• Polymer(Korea)
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• v.33 no.2
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• pp.183-188
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• 2009

Structural rearrangements of uni-axially deformed polyethylenes containing 1-octene comonomer and HDPE upon heating were investigated by time-resolved small and wide angle X-ray scattering techniques. During heating, structural changes including crystal transformation and lamellar rearrangement noted were very different depending on the comonomer contents. At low comonomer content below 2 wt%, inverse martensitic transformation of crystal lattice from monoclinic to orthorhombic cell and the rearrangement of broken lamellar units into more ordered and perfect lamellar stacks were noted with the temperature increase. At high contents above 9.5 wt%, however, polyethylene copolymers showed neither the crystal transformation nor lamellar rearrangement that can be attributed to low crystallinity and high content of branch units.

• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.