Ultra low density and highly crosslinked biocompatible shape memory polyurethane foams

Abstract

We report the development of highly chemically crosslinked, ultra low density (~0.015 g/cc) polyurethane shape memory foams synthesized from symmetrical, low molecular weight and branched hydroxyl monomers. Sharp single glass transitions (Tg) customizable in the functional range of 45–70 °C were achieved. Thermomechanical testing confirmed shape memory behavior with 97–98% shape recovery over repeated cycles, a glassy storage modulus of 200–300 kPa and recovery stresses of 5–15 kPa. Shape holding tests under constrained storage above the Tg showed stable shape memory. A high volume expansion of up to 70 times was seen on actuation of these foams from a fully compressed state. Low in-vitro cell activation induced by the foam compared to controls demonstrates low acute bio-reactivity. We believe these porous polymeric scaffolds constitute an important class of novel smart biomaterials with multiple potential applications.

Shape memory polyurethanes with oxidation-induced degradation: In vivo and in vitro correlations for endovascular material applications

“…Increasing TEA percentage of the material decrease the T g , while increasing HPED percentage results in increased T g , along with greater crosslink density, higher elastic modulus, and greater hydrophobicity (HH100 contact angle of 77.0 ± 0.6°, HH0 contact angle of 61.3 ± 1.2°, TMH0 contact angle of 84.5 ± 0.5°, and IP/TMH0 97.3 ± 0.4°), results which are better detailed elsewhere [22,25]. These same trends will occur as the diisocyanate is changed from HDI to THMDI to IPDI, in increasing order of modulus, thermal transition, and hydrophobicity.…”

“…Substitution of the diisocyanates or alcohols does not affect gel fraction of the materials (all greater than 98%). Porosity and pore size of the SMPs can be partially controlled through a combination of NCO index, premix viscosity, catalyst concentrations, and concentration of physical blowing agents that are used, as demonstrated by Singhal et al [25]. By removing the catalysts and blowing agents, non-porous films were produced; decreasing premix viscosity and NCO index results in larger pore sizes and reduced densities of the SMPs [22].…”

“…9). Characterization of urea content in similar materials is presented in greater depth by Singhal et al [25]. Solid state 13 C NMR showed no change in the urethane peak resonance (155 ppm); and any potential formation of an aldehyde may be obscured by a spinning side band.…”

Responsive Biomaterials: Advances in Materials Based on Shape‐Memory Polymers

“…[18] Therapeutic embolization entails deliberately blocking a blood vessel (e.g., clipping an aneurysm to prevent internal bleeding, or reducing/stopping blood flow to tumors), and body temperature-responsive poly(ether urethane) SMP-based foams have been shown to be cytocompatible and enable the infiltration of mouse L929 fibroblast cells in vitro which is promising for potential future applications as aneurysm fillers in vivo. [19] Different temperature-responsive polyurethane SMPs that responded to temperature by expanding up to 70 times their original volume were shown to be relatively non-immunogenic in vitro [20] and after 90 days of implantation of radio-opaque analogues in a pig aneurysm model these materials showed low inflammation and good healing responses. [21] 3.…”

Particulate Release From Nanoparticle-Loaded Shape Memory Polymer Foams

“…SMP foams are materials capable of maintaining a temporary shape and, upon application of a thermal, chemical, or optical stimulus, recovering their primary shape [6]. These materials possess tunable thermal and mechanical properties [7][8][9] and are deliverable via catheter [10]. Other potential applications of SMP foams include peripheral vascular occlusion for disease treatment.…”