Revealing the morphological architecture of a shape memory polyurethane by simulation

Abstract

The lack of specific knowledge of the network structure in shape memory polymers (SMPs) has prevented us from gaining an in-depth understanding of their mechanisms and limited the potential for materials innovation. This paper firstly reveals the unit-cell nanoscale morphological architecture of SMPs by simulation. The phase separated architecture of a segmented shape memory polyurethane (SMPU) with a 30 wt% hard segment content (HSC, 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO)) showing good shape memory properties was investigated by dissipative particle dynamics (DPD) simulations. A linked-spherical netpoint-frame phase of MDI, a matrix-switch phase of polycaprolactone (PCL) and a connected-spider-like interphase for BDO were obtained for this SMPU. The BDO interphase can reinforce the MDI network. Based on these simulation results, a three-dimensional (3D) overall morphological architectural model of the SMPU can be established. This theoretical study has verified, enriched and integrated two existing schematic models: one being the morphological model deduced from experiments and the other the frame model for SMPs reported before. It can serve as a theoretical guide for smart polymeric materials design. This method for the simulation of polymer structure at the nanoscale can be extended to many areas such as photonic crystals where nanoscale self-assembly plays a vital role.

Thermal, optical, interfacial and mechanical properties of titanium dioxide/shape memory polyurethane nanocomposites

“…Among these SMPs, SMPUs have attracted more and more attention during the past decades because of their excellent properties such as high tensile strength, high flexibility, high abrasion resistance, good adhesion ability, and so on [9]. SMPUs have become one of the most rapidly developing members of PU industry, and have been applied in many aspects such as coatings, textiles, adhesives, sealant, films, etc [10].…”

“…SMPUs have become one of the most rapidly developing members of PU industry, and have been applied in many aspects such as coatings, textiles, adhesives, sealant, films, etc [10]. However, SMPU still has such limitations as lower stiffness and weaker shape recovery force when compared with shape memory alloys and ceramics [9]. Further, like other polymer materials, SMPU is vulnerable to aging and ultimately fails to meet the performance requirements and subsequently limits its practical application when exposed to heat, oxygen or ultraviolet (UV) light during its service life.…”

The Difference in Molecular Orientation and Interphase Structure of SiO2/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process

“…Easley et al [ 8 ] compared the mechanical test and micro crack analysis of the SMP foam prepared by the monomer diethanolamine (DEA) and triethanolamine (TEA), and proved that DEA could effectively improve the toughness of materials and reduce micro-cracks. A thermodynamic incompatibility between the soft and hard segments leads to microphase separation and the aggregation of hard segments, which then forms a two-phase structure in SMPU [ 9 ]. The hard segment usually acts as a stationary phase in order to fix the soft segment.…”

On the Size Effect of Additives in Amorphous Shape Memory Polymers

“…The shape memory behavior in polymers has also been investigated by means of molecular dynamics (MD) computer simulations [47][48][49][50][51][52][53]. In a recent MD-work [51], different models of polymers were analyzed in a shape memory cycle, highlighting the importance of temperature-dependent chain mobility.…”

“…In a recent MD-work [51], different models of polymers were analyzed in a shape memory cycle, highlighting the importance of temperature-dependent chain mobility. Another study [53] employed dissipative particle dynamics (DPD) to investigate phase-separation in the polymer network and individual functions of different segments in a polyurethane-based shape memory polymer. As to additive-induced shape recovery, it has been shown that plasticizing effect of additive molecules on structural relaxation in polymers leads to an enhancement of shape recovery rate [50,54,55].…”