Shape memory polymer composites (SMPCs) using interconnected nanowire network foams as reinforcements.

Nanotechnology

Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, United States of America.

Published: November 2022

AI Article Synopsis

  • Shape memory polymers (SMPs) have advantages like low density and easy processing but lack mechanical strength compared to shape memory alloys, making reinforcement with materials like inorganic nanowires and carbon nanotubes (CNTs) a promising approach for improving their properties.* ! -
  • The typical method of creating SMP composites (SMPCs) by mixing nanowires with monomers results in only slight mechanical improvements due to the limitations of mixing rules.* ! -
  • A new fabrication technique is introduced, which uses pre-fabricated nanowire foams combined with SMPs, leading to a 300% improvement in elastic modulus, significantly surpassing traditional methods.* !

Article Abstract

Shape memory polymers (SMPs), although offer a suite of advantages such as ease of processability and lower density, lag behind their shape memory alloy counterparts, in terms of mechanical properties such as recovery stress and cyclability. Reinforcing SMPs with inorganic nanowires and carbon nanotubes (CNTs) is a sought-after pathway for tailoring their mechanical properties. Here, inorganic nanowires also offer the added advantage of covalently binding the fillers to the surrounding polymer matrices via organic molecules. The SMP composites (SMPCs) thus obtained have well-engineered nanowire-polymer interfaces, which could be used to tune their mechanical properties. A well-known method of fabricating SMPCs involving casting dispersions of nanowires (or CNTs) in mixtures of monomers and crosslinkers typically results in marginal improvements in the mechanical properties of the fabricated SMPCs. This is owed to the constraints imposed by the rule-of-mixture principles. To circumvent this limitation, a new method for SMPC fabrication is designed and presented. This involves infiltrating polymers into pre-fabricated nanowire foams. The pre-fabricated foams were fabricated by consolidating measured quantities of nanowires and a sacrificial material, such as (NH)CO, followed by heating the consolidated mixtures for subliming the sacrificial material. Similar to the case of traditional composites, use of silanes to functionalize the nanowire surfaces allowed for the formation of bonds between both the nanowire-nanowire and the nanowire-polymer interfaces. SMPCs fabricated using TiOnanowires and SMP composed of neopentyl glycol diglycidyl ether and poly(propylene glycol) bis(2-aminopropyl ether) (Jeffamine D230) in a 2:1 molar ratio exhibited a 300% improvement in the elastic modulus relative to that of the SMP. This increase was significantly higher than SMPC made using the traditional fabrication route. Well-known powder metallurgy techniques employed for the fabrication of these SMPCs make this strategy applicable for obtaining other SMPCs of any desired shape and chemical composition.

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Source
http://dx.doi.org/10.1088/1361-6528/ac9d40DOI Listing

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