In designing copolymers for thermally induced shape-memory effect it is very important to keep in mind that a slight change in chemical structure (cis/trans ratios, tacticity, molecular mass, etc.) produces a significant change in the shape-memory polymer. An example is the copolymer of poly(methylmethacrylate-co-methacrylic acid) or poly(MAA-co-MMA) compared to poly(MAA-co-MMA)-PEG, where PEG is short for poly(ethylene glycol) which forms complexes in the copolymer.
Changes in the morphology of the material including PEG provide shape-memory effect to the copolymer, showing two phases, the three-dimensional network providing a stable phase and the reversible phase formed by the amorphous part of the PEG-PMAA complexes. The complexes show a high modulus storage capacity, so when a PEG of higher molecular mass is introduced into the copolymer, an increase in the elastic modulus, higher modulus in the glassy state and faster recovery are observed.
Its properties can be studied with differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and dynamic mechanical analysis (DMA) techniques to determine its physicochemical arrangement.