:10.1021/la102258b
The structural evolution of a colloidal crystal fiber during heating and annealing was followed by in situ synchrotron small-angle X-ray scattering. The polymer dispersion (with a particle size of 118 nm) from which the fibers were formed by directed drying contained emulsifier and salt. A cellular structure formed upon drying in which the percolating phase (the “membrane phase”) is composed from these components; this membrane phase gives rise to the scattering contrast on which the present observations build. Changes of the lattice constant of the colloidal crystallites and the intensity evolution of the scattering from the crystalline and the amorphous phases during heating and annealing indicate characteristic temperatures where the system exhibits pronounced structural changes. The first characteristic temperature was identified as 125 °C above which residue water in the membrane material was evaporated leading to shrinkage of the colloidal crystalline lattice. At a temperature above about 140 °C the membrane material was expelled out of the crystalline domains. This effect is accompanied by the progressive interdiffusion of polymer chains between adjacent latex particles and leads to further thermal shrinkage of the colloidal crystals. The second characteristic temperature is defined by a rapid increase in isotropic scattering. This effect is attributed to the formation of increasingly large domains of the membrane material and the concomitant disappearance of the membrane phase from the former crystal domains.
Co-reporter:Binbin Sun;Yuqing Lai;Yoong Kim
Frontiers of Chemistry in China 2009 Volume 4( Issue 3) pp:265-268
Publication Date(Web):2009 September
DOI:10.1007/s11458-009-0089-5
Polystyrene film of about 50 nm in thickness on silicon wafer was obtained by spin-coating in tetrahydrofuran solution. The film exhibits a rough surface as shown by atomic force microscopy images and ellipsometry data. Furthermore, such surface roughness produced a characteristic lateral correlation peak in an “out-ofplane” scan in the synchrotron grazing incidence ultra-small angle X-ray scattering pattern. The film was treated with liquids of solvent and non-solvent sequentially, resulting in a process of swelling and precipitation of the polystyrene film. Such a solvent/non-solvent treatment completely changed the original surface structure of the film. Aggregates of polystyrene of different sizes were observed both in atomic force microscopy and synchrotron grazing incidence ultra-small angle X-ray scattering measurements. The results demonstrate that synchrotron grazing incidence ultra-small angle X-ray scattering is a unique means to investigate large area micro-structural features of thin films supported on smooth surfaces.
Co-reporter:Shanshan Hu, Jens Rieger, Stephan V. Roth, Rainer Gehrke, Reinhold J. Leyrer and Yongfeng Men
Langmuir 2009 Volume 25(Issue 7) pp:4230-4234
Publication Date(Web):October 17, 2008
DOI:10.1021/la801527y
The structural evolution of a single-layer latex film during annealing was studied via grazing incidence ultrasmall-angle X-ray scattering (GIUSAXS) and atomic force microscopy (AFM). The latex particles were composed of a low-Tg (−54 °C) core (n-butylacrylate, 30 wt %) and a high-Tg (41 °C) shell (t-butylacrylate, 70 wt %) and had an overall diameter of about 500 nm. GIUSAXS data indicate that the qy scan at qz = 0.27 nm−1 (out-of-plane scan) contains information about both the structure factor and the form factor. The GIUSAXS data on latex films annealed at various temperatures ranging from room temperature to 140 °C indicate that the structure of the latex thin film beneath the surface changed significantly. The evolution of the out-of-plane scan plot reveals the surface reconstruction of the film. Furthermore, we also followed the time-dependent behavior of structural evolution when the latex film was annealed at a relatively low temperature (60 °C) where restructuring within the film can be followed that cannot be detected by AFM, which detects only surface morphology. Moreover, compared to AFM studies GIUSAXS provides averaged information covering larger areas.
Co-reporter:Zhiyong Jiang, Yujing Tang, Jens Rieger, Hans-Friedrich Enderle, Dieter Lilge, Stephan V. Roth, Rainer Gehrke, Zhonghua Wu, Zhihong Li, Yongfeng Men
Polymer 2009 50(16) pp: 4101-4111
Publication Date(Web):
DOI:10.1016/j.polymer.2009.06.063
Co-reporter:Jianqi Zhang, Shanshan Hu, Jens Rieger, Stephan V. Roth, Rainer Gehrke and Yongfeng Men
Macromolecules 2009 Volume 42(Issue 13) pp:4795-4800
Publication Date(Web):April 29, 2009
DOI:10.1021/ma900503h
The deformation mechanism of styrene/n-butyl acrylate copolymer latex films with fiber symmetric crystalline structure subjected to uniaxial stretching was studied using synchrotron small-angle X-ray scattering technique. The fibers were drawn at angles of 0, 35, and 55° with respect to the fiber axis. In all cases, the microscopic deformation within the crystallites was found to deviate from affine deformation behavior with respect to the macroscopic deformation ratio. Moreover, the extent of this deviation is different in the three cases. This peculiar behavior can be attributed to the relative orientation of the (111) plane of the crystals, the plane of densest packing, with respect to the stretching direction in each case. When the stretching direction coincides with the crystallographic (111) plane, which is the case for stretching directions of 0 and 55° with respect to the fiber axis, the microscopic deformation deviates less from affine behavior than when the stretching direction is arbitrarily oriented with respect to the crystallographic (111) plan. The dependence of tilting angle and d-spacing of selected (111) or (220) planes from the microscopic crystalline draw ratio are fully in accordance with theoretical considerations.
Co-reporter:Shanshan Hu, Jens Rieger, Yuqing Lai, Stephan V. Roth, Rainer Gehrke and Yongfeng Men
Macromolecules 2008 Volume 41(Issue 13) pp:5073-5076
Publication Date(Web):2017-2-22
DOI:10.1021/ma800451n
Co-reporter:Jianqi Zhang, Shanshan Hu, Jens Rieger, Stephan V. Roth, Rainer Gehrke and Yongfeng Men
Macromolecules 2008 Volume 41(Issue 12) pp:4353-4357
Publication Date(Web):May 16, 2008
DOI:10.1021/ma800435f
The deformation mechanism of a styrene/n-butyl acrylate copolymer latex film subjected to uniaxial tensile stress was studied by small-angle X-ray scattering. The influence of annealing at 23, 60, 80, and 100 °C for 4 h on microscopic deformation processes was elucidated. It was demonstrated that the microscopic deformation mechanism of the latex films transformed gradually from nonaffine deformation behavior to affine deformation behavior with increasing annealing temperature. This behavior was attributed to the interdiffusion of polymeric chains between adjacent latex particles in the film, the extent of which increases with annealing temperature. The polycrystalline structure of the latex films was preserved even after annealing for 4 h at temperatures 80 K above the glass transition temperature; i.e., the structure is not completely homogenized by interdiffusion.
Co-reporter:Zhiyong Jiang ; Lianlian Fu ; Yingying Sun ; Xiuhong Li
Macromolecules () pp:
Publication Date(Web):August 15, 2011
DOI:10.1021/ma201346v
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