Synthesis of novel thermotropic liquid crystalline poly(2,3-quinoxalines)

Ito, Yoshihiko; Ihara, Eiji; Uesaka, Tetsuya; Murakami, Masahiro

doi:10.1021/ma00050a050

Cited by 21 publications

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“…4,7 Dibromo 5,6 di(bromomethyl) 2,1,3 benzothiadiazole 1 was utilized conveniently as a versatile synthetic intermediate for substituted 1,2 diisocyanobenzenes. 15 Its reaction with alkoxides under the S N 2 conditions followed by introduction of 4,7 substituents by C C bond forming cross coupling reaction allows synthesis of various benzothiadiazoles, which can be easily converted to 1,2 diisocyanobenzenes through three steps consisting of desulfurization (Red Al (sodium bis(2 methoxyethoxy)aluminumhydride)/H 2 O), formylation (AcOCHO), and dehydration (ClCO 2 CCl 3 /Et 3 N). Liquid crystallinity was observed by the introduction of alkoxy side chains into PQX, depending on the balance of the polymerization degree and the exibility of the alkyl chains.…”

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confidence: 99%

Poly(quinoxaline-2,3-diyl)s: A Fascinating Helical Macromolecular Scaffold for New Chiral Functions

Suginome

Yamamoto²,

Nagata³

2015

J. Synth. Org. Chem. Jpn.

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This paper is dedicated to late Prof. Yoshihiko Ito for his great enthusiasm and contribution to synthetic organic chemistry.Abstract: Studies on the synthesis, helical structure, switchable screw sense induction, catalytic function, and chiroptical properties of poly(quinoxaline 2,3 diyl)s since late 1980 s are described.1141 benzenes. Although there are some other options currently, in the typical procedure, the 3,6 substituted 1,2 phenylenediamines are treated with acetic formic anhydride to obtain the corresponding diformamides, which are subsequently dehydrated by phosgene dimer or POCl 3 in the presence of base, giving substituted 1,2 isocyanobenzanes in moderate to good yields (Scheme 2). 10 The obtained 3,6 substituted 1,2 diisocyanobenzenes are puri ed by column chromatography on silica gel and used in polymerization.Initial attempts at polymerization of those 1,2 diisocyanobenzenes are examined by using nucleophilic organometallic initiators. Reaction of 1,2 diisocyano 3,4,5,6 tetramethylbenzene (M1) in the presence of primary, secondary, and tertiary alkyl Grignard reagents (33 50 mol%) afforded quinoxaline dimer to hexamer in moderate yields (25 34% total isolated yields) (Scheme 3). 11This report was followed by the report on living polymerization of 1,2 diisocyanobenzene using an organopalladium complex as an initiator. 12 1,2 Diisocyanobenzene M1 was oligomerized with monomer/initiator ratios of 2, 3, 5, and 7 at re ux temperature in THF (Scheme 4). After oligomerization, the living palladium center was still at one of the two polymer terminus, being con rmed by isolation and single crystal X ray analysis of a terquinoxalinylpalladium complex. The living oligomers were quenched by Grignard reagents before isolation of the oligomers bearing an organic group derived from the Grignard reagent at the terminus. The degree of oligomerization was dependent on the monomer/initiator ratio with formation of up to octamer in good total yields. Application of this protocol to polymerization of 1,2 diisocyano 3,6 di(trimethylsilylmethyl)benzene (M2) afforded PQX with high molecular weight (M n 4830, vapor pressure osmometry (VPO)) with remarkably small PDI (polydispersity index, 1.08).In addition to the organopalladium complexes, it was also found that organonickel complexes served as highly active initiator in the polymerization of 1,2 diisocyanobenzenes (Scheme 5).13 Isolated 3 arylquinoxalin 2 ylnickel complex was used in the polymerization of 7 and 15 equivalents of M2, giving PQX in high yields with narrow PDI after quenching by Grignard reagents. It should be noted here that direct use of simple arylnickel(II) complex was not attempted in this report. Furthermore, use of Ni(acac) 2 , which is effective in the polymerization of monoisocyanides, was reported to form tarry material. More recently, it has been revealed that simpler nickel compounds including Ni(acac) 2 and NiCl 2 also give PQXs efciently albeit with large PDI (Scheme 6). 14 1,2 Diisocyanobenzene monomers bearing alkoxymethyl side chains was ...

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confidence: 99%

Poly(quinoxaline-2,3-diyl)s: A Fascinating Helical Macromolecular Scaffold for New Chiral Functions

Suginome

Yamamoto²,

Nagata³

2015

J. Synth. Org. Chem. Jpn.

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“…Scheme outlines the synthetic routes of the monomer and the PFO‐P2C 10 BT . 5,6‐Bis(3,7‐dimethyloctyloxymethyl)‐4,7‐dibromo‐2,1,3‐benzothiadiazole ( 4 ) and fluorene‐based monomers 5 and 6 were synthesized using published procedures 26–28. The narrow band gap monomer ( 4 ) was copolymerized with 2,7‐dibromo‐9,9‐dioctylfluorene ( 5 ) and 9,9‐dioctylfluorene‐based diboronic ester ( 6 ) using the Suzuki cross‐coupling method, as described by Chan et al29 The resulting statistical PFO‐P2C 10 BT was precipitated in methanol, filtered, and redissolved in chloroform.…”

Section: Resultsmentioning

confidence: 99%

“…5,6-Bis(3,7dimethyloctyloxymethyl)-4,7-dibromo-2,1,3-benzothiadiazole (4) and fluorene-based monomers 5 and 6 were synthesized using published procedures. [26][27][28] The narrow band gap monomer (4) was copolymerized with 2,7-dibromo-9,9-dioctylfluorene (5) and 9,9-dioctylfluorene-based diboronic ester (6) using the Suzuki cross-coupling method, as described by Chan et al 29 The resulting statistical PFO-P2C 10 BT was precipitated in methanol, filtered, and redissolved in chloroform. The copolymer solutions were then washed with an aqueous ammonia solution to remove the residual catalyst using the previously reported procedures.…”

Section: Synthesis and Characterization Of The Copolymersmentioning

confidence: 99%

Synthesis and characterization of fluorene‐based copolymers containing benzothiadiazole derivative for light‐emitting diodes applications

Yoon

Park

Lee

et al. 2008

J. Polym. Sci. A Polym. Chem.

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Five new thermally robust electroluminescent fluorene-based conjugated copolymers, including poly[2,7-(9,9-dioctylfluorene)-co-4,7-{5,6-bis(3,7-dimethyloctyloxymethyl)-2,1,3-(benzothiadiazole)}] (PFO-P2C 10 BT) were synthesized and used to fabricate the efficient polymer light-emitting diodes (PLEDs). The glass transition temperatures of the polymers were found to be higher than that of poly(9,9-dialkylfluorenes) and are in the range 113-165 C. We fabricated PLEDs in indium-tin oxide/ PEDOT/light-emitting polymer/cathode configurations using either double-layer LiF/Al or triple-layer Alq 3 /LiF/Al cathode structures. The new copolymers were found to have emission colors that vary from greenish blue (491 nm) to green (543 nm) depending on the copolymer composition. The maximum brightness and luminance efficiency of these PLEDs were found to be up to 5347 cd/m 2 and 1.51 cd/A at 10 V, respectively. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [6762][6763][6764][6765][6766][6767][6768][6769] 2008

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“…4,12 We have developed a new chemistry of poly(quinoxaline-2,3-diyl)s that are prepared by the living polymerization of 1,2-diisocyanobenzenes. [13][14][15][16][17][18][19][20] Poly(quinoxaline-2,3-diyl)s are a unique class of helical polymers prepared by the living polymerization of o-diisocyanobenzenes. 13 They feature an exceptionally robust helical structure that shows no change even at 80 1C in solution for several days.…”

Section: Introductionmentioning

confidence: 99%

Langmuir–Blodgett films of helical rigid-rod poly(quinoxaline-2,3-diyl)s

Ito

Miyake

Suginome

et al. 2010

Polym J

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Optically pure, helical poly(quinoxaline-2,3-diyl)s (degree of polymerization, n¼10-100), prepared by asymmetric living polymerization of 1,2-diisocyano-3,6-dimethyl-4,5-di(propoxymethyl)benzene with an optically pure organopalladium initiator, formed stable monolayers on a water surface. As the polymerization degree increased, more closely packed monolayers were formed, as indicated by surface pressure-area (p-A) isotherms. Up to 54 monolayers were deposited onto the solid support using the Langmuir-Blodgett (LB) technique. Polarized ultraviolet spectra of LB films showed that the helical axis was orientated parallel to the dipping direction. This optical property indicates that polymer molecules are organized anisotropically in LB films. Polymer Journal (2010) 42, 406-410; doi:10.1038/pj.2010.14; published online 31 March 2010Keywords: Langmuir-Blodgett; helical polymer; quinoxaline INTRODUCTION Well-ordered assemblies of molecules are highly important for the ultimate design of functional materials. Even if a molecule possessing potentially intriguing properties is synthesized on the basis of appropriate design, the bulk materials prepared from the molecule often fail to exhibit desired functions because of a lack of appropriate assembling. The Langmuir-Blodgett (LB) technique is one of the most efficient methods for assembling organic molecules two dimensionally within a monolayer. 1-3 By virtue of the monolayer-to-monolayer deposition processes, film materials with desired thickness are easily prepared, keeping the two-dimensional regularity of the molecular orientation.Unlike traditional LB films that are formed from low-molecularweight compounds, it is known that long hydrophobic alkyl chains are not necessary for the formation of stable polymer LB films. 4,5 Instead, attractive interactions between polymer backbones through a twodimensional hydrogen bonding network, as well as through van der Waals forces, are proposed to be highly important for proper LB assembly, in which polymer molecules are tightly packed in a wellordered manner. This suggests that perfectly linear-shaped polymer backbones, for example, rigid-rod-like polymers and extended forms of flexible polymers, are highly suitable for the formation of stable LB films, as such linear-shaped polymers can be packed effectively in the two-dimensional water surface. [6][7][8][9][10][11] In fact, one of us found that poly(N-alkylacrylamide)s adopted a perfectly extended, zigzag

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Synthesis of novel thermotropic liquid crystalline poly(2,3-quinoxalines)

Cited by 21 publications

References 1 publication

Poly(quinoxaline-2,3-diyl)s: A Fascinating Helical Macromolecular Scaffold for New Chiral Functions

Poly(quinoxaline-2,3-diyl)s: A Fascinating Helical Macromolecular Scaffold for New Chiral Functions

Synthesis and characterization of fluorene‐based copolymers containing benzothiadiazole derivative for light‐emitting diodes applications

Langmuir–Blodgett films of helical rigid-rod poly(quinoxaline-2,3-diyl)s

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