Shape Memory Polymers Based on Naturally-Occurring Bile Acids

Abstract

Naturally occurring bile acids are ideal building blocks for a new generation of biomaterials displaying low systemic toxicity and engineered properties. Herein we report the synthesis of bile acid-based polyesters using entropy-driven ring-opening metathesis polymerization (ED-ROMP) and characterization of the structure of the resulting polymers. The materials synthesized display high molecular weights (M n above 100000), typical of ED-ROMPs. The mechanical and responsive behavior of these bile acid-based polyesters (BAPs) is studied by dynamic mechanical analysis (DMA) and thermomechanical cycling. Although BAPs are amorphous thermoplastics, they display typical rubber-like elasticity with tunable mechanical behavior, glass transitions close to body temperature, and outstanding shape memory properties. By introducing small changes in the chemical structure of BAPs (amide bonds or additional hydroxyl groups), we were able to correlate the materials' stiffness, their T g and shape recovery temperature to their structure. In addition, we show that BAPs can be deformed to high strains even at low temperature and still display shape recovery.

Polymers made of bile acids: from soft to hard biomaterials

“…Upon warming to room temperature, the shape recovery process triggers the tightening of the knot. 77 (Reprinted with permission from Gautrot and Zhu. 77 Copyright 2009 American Chemical Society.)…”

“…77 (Reprinted with permission from Gautrot and Zhu. 77 Copyright 2009 American Chemical Society.) Fig.…”

“…73,74 Gautrot et al demonstrated the use of a second-generation Grubbs catalyst in the ring-opening polymerization of cyclic CA monomers yielding high (M n above 100 kDa) molecular weight polymers. [75][76][77][78] The resulting polymers had elastomeric properties and were degradable with rates in the order of several months in phosphate-buffered saline solution at 37°C. Alternatively, these polymers may be synthesized by the use of lipase in the ringopening polymerization of the macrocyclic monomers.…”

Synthesis of Terpene-Based Polymers

“…The same procedure has been applied to synthesize shape memory polymers based on cholic and lithocholic acid [105]. Also, high molecular weight copolyesters Scheme 10 Entropy-driven ROMP of a lithocholic acid-based macrocycle [104] (M n ¼ 70-226 kg/mol, PDI ¼ 2.0-2.5) based on lithocholic and ricinoleic acid have been prepared [106].…”

Review on the Functional Determinants and Durability of Shape Memory Polymers

“…Biodegradable SMPs with controllable degradation behavior provide interesting advantages over other implant materials, because much of today's follow-on surgery in removing the implants can thus be avoided. With this concept in mind, biodegradable SMPs based on poly(DL-lactide) and PCL [78,148,[244][245][246][247][248][249], blends based on poly(L-lactide-co-ε-caprolactone) and poly(L-lactide-co-glycolide) [250], SMPs based on bile acids [251,252] and many others [253][254][255][256][257] have been synthesized. Recent research trends regarding medical applications of SMPs have been summarized by Sokolowski et al [149], Mather et al [13], Small et al [258] and Lendlein et al [259].…”