Influence of Coupling Agent on the Morphology of Multifunctional, Degradable Shape-Memory Polymers
- PDF / 287,731 Bytes
- 8 Pages / 432 x 648 pts Page_size
- 115 Downloads / 225 Views
Influence of Coupling Agent on the Morphology of Multifunctional, Degradable ShapeMemory Polymers Liang Fang, Wan Yan, Ulrich Nöchel, Michael Zierke, Marc Behl, Karl Kratz, Andreas Lendlein Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, 14513 Teltow, Germany.
ABSTRACT Multifunctional polymer-based biomaterials, which combine degradability and shapememory capability, are promising candidate materials for biomedical implants. An example is a degradable multiblock copolymer (PDC), composed of poly(p-dioxanone) (PPDO) as hard and poly(ε-caprolactone) (PCL) as switching segments. PDC exhibits a unique linear mass loss during hydrolytic degradation, which can be tailored by the PPDO to PCL weight ratio, as well as an excellent thermally induced dual-shape effect. PDC can be synthesized by co-condensation of two oligomeric macrodiols (PCL-diol and PPDO-diol) using aliphatic diisocyanates as coupling agent. Here, we investigated whether different morphologies could be obtained for PDCs synthesized from identical oligomeric macrodiols (PCL-diol with Mn = 2000 g·mol-1 and PPDO-diol with Mn = 5300-5500 g·mol-1) with 2, 2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) and 1, 6-hexamethylene diisocyanate (HDI), respectively. More specifically, atomic force microscopy (AFM) was utilized for an investigation of the surface morphologies in solution casted PDC thin films in the temperature range from 20 °C to 60 °C. The results obtained in differential scanning calorimetry (DSC) and AFM demonstrated that different morphologies were obtained when TMDI (PDC-TMDI) or HDI (PDC-HDI) were used as linker. PCL related crystals in PDC-HDI were more heterogeneous and less ordered than those in PDCTMDI, while HDI resulted in a larger degree of crystallinity than TMDI. This research provides some new suggestions for choosing a suitable coupling agent to tailor the required morphologies and properties of SMPs with crystallizable switching segments. INTRODUCTION Shape-memory polymers (SMPs) have attracted increasing interests recently because they can change from their programmed temporary shape to their permanent (original) shape upon exposure of an external stimulus such as heat [1, 2]. In addition to covalently crosslinked polymer networks with a suitable thermal glass or melting transition acting as switching domains [3, 4], thermoplastic SMPs have also been reported [5-10]. More recently, multifunctional SMPs such as thermoplastic copolyester urethanes, which combine degradability and the capability of a shape-memory effect, have been introduced as candidate implant materials, including the suture [5, 6]. Such copolyester urethanes can be synthesized by the prepolymer method via cocondensation of two oligomeric macrodiols coupled with an (aliphatic) diisocyanate as
57
coupling agent. One example are multifunctional PDC copolyester urethanes, composed of poly(ε-caprolactone) (PCL) and poly(p-dioxanone) (PPDO) segments [5-8]. In PDC, PCL segments are forming the c
Data Loading...
