• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1491-1494
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• 2014

High-crystallinity poly(3-hexylthiophene) (P3HT) thin films were prepared by aging the precursor solutions, prepared using a good solvent, chloroform, at low temperatures prior to spin-casting. Lower solution temperatures significantly improved the molecular ordering in the spin-cast P3HT films and, therefore, the electrical properties of field-effect transistors prepared using these films. Solution cooling enhanced the electrical properties by shifting the P3HT configuration equilibrium away from random coils and toward more ordered aggregates. At room temperature, the P3HT molecules were completely solvated in chloroform and adopted a random coil conformation. Upon cooling, however, the chloroform poorly solvated the P3HT molecules, favoring the formation of ordered P3HT aggregates, which then yielded more highly crystalline molecular ordering in the P3HT thin films produced from the solution.

• Korean Journal of Crystallography
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• v.12 no.2
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• pp.81-87
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• 2001

We have studied the effect of sintering temperature and time on the cation ordering and second phase formation in Ba(Mg/sub 1/3/Nb/sub 2/3/)O₃(BMN) microwave ceramics by using transmission electron microscopy. The relationship between the structural-chemical behavior arid microwave dielectric properties has also been investigated. It is revealed that according to the sintering conditions the BMN ceramics show very diverse local ordering behavior, such as the development of domain twinning and "core-shell"-structured grains and the formation of local disordered domains, though having 1 : 2 cation ordering structure basically. The disordered structure is found in Mg-excess region. Such local chemical variation seems to be caused by the formation of BaNb₂O/sub 6/-like second phase in its neigh-boring grain boundary. The microwave dielectric quality factor of the ceramics decreases greatly with the increase of the structural-chemical inhomogeneity and diversity.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.352-356
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• 2011

In this paper, we prepared new type of hydrophilic block copolymers that exhibit the long-ranged lateral ordering in thin film. It was previously demonstrated that poly(ethyleneoxide-b-styrene) and poly(ethyleneoxide-b-metharylate-b-styrene) block copolymer thin films have a high degree of lateral ordering after solvent annealing process. In these cases, the relative humidity plays an important role in long-ranged lateral ordering. However, the origin of the humidity effect on the orders of these hydrophilic block copolymers is not fully understood. To investigate the effect of the humidity further, we prepared other hydrophilic poly(N,N-dimethylacrylamide-b-styrene)(PDMA-b-PS) block copolymers via RAFT polymerization. As with PEO-containing block copolymers, PDMA-b-PS block copolymers exhibit the long-ranged lateral ordering after solvent annealing process.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.199-206
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• 1991

A statistical thermodynamic theory of thermotropic main-chain polymeric liquid crystalline melts is developed within the framework of the lattice model by a generalization of the well-known procedure of Flory and DiMarzio. According to the results of Vasilenko et al., the theory of orientational ordering in melts of polymers containing rigid and flexible segments in the main chain is taken into account. When the ordering of flexible segments in the nematic melt is correlated with that of rigid mesogenic groups, the former is assumed to be given as a function of the ordering of rigid mesogenic cores. A free energy density that includes short-range packing contributions is formulated. The properties of the liquid-crystalline transiton are investigated for various cases of the system. The results calculated in this paper show not only the order-parameter values but also the first-order phase transition phenomena that are similar to those observed experimentally for the thermotropic liquid-crystalline polymers and show the transitional entropy terms which actually increase upon orientational ordering. In the orientational ordering values, it is shown that mesogenic groups, flexible segments, and gauche energy (temperature) may be quite substantial. Finally, by using the flexibility term, we predict the highly anisotropic mesophase which was shown by Vasilenko et al.

• Applied Microscopy
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• v.32 no.1
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• pp.9-15
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• 2002

Microstructural investigations of $(1-x)NdAlO_3-xCaTiO_3$ (NACT) complex perovskite compounds were carried out using X-ray diffractometry, neutron diffraction and transmission electron microscopy. When $0.3{\leq}x{\leq}0.9$, NACT had not only the 1 : 1 chemical ordering of cations but also the antiphase and inphase tilting of oxygen octahedron and the antiparallel shift of cations. Both the antiphase boundaries and the ferroelastic domains were present in the microstructure. The long and straight ferroelastic domains became degenerate as x decreases. When x was smaller than 0.3, the chemical ordering was absent and the antiphase tilting of oxygen octahedron was observed. The defects like tangled dislocations and the second phase were also found in the microstructure.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.147-148
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• 2005

We report on high-performance organic field-effect transistors by promoting surface-mediated two-dimensional molecular ordering in organic semiconductor. To achieve this goal, we have controlled the intermolecular interaction at the interface between organic semiconductor and the insulator substrate.

• Polymer(Korea)
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• v.38 no.2
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• pp.188-192
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• 2014

In this work, it is possible to simply improve the molecular ordering of a conjugated polymer thin film by dipping into poor solvent. The structural order, optical, and electrical properties of poly(3-hexylthiophene) (P3HT) films were profoundly influenced by dipping time and solubility of solvent. Especially the dipping time in methylene chloride was controlled to efficiently improve the molecular ordering of the P3HT. The correlation between the structural order and the electrical properties was used to optimize the dipping time in the appropriate solvent.

• International Journal of Advanced Culture Technology
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• v.9 no.3
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• pp.271-276
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• 2021

In this paper we analyze the effect of the credit period on inventory policy under trade credit with ordering cost including a fixed cost and freight cost, where the freight cost has a quantity discount. For marketing purposes, some supplier offers credit period to his buyer to stimulate the demand for the product he produces. The delay in payments during the credit period has the effect of reducing the buyer's capital opportunity cost. It is also assumed that the buyer pays the freight cost for the order and hence, the ordering cost consists of a fixed ordering cost and a variable freight cost which depends on the order quantity. As a result, the possibilities of trade credit and discounts on freight costs are expected to play an important role in the buyer's inventory policy. Based on the economic order quantity inventory model, we analyze how the buyer can determine the optimal inventory policy and we examine the effect of the length of credit period on the buyer's inventory policy.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1210-1213
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• 1997

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.189-189
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• 2006

The self-assembly of supramolecular dendrimers allows the rapid construction of nanosized structures with regularly ordered features that depend on the shape of the molecules and the relative strength of the intra-and intermolecular interactions. Here we report on a dramatic improvement in the degree of control and selectivity in the orientation of fan-shaped supramolecular molecules over a large area, which has been achieved by confined geometries and applied fields. The order and orientation of supramolecular dendrimers can be controlled by surface anchoring in confined geometries. POM, SEM, TEM, AFM and XRD results show that the molecules form the complicated defect-ordering in the microchannels with different feature sizes. We show that these defect domains are strongly influenced by the boundary and feature size of the surfaces. This technique can be used to create a grain size in the plane of the film that is much larger than that which can be achieved using previously reported soft-material based pattering.