화학공학소재연구정보센터
Macromolecules, Vol.46, No.21, 8509-8518, 2013
Synthesis and Stereocomplex Formation of Star-Shaped Stereoblock Polylactides Consisting of Poly(L-lactide) and Poly(D-lactide) Arms
The synthesis of star-shaped polylactides (PLAs) having both poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) arms in one molecule, i.e., stereo-miktoarm star-shaped PLAs, is described. The azido-functionalized PDLAs and ethynyl-functionalized PLLA possessing linear and two- and three-branched structures were prepared by the ring-opening polymerization of D-lactide and L-lactide using azido- or ethynyl-functionalized initiators. The number-average molecular weights (M(n,NMR)s) of the PLAs were ca. 5000 g, mol(-1) with narrow molecular weight distributions (M-w/M(n)s) of less than 1.18. The click reaction of the azido-functionalized PDLAs and the ethynyl-functionalized PLLAs using the copper(I) bromide/N,N,N',N '',N ''-pentamethyldiethylenetriamine catalyst in a mixed solvent of dichloromethane/1,1,1,3,3,3-hexafluoro-2-propanol (14/1, v/v) gave a linear stereoblock PLA as well as 3-, 4-, 5-, and 6-armed stereo-miktoarm star-shaped PLAs with M(n,NMR)s of ca. 10 000 g mol(-1) and M-w/M(n)s of less than 1.16. The wide-angle X-ray scattering and differential scanning calorimetry measurements proved that these stereo-miktoarm star-shaped PLAs formed stereocomplex crystals without any trace of homochiral crystallization.