Premium
Surface structures of poly[( R )‐3‐hydroxybutyrate] and its copolymer single crystals before and after enzymatic degradation with an extracellular PHB depolymerase
Author(s) -
Iwata Tadahisa,
Shiromo Masakatsu,
Doi Yoshiharu
Publication year - 2002
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(200207)203:10/11<1309::aid-macp1309>3.0.co;2-p
Subject(s) - copolymer , crystallization , materials science , polymer chemistry , crystallography , crystal (programming language) , single crystal , polyethylene , lamellar structure , small angle x ray scattering , monomer , chemical engineering , polymer , chemistry , organic chemistry , scattering , composite material , physics , computer science , optics , programming language , engineering
Lamellar single crystals of poly[( R )‐3‐hydroxybutyrate] (P(3HB)) with three types of molecular weights and four kinds of P(3HB) copolymers with different secondary monomer units were grown from dilute solutions of chloroform and ethanol under isothermal crystallization conditions. The surface morphologies of all the single crystals, before and after enzymatic degradation by an extracellular PHB depolymerase purified from Alcaligenes faecalis T1, were investigated by the coating of these crystals with polyethylene and observation by transmission electron microscopy. All the single crystals have a lath‐shaped morphology with a crystallographic a axis along the long axis of the crystals. The surface regularity of P(3HB) single crystals was dependant on molecular weight. The crystal surfaces of the copolymer single crystals were disordered to a degree which depended on the copolymer composition, and tightly chain‐packed crystalline regions in copolymer single crystals were reduced by the introduction of secondary monomer units. The surface regularity of the copolymer single crystals corresponded to the thickness of the crystalline core regions measured by small‐angle X‐ray scattering. Furthermore, it was revealed that chain‐folding regions of copolymer single crystals were embedded under the crystal surfaces which consisted of molecular chains excluded from the crystalline core. It was directly confirmed by the polyethylene‐coating method that enzymatic degradation does not progress along the chain‐folded regions of the crystal surface.Schematic model of a P(3HB) copolymer single crystal