Isotactic and Syndiotactic Pentacontamers (50mers) of Methyl Methacrylate Obtained by Fractionation with Preparative SFC: The GPC Analysis of the 50mers and Their Stereocomplex

Ute, Koichi; Miyatake, Nobuo; Osugi, Yasuko; Hatäda, Koichi

doi:10.1295/polymj.25.1153

Cited by 51 publications

(59 citation statements)

References 22 publications

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“…The optimum ratio of sPMMA and iPMMA for the stereocomplex formation is a matter of controversy. Although the 2/1 s/i weight ratio is most often reported [10,14], Miyamoto et al [15] and Ute et al [16] have proposed a 1/1 weight ratio and Spevacek et al [17] and Katime et al [18] have published a 1.5/1 weight ratio. One of the reasons for this discrepancy might be a difference in the PMMA stereoregularity.…”

Section: Dependence Of Stereocomplexation On Experimental Parametersmentioning

confidence: 99%

Stereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA: 1. Thermal and mechanical properties of stereocomplexes

Dubois

et al. 1997

Polymer

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A novel thermoplastic elastomer consisting of a triblock copolymer (MBM) with outer syndiotactic poly(methyl methacrylate) (sPMMA) blocks associated to an inner polybutadiene (PBD) block has been modified by stereocomplexation with isotactic PMMA (iPMMA). Solution cast films of stereocomplexes have been analysed by thermal analysis as a function of the iPMMA/sPMMA (i/s) mixing ratio and the solvent used for the film casting. Although self-aggregation of iPMMA is currently observed, this phenomenon does not occur in solvent cast films of iPMMA with the MBM copolymers. Extent of complexation depends on the i/s mixing ratio and the casting solvent. At a constant i/s ratio, molecular weight of iPMMA has no significant effect on the extent of stereocomplexation. Thermal stability of the stereocomplexes is only affected by the casting solvent, in contrast to tensile strength which is greatly influenced by the mixing ratio of the two PMMA stereoisomers. Tensile strength is increased when increasing amounts of iPMMA are blended with a triblock copolymer of low PMMA content (e.g. 12%). In case of triblocks of high PMMA content (ca. 30% or higher), a low i/s ratio (

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Section: Dependence Of Stereocomplexation On Experimental Parametersmentioning

confidence: 99%

Stereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA: 1. Thermal and mechanical properties of stereocomplexes

Dubois

et al. 1997

Polymer

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“…11 SFC fractionation of it-and st-PMMA-OHs was performed under the following conditions: flow rate of liquefied CO 2 : 9.0 ml min À1 ; flow rate of methanol entrainer: 1.80 ml min À1 (for it-PMMA-OH) or 1.88 ml min À1 (for st-PMMA-OH); fluid pressure: 200 kgf cm À2 ; initial column temperature: 80 1C (for it-PMMA-OH) or 70 1C (for st-PMMA-OH); and rate of cooling: 1 1C min À1 . SFC chromatograms were recorded using a ultraviolet detector operated at a wavelength of 220 nm.…”

Section: Supercritical Fluid Chromatographymentioning

confidence: 99%

“…11 Later, they analyzed the uniform PMMA stereocomplex formed in acetone using an online SEC-NMR method to identify the stoichiometry of the complexed component. The st-/it-compositions of the stereocomplex in the mixtures were determined to be 1.61-1.94, indicating the coexistence of at least two types of stereocomplexes with different compositions (for example, st-/it-¼ 1/1 and 2/1).…”

Section: Introductionmentioning

confidence: 99%

Uniform poly(methyl methacrylate) stereostars: synthesis, separation and stereocomplex formation

Nishiura

Abe

Kitayama

2010

Polym J

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Isotactic (it-) and syndiotactic (st-) uniform poly(methyl methacrylate)s (PMMAs) with hydroxyl end groups were isolated by supercritical fluid chromatography (SFC) and reacted with benzene-1, 3, 5-tricarbonyl trichloride. Two types of uniform threearm star-PMMAs with different stereoregular arms, [it/it/st]-and [it/st/st]-3-star-PMMAs, that is, 'stereostar PMMAs', were isolated by SFC from the product mixture (According to IUPAC nomenclature for nonlinear polymers, star PMMA with three arms is named 3-star-PMMA. In this paper, the stereoregularity of the three arms is designated as [it/it/st], for example, and thus, the polymer is named [it/it/st]-3-star-PMMA. By analogy to 'stereoblock' PMMAs, these star PMMAs are termed 'stereostar' PMMAs). proposed another model known as a double-stranded helix model, in which a helix of the it-PMMA chain with a smaller radius is surrounded by an st-PMMA helical chain with a larger radius.Recently, Kumaki et al. 5 demonstrated multistranded models based on atomic force microscopic observation of PMMA stereocomplexes formed at the air-water interface through two-dimensional crystallization, in which the double-stranded it-PMMA helix was surrounded by the st-PMMA helix. Both helix models developed in that work indicated that a 1:2 ratio of associated monomeric units in it-and stPMMAs is required for complex formation. Although most experimental results indicate that the stoichiometry of the stereocomplex is st-/it-¼2/1, 2,6 a number of contradictory results have been reported about the stoichiometry, 7 with some results suggesting st-/it-¼1/1 8 or st-/it-¼1.5/1. 9,10 Previous stoichiometry results were related to the ratio of associated monomeric units or the mass fractions of it-and st-PMMAs. To obtain a molecular-level understanding of the mechanism and stoichiometry of stereocomplex formation, however, the critical factor should be the stoichiometry of the complex, that is, the ratio of it-and st-PMMA molecules, rather than the monomeric unit ratio.

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“…In fact, thin needle crystals with an mp of 101. 4 Figure 6 shows the crystal structure. Fractional atomic coordinates and isotropic thermal parameters for the 7mer are given in Table I.…”

Section: Analysis Of Conjigurational Purity Of the Iso-mentioning

confidence: 99%

Controlled Synthesis of Isotactic and Symmetrical Poly(methyl methacrylate) Directed toward Uniform Polymers with High Crystallinity

Ute

Yamasaki

Naito

et al. 1995

Polym J

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ABSTRACT:The synthesis and fractionation by supercritical fluid chromatography (SFC) of an isotactic and symmetrical poly(methyl methacrylate) (PMMA) containing very few configurational defects, H+MMA+.-CH 3 (2), are described. Detailed analysis by 1 H NMR spectroscopy showed that the PMMA 2 was almost perfectly isotactic ( -100%) except a small amount (11 % ) of racemo sequence at the first tactic diad from the initiating chain-end. The uniform PMMAs 2 with 31, 36, 41, and 44 repeating units (n) had melting points higher by 4.5-12.2°C than those of the uniform PMMAs prepared in a previous work, t-C4 H 9 +MMA+.-H (1) with a triad isotacticity of 96.1 %. The degrees of crystallinity of the uniform PMMA 2 samples were determined to be 92-97%, also high as compared with those of uniform PMMA 1 samples. Single crystals were grown from a solution of the 7mer of 2 (n = 7), and the crystal structure was determined by X-ray analysis.KEY WORDS Uniform Polymer / Supercritical Fluid Chromatography / Living Polymerization / Tacticity / End-Group / Melting Temperature / Degree of Crystallinity / X-Ray Crystallographic Analysis/ Polymerization of methyl methacrylate (MMA) initiated with t-C 4 H 9 MgBr in toluene at -78°C proceeds in a living manner to yield a highly isotactic PMMA with a well-defined chain structure ( Recently, we have succeeded in fractionating this PMMA into the individual homologues from 3mer (C 19 H 34 0 6 =358.5) to lOOmer (C 504 H 810 0 200 = 10069.9) by means of supercritical fluid chromatography (SFC). 2 -6 A series of the uniform isotactic PMMAs was subjected to investigations of its glass transition temperature (Tg), 3 • 5 • 7 crystalline melting ternperature (Tm), 5 • 7 and of the stereocomplexation with uniform syndiotactic PMMAs. 3 • 4 Usefulness of the uniform PMMAs as a standard material for molecular weight determinations has also been demonstrated. 4 • 5 Although the purity of the uniform PMMAs with respect to degree of polymerization (DP) was proved to be higher than 99% by SFC 3 • 4 and mass spectrometry, 8 there still remains a purity problem at the stereochemical level. The isotacticity of the parent PMMA 1 is 96-97% in triads, and thus the isolated 50mer, for example, should contain statistically one racemo (r) oiad somewhere in its configurational sequence. Moreover, the uniform PMMAs have configurational disorder at the chain-end diads (the a-band y-z diads in eq 1) because the stereospecificity in the initiation 9 and termination processes 10 of the polymerization was found to be 90 and 94% in mesa (m) 951

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Isotactic and Syndiotactic Pentacontamers (50mers) of Methyl Methacrylate Obtained by Fractionation with Preparative SFC: The GPC Analysis of the 50mers and Their Stereocomplex

Cited by 51 publications

References 22 publications

Stereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA: 1. Thermal and mechanical properties of stereocomplexes

Stereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA: 1. Thermal and mechanical properties of stereocomplexes

Uniform poly(methyl methacrylate) stereostars: synthesis, separation and stereocomplex formation

Controlled Synthesis of Isotactic and Symmetrical Poly(methyl methacrylate) Directed toward Uniform Polymers with High Crystallinity

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