Long term in vitro biostability of segmented polyisobutylene‐based thermoplastic polyurethanes

Abstract

Long term in vitro biostability of thermoplastic polyurethanes (TPUs) containing mixed polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) soft segment was studied under accelerated conditions in 20% H(2)O(2) solution containing 0.1M CoCl(2) at 50 °C to predict resistance to metal ion oxidative degradation (MIO) in vivo. The PIB-based TPUs showed significant oxidative stability as compared to the commercial controls Pellethane 2363-55D and 2363-80A. After 12 weeks in vitro the PIB-PTMO TPUs with 10-20% PTMO in the soft segment showed 6-10% weight loss whereas the Pellethane TPUs degraded completely in about 9 weeks. Attenuated total reflectance Fourier transform infrared spectroscopy confirmed the degradation of Pellethane samples via MIO by the loss of the ∼1110 cm(-1) aliphatic C-O-C stretching peak height attributed to chain scission, and the appearance of a new peak at ∼1174 cm(-1) attributed to crosslinking. No such changes were apparent in the spectra of the PIB-based TPUs. The PIB-based TPUs exhibited 10-30% drop in tensile strength compared to 100% for the Pellethane TPUs after 12 weeks. The molecular weight of the PIB-based TPUs decreased slightly (10-15%) at 12 weeks. The Pellethane TPUs showed a dramatic decrease in M(n) and an increase in low molecular weight degradation product. Scanning electron microscopy (SEM) showed severe cracking in the Pellethane samples after 2 weeks, whereas the PIB-based TPUs exhibited a continuous surface morphology. The weight loss, tensile, and SEM data correlate well with each other and indicate excellent biostability of these materials.

Polyurethane for biomedical applications: A review of recent developments

“…One way is to replace the soft segment of polyurethane with more stable materials, such as polyolefi ns, polysiloxane, etc. (Ward et al, 2006;Cozzens et al, 2010;Kang et al, 2010), based on the fi ndings that the soft segment played an important role in biostability . With mixed poly-isobutylene (PIB)/poly (tetramethylene oxide) (PTMO) soft segments, Cozzens synthesized a new polyurethane and demonstrated that under accelerated conditions (20% H 2 O 2 solution containing 0.1 M CoCl 2 at 50°C to predict resistance to metal ion oxidative degradation in vivo ), the PIB-based TPUs showed signifi cant oxidative stability when compared to the commercial controls, Pellethane ™ 2363-55D and 2363-80A (Cozzens et al, 2010).…”

Morphology and Mechanical Properties of Thermoplastic Polyurethanes Containing Polyisobutylene/Poly(tetramethylene oxide) Mixed Segments

“…Recently, PIB-based TPUs (including the similar segmented polyureas and polyurethaneureas) have been successfully synthesized (7)(8)(9)(10)(11). As expected, PIB-based TPUs show significantly enhanced biostability (11,12), and their biocompatibility is also comparable to conventional TPUs based on polyether or polyester (13). However, these TPUs exhibited very poor mechanical strength, which limits their practical applications (7)(8)(9)14).…”

Effects of Catalyst Concentration on the Morphology and Mechanical Properties of Polyisobutylene-based Thermoplastic Polyurethanes

“…To solve this problem, TPUs with the SS based on polyisobutylene (PIB), which is wellknown for superior biostability (7), have been successfully developed (8)(9)(10). Although these PIB-based TPUs show significantly enhanced biostability (11,12), their mechanical strength is low (8,9,13,14), and TPUs with high weight fraction of the HS cannot be processed below the decomposition temperature (9). It was later demonstrated that the mechanical properties of PIB-based TPUs can be significantly enhanced by incorporating a small amount of polyether diols into the SS (9,10,15).…”

“…These results provide a very promising approach to prepare biostable TPUs with high mechanical strength. However, since the introduction of polyether diol still decreases the biostability of PIB/PTMO-based TPUs (11), it will be Downloaded by [Umeå University Library] at 21:18 05 April 2015 highly desirable if the mechanical properties of the PIBbased TPUs can be improved without incorporating any ether or ester structure.…”