Abstract
The effect of configuration of an asymmetric bulky initiator 2,2′-[1,1′-binaphtyl-2,2′-diyl- bis-(nitrylomethilidyne)]diphenoxy aluminum isopropoxide (Ini) on structure of copolymer of asymmetric monomer l,l-lactide (Lac) with symmetric comonomer trimethylene carbonate (Tmc) was studied using polarimetry, dilatometry, Size Exclusion Chromatography (SEC), and Carbon Nuclear Magnetic Resonance (13C NMR). When the S-enantiomer of Ini was used the distribution in copolymer chains at the beginning of polymerization is statistical, with alternacy tendency, changing next through a gradient region to homoblocks of Tmc. However, when R-Ini was used, the product formed was a gradient oligoblock one, with Tmc blocks prevailing at the beginning, changing to Lac blocks dominating at the end part of chains. Initiation of copolymerization with the mixture of both initiator enantiomers (S:R = 6:94) gave a multiblock copolymer of similar features but shorter blocks. Analysis of copolymerization progress required complex analysis of dilatometric data, assuming different molar volume contraction coefficients for units located in different triads. Comonomer reactivity ratios of studied copolymerizations were determined.
Highlights
Synthetic biodegradable polymers, e.g., aliphatic polyesters and polycarbonates, as well as copolymers of the corresponding monomers, have attracted increasing attention because of their useful properties for applications in the medical field as materials for temporary medical devices, such as scaffolds in tissue engineering or tissue reconstruction and drug-controlled-delivery systems [1,2].high modulus and high strength polylactides (PLac) have received special interest, as lactide (Lac) derives from annually renewable resources
We determined that the relative reactivities of trimethylene carbonate (Tmc) and Lac in the copolymerization differ considerably from their reactivities in homopolymerizations, as it was observed for ε-caprolactone/Lac systems initiated with the same initiator Ini [32]
One cannot expect any differences in Tmc homopolymerization rates, what was homopolymerization rates, what was confirmed experimentally (initial rate coefficients equal to confirmed experimentally (initial rate coefficients equal to about 0.088 and 0.093 (±5%) L·mol−1 ·s−1
Summary
E.g., aliphatic polyesters and polycarbonates, as well as copolymers of the corresponding monomers, have attracted increasing attention because of their useful properties for applications in the medical field as materials for temporary medical devices, such as scaffolds in tissue engineering or tissue reconstruction and drug-controlled-delivery systems [1,2]. Due to PLac brittleness and relatively low resistance to oxygen and water vapor permeation, the range of possible applications of polylactides is restricted. Those properties could be altered by incorporation of different, suitable comonomer units into the main chain of PLac. Copolymers containing lactide and carbonate units (e.g., trimethylene carbonate (Tmc), Scheme 1): Polymers 2018, 10, 70; doi:10.3390/polym10010070 www.mdpi.com/journal/polymers. 2018, 10, 70 containing lactide and carbonate units (e.g., trimethylene carbonate (Tmc), Scheme
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
