Abstract
A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO-(CH2)n-OH, n = 5-10 or 12] in diphenyl sulfone at temperature greater than 230°C with K2CO3 as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14-0.51 dL/g, and the decomposition temperatures were greater than 350°C and decreased from 436 to 379°C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd-even effect: odd ones showed higher transition temperatures (melting and clearning temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed.
| Original language | English |
|---|---|
| Pages (from-to) | 293-301 |
| Number of pages | 9 |
| Journal | Journal of Polymer Science, Part A: Polymer Chemistry |
| Volume | 40 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 2002 Feb 1 |
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All Science Journal Classification (ASJC) codes
- Materials Chemistry
- Polymers and Plastics
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Thermotropic liquid-crystalline poly(oxadiazole)s with poly(methylene) spacers : Preparation and extraordinary odd-even effect. / Tsai, Cheng Jang; Chen, Yun.
In: Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 40, No. 3, 01.02.2002, p. 293-301.Research output: Contribution to journal › Article
TY - JOUR
T1 - Thermotropic liquid-crystalline poly(oxadiazole)s with poly(methylene) spacers
T2 - Preparation and extraordinary odd-even effect
AU - Tsai, Cheng Jang
AU - Chen, Yun
PY - 2002/2/1
Y1 - 2002/2/1
N2 - A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO-(CH2)n-OH, n = 5-10 or 12] in diphenyl sulfone at temperature greater than 230°C with K2CO3 as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14-0.51 dL/g, and the decomposition temperatures were greater than 350°C and decreased from 436 to 379°C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd-even effect: odd ones showed higher transition temperatures (melting and clearning temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed.
AB - A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO-(CH2)n-OH, n = 5-10 or 12] in diphenyl sulfone at temperature greater than 230°C with K2CO3 as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14-0.51 dL/g, and the decomposition temperatures were greater than 350°C and decreased from 436 to 379°C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd-even effect: odd ones showed higher transition temperatures (melting and clearning temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed.
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U2 - 10.1002/pola.10106
DO - 10.1002/pola.10106
M3 - Article
VL - 40
SP - 293
EP - 301
JO - Journal of Polymer Science, Part A: Polymer Chemistry
JF - Journal of Polymer Science, Part A: Polymer Chemistry
SN - 0887-624X
IS - 3
ER -