POxylated stereocomplexes from PEtOx-b-PLA diblock copolymers

Résumé fourni par la source

• ROP of l - and d -lactide from a PEtOx macroinitiator yielded block copolymers. • Stereocomplexes formed in racemic blends of PEtOx- b -PLA with opposing chirality. • The amorphous PEtOx block did not affect the modification of the SC crystallites. • Degree of crystallinity and T m decrease with increasing molar mass of the PLA. An ω-hydroxyl terminated poly(2-ethyl-2-oxazoline) (PEtOx) was obtained by termination of the cationic ring-opening polymerization of 2-ethyl-2-oxazoline with acetate and subsequent transesterification with methanol. The resulting PEtOx-OH featuring a degree of polymerization (DP) of 20 was used as a macroinitiator for the ring-opening polymerization of l -lactide as well as d -lactide. The resulting PEtOx- b -PLA block copolymers featured DP values of 25, 50, 100 and 150, respectively, and were characterized by means of size exclusion chromatography, 1 H NMR spectroscopy as well as matrix-assisted laser desorption ionization mass spectrometry. Differential scanning calorimetry, wide-angle x-ray scattering and polarized light microscopy indicated the formation of stereocomplexes in racemic blends of PEtOx- b -PLA with opposing chirality. Thereby, the amorphous PEtOx block did not affect the modification of the stereocomplex crystallites, as shown by comparison with data obtained from PLA homopolymer stereocomplexes. Similar to those, the degree of crystallinity and melting temperature decreased with increasing molar mass of the PLA in the stereocomplexes formed from PEtOx- b -PLA block copolymers.

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