Polylactide crystal forms

Crystalline structure and molecular dynamics in alpha and alpha crystals of poly(L-lactide) (PLLA) and PLLA/poly(D-lactide) (PDLA) stereocomplex crystals have been investigated by solid-state C CPMAS NMR spectroscopy. The crystal forms of polylactide (PLA) have different line shapes, and resonance splittings in solid-state NMR spectra due to the crystallographically inequivalent sites within crystal unit cell. 

Polylactides (PLAs) have two enantiomeric forms, PLLA and PDLA. It is well known that a 1 1 mixture of PLLA and PDLA can form stable stereocomplex (SC) crystals, which have... 

The subject of crystallization from stressed melts has been reviewed (Kumaraswamy 2005) and one frequent occurrence in the time sequence of this crystallization is the formation of row nuclei which give rise to structures known as shish-kebabs . Polypropylene is the polymer best known for its remarkable propensity for forming row structures, which often contain considerable amounts of P-phase material (Olley et al. 2014), and are a major feature of the skin-core stmcture of injection-moulded polypropylene (Shinohara et al. 2012), but they are also found in polyethylene (An et al. 2006), isotactic polystyrene (Azzurri and Alfonso 2008), poly(phenylene sulfide) (Zhang et al. 2008) and polylactide (Xu et al. 2013). 

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