Crystal Structure of Atactic and Isotactic Poly(3-hydroxy-2,2-dimethylbutyrate): A Chemically Recyclable Poly(hydroxyalkanoate) with Tacticity-Independent Crystallinity

• DOI: 10.1021/acs.macromol.4c00165
• Publication Date: 2024-04-19T14:25:20Z
• Authors: Miriam Scoti; Li Zhou; Eugene Y.-X. Chen; Claudio De Rosa
• Keywords: Tacticity; Crystal (programming language)

The crystal structures of isotactic and atactic poly(3-hydroxy-2,2-dimethylbutyrate) (P3H(Me)2B) are presented. Samples P3H(Me)2B (at-(R/S)-P3H(Me)2B) the R S enantiomers (it-(R)-P3H(Me)2B it-(S)-P3H(Me)2B, respectively) have been synthesized by ring opening polymerization racemic chiral dimethyl-butyrolactones employing a superbase catalyst. A 1:1 mixture two (it-(R,S)-P3H(Me)2B) has also prepared. Both pure enantiomer polymers crystallize showing identical diffraction patterns, indicating crystallization in same crystalline form structure. it-(R,S)-P3H(Me)2B crystallizes giving pattern. This is one few examples an polymer despite configurational disorder probably it first structurally confirmed example fascinating tacticity-independent crystallinity explains remarkable thermal mechanical behaviors P3H(Me)2B, which thermally stable melt-processable chemically recyclable to monomer. structure resolved analysis X-ray powder fiber oriented fibers, combined with conformational based on methods density functional theory. ordered it-(R)-P3H(Me)2B (or it-(S)-P3H(Me)2B) described chains nearly trans-planar conformation chain axis 4.7 Å packed orthorhombic unit cell axes = 13.30 Å, b 9.99 c 4.75 according space groups P21212 or P212121. at-(R/S)-P3H(Me)2B having only slightly larger axis, 13.94 10.03 characterized disordered succession monomers distorted that keeps straight periodicity enantiomer. proposed model polymer. is, therefore, packing both P212121 achiral Pna21 Pnn2.