A latent crosslinkable PCL-based polyurethane: Synthesis, shape memory, and enzymatic degradation
- PDF / 829,822 Bytes
- 14 Pages / 584.957 x 782.986 pts Page_size
- 73 Downloads / 183 Views
INVITED PAPER A latent crosslinkable PCL-based polyurethane: Synthesis, shape memory, and enzymatic degradation Wenbin Kuang and Patrick T. Mathera) Syracuse Biomaterials Institute and Biomedical and Chemical Engineering Department, Syracuse University, Syracuse, New York 13244, USA (Received 11 April 2018; accepted 13 June 2018)
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(e-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 crystallizationinduced 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.
I. INTRODUCTION
Shape memory polymers (SMPs) have attracted a lot of interest, both academically and industrially, based on the ability to set a temporary, nonequilibrium shape until they are triggered to revert to original shape by a specific external stimulus.1–3 Several environmental stimuli that can trigger shape changing of SMPs have been well studied thus far, such as heat, light, humidity, electric field, magnetic field, and variation of pH. Among the external stimuli, heat is the most widely investigated and used, as a result of the ease in ability to tailor thermomechanical properties of thermally actuated SMPs.3 Consequently, thermally activated SMPs offer complexity of material response, including multistage shape change behavior4–6 and reversible (two-way shape memory) actuation.7,8 Such response complexity can then be manipulated and tuned through variations in material composition, fabrication method, and post-synthesis processes. A need exists for rapid and reliable reversible actuation in SMPs to make artificial muscles or other actuators.6,9,10 Addressing this need, liquid crystalline elastomers (LCEs)11,12 have been shown to exhibit excellent performance, attributed to the coupling of the self-organization a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.220 J. Mater. Res., 2018
of the liquid crysta
Data Loading...
