Abstract
The living ring-opening polymerization of l-lactide was carried out by using organocatalyst to synthesize the molecular weight controlled poly( l-lactide) with an phenylacetylenyl end group (HC C PLLA), then the homopolymerization of HC C PLLA was performed by using two different rhodium catalysts. Low molecular weight poly-PLLA 6-1 ( M w,SEC-MALLS = 46,700) was synthesized by using Rh(nbd)BPh 4 as the catalyst, and higher molecular weight poly-PLLA 6-2 ( M w,SEC-MALLS = 471,000) was synthesized by using the [Rh(nbd)Cl] 2/Et 3N catalyst system. Then high molecular weight poly-PLLA 20, poly-PLLA 29, and poly-PLLA 68 were successfully synthesized by using the [Rh(nbd)Cl] 2/Et 3N catalyst system. The α values of the poly-PLLAs using [Rh(nbd)Cl] 2/Et 3N catalyst system were all in the range of 0.6–0.8, this means that these polymers possess linear flexible chain. It is concluded that [Rh(nbd)Cl] 2/Et 3N was more suitable for the synthesis of the cylindrical polymer brush, poly-PLLA with high molecular weight. The analyses of the CD spectra indicated that poly-PLLA possesses a predominantly one-handed helical conformation, temperature and solvents had significant influences on the helical structure of poly-PLLA.
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