Study on the effect of linear alkyl [CH 2 CH 2 ] m and ether [CH 2 CH 2 O] 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 (HOPLLA_aOH)] and ether group (EG) [HO−PLLA−(CH₂−CH₂−O)_m−PLLA−OH (HOPLLA_eOH)] 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 HOPLLA_aOH (from 19 to 3 °C) and HOPLLA_eOH (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 HOPLLA_aOH (PEU_a) and HOPLLA_eOH (PEU_e) 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 (HOPLLA_4aOH) to 39 °C (PEU_4a) where 4a is indicating four aliphatic methylenes. However, the systematic variation in the repetitive unit from AG and EG in the PEU_a and PEU_e, respectively, it had also the similar effect on the T _g, decreasing the values, for example, PEU_a from 39 to 19 °C and PEU_e from 39 to 17 °C, consistently as such as the previous HOPLLAOH species.

http://ift.tt/2iLbBWP