Buwalda S.J. - Stereocomplexed 8-armed poly(ethylene glycol)epoly(lactide) star blockcopolymer hydrogels: Gelation mechanism, mechanical properties and degradation behavior

Sytze J. Buwalda, Lucia Calucci, Claudia Forte, Pieter J. Dijkstra, Jan Feijen

Polymer 2012

Abstract

Mixing aqueous poly(ethylene glycol)-poly(D-lactide) and poly(ethylene glycol)-poly(L-lactide) star block
copolymer solutions resulted in the formation of stereocomplexed hydrogels within 1 min. A study
towards the mechanism of the temperature dependent formation of stereocomplexes in the hydrogels
using rheology and nuclear magnetic resonance experiments revealed that the formation of stereocomplexes
is facilitated at higher temperatures, due to rearrangement in the micellar aggregates thereby
exposing more PLA units available for stereocomplexation. The formed gels became temperature irreversible
due to the presence of highly stable semi-crystalline stereocomplexed PLA domains. An enantiomeric
mixture of 8-armed star block copolymers linked by an amide group between the poly(ethylene
glycol) core and the poly(lactide) arms (PEGe(NHCO)e(PLA)8) yielded hydrogels with improved
mechanical properties and stability at 37 C in PBS compared to 8-armed star block copolymers linked by
an ester group. The possibility to be formed in situ in combination with their robustness make PEG
e(NHCO)e(PLA)8 hydrogels appealing materials for various biomedical applications.