Elastomeric polyamide biomaterials with stereochemically tuneable mechanical properties and shape memory

Abstract

Biocompatible polymers are widely used in tissue engineering and biomedical device applications. However, few biomaterials are suitable for use as long-term implants and these examples usually possess limited property scope, can be difficult to process, and are nonresponsive to external stimuli. Here, we report a class of easily processable polyamides with stereocontrolled mechanical properties and high-fidelity shape memory behaviour. We synthesise these materials using the efficient nucleophilic thiol-yne reaction between a dipropiolamide and dithiol to yield an α,β − unsaturated carbonyl moiety along the polymer backbone. By rationally exploiting reaction conditions, the alkene stereochemistry is modulated between 35-82% cis content and the stereochemistry dictates the bulk material properties such as tensile strength, modulus, and glass transition. Further access to materials possessing a broader range of thermal and mechanical properties is accomplished by polymerising a variety of commercially available dithiols with the dipropiolamide monomer.

Concomitant control of mechanical properties and degradation in resorbable elastomer-like materials using stereochemistry and stoichiometry for soft tissue engineering

“…This behavior is consistent with a more elastic material that is expected from the interruption of crystallinity through the introduction of ester groups into the main chain that disrupt chain packing and increase chain mobility. These findings were confirmed via differential scanning calorimetry (DSC) which showed that increasing % cis without altered succinate content increased the glass transition temperature in line with results from our previous work 5 , 29 . Significantly, the materials exhibit high thermal stability and the onset of degradation temperatures exceeds 350 °C.…”

“…Until now, no synthetic resorbable elastomer or elastomer-like polymer system have afforded independent control of mechanical properties and degradation de novo 2 . We recently reported the first metal-free, stereocontrolled step-growth polymerization via a nucleophilic thiol-yne addition which yielded a series of thermally-processable elastomers in which the mechanical properties were controlled by the double bond stereochemistry 5 , 29 . The double bond stereochemistry (% cis ) in each thiol-yne step growth polymer was tuned based on solvent polarity and organic base which is able to preferentially direct the thiol addition to the cis stereochemistry.…”

“…These materials also exhibit anisotropic degradation as a consequence of the presence of both amorphous and crystalline domains which leads to limited control over the resorption timelines [2][3][4] . Attempts to engineer elastomeric materials with mechanical properties similar to native tissues have been focused on non-degradable systems 5,6 . While these have been directed towards obtaining materials that possess the elastic properties of natural rubber, they have not followed its design principles, namely the incorporation of cis-1,4 alkene segments, to control the mechanical properties.…”

Shape memory elastomers: A review of synthesis, design, advanced manufacturing, and emerging applications

“…Elastomeric materials have also been utilized in biomedical applications such as biomaterial design and tissue engineering. Worch et al 202 have developed a biocompatible elastomeric polyamide with shape memory properties to be used in long‐term implants. They have also studied high trans samples with 67% trans and high cis samples with 86% cis for their hydrolytic stability and water uptake behaviors in relation to biocompatibility and shape memory properties.…”

3D-printed NIR-responsive shape memory polyurethane/magnesium scaffolds with tight-contact for robust bone regeneration

“…Shape memory polymers (SMPs), a kind of burgeoning smart materials, have captured extensive attention in the biomedical field [ [17] , [18] , [19] , [20] , [21] ]. SMPs have the ability to switch its shape between a programmed and an initial state under various stimuli such as heat [ 22 , 23 ], light [ 24 , 25 ], water [ 26 , 27 ], or magnetism [ 28 , 29 ].…”