Random copolymerizations of L-lactide with (R)-, (S)-, or rac-1-methyltrimethylene carbonate with bis(pentamethylcyclopentadienyl) samarium-methyl tetrahydrofuranate [(C 5 Me 5 ) 2 SmMe(THF)] as a novel initiator provided high molecular weight polymers with low polydispersities. Biodegradation of the resulting polymers with tricine and {N-[tris(hydroxymethyl)methyl]-2-aminoethane sulfonic acid (TES) buffers as well as activated sludge showed only a small weight loss, whereas the polymer with proteinase K revealed high biodegradability independent of the optical activity of 1-methyltrimethylene carbonate.

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Diblock copolymerizations of L‐ or D,L‐lactide (LA) with trimethylene carbonate (TMC) or 2,2‐dimethyltrimethylene carbonate (2,2‐DTMC) with SmMe(C5Me5)2‐(tetrahydrofuran) as an initiator and triblock copolymerizations of L‐ or D,L‐LA/cyclic carbonates/L‐ or D,L‐LA with [Sm(C5Me5)2]2(PhCCCCPh) as an initiator generated the desired block copolymers. This article describes the comparison of biodegradabilities by proteinase K and a compost and mechanical properties between the resulting di‐ or triblock copolymers and random copolymers composed of L‐ or D,L‐LA and cyclic carbonates. The scanning electron microscopic profiles of resulting polymers were measured to understand the morphological change during biodegradation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3572–3588, 2003

Random and block copolymerizations of L‐ or D‐lactide with ε‐caprolactone (CL) were performed with a novel anionic initiator, (C5Me5)2SmMe(THF), and they resulted in partial epimerization, generating D,L‐ or meso‐lactide polymers with enhanced biodegradability. A blend of PLLA‐r‐PCL [82/18; PLLA = poly(L‐LA) and PCL = poly(ε‐caprolactone)] and PDLA‐r‐PCL [79/21; PDLA = poly(D‐LA)] prepared by the solution‐casting method generated a stereocomplex, the melting temperature of which was about 40 °C higher than that of the nonblended copolymers. A blend of PLLA‐b‐PCL (85/15) and PDLA‐b‐PCL (82/18) showed a lower elongation at break and a remarkably higher tensile modulus than stereocomplexes of PLLA‐r‐PCL/PDLA‐r‐PCL and PLLA/PDLA. The biodegradability of a blend of PLLA‐r‐PCL (65/35) and PDLA‐r‐PCL (66/34) with proteinase K was higher than that of PLLA‐b‐PCL (47/53) and PDLA‐b‐PCL (45/55), the degradability of which was higher than that of a PLLA/PDLA blend. A blend film of PLLA‐r‐PDLLA (69/31)/PDLA‐r‐PDLLA (68/32) exhibited higher degradability than a film of PLLA/PDLLA [PDLLA = poly(D,L‐LA)]. A stereocomplex of PLLA‐r‐PCL‐r‐PDMO [80/18/2; PDMO = poly(L‐3,D,L‐6‐dimethyl‐2,5‐morpholinedion)] with PDLA‐r‐PCL‐r‐PDMO (81/17/2) showed higher degradability than PLLA‐r‐PDMO (98/2)/PDLA‐r‐PDMO (98/2) and PLLA‐r‐PCL (82/18)/PDLA‐r‐PCL (79/21) blends. The tensile modulus of a blend of PLLA‐r‐PCL‐r‐PDMO and PDLA‐r‐PCL‐r‐PDMO was much higher than that of a blend of PLLA‐r‐PDMO and PDLA‐r‐PDMO. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 438–454, 2005