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Volumn 130, Issue 20, 2008, Pages 6373-6380

Molecular weight recognition in the multiple-stranded helix of a synthetic polymer without specific monomer-monomer interaction

Author keywords

[No Author keywords available]

Indexed keywords

MOLECULAR WEIGHT; MONOMERS; SUPRAMOLECULAR CHEMISTRY; VAN DER WAALS FORCES;

EID: 43949144209     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja077861t     Document Type: Article
Times cited : (65)

References (61)
  • 23
    • 43949105230 scopus 로고    scopus 로고
    • Because of the difficulty in the synthesis of high molecular weight uniform PMMAs by fractionation, high molecular weight it- and st-PMMAs with a narrow molecular weight distribution were also prepared and used for SC formation see Experimental Section
    • Because of the difficulty in the synthesis of high molecular weight uniform PMMAs by fractionation, high molecular weight it- and st-PMMAs with a narrow molecular weight distribution were also prepared and used for SC formation (see Experimental Section).
  • 24
    • 0030567370 scopus 로고    scopus 로고
    • AFM is a powerful tool to study polymer chains on substrate, and various isolated and self-assembled synthetic polymers deposited on substrates have been observed from linear polymers to specially structured polymers, such as polymer brushes, monodendron-jacketed polymers, polyelectrolytes, heteroarm star copolymers, helical polymers, fullerene end-capped polymers, and block copolymers composed of architecturally different components, etc. For examples, see: (a) Kumaki, J.; Nishikawa, Y.; Hashimoto, T. J. Am. Chem. Soc. 1996 118, 3321-3322.
    • AFM is a powerful tool to study polymer chains on substrate, and various isolated and self-assembled synthetic polymers deposited on substrates have been observed from linear polymers to specially structured polymers, such as polymer brushes, monodendron-jacketed polymers, polyelectrolytes, heteroarm star copolymers, helical polymers, fullerene end-capped polymers, and block copolymers composed of architecturally different components, etc. For examples, see: (a) Kumaki, J.; Nishikawa, Y.; Hashimoto, T. J. Am. Chem. Soc. 1996 118, 3321-3322.
  • 46
    • 0034599146 scopus 로고    scopus 로고
    • For reviews of single chain observations, see: w
    • For reviews of single chain observations, see: (w) Schlüter, A. D.; Rabe, J. P. Angew. Chem., Int. Ed. 2000, 39, 864-883.
    • (2000) Angew. Chem., Int. Ed , vol.39 , pp. 864-883
    • Schlüter, A.D.1    Rabe, J.P.2
  • 55
    • 43949127162 scopus 로고    scopus 로고
    • The solid green line in Figure 3d shows the calculated length for a 10/1 double helix of two it-PMMA chains. The experimental values fit well with the calculated ones, suggesting that the it-PMMA helix seems to be wound more loosely than 9/1.
    • The solid green line in Figure 3d shows the calculated length for a 10/1 double helix of two it-PMMA chains. The experimental values fit well with the calculated ones, suggesting that the it-PMMA helix seems to be wound more loosely than 9/1.
  • 56
    • 43949133625 scopus 로고    scopus 로고
    • If one assumes that a single it-PMMA chain folds back on itself to form a double-stranded helix, followed by inclusion by an st-PMMA helix to produce an SC, the length of the resulting SC will be reduced by half (dotted black line in Figure 3d), and therefore, this possibility can be excluded.
    • If one assumes that a single it-PMMA chain folds back on itself to form a double-stranded helix, followed by inclusion by an st-PMMA helix to produce an SC, the length of the resulting SC will be reduced by half (dotted black line in Figure 3d), and therefore, this possibility can be excluded.
  • 57
    • 43949115661 scopus 로고    scopus 로고
    • In addition to the triple-stranded helix model, we compared the observed lengths of the SCs with those calculated on the basis of the double-stranded (Figure 1a) and quadruple-stranded (Figure S2 in Supporting Information) helix models. As shown in Figure 3d, the molecular lengths of the it-PMMA double-stranded helix in the triple-stranded helix can be expressed as Lntriple,two-it(it, Pn/ 9(monomer units/turn) x 1.84(nm/pitch, 0.204Pn and Lntriple,one-it(it, Pn/ 9(monomer units/turn) x 1.84(nm/pitch)/2, 0.102Pn for an it-PMMA double-stranded helix composed of two it-PMMA chains and a folded single it-PMMA chain, respectively. The experimental results support the former structure, the it-PMMA double-stranded helix composed of two it-PMMA chains Figure 3d, In the same way, the molecular lengths of the st-PMMA in the triple-stranded helix can be expres
    • 13 which also supports the triple-stranded-helix as a plausible model for the SC.
  • 60
    • 43949113367 scopus 로고    scopus 로고
    • One may suspect that, if the it-PMMA in SCs are not the double-stranded helices shown in Figure 1b but are the single helices shown in Figure 1a, then the same mixtures of short and long SCs corresponding to the mixing ratio of it-PMMAs shown in Figure 5c,d should be obtained without specific molecular weight recognition between it-PMMAs because, in this case, formation of double-stranded helices between it-PMMAs is not necessary. Here, we therefore reconsider the experimental results without any hypothesis to make clear which model, the single- or double-stranded helix, is reasonable for it-PMMA chains. Let us consider the degree of polymerizations of an it-PMMA and st-PMMA that form an SC with the same length on the basis of the experimental results of the length of SCs given as a function of the molecular weights of it-PMMA and st-PMMA Figures 3d and 4c, For instance, an SC of 10 μm corresponds to a 58-mer of it-PMMA and a 224-mer of st-PMMA, respectively. Note that only the ex
    • One may suspect that, if the it-PMMA in SCs are not the double-stranded helices shown in Figure 1b but are the single helices shown in Figure 1a, then the same mixtures of short and long SCs corresponding to the mixing ratio of it-PMMAs shown in Figure 5c,d should be obtained without specific molecular weight recognition between it-PMMAs because, in this case, formation of double-stranded helices between it-PMMAs is not necessary. Here, we therefore reconsider the experimental results without any hypothesis to make clear which model, the single- or double-stranded helix, is reasonable for it-PMMA chains. Let us consider the degree of polymerizations of an it-PMMA and st-PMMA that form an SC with the same length on the basis of the experimental results of the length of SCs given as a function of the molecular weights of it-PMMA and st-PMMA (Figures 3d and 4c). For instance, an SC of 10 μm corresponds to a 58-mer of it-PMMA and a 224-mer of st-PMMA, respectively. Note that only the experimental data are used. Assuming that an SC is composed of a single it-PMMA and a single st-PMMA chain, the ratio becomes it/st = 58/224 = 1/3.9, which does not agree with the experimentally determined stoichiometry of 1/2. To agree with 1/2, it is reasonable to assume that an SC is composed of two it-PMMA chains and one st-PMMA chain, i.e., the SC is composed of a double-stranded helix of it-PMMA and a single helix of st-PMMA.
  • 61
    • 0026634324 scopus 로고
    • Orgel, L. E. Nature 1992, 358, 203-207.
    • (1992) Nature , vol.358 , pp. 203-207
    • Orgel, L.E.1


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.