Study on the effect of linear alkyl [CH2CH2]m and ether [CH2CH2O]m groups in the α,ω-hydroxy telechelic poly(L-lactide) (HOPLLAOH) and their poly(ester-urethanes) (PEUs). Synthesis and Characterization

Abstract

α,ω-Hydroxy telechelic poly(L-lactides) (HOPLLAOH) were synthesized by ring-opening polymerization of the L-lactide (L-LA) catalyzed by tin octoate [Sn(Oct)2] in the presence of two different types of initiators such as alkyl diols [HO−(CH2−CH2)m−OH] and ether diols [HO−(CH2−CH2−O)m−H] (where m = 2, 3, 4, 5, 6, and 8), and eventually, two different families of HOPLLAOH where the alkyl group (AG) [HO−PLLA−(CH2−CH2)m−PLLA−OH (HOPLLAaOH)] and ether group (EG) [HO−PLLA−(CH2−CH2−O)m−PLLA−OH (HOPLLAeOH)] are part of the backbone of the polymer with a systematic increase in these segments were synthesized. The number average molecular weight (M n) for all samples were similar [M n(NMR) = 1610–1980]. The weight percent (wt.%) of AG and EG had a dramatic effect on the glass transition temperature (T g) of HOPLLAaOH (from 19 to 3 °C) and HOPLLAeOH (from 19 to −1 °C), respectively, where the wt.% of AG or EG induced a decrease on the T g with a relationship that was inversely proportional. For poly(ester-urethanes) (PEUs) derived from HOPLLAaOH (PEUa) and HOPLLAeOH (PEUe) and 1,6-hexamethylene diisocyanate (HDI) showed an increase in the values of T g attributed to the hydrogen bonding of the urethanes groups in the main chain, for example from 19 (HOPLLA4aOH) to 39 °C (PEU4a) where 4a is indicating four aliphatic methylenes. However, the systematic variation in the repetitive unit from AG and EG in the PEUa and PEUe, respectively, it had also the similar effect on the T g, decreasing the values, for example, PEUa from 39 to 19 °C and PEUe from 39 to 17 °C, consistently as such as the previous HOPLLAOH species.