Compression-Induced Stereocomplexation of Polylactides at the Air/Water Interface

Abstract

The conformational and morphological changes occurring at the air/water interface during the compression of pure poly(d-lactide) (PDLA), pure poly(l-lactide) (PLLA), and their equimolar blend have been thoroughly investigated using polarization−modulation infrared reflection−absorption spectroscopy and Brewster angle microscopy. The results obtained show that the plateau region observed in the isotherm of the pure polylactides corresponds to an equilibrium between free 103 helices in a fluid phase and 103 helices in unstable solidlike domains. For the blend, this plateau corresponds to an equilibrium between free 103 helices in the fluid phase, 103 helices in unstable solidlike domains of pure polyenantiomers, and 31 helices in very stable solidlike domains of the PDLA/PLLA stereocomplex. The results obtained also suggest that the proportion of stereocomplex and pure polyenantiomers domains formed during the compression of the monolayer of the blend can be modulated by different experimental parameters such as the molecular weight of the polymers, the subphase temperature, the compression rate, and the “incubation” time.

Poly(lactide) Stereocomplexes: Formation, Structure, Properties, Degradation, and Applications

“…Bourque et al75 and Pelletier and Pézolet76 reported that stereocomplexation occurs upon the compression of the monolayer of PLLA/PDLA mixture films. They prepared Langmuir films of PLLA and PDLA and then observed their structural changes by the use of surface‐pressure measurements and polarization modulation infrared reflecting‐absorption spectroscopy (PM‐IRRAS).…”

Poly(lactide) Stereocomplexes: Formation, Structure, Properties, Degradation, and Applications

“…Bourque et al [75] and Pelletier and Pézolet [76] reported that stereocomplexation occurs upon the compression of the Figure 15. TEM photographs and electron diffraction patterns of PLA stereocomplex single crystal (A) and particle (B) formed in dilute acetonitrile solutions.…”

Hollow Microcapsules with Enhanced Stability via Stereocomplex Assemblies

“…The interfacial assembly of dually associated polymeric chains in stereocomplexes to form microcapsules shell has not been demonstrated. Stereocomplexation arising from the stereoselective association between the optically active l ‐ and d ‐lactide causes the poly( l ‐ and d ‐lactides) molecules to undergo a conformational change from 10 3 helices to 3 1 helices during the solidification process . Inspired by this phenomenon, I hypothesized that the shell stability of stereocomplexed microcapsule can be greatly enhanced at the water–chloroform interface.…”