Observation of strain-induced β form in poly(β-hydroxyalkanoates)

Orts, William J.; Marchessault, R. H.; Bluhm, Terry L.; Hamer, Gordon K.

doi:10.1021/ma00228a014

Cited by 154 publications

(156 citation statements)

References 5 publications

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“…~n o t h e r . a r~u m e n t that counters-the idea that annealing "irons out" defects is the previously reported (19,20) observation that, at a given crystallization temperature, the crystalline stem length (or lamellar long period) increases with increasing 3HV content. For example, at a constant crystallization temperature of 115"C, the long period measured by SAXS for the 21% 3HV copolymer (with a melting temperature of 1 18°C) is 22 nm, whereas for PHB (with a melting temperature of 180°C) the long period is 1 1.4 nm.…”

Section: Nmr Analysismentioning

confidence: 90%

Cocrystallization in random copolymers of poly(β-hydroxybutyrate-co-β-hydroxyvalerate) and its effect on crystalline morphology

Orts¹,

VanderHart²,

Bluhm³

et al. 1995

Can. J. Chem.

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Small-angle X-ray scattering (SAXS) and solid state CPMAS I3c NMR were used to describe the crystalline morphology of a series of bacterially produced poly((3-hydroxybutyrate-co-P-hydroxyvalerate) copolymers containing random distributions of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Modeling of SAXS results showed that the morphology of this isodimorphic system is better described by two phases, crystalline and amorphous, having defects within each domain. This is in contrast to a model with a large interfacial region between phases. For the 3HV composition range 0-27 mol%, the polymer crystallizes in a poly(P-hydr0xybutyrate)-type crystalline lattice. Solid state NMR results showed that there is significant incorporation of the 3HV minor component into the poly(P-hydroxybutyrate) crystalline phase over this composition range. The ratio of the 3HV content in the crystalline phase relative to the overall 3HV content is not linear, but increases with increasing 3HV. For the 21 and 27% 3HV samples, the 3HV content in the crystalline phase is as much as 213 of the overall 3HV content. Inclusion of 3HV is correlated to an increase in crystalline disorder (as measured by SAXS), implying that it is easier to accommodate the bulkier 3HV comonomer into a crystalline region that already contains defects.Key words: bacterial polyesters, poly(3-hydroxyalkanates), small-angle X-ray scattering, solid state NMR, cocrystallization.RCsumC : On a utilisC la diffraction des rayons X B de petits angles (SAXS) et la RMN du 13c CPMAS B 1'Ctat solide pour dCcrire la morphologie cristalline d'une sCrie de copolymkres poly(P-hydroxybutyrate-co-phydroxyvalCrate) produits par une voie bactCrienne et contenant des distributions au hasard de 3-hydroxybutyrate (3HB) et de 3-hydroxyvalCrate (3HV). Un modelage des resultats SAXS a montrC que la meilleure f a~o n de dCcrire la morphologie de ce systkme isodimorphique est B l'aide de deux phases, l'une cristalline et l'autre amorphe, ayant des dkfauts dans chaque domaine. Pour une composition de 3HV allant de 0 i 27 mol%, le polymkre cristallise dans une rCseau cristallin du type poly(P-hydroxybutyrate). Les rCsultats de la RMN B l'etat solide ont montrC que, sur cette plage decomposition, il se produit une incorporation importante du composant mineur du 3HV dans la phase cristalline du poly(P-hydroxybutyrate). Le rapport de la quantitC de 3HV contenue dans la phase cristalline par rapport B la quantitC totale de 3HV n'est pas linCaire; il augmente avec une augmentation du 3HV. Pour les Cchantillons contenant 21 et 27% de 3HV, la quantitC de 3HV contenue dans la phase cristalline reprksente pratiquement les 213 de la quantitC totale de 3HV. I1 existe une corrClation entre l'inclusion du 3HV et l'augmentation du dCsordre cristallin (tel que mesurC par SAXS); ceci implique qu'il est plus facile d'accommoder le gros comonombre 3HV dans une region cristalline qui contient dCjB des dCfauts.

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Section: Nmr Analysismentioning

confidence: 90%

Cocrystallization in random copolymers of poly(β-hydroxybutyrate-co-β-hydroxyvalerate) and its effect on crystalline morphology

Orts¹,

VanderHart²,

Bluhm³

et al. 1995

Can. J. Chem.

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“…Molecular weight of the polymer was 5.3x10 5 . The glass transition and melting temperatures are -0.1and 141.5 o C, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…In addition, β-form with planar zig-zag conformation, which is represented by a reflection on the equator at 2θ=19.7° in the WAXD measurement, can be observed in the highly drawn PHB fibers. Orts et al suggested that the β-form was introduced by the orientation of free chains in the amorphous regions between α-form lamellar crystals [5]. Furuhashi et al proposed another formation mechanism that the β-form is formed as the crystals of pseudohexagonal structure [6].…”

Section: Introductionmentioning

confidence: 99%

Fiber structure formation in melt spinning of bio-based aliphatic co-polyesters

Qin¹,

Takarada²,

Kikutani³

2015

AIP Conference Proceedings

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“…In addition, another crystal form with a planar zig-zag conformation (β-form) was observed in the highly drawn PHB fibers [10]. Orts et al suggested that the β-form chains emanate upon stretching from the amorphous domains between 21 helix α-form lamellae [14]. However Furuhashi et al demonstrated that another formation mechanism of β-form is also possible [15].…”

Section: Higher Order Structure Of the Uniaxially Drawn Phbh Filmsmentioning

confidence: 99%

Mechanical Properties and Higher Order Structures of the Bacterial Polyester Highly Oriented Films

et al. 2006

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IntroductionPoly(3-hydroxybutyrate)(PHB) is produced by a wide variety of microorganisms as intracellular carbon and energy storage material [1], and has been extensively studied as a biodegradable and biocompatible thermoplastic [2][3][4]. However, it is well known that the processing of PHB and its copolymers into fibers, films, and other products is very hard. These polyesters have a glass transition point below room temperature, and the crystallization rate is quite low [5]. Because of these properties, the melt cools down to the room temperature without crystallization and the spherulitic crystallization occurs after processing resulting in the brittle character. Further the defect in the spherulites formed during the secondary crystallization deteriorates the mechanical properties [6,7].Several groups have attempted to improve the mechanical properties of PHB solution cast films. Holmes tried to obtain uniaxially and biaxially oriented films of PHB to improve the mechanical properties [4]. However, these films were too brittle to draw either uniaxially or biaxially to high ratio. De Koning et al. have reported that the stiffness and brittleness of PHB film was avoided by annealing at elevated temperatures [8]. This procedure seems to eliminate the defect in the spherulites. Barham and Keller [9] reported that the ductility of PHB films can be significantly improved by the application of cold drawing. The elongation at break measured at room temperature increases up to 300 % after 300 % of elongation by rolling, while as compression molded PHB film shows the elongation at break as low as 7 %. One can apply similar process to obtain highly oriented PHBH films with good mechanical properties.In this study, the roll drawing was applied to the compression molded poly ( 3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) films. While brittle spherulite structure tends to break easily by extension, it is possible to make a crystal orientation to some extent, without breaking in roll drawing. Roll drawn PHBH films are ductile and can be stretched to high extension ratio without breaking. Films obtained were further annealed at an elevated temperature. The objective of this study is to investigate the changes in mechanical properties and higher order structures of PHBH films during these processes.Abstract : Bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)(PHBH) highly oriented films were prepared by the combination of roll and uniaxial drawing processes. Compression molded films, which is rather brittle, turned to be ductile after roll drawing up to x 2, and the films were further uniaxially drawn to a draw ratio as high as 1000 %. The PHBH film with the tensile strength of 178 MPa and the modulus of 1.4 GPa were obtained. The roll drawn PHB film showed a slight crystalline orientation of α-form. The orientation advanced with uniaxial draw ratio and the formation of β-form crystal was observed. Relations among the processing conditions, higher order structures and mechanical properties were investigated using...

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Observation of strain-induced β form in poly(β-hydroxyalkanoates)

Cited by 154 publications

References 5 publications

Cocrystallization in random copolymers of poly(β-hydroxybutyrate-co-β-hydroxyvalerate) and its effect on crystalline morphology

Cocrystallization in random copolymers of poly(β-hydroxybutyrate-co-β-hydroxyvalerate) and its effect on crystalline morphology

Fiber structure formation in melt spinning of bio-based aliphatic co-polyesters

Mechanical Properties and Higher Order Structures of the Bacterial Polyester Highly Oriented Films

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