Biodegradable shape memory polyurethanes with controllable trigger temperature

Abstract

A series of random copolymers (PCLAs) were synthesized by ring-opening polymerization of D,L-lactide (LA) and ε-caprolactone (CL) with different molar ratios. PCLA based polyurethanes (PCLAUs) were obtained by chain-extending of PCLA and polytetramethylene ether (PTMEG) with hexamethylene diisocyanate (HDI). All the PCLAUs exhibit good shape memory properties with high shape fixity ratios above 98% and shape recovery ratios above 82% in the first cycle and 91% in the second cycle. PCLAUs with less CL content show faster recovery speed and PCLAUs with more CL content show higher shape recovery ratio. The trigger temperature can be tuned or controlled around body temperature by adjusting the molar ratio of LA to CL. The PCLAUs have potential applications in implant biomedical devices, especially for minimally invasive deployable devices.

A dual‐induced self‐expandable stent based on biodegradable shape memory polyurethane nanocomposites (PCLAU/Fe3O4) triggered around body temperature

“…Based on our previous work, the glass transition temperature of PCLA could be tuned by adjusting the LA/CL molar ratio . The 1 H NMR spectrum of PCLA is presented in Figure .…”

“…Poly( d , l ‐lactide‐ co ‐ɛ‐caprolactone) (PCLA) was synthesized via ring‐opening polymerization of d , l ‐LA and CL catalyzed by Sn(Oct) 2 and initiated by BDO as reported . d , l ‐LA (18.355 g, 0.127 mol), CL (1.615 g, 0.014 mol), BDO (31.5 μL), and Sn(Oct) 2 (0.1 wt %) were added into a round‐bottomed flask with a magnetic stir bar.…”

“…The air in the flask was exchanged with argon. The LA/CL molar ratio was 9:1 to control the trigger temperature of PCLA around body temperature based on our previous work . Shape memory PCLAU was obtained by chain‐extending of the obtained PCLA and PTMEG with HDI .…”

“…1 H NMR spectrum from Bruker DMX 500 NMR spectrometer was used to determine the composition and molecular weight ( M n ) of the copolymer PCLA using CDCl 3 as the solvent and tetramethylsilane as the internal standard. The actual LA/CL molar ratio and the M n of PCLA were calculated from the integral heights of the specific representative hydrogen peaks in the 1 H NMR spectrum . FT‐IR spectrum was monitored on a Bruker Avatar 360 ESP in the range from 4000 to 400 cm −1 to verify the existence of OA wrapped on the surface of Fe 3 O 4 nanoparticles.…”

“…The incorporation of CL into the PLA segments would create an opportunity to tune the trigger temperature of polylactide‐based PUs. Based on our previous work, the transition temperature of PCLAU from random copolymer (PCLA) could be tuned around body temperature by adjusting the LA/CL molar ratio . The present work would present a kind of dual‐induced biodegradable PU nanocomposites for self‐expandable stents triggered around body temperature and also could ensure enough operation time in vivo .…”