Segmented linear shape memory polyurethanes with thermoreversible Diels-Alder coupling: Effects of polycaprolactone molecular weight and diisocyanate type

Abstract

Abstract. Segmented linear polyurethanes (PUs) containing Diels-Alder (DA) adduct were synthesized in toluene solution from poly("-caprolactone) (PCL, M n = 10, 25 and 50 kg/mol), diisocyanate (methylene diphenyl diisocyanate (MDI), 2,4-toluene diisocyanate (TDI), 1,6-hexamethylenediisocyanate, (HDI)), furfurylamine (FA) and bismaleimide (BMI). The order of the segments in the PUs was -PCL-MDI-FA-BMI-. The PUs were characterized by size-exclusion chromatography (SEC), different spectroscopic ( 1 H-NMR, attenuated total reflectance Fourier-transform infrared, AT-FTIR), thermal and mechanical analysis (differential scanning calorimetry, DSC, dynamical mechanical analysis, DMA). The DA and retro-DA reactions were identified by 1 H-NMR for both the synthesized PU and the coupling components (i.e. FA and BMI). Tensile mechanical and shape memory (SM) properties of the PUs were also determined. The DA coupling in the PU was improved by heat treatment above the melting temperature (T m ) of PCL. DMA traces showed a plateau-like region above T m of PCL confirming the presence of a physical network the netpoints of which are given by the hard segments including the DA couplers. This feature suggested good SM behavior that was confirmed both qualitatively and quantitatively.

One-Pot Synthesis and Characterization of Novel Shape-Memory Poly(ε-Caprolactone) Based Polyurethane-Epoxy Co-networks with Diels–Alder Couplings

“…According to Figure 4 and the data in Table 3 , the glass transition temperature ( T g ) of the samples containing PCD with M n = 2 kg/mol appears in the range from −50 to −40 °C, while T m values are around 20 °C (see Table 3 ). However, T m -s of higher molecular weight PCL segments (e.g., M n = 10 kg/mol) appear at around 60 °C, which is in good agreement with former works on PUs with PCL segments [ 30 , 31 ]. In the case of samples with increasing EP contents (see EP-PU 2 and 6), the Δ H m , and thus the crystallinity values, decreased considerably.…”

Influence of the soft segment nature on the thermomechanical behavior of shape memory polyurethanes

“…Furthermore, T g,DSC increases with increase in the NCO/OH molar ratio. This fact might be due to the increase in the H‐bonding as well as the crosslinking density with the increase in the NCO/OH molar ratio . On Table , it can be observed that T g,DSC values of PTMG‐based SMPUs are higher than T g,DSC values of PEG‐based SMPUs.…”

“…Nowadays, a large number of works have reported the synthesis and characterization of SMPUs. For example, Lakatos synthesized various segmented linear SMPUs containing Diels‐Alder coupling in the main chain and studied their basic mechanical, shape memory and thermomechanical behavior. Moreover, Zhuo et al studied systematically the thermal properties of shape memory polyurethane nanofibrous nonwoven, from the morphology of nanofibers, crystalline structure, isothermal crystallization behavior, and thermal dependent strain recovery.…”

Polyurethane adhesives containing Diels–Alder‐based thermoreversible bonds

“…Crosslinked polymers containing furfuryl and maleimide groups have been reported as well as linear alternatives but the synthetic routes are susceptible toward irreversible side‐reactions (particularly the Michael‐addition which occurs when maleimides are reacted in the presence of free nucleophiles at elevated temperature) or they involve the use maleimides that are not readily commercially available or the perspective is different from ours focusing on other applications including shape memory materials . An elegant approach is presented by Defize et al .…”