Stress-induced melting of crystals in natural rubber: a new way to tailor the transition temperature of shape memory polymers.

Lightly cross-linked natural rubber (NR, cis-1,4-polyisoprene) was found to be an exceptional cold programmable shape memory polymer (SMP) with strain storage of up to 1000%. These networks are stabilized by strain-induced crystals. Here, we explore the influence of mechanical stress applied perpendicular to the elongation direction of the network on the stability of these crystals. We found that the material recovers its original shape at a critical transverse stress. It could be shown that this is due to a disruption of the strain-stabilizing crystals, which represents a completely new trigger for SMPs. The variation of transverse stress allows tuning of the trigger temperature T(trig) (σ) in a range of 45 to 0 °C, which is the first example of manipulating the transition of a crystal-stabilized SMP after programming.

[1]  Andreas Lendlein,et al.  Temperature‐Memory Polymer Networks with Crystallizable Controlling Units , 2011, Advanced materials.

[2]  J. Carretero‐González,et al.  Uncertainties in the Determination of Cross-Link Density by Equilibrium Swelling Experiments in Natural Rubber , 2008 .

[3]  H. Marand,et al.  Determination of the equilibrium melting temperature of polymer crystals : linear and nonlinear hoffman-weeks extrapolations , 1998 .

[4]  G. Yeh,et al.  Strain‐induced crystallization, Part IV: Induction time analysis , 1979 .

[5]  G. Yeh,et al.  Morphology of strain‐induced crystallization of natural rubber. I. Electron microscopy on uncrosslinked thin film , 1972 .

[6]  N. Goo,et al.  Electroactive Shape‐Memory Polyurethane Composites Incorporating Carbon Nanotubes , 2005 .

[7]  Frank Katzenberg,et al.  Superheated rubber for cold storage. , 2011, Advanced materials.

[8]  Shinzo Kohjiya,et al.  Orientation and Crystallization of Natural Rubber Network As Revealed by WAXD Using Synchrotron Radiation , 2004 .

[9]  G. Yeh,et al.  Morphology of strain-induced crystallization of natural rubber. Part II. X-Ray studies on cross-linked vulcanizates , 1973 .

[10]  R. Langer,et al.  Light-induced shape-memory polymers , 2005, Nature.

[11]  Paul J. Flory,et al.  Thermodynamics of Crystallization in High Polymers. I. Crystallization Induced by Stretching , 1947 .

[12]  R. Caston,et al.  Equations of state for natural and synthetic rubber-like materials. I. Unaccelerated natural soft rubber , 1942 .

[13]  G. Yeh,et al.  Strain‐induced crystallization I. Limiting extents of strain‐induced nuclei , 1976 .

[14]  T. Xie,et al.  Strain‐Based Temperature Memory Effect for Nafion and Its Molecular Origins , 2011 .

[15]  M. Maugey,et al.  Shape and Temperature Memory of Nanocomposites with Broadened Glass Transition , 2007, Science.

[16]  G. Yeh,et al.  Strain‐induced crystallization, Part III: Theory , 1979 .

[17]  K. Gall,et al.  Impact of shape-memory programming on mechanically-driven recovery in polymers , 2011 .

[18]  A. Lendlein,et al.  Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[19]  Shinzo Kohjiya,et al.  Crystallization and stress relaxation in highly stretched samples of natural rubber and its synthetic analogue , 2006 .

[20]  S. Toki,et al.  Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique , 2000 .

[21]  G. Yeh.  Strain‐induced crystallization II. Subsequent fibrillar‐to‐lamellar transformation , 1976 .

[22]  Melodie F Metzger,et al.  Photothermal properties of shape memory polymer micro‐actuators for treating stroke * , 2002, Lasers in surgery and medicine.

[23]  I. Šics,et al.  Molecular orientation and structural development in vulcanized polyisoprene rubbers during uniaxial deformation by in situ synchrotron X-ray diffraction , 2003 .

[24]  Tao Xie,et al.  Significant Impact of Thermo-Mechanical Conditions on Polymer Triple-Shape Memory Effect , 2011 .