Chen Yixi, Kazerooni Nazanin Afsar, Srinivasa Arun, Chapkin Wesley A, Sihn Sangwook, Roy Ajit K, Vaddiraju Sreeram
Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, United States of America.
Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, United States of America.
Nanotechnology. 2022 Nov 15;34(5). doi: 10.1088/1361-6528/ac9d40.
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.
形状记忆聚合物（SMPs）虽然具有一系列优点，如易于加工和密度较低，但在诸如回复应力和循环性等机械性能方面，落后于其形状记忆合金同类材料。用无机纳米线和碳纳米管（CNTs）增强SMPs是一种备受追捧的调整其机械性能的途径。在此，无机纳米线还具有通过有机分子将填料与周围聚合物基体共价结合的额外优势。由此获得的SMP复合材料（SMPCs）具有精心设计的纳米线 - 聚合物界面，可用于调整其机械性能。一种制造SMPCs的众所周知的方法，即将纳米线（或CNTs）的分散体浇铸在单体和交联剂的混合物中，通常只能使制造的SMPCs的机械性能有微小的改善。这是由于混合法则原理所带来的限制。为了规避这一限制，设计并提出了一种制造SMPCs的新方法。这涉及将聚合物渗透到预制的纳米线泡沫中。预制泡沫是通过将测量好的纳米线和一种牺牲材料（如(NH)CO）固结，然后加热固结混合物以使牺牲材料升华而制成的。与传统复合材料的情况类似，使用硅烷对纳米线表面进行功能化处理能够在纳米线 - 纳米线和纳米线 - 聚合物界面之间形成键。使用二氧化钛纳米线制造的SMPCs以及由新戊二醇二缩水甘油醚和聚（丙二醇）双（2 - 氨基丙基醚）（Jeffamine D230）以2:1摩尔比组成的SMP，其弹性模量相对于SMP提高了300%。这一增长显著高于采用传统制造路线制成的SMPC。用于制造这些SMPCs的著名粉末冶金技术使该策略适用于获得任何所需形状和化学成分的其他SMPCs。
