• Title, Summary, Keyword: the number of methylene units

Search Result 20, Processing Time 0.037 seconds

Miscibility Map for Binary Blends of Poly(m-methylene 2,6-naphthalate) (폴리(m-메틸렌 2,6-나프탈레이트)들의 고분자쌍 블렌드에 대한 상용성 지도)

  • Lee, Mi Jin;Lee, Sang Cheol
    • Textile Science and Engineering
    • /
    • v.50 no.2
    • /
    • pp.83-87
    • /
    • 2013
  • Binary blends of poly(m-methylene 2,6-naphthalate) (PmN, m=2-8) were prepared by the solution-blending method and their miscibility was investigated with glass transition, crystallization, and melting behaviors, which were obtained from differential scanning calorimetry. It was determined that all the blends in which the difference in the number of methylene units between two component polymers was one were miscible. The blends in which the difference in the number of methylene units was two show divergent miscibility: two miscible, two partially miscible, and one immiscible systems. Among the blends in which the difference in the number of methylene units was three, two systems were partially miscible and the other two were immiscible. All the blends in which the difference in the number of methylene units was four or more were immiscible. It was thus found that the difference in the number of methylene units between two component polymers in the blend is the primary structural factor affecting the miscibility of a binary blend of PmN. The border between miscible blends and immiscible ones was found to be at differences in methylene-unit numbers of two or three.

Poly(ether-ester) Multiblock Copolymers Based on Poly(oxymethylene-alt-oxyalkylene) Glycols

  • Kim, Jin-Bong;Chun, Jae-Hwan;Kim, Dong-Hee;Park, Yun-Hee;Lee, Moo-Sung
    • Macromolecular research
    • /
    • v.10 no.4
    • /
    • pp.230-235
    • /
    • 2002
  • Alternating polyols of oxymethylene and oxyalkylene were synthesized and used as precursors for thermoplastic poly(ether-ester) elastomers (TPEs). The polyols were synthesized by reacting diols having different methylene units with dichloromethane in the presence of a phase transfer catalyst. The number of methylene units in the alkylene oxides was varied from 3 to 6. TPEs were prepared using the polyols as soft segments and poly(butylene terephthalate) units as hard segments. The polyols and TPEs synthesized were characterized using FTIR, NMR, GPC, DSC, and polarized optical microscopy. The polyols showed a profound odd-even effect on the melting (T$_{m}$) and glass transition temperatures (T$_{g}$). Polyols with odd numbers of methylene groups in the alkylene units have higher transition temperatures than polyols with odd number of methylene groups. The tendency is still kept in TPEs, even though the T$_{g}$ of soft segment in TPEs are slightly higher than those of corresponding neat polyols. The T$_{m}$ and T$_{g}$ of soft segments are almost constant in the range of 20 to 60 wt % contents of soft segments. On the other hand, the normalized heat of fusion of hard segment decreased with increasing the content of loft segment.ent.t.ent.

The Gas Liquid Partition Coefficients of Eleven Normal, Branched and Cyclic Alkanes in Sixty Nine Common Organic Liquids II: The Effect of Solvent Structure

  • Cheong, Won-Jo
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.8
    • /
    • pp.1207-1210
    • /
    • 2003
  • The effect of solvent structure on the slope in the plot of ln K vs. solute carbon number was examined. It was found that the free energy of methylene group transfer from the gas phase into a solvent was always negative and that the absolute magnitude of interaction free energy between the methylene group and the solvent was always larger than the absolute magnitude of cavity formation free energy of the methylene group in the solvent. Thus, the slope in the plot of ln K vs. solute carbon number was always positive and its value decreases with increase of solvent polarity since the cavity formation energy of the CH₂ unit increases with increase of solvent polarity while the dispersive interaction energy of the CH₂ unit is virtually invariant. We also examined the effect of sequential addition of CH₂ unit to a solvent molecule upon ln K for three homologous series of solvents: n-alkanes, n-alcohols, and n-nitriles. Characteristic trends in the plots of ln K vs. solvent carbon number were observed for individual solvent groups. A decrease of ln K with solvent carbon number was observed for n-alkanes. An abrupt increase in ln K followed by levelling off was observed for n-alcohols while a final slight decrease in ln K after an abrupt increase followed by rapid levelling off was noted for n-nitriles. All of theses phenomena were found related to variation in cavity formation energy. It was clearly shown that a structural change of a polar solvent by sequential addition of CH₂ units causes an abrupt polarity decrease initially, then gradual levelling off, and finally, conversion to a virtually nonpolar solvent if enough CH₂ units are added.

Studies on the Maximum Transfer Rate of Printing Ink (인쇄 잉크의 최대 전이율에 관한 연구)

  • 강상훈
    • Journal of the Korean Printing Society
    • /
    • v.13 no.1
    • /
    • pp.1-12
    • /
    • 1995
  • Polymeric mesogens having a regularly alternating rigid-flexible repeating structure in the main-chain polymer exhibit distinct even-odd oscillation in their thermodynamic quantities with respect to the number of methylene units in the spacer. The even-odd oscillation depends on the number of methylene groups in the spacer the entropy change at the NI(nematic-isotropic) phase transition becomes less distinct when the linking group is replaced by the carbonate. In our previous work, we have suggested that the characteristics arise from the geometrical arrangement of the linkage. In this work, we have prepared a series of carbonate-type monomer and dimer liquid crystals. The thermodynamic behaviors at the NI phase transition have been compared with those previous reported for the ether- or ester-type liquid crystals. For the dimer series, the orientational order parameter of the mesogenic core was determined by using H-NMR technique. The origin of the difference observed among linking groups was found to the geometrical characteristics of chemical structure.

  • PDF

The Ester Interchange Reactions of Poly)n-methylene terephthalate) of Poly(ethylene naphthalate)/Polycaprolactone Melt Blends (폴리(n-메틸렌테레프탈레이트) 또는 폴리에틸렌나프탈레이트/폴리카프로락톤 용융 블렌드들의 에스테르 교환반응 거동)

  • 윤기종;임경율
    • Textile Science and Engineering
    • /
    • v.37 no.9
    • /
    • pp.500-510
    • /
    • 2000
  • To investigate the effects of chain structures, such as the number of methylene groups and different aromatic units in polyesters, on the ester interchange reaction during melt blending, PCL was blended with PET, PTT, PBT of PEN. The ester interchange reaction of blends was characterized by $^{1}H$-NMR and the thermal property, crystal structure and morphology of blends were studied by DSC, X-ray and SEM analyses. The ester interchange reactions could be confirmed in PET/PCL and PTT/PCL blends, but did not occur significantly in PBT/PCL and PEN/PCL blends. At the higher degree of ester interchange reaction, melting temperature of blends decreased and the morphology of blends changed to a homogeneous phase. It appears that ester interchange reaction during melt blending is affected by the chain structure of polyester as well as the concentration of terminal alcohol, carboxyl and ester groups.

  • PDF

Thermotropic Liquid Crystalline Behaviors of 4-{4'-(nitrophenylazo)phenoxy}alkanoic Acids and 4-{4'-(nitrophenylazo)phenoxy}alkanoyl Chlorides (4-{4'-(니트로페닐아조)펜옥시}알칸 산들 그리고 4-{4'-(니트로페닐아조)펜옥시}알카노일 클로라이드들의 열방성 액정 거동)

  • Jeong, Seung Yong;Ma, Yung Dae
    • Applied Chemistry for Engineering
    • /
    • v.19 no.5
    • /
    • pp.504-511
    • /
    • 2008
  • Two kinds of nitroazobenzene derivatives: 4-{4'-(nitrophenylazo)phenoxy}alkanoic acids (NAAn, n = 2~8, 10, number of methylene units in the alkyl chain) and 4-{4'-(nitrophenylazo)phenoxy}alkanoyl chlorides (NACn, n = 2~8, 10) were synthesized, and their thermotropic liquid crystalline behaviors were investigated. NAA6 formed an enantiotropic nematic phase, while the remainders, except NAA2, showed monotropic nematic phases. Isotropic-nematic transition temperature ($T_{iN}$) and change of entropy (${\Delta}S$) at $T_{iN}$ for both of NAAn and NACn varied by the change of n, and pronounced odd-even effects of n were also observed. However, the $T_{iN}$ and ${\Delta}S$ values of NAAn were much higher than those of NACn. This fact may be attributed to the hydrogen bonding between carboxyl groups. Thermal properties and degree of order in the mesophase and the magnitude of the odd-even effects of both NAAn and NACn were significantly different from those reported for 4-(alkoxy)-4'-nitroazobenzenes. It was discussed in terms of the differences in the molecular anisotropy and the temperature-dependent flexibility of the substituted groups.

Liquid Crystal Polymers (X). Synthesis and Properties of New Thermotropic Main Chain Copolyesters with Either Mixed Polymethylene Spacers or Mixed Mesogenic Units (액정 중합체 (제10보). 혼합폴리에틸렌 격자나 메소젠 단위를 갖고 있는 새로운 주사슬 혼성폴리에스테르의 합성 및 성질)

  • Jung-Il Jin;Robert W. Lenz;S. Antoun
    • Journal of the Korean Chemical Society
    • /
    • v.26 no.3
    • /
    • pp.188-193
    • /
    • 1982
  • Four new thermotropic copolyesters were prepared and their liquid crystal properties were investigated by differential scanning calorimetry and on a hot-stage of a polarizing microscope. Three copolyesters had same mesogenic unit, triad aromatic ester structure, interconnected through a random combination of either odd-even, or odd-odd, or even-even number of methylene groups in the polymethylene flexible spacers. Another random copolyester consisted of mesogenic units of 1 : 1 mixture of central methyl-and bromohydroquinone moieties with two flanking p-oxybenzoate units connected by decamethylene spacer. All of the polyesters formed nematic liquid crystal phase upon melting. The transitions for melting and nematic ${\to}$ isotropic transformations could be reversibly observed by DSC as well as by microscopic study. The thermodynamic properties for their liquid crystal ${\to}$ isotropic phase transitions were discussed in relation to their chemical structures.

  • PDF

Sensitization of Periodontitis Disease Causing Bacteria by Low Power He-Ne Laser Radiation

  • Satsangi, Akash Tripathi;Mathur, Manish;Saxena, Parul;Prasad, Guru;Shrivastava, Jitendra Nath;Shrivastava, Jenendra Nath;Roy, Sukhdev
    • Journal of Photoscience
    • /
    • v.11 no.32
    • /
    • pp.55-59
    • /
    • 2004
  • The present investigation is an attempt to create an optimized protocol for a bactericidal modality of different powers of He-Ne laser radiation to eliminate periodontitis disease causing bacteria from dental plaques. Periodontitis is most prevalent infectious disease of men and caused by a limited number of Gram negative oral bacteria. Porphyromonas gingivalis and Streptococcus sanguis are the important bacteria responsible for periodontitis diseases. Effect on periodontitis disease causing bacteria were produced by the exposure of different powers of He-Ne laser light i.e. 9 mW, 17 mW and 26 mW of red colour of wavelength 632.8 nm in two different periods of time i.e. 10 min. and 20 min. in the presence of dye Methylene blue (MB) used as a photosensitizer. The results have been shown in terms of percentage inhibition of colony forming units (cfu.) of bacteria. This study has shown that maximum inhibition of cfu. were observed in Laser+MB-20 min. exposure time. This inhibition was followed by Laser+MB-10 min., but minimum inhibition was seen in Laser only at 10 min. exposure. In case of effect of methylene alone on the cfu. of bacteria, it was seen that MB have not shown more inhibition of cfu. and it had shown that the no. of cfu. are very similar to that of control. The above observation of the present study was seen in case of every 3 different type of used powers of laser for both the bacteria. Maximum percentage inhibition of cfu. were seen in case of 26mW powers of He-Ne laser, which was 67. 28% to 61.42% for Porphyromonas gingivalis and Streptococcus sanguis respectively. So, increasing the power of laser (safe range for dentistry is 3-30 mW) under conditions shows an increased percentage inhibition of cfu. Thus the present investigation may be a useful adjunct with mechanical debridement in the prevention of recolonization of subgingival lesions by pathogenic microorganisms which are harmful and drug resistant.

  • PDF

Thermotropic Liquid Crystalline Behavior of [4-{4'-(Nitrophenylazo)phenoxycarbonyl}]alkanoated Celluloses ([4-{4'-(니트로페닐아조)펜옥시카보닐}]알카노화 셀룰로오스들의 열방성 액정 거동)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer Korea
    • /
    • v.33 no.1
    • /
    • pp.58-66
    • /
    • 2009
  • The thermotropic liquid crystalline behavior of the homologous series of cellulose tri[4-{4'-(nitrophenylazo) phenoxycarbonyl}] alkanoates (NACEn, n=2$\sim$8, 10, the number of methylene units in the spacer) have been investigated. All of the homologoues formed monotropic nematic phases. The isotropic-nematic transition temperature ($T_{iN}$) decreased when n is increased up to 7, but it became almost constant when n is more than 7. The plot of transition entropy at $T_{iN}$ against n had a sharp negative inflection at n=7. The sharp change at n=7 may be attributed to the difference in arrangement of the side groups. The melting temperature ($T_m$) and associated entropy change at $T_m$, in contrast with $T_{iN}$ and associated entropy change at $T_{iN}$, exhibited a distinct odd-even effect, suggesting that the average shape of the side chains in the crystalline phase is different from that in the nematic phase. The thermal stability and degree of order of the nematic phase observed for NACEn were significantly different from those reported for the homologous series of side-chain and combined type liquid crystal polymers bearing azobenzene or biphenyl units in the side chains. The results were discussed in terms of the differences in the chemical structure, the flexibility of the main chain, the mode of chemical linkage of the side group with the main chain, and the number of the mesogenic units per repeating unit.

Thermal and Optical Properties of Poly{1-(Cholesteryloxycarbonylalkanoyloxy)ethylene}s (폴리{1-(콜레스테릴옥시카보닐알카노일옥시)에틸렌}들의 열 및 광학 특성)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer Korea
    • /
    • v.33 no.2
    • /
    • pp.144-152
    • /
    • 2009
  • The thermal and optical properties of poly {1-(cholesteryloxycarbonylalkanoyloxy) ethylene}s (PCALEn, n=2$\sim$8,10, the number of methylene units in the spacer) were investigated. All of the homologues formed monotropic cholesteric phases with left-handed helical structures. PCALEn with n=2 or 10, in constrast with PCALEn with $3{\leq}n{\leq}8$, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the polyethylene chain. The glass transition temperatures decreased with increasing n. The isotropic-cholesteric phase transition temperatures decreased with increasing n up to 7 and showed an odd-even effect. However it became almost constant when n is more than 7. This behavior is rationalized in terms of the change in the average shape of the side chain on varing the parity of the spacer. This rationalization also accounts for the observed variation of the entropy gain for the clearing transition. The thermal stability and degree of order in the mesophase and the temperature dependence of the optical pitch observed for PCALEn were significantly different from those reported for cellulose tri(cholesteryloxycarbonyl)alkanoates. The results were discussed in terms of the differences in the chemical structure and flexibility of main chain and the number of the mesogenic units per repeating unit.