Supporting Information α-amino Acid-Based Poly(Ester Urea)s as Multi-Shape Memory Pol-ymers for Biomedical Applications Gregory I. Peterson, Andrey V. Dobrynin, Matthew L. Becker* The University of Akron, Department of Polymer Science, Akron, OH, 44325-399, USA Supporting Figures Table S1. Molecular weight, dispersity, glass transition (T g ), and storage modulus (E ) characterization for the L-valine (VAL)-based poly(ester urea)s. Polymer M n [kda] a) Ð M a) T g [ºC] b) E at 23 ºC [MPa] E at 37 ºC [MPa] p(1-val-6) 39 1.8 73.1±.5 1429 138 p(1-val-8) 7 1.7 62.1±1.8 1262 1214 p(1-val-1) 5 1.8 47.5±1.4 886 734 p(1-val-12) 18 1.6 43.7±1.9 99 6 a) Determined by comparison to poly(styrene) calibration standards using gel permeation chromatography (GPC) with refractive index detector and N,N-dimethylformamide (DMF) as solvent; b) T g from E. Values with errors are an average of three runs ± one standard deviation. Figure S1. FT-IR spectrum of p(1-val-8) at room temperature. The ester and urea carbonyl stretches are boxed.
X-Ray Diffraction X-ray diffraction (XRD) data was collected on a Rigaku Ultima IV X-ray diffractometer. 15 1 5 1 2 3 4 5 6 7 Figure S2. XRD spectrum for p(1-val-6). 4 3 2 1 1 2 3 4 5 6 7 Figure S3. XRD spectrum for p(1-val-8). 3 2 1 1 2 3 4 5 6 7 Figure S4. XRD spectrum for p(1-val-1).
1 5 1 2 3 4 5 6 7 Figure S5. XRD spectrum for p(1-val-12). Dynamic Mechanical Analysis (DMA) Temperature Sweep Data Rectangular DMA specimens (25 x 5 x.5 mm) were prepared by compression molding. The T g was characterized with a DMA Q8 instrument (TA Instruments) with elongation/thin film fixtures. Single frequency (1 Hz), strain-based (15 µm amplitude), temperature sweep ( to 12 ºC at a rate of 3 C min -1 ) experiments were conducted on three independent samples. Figures S6 and S7 show the loss modulus (E ) and tan δ curves that correspond to the DMA data in Figure 1 (main text). Figure S6. DMA single frequency (1 Hz) temperature sweep (3 ºC/min) experiment for each PEU. Plotted is the loss modulus as a function of temperature.
Figure S7. DMA single frequency (1 Hz) temperature sweep (3 ºC/min) experiment for each PEU. Plotted is the tan δ as a function of temperature. Sterilization Materials were sterilized in a AN74i Anprolene gas sterilizer (Andersen Sterilizers Inc.) with a 12 h ethylene oxide (EtO) step followed by 48 h purge. Materials were put under high vaccum for an addition 48 h (not optimized) to fully remove all EtO from the material (EtO plasticizes the material and decreases the T g if not fully removed). As shown in Figure S8, the material has the same thermal behavior prior to and after sterilization, indicating that no degradation of the material has occurred. Figure S8. DMA single frequency temperature sweep experiment for p(1-val-8) pre- (normal) and post- (sterile) sterilization showing no loss in material performance. FT-IR IR spectra were collected on a Nicolet i55 FT-IR (Thermo Scientific). Polymer samples were dissolved in chloroform and applied to a KBr salt plate which was fixed in a heated chamber. Samples were equilibrated at a specific temperature for 15 min prior to collection of the spectrum (32 scans, 8 cm -1 resolution).
Shape Memory Characterization Cyclic thermomechanical testing was conducted using a DMA Q8 instrument. Testing was completed in controlled force mode with heating and cooling rates of 1 C min -1. The R f and R r for dual-shape memory testing were calculated using Equation 1 and 2: =, 1% (1) =,,, 1% (2) where ε II,load is the maximum strain achieved in programming the temporary shape (II), ε II is the strain after the load is removed, ε I,rec is the strain after recovering the permanent shape (I), and ε I is the initial strain of the permanent shape. The R f and R r for multi-shape memory testing were calculated using Equation 3 and 4: =, 1% (3) =, 1% (4) where the subscripts y and x indicate the strains of a given fixed shape, the load subscript indicates that it is the maximum strain achieved before the load is removed, and the rec subscript indicates the recovered strain for a given shape.