Abstract
Seeking a latent-crosslinkable, mechanically flexible, fully thermoplastic shape memory polymer, we have developed a simple but effective macromolecular design that includes pendent crosslinking sites via the chain extender of a polyurethane architecture bearing semicrystalline poly(ε-caprolactone) (PCL) soft segments. This new composition was used to prepare fibrous mats by electrospinning and films by solvent casting, each containing thermal initiators for chemical crosslinking. The one-step synthesis strategy proved successful, and the crosslinking sites within PCL segments resulted in two-way (reversible) shape memory: repeatable elongation (cooling) and contraction (heating) under constant tensile stress. Being fully characterized, the crosslinked fiber mats revealed promising one-way and two-way (reversible) shape memory phenomena, with lower storage moduli though, compared to uncrosslinked films. We observed for both fibrous mats and films that increasing the applied tensile stress led to greater crystallization-induced elongation upon cooling as well as smaller strain hysteresis, particularly for covalently crosslinked samples. Relevant to medical applications, the materials were observed to feature unique, two-stage enzymatic degradation that was sensitive to differences in crystallinity and microstructure among samples.
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References
A. Lendlein and S. Kelch: Shape memory polymers. Angew. Chem., Int. Ed. 41, 2034 (2002).
D. Ratna and J. Karger-Kocsis: Recent advances in shape memory polymers and composite: A review. J. Mater. Sci. 43, 254 (2008).
C. Liu, H. Qin, and P.T. Mather: Review of progress in shape memory polymers. J. Mater. Chem. 17, 1543 (2007).
T. Xie: Tunable polymer multi-shape memory effect. Nature 464, 267 (2010).
K. Yu, T. Xie, J. Leng, Y. Ding, and H.J. Qi: Mechanisms of multi-shape memory effects and associated energy release in shape memory polymers. Soft Matter 8, 5687 (2012).
P.T. Mather, X. Luo, and I.A. Rousseau: Shape memory polymer research. Annu. Rev. Mater. Res. 39, 445 (2009).
J. Li, W.R. Rodgers, and T. Xie: Semi-crystalline two-way shape memory elastomer. Polymer 52, 5320 (2011).
K.K. Westbrook, P.T. Mather, V. Parakh, M.L. Dunn, Q. Qi, B.M. Lee, and H.J. Qi: Two-way reversible shape memory effects in a free-standing polymer composite. Smart Mater. Struct. 20, 065010 (2011).
D.K. Shenoy, D.L. Thomsen, III, A. Srinivasan, P. Keller, and B.R. Ratna: Carbon coated liquid crystal elastomer film for artificial muscle applications. Sens. Actuators, A 96, 184 (2002).
J. Leng, X. Lan, Y. Liu, and S. Du: Shape memory polymers and their composites: Stimulus methods and applications. Prog. Mater. Sci. 56, 1077 (2011).
Y. Yu and T. Ikeda: Soft actuators based on liquid-crystalline elastomers. Angew. Chem., Int. Ed. 45, 5416 (2006).
C. Ohm, M. Brehmer, and R. Zentel: Liquid crystalline elastomers as actuators and sensors. Adv. Mater. 22, 3366 (2010).
S. Krause, F. Zander, G. Bergmann, H. Brandt, H. Wertmer, and H. Finkelmann: Nematic main-chain elastomers: Coupling and orientational behavior. C. R. Chim. 12, 85 (2009).
T. Chung, A. Romo-Uribe, and P.T. Mather: Two-way reversible shape memory in a semicrystalline network. Macromolecules 41, 184 (2008).
R.M. Baker, J.H. Henderson, and P.T. Mather: Shape memory poly(ε-caprolactone)-co-poly(ethylene glycol) foams with body temperature triggering and two-way actuation. J. Mater. Chem. B 1, 4916 (2013).
M. Behl, K. Kratz, J. Zotzmann, U. Nőchel, and A. Lendlein: Reversible bidirectional shape memory polymers. Adv. Mater. 25, 4466 (2013).
J. Zhou, S.A. Turner, S.M. Brosnan, Q. Li, J.Y. Carrilo, D. Nykypanchuk, O. Gang, V.S. Ashby, A.V. Dobrynin, and S.S. Sheiko: Shape-shifting: Reversible shape memory in semicrystalline elastomers. Macromolecules 47, 1768 (2014).
N. Teramoto, H. Kogure, Y. Kimura, and M. Shibata: Thermal properties and biodegradability of the copolymers of L-lactide, ε-caprolactone, and ethylene glycol oligomer with maleate units and their crosslinked products. Polymer 45, 7927 (2004).
P. Ping, W. Wang, X. Chen, and X. Jing: The influence of hard-segments on two-phase structure and shape memory properties of PCL-based segmented polyurethanes. J. Polym. Sci., Part B: Polym. Phys. 45, 557 (2007).
B.K. Kim and S.Y. Lee: Polyurethanes having shape memory effects. Polymer 37, 5781 (1996).
A.E. Senador, Jr., M.T. Shaw, and P.T. Mather: Electrospinning of polymeric nanofibers: Analysis of jet formation. Mater. Res. Soc. Symp. Proc. 661, 5.9.1 (2001).
A. Greiner and J.H. Wendorff: Electrospinning: A fascinating method for the preparation of ultrathin fibers. Angew. Chem., Int. Ed. 46, 5670 (2007).
M.M. Demir, I. Yilgor, E. Yilgor, and B. Erman: Electrospinning of polyurethane fibers. Polymer 43, 3303 (2002).
G. Odian: Principles of Polymerization, 4th ed. (A John Wiley & Sons, Inc., New Jersey, 2004); p. 619.
O. Gȕven: Crosslinking and Scission in Polymers (Springer, Netherlands, 1990); p. 1.
P.C. Boire, M.K. Gupta, A.I.L. Zachman, S.H. Lee, D.A. Balikov, K. Kim, L.M. Bellan, and H. Sung: Pendant allyl crosslinking as a tunable shape memory actuator for vascular applications. Acta Biomater. 24, 53 (2015).
M.I. Lawton, K.R. Tillman, H.S. Mohammed, W. Kuang, D.A. Shipp, and P.T. Mather: Anhydride-based reconfigurable shape memory elastomers. ACS Macro Lett. 5, 203 (2016).
Z. Gan, Q. Liang, J. Zhang, and X. Jing: Enzymatic degradation of poly(ε-caprolactone) film in phosphate buffer solution containing lipases. Polym. Degrad. Stab. 56, 209 (1997).
J. Zeng, X. Chen, Q. Liang, X. Xu, and X. Jing: Enzymatic degradation of poly(L-lactide) and poly(ε-caprolactone) electrospun fibers. Macromol. Biosci. 4, 1118 (2004).
X. Gu, J. Wu, and P.T. Mather: Polyhedral oligomeric silsesquioxane (POSS) suppresses enzymatic degradation of PCL-based polyurethanes. Biomacromolecules 12, 3066 (2011).
X. Luo and P.T. Mather: Preparation and characterization of shape memory elastomeric composites. Macromolecules 42, 7251 (2009).
J.M. Robertson, H.B. Nejad, and P.T. Mather: Dual-spun shape memory elastomeric composites. ACS Macro Lett. 4, 436 (2015).
K.A. Burke, I.A. Rousseau, and P.T. Mather: Reversible actuation in main-chain liquid crystalline elastomers with varying crosslink densities. Polymer 55, 5897 (2014).
M.A. Rice, J. Samchez-Adams, and K.S. Anseth: Exogenously triggered, enzymatic degradation of photopolymerized hydrogels with polycaprolactone subunits: Experimental observation and modeling of mass loss behavior. Biomacromolecules 7, 1968 (2006).
V.P. Saraf, W.G. Glasser, G.L. Wilkes, and J.E. McGrath: Structure-property relationships of PEG-containing polyurethane networks. J. Appl. Polym. Sci. 30, 2207 (1985).
E. McMullin, H.T. Rebar, and P.T. Mather: Biodegradable thermoplastic elastomers incorporating POSS: Synthesis, microstructure, and mechanical properties. Macromolecules 49, 3769 (2016).
A. Valério, D.S. Conti, P.H.H. Araújo, C. Sayer, and S.R.P. da Rocha: Synthesis of PEG-PCL-based polyurethane nanoparticles by miniemulsion polymerization. Colloids Surf., B 135, 35 (2015).
B.S. Lee, B.C. Chun, Y.C. Chung, K.I. Sul, and J.W. Cho: Structure and thermomechanical properties of polyurethane block copolymers with shape memory effect. Macromolecules 34, 6431 (2001).
M. Ahmad, B. Xu, H. Purnawali, Y. Fu, W. Huang, M. Miraftab, and J. Luo: High performance shape memory polyurethane synthesized with high molecular weight polyol as the soft segment. Appl. Sci. 2, 535 (2012).
N. Barkoula, T. Peijs, T. Schimanski, and J. Loos: Processing of single polymer composites using the concept of constrained fibers. Polym. Compos. 26, 114 (2005).
N.K. Kim, S. Fakirov, and D. Bhattacharyya: Polymer–polymer and single polymer composites involving nanofibrillar poly(vinylidene fluoride): Manufacturing and mechanical properties. J. Macromol. Sci., Part B: Phys. 53, 1168 (2014).
S. Jiang, C. He, Y. Men, X. Chen, L. An, S.S. Funari, and C. Chan: Study of temperature dependence of crystallization transitions of a symmetric PEO–PCL diblock copolymer using simultaneous SAXS and WAXS measurements with synchrotron radiation. Eur. Phys. J. E: Soft Matter Biol. Phys. 27, 357 (2008).
M. Krumova, D. López, R. Benavente, C. Mijangos, and J.M. Pereňa: Effect of crosslinking on the mechanical and thermal properties of poly(vinyl alcohol). Polymer 41, 9265 (2000).
J. Park, Q. Ye, E.M. Topp, C.H. Lee, E.L. Kostoryz, A. Misra, and P. Spencer: Dynamic mechanical analysis and esterase degradation of dentin adhesives containing a branched methacrylate. J. Biomed. Mater. Res., Part B 91, 61 (2009).
L. Song, Q. Ye, X. Ge, A. Misra, J.S. Laurence, C.L. Berrie, and P. Spencer: Synthesis and evaluation of novel dental monomer with branched carboxyl acid group. J. Biomed. Mater. Res., Part B 102, 1473 (2014).
C. Liu, S.B. Chun, and P.T. Mather: Chemically cross-linked polycyclooctene: Synthesis, characterization, and shape memory behavior. Macromolecules 35, 9868 (2002).
L.S. Nair and C.T. Laurencin: Biodegradable polymers as biomaterials. Prog. Polym. Sci. 32, 762 (2007).
E.M. Christenson, S. Patel, J.M. Anderson, and A. Hiltner: Enzymatic degradation of poly(ether urethane) and poly(carbonate urethane) by cholesterol esterase. Biomaterials 27, 3920 (2006).
ACKNOWLEDGMENT
We gratefully acknowledge the funding for this work under NSF EFRI-1435452.
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A Latent Crosslinkable PCL-based Polyurethane: Synthesis, Shape Memory, and Enzymatic Degradation (approximately 3.21 MB)
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Kuang, W., Mather, P.T. A latent crosslinkable PCL-based polyurethane: Synthesis, shape memory, and enzymatic degradation. Journal of Materials Research 33, 2463–2476 (2018). https://doi.org/10.1557/jmr.2018.220
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DOI: https://doi.org/10.1557/jmr.2018.220