Structural Studies of Polyesters. VII. Molecular and Crystal Structures of Racemic Poly(β-ethyl-β-propiolactone)

Yokouchi, Mitsuru; Chatani, Yôzô; Tadokoro, Hiroyuki; Tani, Hisaya

doi:10.1295/polymj.6.248

Cited by 89 publications

(72 citation statements)

References 7 publications

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“…8. As can be seen, the pitch of the two helices is quite different (5.6 vs. 6.1 A) and both agree with the structures derived from stretch-fibre X-ray diffraction measurements (5.6 vs. 6.0 A) [28] [29]. The 202 1 Fig.…”

Section: Conformationsupporting

confidence: 82%

Preparation and Structure of Oligolides from (R)‐3‐Hydroxypentanoic Acid and comparison with the hydroxybutanoic‐acid derivatives: A small change with large consequences

Seebàch¹,

Hoffmann²,

Kühnle³

et al. 1994

Helvetica Chimica Acta

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Cyclic oligomers of (R)-3-hydroxyvaleric acid (3-HV) are prepared from the monomer by three different methods, giving various ratios of the oligomers. The macrocycles containing three to twelve 3-HV units (12-to 48-membered rings) are isolated in pure form by chromatography. The triolide 3 can be separated by distillation and isolated on large scale. Biopol, the copolymer of(R)-3-hydroxybutanoic acid (3-HB) and (R)-3-hydroxyvaleric acid (3-HV), is degraded to mixtures of Me-and Et-substituted triolides ('mixdides') with high crystallization tendency. The X-ray crystal structures of the tetrolide 4, pentolide 5, hexolide 6, heptolide 7, and of two 'mixolides' (with inclusions of solvent) have been determined (Figs.3-7, 10, and 11) and are compared with those of the corresponding 3-HB derivatives reported previously. From the structural data, a 31 and a 21 helix of 3-HV can be modelled, and the latter one compared with helix structures of P(3-HB) and P(3-HV) derived from stretch-fibre X-ray scattering. Crystals of a water-containing NaSCN complex of the triethyl triolide 3 were obtained in good quality for X-ray analysis. The structure (Figs. 12, 13, and Tublt. 6 ) contains an interesting array of C=O and H 2 0 0-atoms around the Na+ ions along a channel-type tube (a-axis of the crystal) which may be relevant to the role of P(3-HB) and P(3-HV) as components of cellular ion channels.

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Section: Conformationsupporting

confidence: 82%

Preparation and Structure of Oligolides from (R)‐3‐Hydroxypentanoic Acid and comparison with the hydroxybutanoic‐acid derivatives: A small change with large consequences

Seebàch¹,

Hoffmann²,

Kühnle³

et al. 1994

Helvetica Chimica Acta

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“…The crystal and molecular structure of the chemosynthesized racemic poly(3-hydroxyvalerate) (P(3HV)) was firstly studied by X-ray diffraction 48) . P(3HV) crystallized as an orthorhombic form with unit cell parameters: a = 0.932 nm, b = 1.002 nm and c (fiber axis) = 0.556 nm and space group was P2 1 2 1 2 1 .…”

Section: Poly(3-hydroxyvalerate)mentioning

confidence: 99%

Crystal structure and biodegradation of aliphatic polyester crystals

Iwata¹,

Doi

1999

Macromol. Chem. Phys.

140

121

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SUMMARY: The biodegradability of aliphatic polyesters, which are produced by biosynthesis and chemosynthesis, strongly correlates to the polymer morphology such as crystallinity, molecular orientation, chain packing and crystal surface, in addition to the chemical structure. For elucidation of biodegradation mechanism of crystal regions on an atomic level, lamellar single crystals of poly([R]-3-hydroxybutyrate) (P(3HB)) and its copolymers, poly([R]-3-hydroxyvalerate) (P(3HV)), poly(4-hydroxybutyrate) (P(4HB)), poly(L-lactic acid) (PLLA) and poly(ethylene succinate) (PES) were prepared from dilute solution by isothermal crystallization, and the crystal structures and morphologies were investigated by means of mainly transmission electron microscopy and atomic force microscopy. All single crystals were intramolecular single crystals, with spiral growth in some cases, and these crystals gave well-resolved electron diffractograms. The enzymatic degradation of lamellar crystals of P(3HB) and its copolymers was carried out with extracellular PHB depolymerases, and it was revealed that enzymatic degradation of lamellar crystals progressed from crystal edges and ends rather than the chain-folding surfaces of crystals, in spite of the homogeneous adsorption of enzyme molecules on the crystal surfaces by substrate-binding domain. Furthermore, in the case of PLLA single crystals, single crystals were also degraded from the edges to yield a rounded shape without decreasing the molecular weights and lamellar thickness. These results suggest that the attack by the active site of enzyme takes place at disordered regions of the crystals, that is, disordered lateral sites with high mobility of molecular chains are preferentially degraded.

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“…n=l OUn ( 4) where These normal equations may be written in matrix notation and solved in the same way as those given in ref 11.…”

Section: Energy Minimization Proceduresmentioning

confidence: 99%

Conformational and Packing Stability of Crystalline Polymers. VII. A Method for the Minimization of Conformational and Packing Energies of Crystalline Polymers

Kusanagi

Tadokoro

Chatani

1977

Polym J

Self Cite

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ABSTRACT:An energy minimization method for seeking stable crystal structure in terms of the nonbonded repulsive energy alone was derived. The variable parameters are molecular positions and their internal coordinates; the unit cell dimensions and the space group are fixed to those obtained by X-ray analysis. By starting from the crystal structure models composed of uniform helical chains for polyisobutylene, poly(ethylene oxide), and isotactic polypropylene, the present method gave energetically stable structures which are very close to those determined by X-ray analyses. Furthermore, a constrained least-squares method was derived, in which the intra-and intermolecular repulsive energies were taken into account in addition to the differences of the observed and calculated structure factors. This constrained least-squares refinement was successfully applied to the crystal structure analysis of isotactic poly(4-methyl-1-pentene).KEY WORDS Energy Minimization / X-Ray Analysis / Crystal Structure / Polyisobutylene / Poly(ethylene oxide) / Isotactic Polypropylene / Isotactic Poly(4-methyl-1-pentene) / Repulsive Energy / In the previous papers of this series, several methods 1 • 2 for setting up molecular models were derived for X-ray structure analyses of polymers, based upon the intramolecular interaction energy calculations. These methods have been applied successfully to the structure analyses of several polymers. 3 • 4 However, the crystal structure models obtained by packing these molecular models in the unit cell are not always satisfactory as the models for carrying out the analysis, and some cases 5 have been found in which the influence of intermolecular interactions on the flexible molecular chains of polymers cannot be neglected. It is, therefore, quite important to seek more suitable crystal structure models by calculating the potential energy due to both the intra-and intermolecular interactions.parameters; the former uses line searches and quadratic interpolations and the latter the Newton-Raphson method.Although there have been papers concerning the energy minimization of three-dimensional crystals of high polymers by McGuire, et al.,6 and Hermans, et al.,7 their methods require a very large number of computations, because of the optimization problem of a large number ofIn the present work, the internal coordinates (bond lengths, bond angles, and internal rotation angles) were used as the parameters and the quadratic potential functions 8 were introduced as the potentials. Thereby we derived a new method, with fewer calculations, in which the energy minimization was carried out by the leastsquares method. Moreover, a constrained leastsquares refinement method was derived, in which the intra-and intermolecular repulsive energies were taken into account in addition to the differences of the observed and calculated structure factors. This constrained least-squares refinement was applied to the crystal structure analysis of isotactic poly(4-methyl-1-pentene). METHOD AND ASSUMPTION Potential FunctionsIn th...

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Structural Studies of Polyesters. VII. Molecular and Crystal Structures of Racemic Poly(β-ethyl-β-propiolactone)

Cited by 89 publications

References 7 publications

Preparation and Structure of Oligolides from (R)‐3‐Hydroxypentanoic Acid and comparison with the hydroxybutanoic‐acid derivatives: A small change with large consequences

Preparation and Structure of Oligolides from (R)‐3‐Hydroxypentanoic Acid and comparison with the hydroxybutanoic‐acid derivatives: A small change with large consequences

Crystal structure and biodegradation of aliphatic polyester crystals

Conformational and Packing Stability of Crystalline Polymers. VII. A Method for the Minimization of Conformational and Packing Energies of Crystalline Polymers

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