Preparation, Characterization, and Mechanism for Biodegradable and Biocompatible Polyurethane Shape Memory Elastomers

Abstract

Thermally induced shape memory is an attractive feature of certain functional materials. Among the shape memory polymers, shape memory elastomers (SMEs) especially those with biodegradability have great potential in the biomedical field. In this study, we prepared waterborne biodegradable polyurethane SME based on poly(ε-caprolactone) (PCL) oligodiol and poly(l-lactic acid) (PLLA) oligodiol as the mixed soft segments. The ratio of the soft segments in polyurethanes was optimized for shape memory behavior. The thermally induced shape memory mechanism of the series of polyurethanes was clarified using differential scanning calorimeter (DSC), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS). In particular, the in situ SAXS measurements combined with shape deformation processes were employed to examine the stretch-induced (oriented) crystalline structure of the polyurethanes and to elucidate the unique mechanism for shape memory properties. The polyurethane with optimized PLLA crystalline segments showed a diamond-shape two-dimensional SAXS pattern after being stretched, which gave rise to better shape fixing and shape recovery. The shape memory behavior was further tested in 37 °C water. The biodegradable polyurethane comprising 38 wt % PCL segments and 25 wt % PLLA segments and synthesized at a relatively lower temperature by the waterborne procedure showed ∼100% shape recovery in 37 °C water. The biodegradable polyurethane SME also demonstrated good endothelial cell viability as well as low platelet adhesion/activation. We conclude that the waterborne biodegradable polyurethane SME possesses a unique thermally induced shape memory mechanism and may have potential applications in making shape memory biodegradable stents or scaffolds.

Electrospun hyperbranched polylactic acid–modified cellulose nanocrystals/polylactic acid for shape memory membranes with high mechanical properties

“…The shape fixation ratio determines the ability of the switch segment to be deformed or temporarily shaped. The shape recovery ratio determines the competence of the material to remember permanent shapes . As we can see from the figure, the fixed rate of neat PLA and its composite material was about 90%, which was not changed by the addition of H‐PLA‐CNCs.…”

Shape memory properties and unusual optical behaviour of an interpenetrating network of poly(ethylene oxide) and poly(2‐hydroxyethyl methacrylate)

“…Shape memory polymers (SMPs) are a new class of smart materials which can be given a temporary shape and recover their permanent shape on demand using heat or any other external stimuli such as light, electric field etc . The advantage of SMPs over shape memory alloys are that SMPs offer higher recoverable strain and a wider range of mechanical properties .…”

“…Shape memory polymers (SMPs) are a new class of smart materials which can be given a temporary shape and recover their permanent shape on demand using heat or any other external stimuli such as light, electric field etc. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The advantage of SMPs over shape memory alloys are that SMPs offer higher recoverable strain and a wider range of mechanical properties. 1,2 For example, a shape memory alloy (Nitinol, Ni-Ti alloy) shows maximum recoverable strain up to 8%, shape memory ceramics show maximum recoverable strain less than 1%, whereas SMPs can show recoverable strain up to 100% and the same can be tailored as a function of composition.…”

Shape Memory Properties and Enzymatic Degradability of Poly(ε‐caprolactone)‐Based Polyurethane Urea Containing Phenylalanine‐Derived Chain Extender

“…Most PCL‐based SMPU was designed to recover at or slightly below body temperature according to its biomedical application. Chien et al synthesized degradable polyurethanes, which use PCL to fix a temporary shape and recover around body temperature. Deng et al developed a series of highly stretchable electroactive degradable shape memory copolymers with recovery temperature around 37 °C based on PCL with different molecular weight for application in skeletal muscle tissue engineering.…”