Thermoreversibly Crosslinked Poly(ε‐caprolactone) as Recyclable Shape‐Memory Polymer Network

Abstract

A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels-Alder (DA) adducts, star-shaped poly(ε-caprolactones) (PCL) end-functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt-blending complementary end-functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability.

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

“…The latter was obtained by the reaction of isocyanate functionalized prepolymer with FA (see Figure 2). To link the FA-end-functionalized prepolymers to the FA_DGEBA oligomer, BMI was added to the reaction mixture, which led to formation of the DA-adducts (see EP-PU [16][17][18][19][20][21][22][23][24]. It is noteworthy that only selected EP-PU samples were subjected to some investigations to keep this contribution in limits.…”

“…The first synthetic way for the preparation of samples EP-PU 1-15 was the incorporation of a HO-ended DA adduct in the networks composed of isocyanate (HDI) terminated polyurethane prepolymer and DGEBA and followed by crosslinking of the EP-component by polyetheramine (Jeffamine ® EDR 176). The other synthetic route utilized the reaction between furanyl end-functionalized PU polymers and FA_DGEBA oligomer in the presence of BMI as the coupling agent (samples EP-PU [16][17][18][19][20][21][22][23][24]. Thus, the two synthetic routes differed from one another in generation of the DA-adducts and in the composition of the co-networks.…”

“…Table 4. Although the mechanical properties of the EP-PU systems prepared by the second synthetic approach (i.e., containing polymerized EP resin and DA adducts) do not show clear trends, some important conclusions can be drawn from the data in Table 5: (i) at low EP resin content, the increasing amount of the DA coupling agent considerably reduced the elongation at break (see samples EP-PU 16 and EP-PU 17); (ii) increase in the amount of EP resin in the samples prepared with PCL of M n = 10 kg/mol resulted in higher E-moduli (see samples EP-PU [16][17][18][19][20], while an opposite trend can be observed for the samples with PCL of M n = 50 kg/mol (see samples EP-PU 21 to 24); (iii) the elongation at break decreased with increasing EP content and with the M n of PCL; and (iv) the E-moduli are higher and the elongations at break values for the EP-PUs prepared by the second synthetic route (Scheme 2) are lower than those prepared by the first one (Scheme 1).…”

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

“…The authors emphasized that reversible photocrosslinking may be a promising way to produce light-sensitive SMPs. Defize and coworkers [32,33] used the Diels-Alder reaction to create temporary crosslinks. They synthesized star-shaped PCLs with furan, anthracene and maleimide end functionalities, respectively.…”

Shape Memory Systems with Biodegradable Polyesters

“…The SM function was lost when the material was heated to T~160 o C where the retro reaction, disconnecting the crosslinks, took place. Defize et al [23][24] synthesized star-shaped PCLs with furan, anthracene and maleimide end functionalities, respectively. The resulting SMPs showed excellent Rf and Rr values, even after 4 cycles, using Tm of the PCL as Ttrans (=65 o C).…”