Crystallinity of uniform tri(oxyalkylene)s

Bedells, Alison D.; Booth, Colin; Viras, Kyriakos

doi:10.1002/macp.1991.021920918

Cited by 9 publications

(3 citation statements)

References 29 publications

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“…21 As described in a previous paper, 7 uniform PMMA 1 shows crystallinity much higher than that of the non-uniform PMMA 1 with a nearly equivalent DP. For instance, the uniform isotactic 41mer of 1 (C 209 H 338 0 82 =4162.9) crystallized by solvent evaporation had Tm of b 122.3°C which is 2.9°C higher than Tm of its parent PMMA 1 with an average DP of 40.8…”

Section: Analysis Of Conjigurational Purity Of the Iso-mentioning

confidence: 55%

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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Section: Analysis Of Conjigurational Purity Of the Iso-mentioning

confidence: 55%

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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“…Channel 1 comprises a β‐cyclodextrin head group with oligoether chains attached to the primary face of the cyclodextrin through amine linkages. The chains are sufficiently hydrophobic to promote insertion into a phospholipid bilayer membrane13 and possess a length that should allow the channel to span the entire membrane 14. Channel 1 was synthesized (Scheme ) from pentabutylene glycol ( 2 ), which is readily accessible in five steps from commercially available 2,5‐dimethoxytetrahydrofuran 15.…”

Section: Methodsmentioning

confidence: 99%

A Highly Active Anion‐Selective Aminocyclodextrin Ion Channel

2005

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“…10 A pentabutylene glycol tail (33 Å) was selected for anchoring the components of artificial channels due to its matching length with the thickness of the egg yolk phosphatidylcholine (EYPC) lipid membrane (35-40 Å). 11 Additionally, repeating ether moieties were placed in the tail designed to achieve a proper hydrophilic-hydrophobic balance and ensuring partitioning of the lipid membrane. 4b To form target conjugates, pentabutylene glycol 1 was first converted to either the acid 3 or the activated ester 4 via the methyl ester 2.…”

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confidence: 99%