High‐Strain Shape‐Memory Polymers

Abstract

Shape‐memory polymers (SMPs) are self‐adjusting, smart materials in which shape changes can be accurately controlled at specific, tailored temperatures. In this study, the glass transition temperature (Tg) is adjusted between 28 and 55 °C through synthesis of copolymers of methyl acrylate (MA), methyl methacrylate (MMA), and isobornyl acrylate (IBoA). Acrylate compositions with both crosslinker densities and photoinitiator concentrations optimized at fractions of a mole percent demonstrate fully recoverable strains at 807% for a Tg of 28 °C, at 663% for a Tg of 37 °C, and at 553% for a Tg of 55 °C. A new compound, 4,4′‐di(acryloyloxy)benzil (referred to hereafter as Xini) in which both polymerizable and initiating functionalities are incorporated in the same molecule, was synthesized and polymerized into acrylate shape‐memory polymers, which were thermomechanically characterized yielding fully recoverable strains above 500%. The materials synthesized in this work were compared to an industry standard thermoplastic SMP, Mitsubishi's MM5510, which showed failure strains of similar magnitude, but without full shape recovery: residual strain after a single shape‐memory cycle caused large‐scale disfiguration. The materials in this study are intended to enable future applications where both recoverable high‐strain capacity and the ability to accurately and independently position Tg are required.

Thermal Responsive Shape Memory Polymers for Biomedical Applications

“…Deformation temperature memory effect was also observed in PFSA. Such a phenomenon was also observed in a strengthened PVA SMP (Voit, 2010), although no multiple-shape memory effect was reported. A broad glass transition such as the one in PFSA could be viewed as a collection of an infinite numbers of sharp transitions.…”

“…By contrast, thermoset SMPs usually have high R r 's yet their strain-to-failure tend not to be high. Gall's group proposed that an ideal high-strain SMP may exist at the boundary of a thermoset and a thermoplastic, and should have evenly distributed long chains tethered by light enough crosslinking (Voit, 2010). They systematically studied an acrylate crosslinking system to maximize its fully recoverable strain capacity by adjusting the composition of the co-monomers and crosslinkers.…”

Ultraflexible organic electronics

“…Ultrathin OTFTs can be combined with shape-memory polymers (SMPs) 64 to realize mechanically adaptive electronics. 65 For this application, OTFTs are coated with a SMP layer.…”

Review on the Functional Determinants and Durability of Shape Memory Polymers

“…Inherent advantages are their low cost, light weight, dyability, corrosion resistance, electrical insulation, ease of processability (formation and workability), adjustable transition temperature and less-demanding thermo-mechanical treatment, also called training. Beyond this, a maximum strain of several hundred percent can be stored by SMPs [20], in contrast to only about 8% by SMAs [7]. SMPs can be biocompatible and nontoxic.…”

“…Thermoset SMPs have chemical cross-links, which soften, but do not melt at elevated temperatures; instead they either start to burn or decompose. In general, thermoset SMPs have higher stiffness and lower strain capability than thermoplastic SMPs, which are easy to reshape, since they have no covalent bonds between chains (no chemical cross-links) [20]. Physical cross-linking is commonly found in block copolymers, whose morphologies consist of at least two segregated domains.…”