• Title/Summary/Keyword: polybenzoxazole

Search Result 24, Processing Time 0.171 seconds

Preparation of Nanofibers Using Precursor Polymers to Polybenzoxazoles (폴리벤즈옥사졸 전구체를 이용한 나노섬유의 제조)

  • Baik Doo-Hyun;Im Su-Jin
    • Textile Science and Engineering
    • /
    • v.43 no.3
    • /
    • pp.114-120
    • /
    • 2006
  • Polyhydroxyamide, a precursor polymer to polybenzoxazole, was synthesized by low temperature polymerization of dihydroxybenzidine and isophthaloyl chloride. The polyhydroxyamide solution was electro spun under appropriate concentration, viscosity, electrical conductivity, voltage and tip collector distance. Electrospun polyhydroxyamide fibers were heated at the elevated temperature and converted to polybenzoxazole fibers. In this study we investigated the effects of the electrospinning factors, such as solution viscosity, concentration, and electrical conductivity on the fiber formation of polyhydroxyamide during electro spinning. The electrospun polyhydroxyamide nanofibers showed broader DSC endothermic peak as compared to film or powder samples, which was thought to be due to the large sur-face area of nanofiber web.

Hydroxy-Substituted Polyenaminonitrile as a Soluble Precursor for Rigid-Rod Polybenzoxazole

  • Kim, Ji Heung;Lee, Jae Gwan
    • Bulletin of the Korean Chemical Society
    • /
    • v.22 no.9
    • /
    • pp.999-1004
    • /
    • 2001
  • (1-Chloro-2,2-dicyanovinyl)benzene or 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene was reacted with 2-amino-phenol to give the model compound, hydroxy enaminonitrile, which was found to undergo thermal cyclization reaction to form the corresponding benzoxazole. This intramolecular cyclization reaction is expected to occur through nucleophilic attack to electropositive enamine carbon by ortho-hydroxy group on the phenyl ring, which is accompanied by the release of neutral malononitrile through rearrangement. From each bifunctional monomer, o-hydroxy substituted polyenaminonitrile was prepared and characterized as a new precursor polymer for well-known aromatic polybenzoxazole. Also the unusual macrocyclic dimer formation from the 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane polymerization reaction system was discussed. The thermal cyclization reactions and the properties of polymers were investigated using FT-IR and thermal analysis (DSC & TGA).

  • PDF

Preparation and Characterization of Wholly Aromatic Polybenzoxazole Copolymers Bearing Ether and Bulky Units

  • Han, So Hee;Lee, Eung Jae;Choi, Jae Kon
    • Elastomers and Composites
    • /
    • v.55 no.3
    • /
    • pp.205-214
    • /
    • 2020
  • A series of wholly aromatic polyhyroxyamide (PHA) copolymers were prepared by direct polycondensation reaction of isophthalic acid and diacids containing bulky units with 3,3'-dihydroxybenzidine. The inherent viscosities of the PHAs measured at 35℃ in DMAc solution were in the range of 0.31-0.56 dL/g. The solubility study revealed that the PHAs were readily soluble in aprotic solvents such as, dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP) at room temperature and in less polar solvent such as pyridine. However, the polybenzoxazole (PBO) copoymers were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid and partially soluble in NMP containing LiCl. The PBO copolymers showed maximum weight loss temperature in the range of 593-632℃ and high char yields in the range of 65.0-71.2% at 900℃ in a nitrogen atmosphere.

Synthesis and characterization of polybenzoxazole/graphene oxide composites via in situ polymerization

  • Lim, Jun;Kim, Min-Cheol;Goh, Munju;Yeo, Hyeounk;Shin, Dong Geun;Ku, Bon-Cheol;You, Nam-Ho
    • Carbon letters
    • /
    • v.14 no.4
    • /
    • pp.251-254
    • /
    • 2013
  • In this study, poly(amic acid) was prepared via a polycondensation reaction of 3,3'-dihydroxybenzidine and pyromellitic dianhydride in an N-methyl-2-pyrrolidone solution; reduced graphene oxide/polybenzoxazole (r-GO/PBO) composite films, which significantly increased the electrical conductivity, were successfully fabricated. GO was prepared from graphite using Brodie's method. The GO was used as nanofillers for the preparation of r-GO/PBO composites through an in situ polymerization. The addition of 50 wt% GO led to a significant increase in the electrical conductivity of the composite films by more than sixteen orders of magnitude compared with that of pure PBO films as a result of the electrical percolation networks in the r-GO during the thermal treatment at various temperatures within the films.

Effect of Heat-Treatment on Carbonization Behavior of Hetero-cyclic Aromatic Polymers for Carbon Material Precursors (탄소재료 전구체로 사용가능한 헤테로 고리방향족 고분자의 탄화거동에 대한 열처리 온도의 영향)

  • Kang, Chan Sol
    • Textile Science and Engineering
    • /
    • v.57 no.3
    • /
    • pp.133-142
    • /
    • 2020
  • In this study, carbonized polyhydroxyamide (C-PHA) and polybenzoxazole (C-PBO) precursors were prepared from PHA and PBO polymers, respectively, through heattreatment of 600-1200 ℃ for 1 h under nitrogen atmosphere. Fourier-transform infrared spectroscopy (FT-IR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), thermographic and mass spectrometry, wide-angle X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and electrical conductivity test were performed to monitor the changes in the chemical structures of the two precursors. From FT-IR, EA, and XPS results, PHA and PBO polymers were directly converted to C-PHA and C-PBO precursors, respectively, above 800 ℃ without undergoing the oxidative stabilization process. The maximum carbonization yield of the carbonized precursors was 1.36 times (68.3%) higher than that of the commercialized PAN-based carbon fiber (50%). High-resolution transmission electron microscopy images revealed a small amount (~30%) of turbostratic graphite structure around an external area in the C-PBO precursor at 1000 ℃.

Thermal Cyclization behaviors of PHA and PHA-PAA Copolymers (PHA 및 PHA-PAA 공중합체의 열적 고리화 거동)

  • 이광희;김명균;백두현
    • Proceedings of the Korean Fiber Society Conference
    • /
    • /
    • pp.359-360
    • /
    • 2001
  • 헤테로고리 방향족 polybenzoxazole(PBO)은 대표적인 내열성 고분자로서, 고온에서의 열적안정성 및 내화학성, 기계적 물성, 방염성 등에서 우수한 성질을 나타낸다. 그러나 황산과 같은 강산에만 용해되기 때문에 가공성 면에서 단점을 가지고 있어 사용하는데 있어 제약이 따른단 현재 이러한 단점을 보완하기 위해 polyhydroxyamide(PHA)와 같은 전구체 고분자에 대한 연구가 많은 연구자들에 의해 진행되고 있다. (중략)

  • PDF

Optical Transmittance of Polybenzoxazole Precursor (폴리벤조옥사졸 전구체의 광투과도 연구)

  • 김대겸;김종화;최길영;오재민;이무영;박동원;이광섭;진문영
    • Polymer(Korea)
    • /
    • v.26 no.1
    • /
    • pp.18-27
    • /
    • 2002
  • Poly(ο-hydroxyamide)s as polybenzoxazoles precursors were synthesized by polycondensation from 2,2'-bis(3-amino-4-hydroxyphenyl) hexafluoropropane and various bis-acids. And the polymers were modified to acid-sensitive polyamides by introducing tetrahydropyran in order to impart photosensitivity. A study of optical transmittance at 365 nm, according to the chemical structure of bis-acid, revealed that the polymer derived from 4,4'-oxydibenzoic acid showed better optical transparency than those from other bis-acids. This tendency of optical transmittance could be explained by formation of charge transfer complex. In case of the polymer derived from 4,4'-oxydibenzoic acid, the electron accepting characteristic of bis-acid is reduced by introduction of electron donating group, -O-. Thus, optical transmittance increased due to the diminished formation of intramolecular charge transfer complex. In addition, the optical transmittance increased with increasing the THP content in the polymer. This is attributed to the reduced intermolecular interaction by the loosening of the packing density of the polymer chain.