Head-to-tail poly

The microstructure and architecture of polymers can also gready influence die properties of die polymers. For example, poly(3-substituted thiophene)s could have three microstructure joints s-trans (head to tail), s-trans (head to head), and s-cis (head to tail) (Fig. 9.3). The regioregular head-to-tail poly(3-substituted thiophene)s exhibit higher electrical conductivity values and higher... 

T.A. Chen and R.D. Rieke, The first regioregular head-to-tail poly(3-hexylthiophene-2,5-diyl) and a regiorandom isopolymer nickel versus palladium catalysis of 2(5)-bromo-5(2)- (bromozincio)-3-hexylthiophene polymerization, J. Am. Chem. Soc., 114 10087-10088, 1992. 

Y. Zhu, M.M. Alam, and S.A. Jenekhe, Regioregular head-to-tail poly(4-alkylquinoline)s synthesis, characterization, self-organization, photophysics, and electroluminescence of new n-type conjugated polymers, Macromolecules, 36 8958-8968, 2003. 

A partially hydrolyzed head-to-tail poly(vinyl acetate) ... 

Regioregular head-to-tail poly(3-alkylthiophene) Poly(thienylene-vinylene) from soluble precursor... 

A soluble model compound of head-to-tail poly (3-methylbutene-l) was prepared by polymerizing isoprene specifically in the 3,4 position and... 

Molecular orbital calculations on fluorinated butadienes and hexatrienes were used to model the effects of fluorination on the properties of poly(acetylene). Like poly(acetylene), "head-to-head" poly(fluoro- acetylene), (-CH=CF-CF=CH-), is predicted to adopt a planar, all trans structure, but poly(difluoro-acetylene) favors a non-planar skewed chain conformation. "Head-to-tail" poly(fluoroacetylene), (-CH=CF-CH=CF-) is predicted to favor a nearly planar cis structure stabilized by intramolecular CF-HC hydrogen binding. Calculations on 2-fluoroethanol and on both 2-fluoroacetaldehyde enol and its alkali metal (Li, Na, K) enolates reveal moderately strong intramolecular CF—HO hydrogen bonds(1.9 and 3.2 kcal/mol, respectively) and even stronger intramolecular coordination of CF to alkali metal cations (9-12 kcal/mol). 

The electronic structures of poiy(fluoroacetylene) and poly(difluoroacetylene) have been investigated previously using the ab initio Hartree-Fock crystal orbital method with a minimum basis set (42). Only the cis and trans isomers with assumed, planar geometries were studied. The trans isomer was calculated to be more stable in both cases, and the trans compounds were predicted to be better intrinsic semiconductors and more conductive upon reductive doping than trans polyacetylene. However, our results show that head-to-tail poly(fluoroacetylene) prefers the cis structure and that the trans structure for poly(difluoroacetylene) will not be stable. Thus the conclusions reached previously need to be re-evaluated based on our new structural information. Furthermore, as noted above, addition of electrons to these polymers may lead to structural deformations that could significantly change the conductive nature of the materials. 

Low molecular weight head-to-tail poly (y-crotonolactone), VIII, was prepared for comparison with the lactone polymers prepared in this study. The IR spectrum of the anionically prepared material (VIII), with strong absorptions in the region 1760 and... 

McCullough, R.D. et al.. Self-orienting head-to-tail poly(3-alkylthiophenes) New insights on structure-property relationships in conducting polymers, J. Am. Chem. Soc. 115, 4910 911, 1993. 

Wu, X.M., Chen, T.A., and Rieke, R.D., Synthesis of regioregular head-to-tail poly[3-(alkylthio)thiophenes] A highly electroconductive polymer, Macromolecules 28, 2101-2102, 1995. 

The matter of the head-to-head, tail-to-tail polymerization of vinyl fluoride, vinylidene fluoride, and trifluoroethylene and the copolymerization of vinyl fluoride with vinylidene chlorofluoride and l-chloro-2-fluoroethylene has been extensively studied by Cais and Kometani [24-27] and by Bruch, Bovey, and Cais [28]. The synthesis of pure head-to-tail poly(trifluoroethylenes) is described in Ref. [25]. Isomers of poly(vinyl fluoride) with controlled regiosequence microstructure are discussed in Ref. [27]. 

Iraqi, A., Barker, G.W, 1998. Synthesis and characterisation of telechelic regioregular head-to-tail poly(3-alkylthiophenes). J. Mater. Chem. 8,25-29. 

Wang, Q., Takita, R., Kikuzaki, Y., Ozawa, E, 2010. Palladium-catalyzed dehydrohalogenative polycondensation of 2-bromo-3-hexylthiophene an efficient approach to head-to-tail poly(3-hexylthiophene). J.Am. Chem. Soc 132,11420-11421. 

A similar mechanism applies to the diphenyldithianes, i.e., the cyclic styrene polysulfide dimers. However, in this case the most thermally stable compound is not the simplest cyclic dimer (m/z 272), but a thiophene derivative produced by thermal induced loss of H2S and sulfur (Scheme 5.3). As a consequence, 3,4-diphenylthiophene can be generated from head-to-tail poly(styrene tetrasulfide) units and 2,4-diphenylthiophene from tail-to-tail units. The formation of thiophene derivatives from 1,4-dithiadiene rings, by thermal loss of sulfur, is well-known in the literature. ... 

T. Hayakawa, K.-I. Fukukawa, M. Morishima, K. Takeuchi, M. Asai, S. Ando and M. Ueda. Formation of regioregular head-to-tail poly[3-(4-butylphenyl)thiophene] by an oxidative coupling polymerization with vanadium acetylacetonate. J. Polym. Set, Part A Polym. Chem. 39(13), 2287-2295 (2001). 

A. Iraqi and D. F. Pickup. Preparation and characterization of tractable regioregular head-to-tail poly(3-alkylthiophene)s with ferrocene substituents. Polym. Int. 55, 780-783 (2006). 

R. D. McCullough and M. Jayaraman. The tuning of conjugation by recipe the synthesis and properties of random head-to-tail poly(3-alkylthiophene) copolymers. Chem. Commun. (Cambridge) (2), 135-136... 

El. Kokubo, S.-I. Kuroda, S. Sasaki and T. Yamamoto. Electrochemical deposition of regioregular head-to-tail poly(3-hexylthiophene-2,5-diyl) and characterization of the obtained film. Jpn. J. Appl. Phys., Part 2 40(3A), L228-L230 (2001). 

A. Iraqi, D. Clark, R. Jones and A. Krier. Synthesis, characterization and study of photoluminescent properties of head to tail poly(3-pentoxythiophene), poly(3-cyclohexylthiophene) and mixed alkoxy/cyclohexyl 3-substituted polythiophenes. Synth. Met. 102(1-3), 1220-1221 (1999). 

A modified (partially hydrolyzed) head-to-tail poly(l-acetoxyethylene)... 

McCullough, R. D., Tristram-Nagle, S., Williams, S. P., Lowe, R., and Jay-araman, M. "Self-Orienting Head-to-Tail Poly(3-alkylthiophenes) New Insights on Structure-Property Relationships in Conducting Polymers."... 

More dramatic effects were observed with regioregular polyether-substituted polythiophenes. As reported by Levesque and Leclerc, chemically synthesized head-to-tail poly[3-oligo(oxyethy-lene)-4-methylthiophene] poly(5) led to ionochromic effects, with a clear isosbestic point on the UV-visible absorption spectrum, indicating the coexistence of long sequences of nonplanar and planar thiophene units [244, 245]. With the addition of a cation such as the main chain became twisted. However, in contrast to poly(4), this phenomenon was observed only with the polymer in solution. 

In contrast, ionochromic effects were visible with head-to-tail poly[3-(2,5,8-trioxanonyl)thiophene] poly(6) both in solution and in the solid state [24 249]. With the addition of cations such as Pb " and Hg " ", the conjugation of this polymer, characterized by an absorption maximum at 439 nm in CHCI3 and 486 nm in the solid state, was completely eliminated [247]. Thus, the cationic complexation would induce the twisting of the polymer backbone away from planarity. However, although the response was chemoselective (Li+ and Zn + were found not to interfere), the ionochromic effects observed with Pb + and Hg " " were irreversible, as the conjugation of the polymer was not restored after the complexation. 

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