Crystalline structure of poly(hexamethylene succinate) and single crystal degradation studies

• Published in: Polymer (Guilford) Vol. 48; no. 17; pp. 5088 - 5097
• Main Authors: Gestí, Sebastià, Casas, María Teresa, Puiggalí, Jordi
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10-08-2007; Elsevier
• Subjects: Applied sciences; Electron microscopy; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polyester; Properties and characterization; Structure, morphology and analysis; X-ray diffraction; X-ray diffraction; Electron microscopy; Polyester; Stacking sequence; Experimental study; Lattice parameters; Single crystal; Structure processing relationship; Aliphatic polymer; Enzymatic digestion; Solution crystallization; Polysuccinate; Crystal morphology; Isothermal crystallization; Crystalline structure
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2007.06.057

The morphology of solution grown single crystals of poly(hexamethylene succinate) (PE 6 4) was investigated using dilute alcohol or diol solutions by isothermal crystallization. Increasing temperatures changed the morphology of truncated rhombic crystals, which became lenticular crystals. Spiral growths and multilayered crystals as well as characteristic striations which mainly form in the {110} sectors were often observed. A regular folding surface was found by using polyethylene decoration techniques. Lamellar crystals were easily degraded with different lipases. A preferential enzymatic attack was observed to occur on the crystal edges, giving rise in some cases to highly irregular borders with a fringed texture.
Lamellae gave rise to well resolved electron diffraction patterns that allowed the main packing characteristics to be determined. Fiber X-ray diffraction patterns indicate a quasi planar zig-zag conformation and a large unit cell containing eight molecular segments. This cell could not be deduced from the typical hk0 electron diffraction pattern but could be assessed from the patterns of tilted specimens.
Simulation of electron diffraction patterns indicates that molecular segments are arranged with setting angles close to ±46° or ±226°. In addition, neighbouring chains along both a- and b-axis have setting angles differing by 180° in order to justify the deduced cell dimensions.