Combined One-Way and Two-Way Shape Memory in a Glass-Forming Nematic Network

Abstract

Past research in the field of shape memory polymers has led to significant advancements in the areas of so-called one-way and two-way (reversible) shape memory. While one-way shape memory polymers allow indefinite fixing of a temporary shape until triggered thermally to recover to an equilibrium shape, twoway shape memory polymers feature muscle-like contraction on heating and expansion on cooling under tensile load, the latter anomalous elongation occurring due to an ordering transition. Previously, reversible actuation has been reported for liquid crystalline elastomers featuring a monodomain (uniformly aligned) structure, suggesting that such alignment is required for actuation. In this work, we have prepared a glass-forming polydomain nematic network that combines reversible actuation associated with a polydomain-monodomain transition with lower temperature one-way shape memory centered at T g . To test separability of these phenomena, distinct deformations were achieved and temporarily fixed by (1) cooling through the isotropic-nematic transition under tensile load, (2) further bending the sample isothermally above T g , and (3) cooling below T g . Subsequent heating led to complete and sequential recovery of the same deformations in reverse order. Applications in multistage deployment of structures are envisioned.

Mechanisms of the Shape Memory Effect in Polymeric Materials

“…On the other hand, a few new shape memory phenomena have been discovered [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], which not only enhance the flexibility of the current shape memory technology, but also add in new dimensions for extended versatility and adoptability. Consequently, a number of novel concepts have been proposed for a range of engineering applications [45,[48][49][50][51][52][53][54], in particular in the field of biomedical engineering as of the last couple of years [24,43,[55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70].…”

“…However, in recent years, reversible motion during thermal cycling has actually been reported in a couple of polymers [29,33,34,127].…”

Review on the Functional Determinants and Durability of Shape Memory Polymers

“…In some cases, another type of SM phenomenon, which is the so-called "two-way" (reversible, all-round) SM, has been observed. For example, regular temperature-dependent mechanical activity may occur due to crystallization processes, inducing specimen elongation on cooling, and melting transitions, giving specimen shrinkage on heating [58,59]. A detailed mechanism for a glass forming nematic network with reversible SM has been suggested by Qin and Mather [59].…”

“…For example, regular temperature-dependent mechanical activity may occur due to crystallization processes, inducing specimen elongation on cooling, and melting transitions, giving specimen shrinkage on heating [58,59]. A detailed mechanism for a glass forming nematic network with reversible SM has been suggested by Qin and Mather [59]. Alternatively, at least five different "two-way" training procedures were published for SMAs [60].…”

Effects of Polybenzoxazine on Shape Memory Properties of Polyurethanes with Amorphous and Crystalline Soft Segments

“…They have the capability of fixing in one or multiple temporary shapes, and return to the original shape upon application of an external stimulus [2,4,[7][8][9][10][11][12][13]. Shape-memory polyurethanes (SMPUs) attract particular interest because of their biocompatibility, biodegradability, inexpensive raw materials, and…”