• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.156-159
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• 1994

The electrical property of polyvinylalcohol (PVA) films (several hundreds ∼ several $\mu\textrm{m}$ in thickness) formed by sphere bulb blowing technique, has been studied. The electrical conductivity of relatively thick films (>several thousands ) has been very high and enhanced by the exposure either to high humidity fo air or NH$_3$. which can be explained in terms of the role of ionic transport. The use of PVA film as NH$_3$ sensor is also proposed. In PVA films less than 1500 , two conducting states: high conducting and low conducting states, are observed.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.145-146
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• 1994

• Journal of Plant Biology
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• v.36 no.4
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• pp.313-319
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• 1993

Photoproduction of hydrogen by free and polyvinylalcohol (PVA)-immobilized spinach chloroplasts was investigated. Immobilization of chloroplast with PVA increased the functional stability of the chloroplast during storage. PVA-immobilized chloroplasts preserved photosynthetic electron transport activity much better than free chloroplasts. The hydrogen production of free chloroplast decreased to 17% of initial activity after storage of six days. The hydrogen production of the PVA-immobilized chloroplast, however, showed 44% of initial activity after storage of 15 days. The maximal rate of hydrogen production was accomplished at 2$^{\circ}C$ under the light intensity above 116 $\mu$E.m-2.s-1. The amount of hydrogen produced was proportional to the chlorophyll concentration. The hydrogen production was inhibited by DCMU treatment, indicating hydrogen production is dependent on photosynthetic electron transport. These results suggest that PVA is a good candidate for the immobilization matrix of chloroplasts for the photoproduction of hydrogen.

• Journal of Plant Biology
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• v.34 no.3
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• pp.215-221
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• 1991

Photoxynthetic properties of polyvinylalcohol (PVA)-immobilized chloroplast especially regarded to stability of photosynthetic electron transport and the fluorescence induction pattern were studied. When isolated spinach chloroplasts were immobilized with PVA, it showed good preservation of photosynthetic electron transport activity, especially PS II activity, during storage at -15$^{\circ}C$, 4$^{\circ}C$ and 2$0^{\circ}C$. And immobilized chloroplasts revealed similar thermostability of whole chain electron transport to free chloroplsts. And the absorption peak of red band of chloroplasts showed the blue-shift of 2-4 nm after immobilization. Fv/Fm ratio of chlorophyll fluorescence slightly decreased after immobilization. White light pulse after continuous light do not induced the additional fluorescence rise. This means chlorophyll fluorescence at room temperature reached to Fmax under continuous light in the immobilized chloroplasts. It seems that PVA may be a good candidate for immobilization matrix for the preservation of photosynthetic function of thylakoids and for the continuous use of chloroplast membranes of higher plants for solar energy storage and conversion.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.223-226
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• 1998

Polyvinylalcohol (PVA) is a crystalline polymer, capable of hydrogen bonding, which makes the polymer useful for many industrial applications. production of high strength fibers, medical substitutes, adhesives, and so on[1], Specially, among fiber-forming polymers, PVA has the second highest crystal modulus and extreme strength after polyethylene because the polymer chain can take a planar zig-zag conformation. (omitted)

• KSBB Journal
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• v.8 no.2
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• pp.185-191
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• 1993

Highly stable $O_2$-evolving cells and thylakoid membranes have been obtained from the cyanobacterium, Synechococcus PCC7002, by immobilization with polyvinylalcohol(PVA). The absorption peak showed the blue-shift of about 3 nm after immobilization of intact cells and thylakoid membranes as well as isolation of thylakoid membranes. Photosynthetic electron transport activities, especially PS II activity showed greater stability in the PVA-immobilized cells and thylakoid membranes when stored at $4^{\circ}C$ than in those at $25^{\circ}C$. When the cells were threated at higher temperature, the level of Fo and Fv increased. After imobilization, however, Fo showed no change. This suggests that the immobilization can protect against the damages of PS II complex, especially a water-spiliting system, by heat treatment.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.131-136
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• 1992

New graft copolymers were synthesized by grafting 2,2,2-trifluoroethylmethacrylate on polyvinylalcohol in aqueous solution with $Ce^{4+}$ ions as initiator. Surface free energies of copolymers having various grafting percentages were studied by measurements of contact angles for various liquids. As the grafting of perfluoroalkyl group increases, surface free energy of solid decreases. Estimation of critical surface free energy should be accounted for molecular properties because the polar force components of these solids are relatively great. ${\gamma}_c$ was calculated from the plot of ${\gamma}_{si}$ vs ${\Phi}_{sl}$.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.298-304
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• 1992

Flexural strength, microstructure, hydration reaction and moisture sensitivity in macro defect-free (MDF) cement, which basically prepared of high alumina cement (HAC) and hydroxypropyl methylcellulose (HPMC) and polyvinylalcohol (PVA) as water soluble polymer were investigated. Cement composites based on HAC-PVA system were improved in flexural strength than that of HAC-HPMC system especially, the strength of specimens added to 10 wt% of polyvinylalcohol was 160 MPa. These improvements of flexural strength were attributed to not only the effect of water soluble polymer in elimination of macropores (above 100 $\mu\textrm{m}$) and cement grain bridging, but the effect of unhydrate cement as an aggregate. Moisture sensitivity and flexural strength in wet condition of MDF cement composites immersed in water at 80$^{\circ}C$ for 3 days were decreased.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.184-189
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• 1995

The electrical property of ultra thin PVA films(several hundreds .angs.-several .mu.m in thickness) formed by sphere bulb blowing technique, has been studied. The electrical conductivity of relatively thick films(>several thousands .angs.) has been very high and enhanced by the exposure either to high humidity of air or $NH_3$, which can be explained in terms of the role of ionic transport. The use of PVA films as NH$_{3}$ sensor is also proposed. In ultra thin PVA films less than 1500.angs., two conducting states ; high conducting and low conducting states, are observed. The nonlinear current-voltage characteristics in the low conducting state and the switching between these two states are also confirmed. These properties are discussed in terms of electronic conduction processes. The breakdown strength of the ultra thin PVA film is found to be very high(-30MV/cm), supporting the electron avalanche process in a thick polymer films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.211-214
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• 1998

The composite of polyvinylalcohol(PVA) and lithium salts(LiBF$_4$) is prepared for a solid-state electrolyte of electric double layer capacitor. The composite shows a good ionic conductivity. The solid-state electric double layer capacitor is made of PVA-LiBF$_4$ composite, activated carbon and etc.. As evaluation of characteristics of capacitor, capacitance change which measured by charge-discharge test with 2.2V~0V at 8$0^{\circ}C$ for 800 hours, was about 10%. The gravimetric and volumetric capacitance were 10.0 F/g~30.0 F/g and 16.0F/㎤~F/㎤, respectively.