Competitive Effects of Stereocomplexation and Hyper‐Conjugation of Triethoxysilyl‐Terminated Poly( d ‐lactide) in Poly( l ‐lactide) matrices

Triethoxysilyl‐terminated poly( d ‐lactide)s (eSi‐PDLA) were successfully prepared by hydrosilylation of allyl‐terminated PDLAs (A‐PDLA‐ac) which were readily prepared by ring‐opening polymerization of d ‐lactide and the following terminal protection by acetylation. Their acid‐catalyzed hydrolysis produced hyper‐conjugated PDLAs with terminal silanol coupling. Blend PLLA films containing eSi‐PDLA ( M n  = 2.1 kDa) in 5‐25 wt.% were successfully prepared by the solution casting method. The blend films were found to take a nano‐porous or micro‐phase separation structure, being different from that of the blend PLLA films containing trimethoxysilyl‐terminated poly( d ‐lactide) (mSi‐PDLA) which exhibited particle distribution structure. This difference was reasonably attributed to the different rate of hydrolytic polycondensation of the trimethoxy‐ and triethoxy‐silyl terminals. These results revealed that the competing sterecomplexation/ hyper‐conjugation/phase separation can afford specific morphologies, allowing fine control of properties.