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Journal of Polymer Science Part A Polymer Chemistry 03/2007; 45(8):1515 - 1524. · 3.92 Impact Factor
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Macromolecular Rapid Communications 08/2006; 27(17):1460 - 1464. · 4.60 Impact Factor
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ABSTRACT: Propargyl esters (HC≡CCH2OC(=O)R; 1: R = n-C5H11, 2: R = CH3, 3: R = CHBrCH3, 4: R = C6H5, 5: R = C(C6H5)3) were polymerized by using (nbd)Rh+(η6-Ph-B-Ph3) (nbd = 2,5-norbornadiene) to produce poly(1)–poly(5) with molecular weights in the range of Mn = 4,900–40,000. Poly(1), poly(3) and poly(4) were readily soluble in common organic solvents such as toluene, THF and CHCl3, and poly(2) showed similar solubility behavior except that it was insoluble in THF. Poly(5) did not dissolve in any organic solvent. Poly(1) was yellow oil, while poly(2)–poly(5) were yellow solids. Poly(1)–poly(4) exhibited UV-vis absorptions in a range of 300–425nm, which are attributed to the conjugation of the main chain. All the
polymers were thermally stable up to 150–200°C.
Polymer Bulletin 07/2006; 57(4):463-472. · 1.53 Impact Factor
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ABSTRACT: N-Propargylbenzamides 1-7 were polymerized with (nbd)Rh(+)[eta(6)-C(6)H(5)B(-)(C(6)H(5))(3)] to afford polymers with moderate molecular weights (M(n) = 26,000-51,000) in good yields. The (1)H NMR spectra demonstrated that the polymers have fairly stereoregular structures (81-88 % cis). The optically active polymers, poly(1) and poly(2), were proven by their intense CD signals and large optical rotations to adopt a stable helical conformation with an excess of one-handed screw sense when heated in CHCl(3) or toluene. The sign of Cotton effect could be controlled by varying the content in the copolymers of either chiral bulky 1 and achiral nonbulky 3, or chiral nonbulky 2 and achiral bulky 7. The smaller the pendant group in the copolymerization of achiral monomers with 1, the more easily did the preferential helical sense change with the copolymer composition. However, the copolymers of chiral nonbulky 2 and achiral nonbulky 3 did not change the helical sense, irrespective of the composition. The free energy differences between the plus and minus helical states, as well as the excess free energy of the helix reversal, of those chiral-achiral random copolymers were estimated by applying a modified Ising model.
Chemistry 07/2005; 11(12):3591-8. · 5.93 Impact Factor
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Macromolecular Chemistry and Physics 01/2005; 206(3):323 - 332. · 2.36 Impact Factor
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ABSTRACT: A variety of novel N-propargylsulfamide monomers (HC≡CCH2NHSO2R) with alkyl (1−4) or aryl groups (5−10) were polymerized with a Rh catalyst, (nbd)Rh+B-(C6H5)4 (nbd = 2,5-norbornadiene), to provide polymers with moderate molecular weights (3000−15 000) in good yields (above 80%). Polymerization of monomer 4 (R = −(CH2)7CH3) at −15 °C yielded a stereoregular polymer whose cis content was nearly 100%, while the cis content remained 79% at 30 °C. Thus, the stereoregularity of the polymer largely depended on polymerization temperature. On the other hand, polymerization solvents hardly affected stereoregularity. Copolymerization of monomer 4 and N-propargylamide monomer 11 afforded copolymers with various compositions in high yields (above 87%), and the cis contents of the resultant copolymers were located between those of the corresponding homopolymers. The presence of intramolecular hydrogen bonding between the neighboring sulfamide groups was confirmed by IR spectroscopy measured in chloroform, suggesting that these types of polymers with appropriate substitutents also have the potential to form helices under suitable conditions like poly(N-propargylamides).
06/2004;
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Macromolecular Chemistry and Physics 05/2004; 205(8):1103 - 1107. · 2.36 Impact Factor
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ABSTRACT: N-Propargylamides having pendent groups with different lengths (HCCCH2NHCOR, R = (CH2)nH, n = 1−8) were polymerized in the presence of a Rh catalyst [(nbd)Rh+B-(C6H5)4; nbd = 2,5-norbornadiene] to obtain polymers with moderate molecular weight and high stereoregularity [poly(1)−poly(8)] in high yields. The conformational transition behavior of the resultant polymers was investigated by measuring UV−vis spectra in chloroform solution at different temperatures. Among the examined polymers, poly(5) and poly(6) took a stable helical conformation at relatively high temperatures, and their helical contents were the highest. Poly(2)−poly(4), which bear shorter alkyl pendent chains, did not exist in stable helical conformation owing to the lack of chain flexibility and the intermolecular hydrogen bonding. Poly(1) was not completely soluble in any solvents. Poly(7) and poly(8), which contain longer pendent chains, took helical conformation only at low temperatures because of the lower cis content of the polymer main chain. Both ΔH and ΔS for the conformational transition from random coil to helix assumed negative values, which also greatly depended on the length of the pendent groups. Whereas the helical conformation of poly(5) and poly(6) was readily generated in chloroform, neither THF nor toluene was favorable for helix formation.
02/2004;
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