Issue 28, 2012
From the journal:

Soft Matter

Effect of crosslinking and long-term storage on the shape-memory behavior of (meth)acrylate-based shape-memory polymers†

Alicia M. Ortega,*a   Christopher M. Yakacki,b   Sean A. Dixon,c   Roxanne Likos,c   Alan R. Greenberga  and  Ken Gallcde  

* Corresponding authors

a Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, CO, USA
E-mail: alicia.ortega@colorado.edu
Fax: +1 303 492 3498
Tel: +1 303 492 7151

b Department of Mechanical Engineering, University of Colorado Denver, Denver, CO, USA
Fax: +1 303 556 6371
Tel: +1 303 556 8516

c School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA
Fax: +1 404 894 9140
Tel: +1 404 894 2888

d George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
Fax: +1 404 894 1658
Tel: +1 404 894 3200

e Research and Development, MedShape, Inc., Atlanta, GA, USA
Fax: +1 404 249 9158
Tel: +1 404 249 9155

Abstract

This work highlights the free- and fixed-strain shape-memory response of amorphous (meth)acrylate-based shape-memory polymers as the level of crosslinking is varied from uncrosslinked to highly crosslinked (corresponding to a decrease in failure strains and overall increase in rubbery moduli and failure stresses). The effect of long-term storage on the free-strain shape-memory response is also considered. Tensile deformation levels during the shape-memory cycle are 90% of failure strain values to determine the full extent of free- and fixed-strain recovery behavior. All materials demonstrate full shape-recovery under free-strain conditions (material is unconstrained during recovery); however, total recoverable strains increase with decreasing crosslinking level, with uncrosslinked and lightly crosslinked materials recovering strains on the order of 3–10× that of moderately and highly crosslinked materials. In contrast, under fixed-strain conditions (material is fully constrained in the fixed shape during recovery), the magnitude of recovery stress generation increases with increasing crosslinking level, with highly crosslinked materials demonstrating recovery stress levels 4–20× that of lightly crosslinked and uncrosslinked materials. The ability to produce recovery stresses on par with those reached during deformation also increases with crosslinking level. Stored-shape fixation and free-strain recovery levels remain stable after long-term storage in the deformed temporary state at 20 °C; however, recovery onset temperatures increase (by up to 9 °C) with storage time spanning ∼1 year, as do rates of free-strain recovery (by up to 9×), due to physical aging. Results indicate that aging could potentially be used as a method for shape-memory response optimization.

Graphical abstract: Effect of crosslinking and long-term storage on the shape-memory behavior of (meth)acrylate-based shape-memory polymers

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Article information

DOI
https://doi.org/10.1039/C2SM25298H
Article type
Paper
Submitted
09 Feb 2012
Accepted
10 May 2012
First published
12 Jun 2012

Soft Matter, 2012,8, 7381-7392

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Effect of crosslinking and long-term storage on the shape-memory behavior of (meth)acrylate-based shape-memory polymers

A. M. Ortega, C. M. Yakacki, S. A. Dixon, R. Likos, A. R. Greenberg and K. Gall, Soft Matter, 2012, 8, 7381 DOI: 10.1039/C2SM25298H

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