Poly(L-lactide) macrodiols (HOPLLAOH): Influence of linear alkyl diols as initiators: Synthesis and characterization

A series of α,ω-hydroxy telechelic poly(L-lactide)s (HOPLLAOHs) were synthesized by ring-opening polymerization (ROP) of L-lactide (L-LA) using tin octoate [Sn(Oct)₂] as catalyst and a family of linear alkyl diols as initiators [HO–[CH₂]_m–OH, where m = 2, 4, 6, 8, 10, and 12]. A systematic analysis of these HOPLLAOHs species in terms of their thermal properties was realized by DSC. In this sense, the linear alkyl group had an important influence on the glass transition temperature (T_g); a relatively high content of alkyl group on the HOPLLAOH increased the flexibility of the polyester, evidenced by a value of T_g inversely proportional to the weight percent of the alkyl group. Besides, the alkyl groups had an effect on the crystallization temperature (T_c), melting temperature (T_m), and crystallinity (x_i). Additionally, HOPLLAOHs were characterized by ¹H and ¹³C NMR, FT-IR, MALDI-TOF, and GPC.     

Polyurethanes with separately tunable biodegradation behavior and mechanical properties for tissue engineering

Two series (random and block) poly(glycolide‐co‐ε‐caprolactone) macrodiols with various glycolide to ε‐caprolactone ratios (50/50 and 30/70, R‐PG50C, R‐PG30C, B‐PG50C, and B‐PG30C) were synthesized. Next, segmented polyurethanes (PUs) were synthesized based on the synthesized macrodiols, 1,6‐hexamethylene diisocyanate and 1,4‐butanediol (PU‐R30, PU‐R50, PU‐B30, and PU‐B50). Effect of glycolide (G) and ε‐caprolactone (C) monomers arrangement (random or block) on the PUs properties were investigated via FTIR, ¹H NMR, DSC, TGA, DMA, SEM, and mechanical tests. All PUs illustrated T_g (−33°C to −48°C) and T_m (102°C to 139°C) corresponding to the soft and the hard segments, respectively. Polymers based on block macrodiols also showed T_m related to the soft segments. While PUs underwent a two‐step thermal degradation, the PUs based on block macrodiols indicated higher degradation temperature. Dynamic mechanical analysis results evidenced development of a well‐defined microphase separated structure in PU‐R30. Contact angle (about 70°‐80°) and water uptake (around 20% after 24 hours) of the PU films are close to those suitable for tissue engineering materials. The PU based on R‐PG30C (PU‐R30) exhibited the highest tensile strength (2.87 MPa) followed by PU‐B50 and PU‐R50. Over a 63‐day in vitro degradation study in phosphate buffered saline, the PUs showed variable weight loss (up to 40%) depending on their soft segments composition and arrangement. Also, the PUs showed no cytotoxicity. Thus, these PUs with tunable biodegradation rate and mechanical properties are suitable candidates for tissue engineering.