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Crystal Structures of Sustainable Long-Spaced Aliphatic Polyesters
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DOI：10.1021/acs.macromol.6c00020.png)
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Abstract
En 中文
Polyethylene mimics such as long-spaced aliphatic polyesters (LSAPE) are biodegradable and recyclable in a close-loop path. They are viewed as possible alternatives to classical polyethylenes that are inert and difficult to recycle. However, inclusion of the ester groups as crystalline layers inside the core crystalline regions bestow LSAPE features in their crystal structures that differ from the simple orthorhombic packing of linear polyethylene. In this work, we have determined the crystal structures of long-spaced aliphatic polyesters PE-X,18 (–[–(CH2)X–OCO–(CH2)16–COO–]n–; X = 2, 3, 4 or 6) and polyester PE-2,13 (–[–(CH2)2–OCO–(CH2)11–COO–]n–) by analyzing their 2D-wide-angle X-ray fiber diffraction data. The chain conformation is different depending on the odd or even number of X. Even-X congeners take a vertically oriented and almost straight chain form with local kinks (gauche conformers) at the CH2–O bonds, while the odd-X member packs into large and long zigzag arms of the almost fully extended 16 methylene segments, also with gauche bonds at the CH2–O junction. The methylene segments are packed closely in the sublattice similarly to the herringbone-type structure of orthorhombic polyethylene. This packing is supported by IR spectral observations of the correlation splitting and by adherence to the n-alkane dispersion curve of the series of progression bands in the frequency region of rocking-twisting CH2 modes. The asub and bsub values of the subcell structure, composed of methylene zigzag segments, are very close to those of the orthorhombic-type of the linear polyethylene crystal.
Keywords:
Carbene compounds
Crystal structure
Diffraction
Hydrocarbons
Organic polymers
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5.2
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3.6W
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9.4W
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