基于热塑性弹性体的多形状记忆材料及性能调控相关基础问题初探

Recently, the field of shape memory polymers (SMPs) investigation has witnessed an accelerated pace of development, and the multi-SMPs is one of the most exciting discoveries. This kind of SMPs is provided with the capability to memorize multiple temporary shapes in each shape memory cycle, and recover them consecutively upon exposure to appropriate external stimulus. This unique ability endows multi-SMPs with obvious advantages in medical applications, intelligent actuation as well as multi-shape coatings and adhesives. Due to the promising prospect, lots of researchers have been devoted to constructing multi-SMPs. Up to now, the most widely used strategies to construct multi-SMPs are synthesizing a polymer with more than two distinctive and strongly bonded reversible transitions as well as fabricating polymer blends with multiple isolated transition components. However, there are some drawbacks still exist for these approaches: the complex synthesizing process of hinders the realization of large-scale fabrications, and it is quite difficult to keep each transition component isolated during blending. Considering the great potential applications of multi-SMPs, the exploration of a simple and inexpensive method to fabricate multi-SMPs with tunable apparent properties is still essential. The purpose of the present proposal is to develop a simple preparation approach for multi-SMPs with satisfactory shape memory performance using inexpensive and flexible raw materials, as well as to understand the probable relationship between the shape memory performance of the polymers investigated and their multi-scale structures. In our strategy, various kinds of physically crosslinked thermoplastic block copolymer elastomers were used as network-forming compositions and crystalline molecules were used as transition compositions. It is expected that, by changing the soft-block-selectivity of crystalline molecules as well as the Huggins parameter of block copolymer elastomers, the different preferential entry and swell soft blocks as well as phase-separation may be constracted, which endows the blends with various multi-shape memory properties.

多重形状记忆高分子(Mutil-SMPs)具有记忆多个临时形状的能力，在人工智能、生物医学、虚拟现实、智能控制等新兴领域具有广阔的应用潜力。本项目拟开展两方面的工作：一是以热塑性弹性体类嵌段共聚物与可结晶小分子为原料，通过改变共混体系的化学组成及聚集态结构，构建包括开关相转变温度固定且明确不同以及临时形状具有温度记忆效应的两类Mutil-SMPs；二是初步建立此类嵌段共聚物/可结晶小分子共混体系的形状记忆功能与体系不同层次结构等之间可能的关系，为此类多重形状记忆材料的功能设计、结构调控及性能优化提供基础数据。我们期望通过本项目研究，建立和发展一种原料成本便宜、制备过程简单、临时形状转变温度适用面广的多重形状记忆材料设计、制备新方法，并从实验研究的角度获得嵌段共聚物在嵌段选择性溶剂(或共溶剂)中聚集态结构演化及结构性能关系的新知识，丰富通用高分子高性能化及功能化的内容。

多重形状记忆高分子(Mutil-SMPs)具有记忆多个临时形状的能力，在人工智能、生物医学 、虚拟现实、智能控制等新兴领域具有广阔的应用潜力。本项目以热塑性弹性体类嵌段共聚物/可结晶小分子混合体系为主要研究对象，主要开展了以下两个方面的研究：一是通过改变嵌段共聚物的种类与结构、改变结晶小分子的种类与比例、调控共混体系的相态结构或结晶组分的结晶特性，制备了一系列能够记忆多个可调临时形状的多重形状记材料和能记忆多个固定临时形状的多重形状记忆材料。基于对此类材料形状记忆特性的物理本质和结构性能关系的理解，我们还将材料从热塑性弹性体/结晶小分子共混体系扩展到热塑性弹性体/结晶高分子共混体系，将制备技术从溶液共混扩展到高分子工业广泛采用的挤出、模压等熔融加工技术，将形状记忆材料的结构从单层结构扩展到多层结构，成功制备了多种高性能形状记忆材料；二是我们以三嵌段共聚物SEBS与多种石蜡形成的混合物为模型，系统研究了此类体系在升降温过程中有序结构的形成与破坏、不同加工温度下结构演化行为的差异、石蜡的结晶或熔融对有序-无序转变过程的影响、剪切等外场作用对体系结构演化的影响以及不同配比情况下石蜡在共混体系中的结晶行为及结晶结构，并对比研究了各种结构下材料所表现出的形状记忆特性。通过本项目工作，我们形成了一系列以价格低廉、来源广泛且无毒无害的热塑性弹性体、可结晶小分子或高分子等为原料，利用便捷、环保的加工方法，制备临时形状转变温度等重要应用性能可调、适用面广的多形状记忆材料的新方法；同时，对此类形状记忆材料具有形状记忆功能的机理形成较全面的理解，并加深了对形状记忆功能与不同层次结构之间关系的认识。研究结果为热塑性弹性体等通用高分子材料实现高性能化与功能化提供了新的途径，也对高性能形状记忆材料的开发与应用具有重要参考价值。