Strain‐Based Temperature Memory Effect for Nafion and Its Molecular Origins

Abstract

A shape memory polymer traditionally refers to a polymer that can memorize one temporary shape and recover to its permanent shape upon exposure to an external stimulus. Although this basic concept has been known for at least half a century, recent advances have led to the discoveriy of previously uncovered memory properties that challenge the traditional concept of shape memory polymers. In particular, a temperature memory effect refers to the capability of a polymer to memorize temperatures instead of shapes. Thus far, the reported temperature memory effect has been established under iso‐strain stress recovery conditions, in which the maximum recovery stress appears at a temperature roughly identical to the deformation temperature. This effect can be called recovery stress based temperature memory effect. In this work, experiments were designed in an attempt to establish a temperature memory effect based on the stress free strain recovery behaviors of Nafion. The results show that, under carefully selected conditions, the temperature at which a maximum strain recovery rate is observed can indeed be quantitatively related to the deformation temperature. In addition, indications that the polymer is capable of memorizing more than one deformation temperature (i.e., multi‐temperature memory effect) are shown. The molecular origin of Nafion’s temperature memory effect is elucidated through small angle neutron scattering study.

Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers

“…Hence, the thermal history of the membrane changes the whole membrane morphology as evidenced from the differences in the entire q -spectra, from small to wide angles. The findings reported here also support and explain the origin and shed light on the mechanism of the previously observed effects of annealing temperature on the matrix knee and ionomer peak. , …”

Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers

“…Hence, the thermal history of the membrane changes the whole membrane morphology as evidenced from the differences in the entire q -spectra, from small to wide angles. The findings reported here also support and explain the origin and shed light on the mechanism of the previously observed effects of annealing temperature on the matrix knee and ionomer peak. , …”

Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

“…In addition, overlapping between recoveries at 65 and 94 °C appears limited (Figure ), and only slight differences by 5 °C between switch temperature and stretching temperature are observed. Similar discrepancies were also observed for several SMPs ,, and could be attributed to the width of the glass transition and of the α-relaxation (Figure and Table ). However, switch temperatures are also sensitive to the heating rate during recovery and creep during cooling, in accordance with the broad recovery profile observed at high stretching temperature (Figure ).…”

“…As a conclusion, the double stretching step at 94 and 65 °C modifies the recovery process and generates a convolution of the corresponding recoveries in dual-shape memory experiments (Figure 4). A similar behavior was observed for Nafion 15,18 and undoubtedly demonstrates that the symmetric PLLA/PMMA blend could store multiple shapes upon a specific programming step. Two recovery events with well-defined switch temperatures could be programmed using a double stretching step, and triple-shape memory effects were subsequently attempted with a recovery step performed at staged temperatures of 70 and 94 °C (according to the switch temperatures of the corresponding dual-shape memory experiments).…”

Tunable Shape Memory Polymers from α-Amino Acid-Based Poly(ester urea)s

“…With the exception of the tests completed using a T d of 30 °C, which is below the T g of the material, the peak recovery stress was within ca. 5 °C from the T d , which is consistent with other temperature memory materials . To confirm that the material would also show a strain-based TME, multiple samples were heated at various T d s and then stretched to 100% strain; then the samples were heated in the absence of a tensile load, and the recovery of the permanent shape was monitored as a function of time and temperature.…”

Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers

“…Hence, the thermal history of the membrane changes the whole membrane morphology as evidenced from the differences in the entire q -spectra, from small to wide angles. The findings reported here also support and explain the origin and shed light on the mechanism of the previously observed effects of annealing temperature on the matrix knee and ionomer peak. , …”

Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

“…In addition, overlapping between recoveries at 65 and 94 °C appears limited (Figure ), and only slight differences by 5 °C between switch temperature and stretching temperature are observed. Similar discrepancies were also observed for several SMPs ,, and could be attributed to the width of the glass transition and of the α-relaxation (Figure and Table ). However, switch temperatures are also sensitive to the heating rate during recovery and creep during cooling, in accordance with the broad recovery profile observed at high stretching temperature (Figure ).…”

“…As a conclusion, the double stretching step at 94 and 65 °C modifies the recovery process and generates a convolution of the corresponding recoveries in dual-shape memory experiments (Figure 4). A similar behavior was observed for Nafion 15,18 and undoubtedly demonstrates that the symmetric PLLA/PMMA blend could store multiple shapes upon a specific programming step. Two recovery events with well-defined switch temperatures could be programmed using a double stretching step, and triple-shape memory effects were subsequently attempted with a recovery step performed at staged temperatures of 70 and 94 °C (according to the switch temperatures of the corresponding dual-shape memory experiments).…”

Tunable Shape Memory Polymers from α-Amino Acid-Based Poly(ester urea)s

“…With the exception of the tests completed using a T d of 30 °C, which is below the T g of the material, the peak recovery stress was within ca. 5 °C from the T d , which is consistent with other temperature memory materials . To confirm that the material would also show a strain-based TME, multiple samples were heated at various T d s and then stretched to 100% strain; then the samples were heated in the absence of a tensile load, and the recovery of the permanent shape was monitored as a function of time and temperature.…”

Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers

“…Hence, the thermal history of the membrane changes the whole membrane morphology as evidenced from the differences in the entire q -spectra, from small to wide angles. The findings reported here also support and explain the origin and shed light on the mechanism of the previously observed effects of annealing temperature on the matrix knee and ionomer peak. , …”

Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

“…In addition, overlapping between recoveries at 65 and 94 °C appears limited (Figure ), and only slight differences by 5 °C between switch temperature and stretching temperature are observed. Similar discrepancies were also observed for several SMPs ,, and could be attributed to the width of the glass transition and of the α-relaxation (Figure and Table ). However, switch temperatures are also sensitive to the heating rate during recovery and creep during cooling, in accordance with the broad recovery profile observed at high stretching temperature (Figure ).…”

“…As a conclusion, the double stretching step at 94 and 65 °C modifies the recovery process and generates a convolution of the corresponding recoveries in dual-shape memory experiments (Figure 4). A similar behavior was observed for Nafion 15,18 and undoubtedly demonstrates that the symmetric PLLA/PMMA blend could store multiple shapes upon a specific programming step. Two recovery events with well-defined switch temperatures could be programmed using a double stretching step, and triple-shape memory effects were subsequently attempted with a recovery step performed at staged temperatures of 70 and 94 °C (according to the switch temperatures of the corresponding dual-shape memory experiments).…”

Tunable Shape Memory Polymers from α-Amino Acid-Based Poly(ester urea)s

“…With the exception of the tests completed using a T d of 30 °C, which is below the T g of the material, the peak recovery stress was within ca. 5 °C from the T d , which is consistent with other temperature memory materials . To confirm that the material would also show a strain-based TME, multiple samples were heated at various T d s and then stretched to 100% strain; then the samples were heated in the absence of a tensile load, and the recovery of the permanent shape was monitored as a function of time and temperature.…”