• Polymer(Korea)
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• v.26 no.6
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• pp.745-751
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• 2002

The anisotropic Raman scattering properties of oriented syndiotactic poly propylene have been investigated using FT-Raman spectrometer in which the fluore scent problem of polymer samples can be removed. To assign the observed Raman bands to their respective symmetry species, the anisotropic scattering results for four different combinations of incident and scattered polarization were compared with those predicted by normal coordinate analysis and infrared dichroism measurement data.

• Polymer(Korea)
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• v.35 no.4
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• pp.314-319
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• 2011

The syndiotactic and atactic poly (2-N-carbazoylrnethyl) styrenes were obtained by a half-titanocene catalyst and a radical initiator for the investigation of photophysical properties, especially excimer formation. The atactic polymer exhibited only monomer emission, but the syndiotactic polymer showed both excimer emission and monomer emission resulting from the partial overlapping arrangement of carbazole pendants, The emission band of syndiotactic polymer was considerably dependent on solution concentration and temperature, however atactic polymer was independent because the excimer formation of syndiotactic helical conformation was more favorable than that of the random coil conformation of atactic polymer.

• Polymer Science and Technology
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• v.3 no.6
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• pp.475-480
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• 1992

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.792-797
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• 1994

Force fields of syndiotactic isoregic PVF crystal have been extracted by optimizing a structure of 2,4,6-trifluoroheptane with ab initio Quantum mechanical method with 6-31G * * basis set, and applied to calculate the structure parameters and elastic constants of the material. The cell parameters turned out to be 5.205$\AA$, of a axis(chain axis), 8.457$\AA$, of b axis and 4.621$\AA$ of c axis. These parameters are in fair agreement with those of the atactic X-ray structure(5.04$\AA$, 8.57$\AA$, and 4.95$\AA$,respectively). The young's modulus of defect free syndiotactic PVF crystal was computed to be 267 GPa comparable to those of polyvinilidene fluoride(277-293 GPa) and polyethylene(264-337 GPa) crystals. Bulk modulus value obtained at optimum geometry is more than twice greater than that obtained at experimental geometry due to large difference of elastic compliance constant (especially Sgj element) at these two different geometries.

• Polymer(Korea)
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• v.24 no.5
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• pp.713-720
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• 2000

A polymer/iodine complex film was prepared using syndiotactic poly(vinyl alcohol) (s-PVA) with number-average degree of polymerization of 900 and syndiotactic diad content of 63.1%. In comparison with atactic-PVA/iodine films, degree of polarization of the s-PVA/iodine film was improved up to over 99% although a lower transmittance was obtained. By soaking in iodine/potassium iodide aqueous solution of a lower iodine concentration and subsequent drawing by 4 times, s-PVA/iodine film of a higher transmittance and degree of polarization was produced. The degree of iodine desorption of the s-PVA/iodine film in water were very low. The crystallinity and the d-spacing and crystal size of (100) plane increased at the early stage of soaking time, however, remained constant or decreased slightly with increasing soaking time. In consequence, s-PVA/iodine complex formation took place mainly inside crystal region at the initial stage of soaking time, whereas it occurred outside crystal region or physical adsorption of iodine dominated after sufficient soaking.

• Macromolecular Research
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• v.8 no.6
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• pp.292-297
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• 2000

The theoretical synthesis of the isotactic and syndiotactic poly(methyl methacrylate) were carried out as a model for real polymerization reactions following the normal chain reaction processes by repeating the uniform localization of wave functions with inclusion of the interaction between the end group of the cluster and an attaching molecule by the elongation method, and then, the calculated value was compared with the usual PM$_3$ calculation. The results revealed that a reaction of cluster with monomer molecules has made it possible to calculate the electronic structure and total energy of polymer with nearly infinite length and a matrix of constant dimension. The isotactic poly(methyl methacrylate) is more stable than syndiotactic one. The same tendency have been found between the experimentally measured properties and a calculated total energy to explain the chain motion in isotatic and syndiotactic poly(methyl methacrylate).

• Polymer(Korea)
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• v.25 no.1
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• pp.115-121
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• 2001

High molecular weight syndiotactic poly(vinyl alcohol)(HMW s-PVA) with number-average degree of polymerization of 10000 and syndiotactic diad content of 61.5%/iodine complex film was prepared. Its adsorption and desorption behaviors of iodine in hot water were investigated. In comparison with atactic PVA film or low molecular weight s-PVA film, the degree of solubility of s-PVA film and the iodine desorption of HMW s-PVA/iodine film in hot water were limited to an extremely lower level. As the soaking time increased, the iodine desorption in hot water was increased. This reason might be explained by the fact that as the soaking time increased, so the iodine adsorption increased not by the stable molecular complex between PVA and iodine but by the simple physical adsorption of iodine.

• Korea-Australia Rheology Journal
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• v.13 no.2
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• pp.83-87
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• 2001

The morphology and mechanical properties of the blends of a syndiotactic polystyrene (SPS) and poly-styrene-block-poly(ethylene-co-butylene)-block-polystyrene copolymers (SEBS) with various polystyrene block contents are studied. Mechanical properties, especially elongation at break and impact strength (IS), of the blend depend upon the morphology and interfacial adhesion, which in rum are affected by the viscosity ratio of constituent components and the styrene block content in SEBS. The IS of a blend was affected by the combined effect of rubber content and the interfacial adhesion. A maximum IS was found for a blend with the weight fraction of the PS block in an SEBS of 0.18. The IS of blends with smaller weight fractions of the PS block exhibited lower due to poor interfacial adhesion between SPS/SEBS in spite of a larger amount of rubber block. On the other hand, the IS of blends with larger weight fraction of the PS block becomes smaller due to lower amounts of rubber block in spite of better interfacial adhesion.

• Journal of Adhesion and Interface
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• v.6 no.2
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• pp.1-5
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• 2005

Single crystals of metallocene-catalyzed isotactic polypropylene (iPP) and/or syndiotactic PP (sPP) were prepared and preliminarily characterized. The crystallization was performed utilizing 0.1 % by weight concentrations of each PP in o-xylene in the range of temperature of $40{\sim}90^{\circ}C$. Following the XRD patterns, samples were ${\alpha}$-iPP and antichiral Cell III of sPP. The XRD pattern of iPP shows three ${\alpha}$-form peaks due to the (110), (040), (130) planes at $2{\theta}=14.2^{\circ}$, $17^{\circ}$, $18.8^{\circ}$, respectively. The XRD pattern of sPP is characterized by the presence of the (020) reflection at $16^{\circ}$. The melting point ($123^{\circ}C$ and $148^{\circ}C$, respectively) of the metallocene catalyzed iPP and sPP were generally lower than that of conventional PP ($160{\sim}170^{\circ}C$) due to the misinsertion of the monomer. When metallocene-catalyzed iPP samples were crystallized isothermally from solution grown at a lower temperature, lozenge shape single crystals were observed by transmission electron microscopy (TEM).

• Polymer(Korea)
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• v.27 no.6
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• pp.603-608
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• 2003

Syndiotactic polystyrene (s-PS) presents a very complex polymorphic behavior depending on the sample preparation history and exhibits a solid-solid phase transition. Each different polymorphic structures of the s-PS sample were prepared by annealing the samples from room temperature to 220 $^{\circ}C$. The structural changes induced by annealing were investigated using FTIR and FT-Raman spectroscopy. Although the crystallization kinetics of s-PS are difficult to investigate with DSC due to its fast crystallization rate, it was possible to determine crystallinity changes in the s-PS sample using infrared characteristic peaks with Beer-Lambert's law.