Synthesis and properties of liquid crystalline polyacetylenes with different spacer lengths and bridge orientations

Jacky W.Y. Lam, Xiangxing Kong, Yuping Dong, Kevin K.L. Cheuk, Kaitian Xu, Ben Zhong Tang

Research output: Contribution to journalArticle

135 Citations (Scopus)

Abstract

A group of mesomorphic polyacetylenes with different lengths of alkyl spacer -{HC=C[(CH2)m- OCO-Biph-OC7H15]}n-[1(m), m = 2, 3, 4, 9] and orientations of ester bridge -{HC=C[(CH2)3-CO2- Biph-OC7H15]}n- [2(3)] are synthesized, and the effects of the structural variables on the properties of the polymers are investigated. The liquid crystalline acetylene monomers n-{[(4′-heptoxy-4-biphenylyl)oxy]carbonyl }-1-alkynes 3(m) and 5-{[(4′-heptoxy-4- biphenylyl)carbonyl]oxy}-1-pentyne 4(3) are prepared by consecutive etherification and esterification reactions. The Tm and Ti values of 3(m) decrease with an increase in the spacer length (m). While 3(3) shows a monotropic SmA phase, its counterpart with a different ester orientation 4(3) exhibits an enantiotropic SmB phase. The monomers are polymerized by transition-metal halides and carbonyls, and the polymerizations catalyzed by WCl6-Ph4Sn under optimal conditions produce polymers with high molecular weights (up to 1.2 × 105) in high yields (up to 92%). The structures and properties of the polymers are characterized and evaluated by IR, UV, TGA, DSC, POM, and XRD analyses. With the increase in the spacer length, the thermal stability of the polymers increases, their Tg and Ti decrease, and the packing arrangements in their mesophases change from mixed mono- and bilayer structures to a homogeneous monolayer structure. Compared to 1(3), 2(3) shows a blue-shifted absorption spectrum (Δλmax >30 nm), a higher Tg and Ti (ΔT approx. 40°C), and a better packed SmAd structure.

Original languageEnglish (US)
Pages (from-to)5027-5040
Number of pages14
JournalMacromolecules
Volume33
Issue number14
DOIs
StatePublished - Jul 11 2000

Fingerprint

Polyacetylenes
Crystal orientation
Polymers
Crystalline materials
Liquids
Monolayers
Esters
Monomers
Metal halides
Acetylene
Alkynes
Esterification
Transition metals
Absorption spectra
Thermodynamic stability
Molecular weight
Polymerization

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

Lam, Jacky W.Y. ; Kong, Xiangxing ; Dong, Yuping ; Cheuk, Kevin K.L. ; Xu, Kaitian ; Tang, Ben Zhong. / Synthesis and properties of liquid crystalline polyacetylenes with different spacer lengths and bridge orientations. In: Macromolecules. 2000 ; Vol. 33, No. 14. pp. 5027-5040.
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abstract = "A group of mesomorphic polyacetylenes with different lengths of alkyl spacer -{HC=C[(CH2)m- OCO-Biph-OC7H15]}n-[1(m), m = 2, 3, 4, 9] and orientations of ester bridge -{HC=C[(CH2)3-CO2- Biph-OC7H15]}n- [2(3)] are synthesized, and the effects of the structural variables on the properties of the polymers are investigated. The liquid crystalline acetylene monomers n-{[(4′-heptoxy-4-biphenylyl)oxy]carbonyl }-1-alkynes 3(m) and 5-{[(4′-heptoxy-4- biphenylyl)carbonyl]oxy}-1-pentyne 4(3) are prepared by consecutive etherification and esterification reactions. The Tm and Ti values of 3(m) decrease with an increase in the spacer length (m). While 3(3) shows a monotropic SmA phase, its counterpart with a different ester orientation 4(3) exhibits an enantiotropic SmB phase. The monomers are polymerized by transition-metal halides and carbonyls, and the polymerizations catalyzed by WCl6-Ph4Sn under optimal conditions produce polymers with high molecular weights (up to 1.2 × 105) in high yields (up to 92{\%}). The structures and properties of the polymers are characterized and evaluated by IR, UV, TGA, DSC, POM, and XRD analyses. With the increase in the spacer length, the thermal stability of the polymers increases, their Tg and Ti decrease, and the packing arrangements in their mesophases change from mixed mono- and bilayer structures to a homogeneous monolayer structure. Compared to 1(3), 2(3) shows a blue-shifted absorption spectrum (Δλmax >30 nm), a higher Tg and Ti (ΔT approx. 40°C), and a better packed SmAd structure.",
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Synthesis and properties of liquid crystalline polyacetylenes with different spacer lengths and bridge orientations. / Lam, Jacky W.Y.; Kong, Xiangxing; Dong, Yuping; Cheuk, Kevin K.L.; Xu, Kaitian; Tang, Ben Zhong.

In: Macromolecules, Vol. 33, No. 14, 11.07.2000, p. 5027-5040.

Research output: Contribution to journalArticle

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T1 - Synthesis and properties of liquid crystalline polyacetylenes with different spacer lengths and bridge orientations

AU - Lam, Jacky W.Y.

AU - Kong, Xiangxing

AU - Dong, Yuping

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AB - A group of mesomorphic polyacetylenes with different lengths of alkyl spacer -{HC=C[(CH2)m- OCO-Biph-OC7H15]}n-[1(m), m = 2, 3, 4, 9] and orientations of ester bridge -{HC=C[(CH2)3-CO2- Biph-OC7H15]}n- [2(3)] are synthesized, and the effects of the structural variables on the properties of the polymers are investigated. The liquid crystalline acetylene monomers n-{[(4′-heptoxy-4-biphenylyl)oxy]carbonyl }-1-alkynes 3(m) and 5-{[(4′-heptoxy-4- biphenylyl)carbonyl]oxy}-1-pentyne 4(3) are prepared by consecutive etherification and esterification reactions. The Tm and Ti values of 3(m) decrease with an increase in the spacer length (m). While 3(3) shows a monotropic SmA phase, its counterpart with a different ester orientation 4(3) exhibits an enantiotropic SmB phase. The monomers are polymerized by transition-metal halides and carbonyls, and the polymerizations catalyzed by WCl6-Ph4Sn under optimal conditions produce polymers with high molecular weights (up to 1.2 × 105) in high yields (up to 92%). The structures and properties of the polymers are characterized and evaluated by IR, UV, TGA, DSC, POM, and XRD analyses. With the increase in the spacer length, the thermal stability of the polymers increases, their Tg and Ti decrease, and the packing arrangements in their mesophases change from mixed mono- and bilayer structures to a homogeneous monolayer structure. Compared to 1(3), 2(3) shows a blue-shifted absorption spectrum (Δλmax >30 nm), a higher Tg and Ti (ΔT approx. 40°C), and a better packed SmAd structure.

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