高分子材料 论文.docx

1、高分子材料 论文AbstractTraditional shape memory polymers (SMPs) are those capable of memorizing a temporary shape and recovering to the permanent shape upon heating. Although such a basic concept has been known for half a century, recent progresses have challenged the conventional understanding of the poly

2、mer shape memory effect and significantly expanded the practical potential of SMPs. In this article, notable recent advances in the field of SMPs are highlighted. Particular emphasis is placed on how the new developments have changed the conventional view of SMPs, what they mean for practical applic

3、ations, and where the future opportunities are.Graphical abstractKeywords Shape memory polymer; Stimuli-responsive polymer; Polymer actuator1. IntroductionShape memory polymers (SMPs) represent a technologically important class of stimuli-responsive materials for which the response lies in the shape

4、 change. More specifically, the conventional definition of an SMP is a polymer can be deformed and subsequently fixed into a temporary shape, which would remain stable unless it is exposed to an appropriate external stimulus that triggers the polymer to recover to its original (or permanent) shape.

5、Accordingly, the associated behavior of SMP is called polymer shape memory effect (SME). Although various forms of external stimuli may be utilized as the recovery trigger, the most typical one is direct heating that leads to a temperature increase.The first recognition of polymer SME, as suggested

6、by Mather et al., can be traced back to a patent in 1940s in which “elastic memory” was mentioned 1. The well-known heat shrinkage tubing that appeared in 1960s, on the other hand, represents a commercial application of SMP even before the terminology became being used. It is thought that the first

7、official use of the SMP term may have started in 1984, with the development of the polynorbornene based SMP by CDF Chimie Company (France) 2. Despite the long history of SMP, however, the phenomenon of polymer SME had remained little known and the scientific paper in this area had been rather limite

8、d until 1990s. Along this time frame, the discovery of segmented polyurethane SMP by Mitsubishi Heavy Industries Ltd. stimulated significant interests in SMPs, presumably due to the versatility of urethane chemistry that allows easy structural tuning and the industrial significance of polyurethane.

9、For the same reasons, research on shape memory polyurethanes has remained quite active even today, despite many different SMPs that have since been discovered.Historically, the advancement of the SMP field has been closely associated with its practical potential. As such, the lack of excitement and

10、research activities in the early days of SMPs can be attributed to the limited applications envisioned for such materials. In 2002, Lendlein et al. demonstrated that SMP could be used as self-tightening suture for minimum invasive surgery 3. The SMP in the form of suture was first deformed into an e

11、longated form. The SMP suture in this temporary shape was applied loosely to the wound (the left image in Fig. 1). The shape recovery of the suture was then triggered by human body heat, leading to the shrinkage of the suture and the tightening of the knot (the right images in Fig. 1) without extern

12、al intervention. Here, the polymeric nature of the material can be conveniently utilized to incorporate additional functionalities such as biodegradability, which eliminates the need for an additional operation for suture removal. This prototype demonstration has raised significant interests in othe

13、r biomedical uses of SMP. Today, tailoring SMP for various biomedical uses represents a significant portion of the SMP research 4 and 5. This intense focus on biomedical applications of SMP is in part due to the associated high value that is unmatched by most non-biomedical applications. An addition

14、al driving force lies presumably in the relatively large funding allocated to biomedical research in general.Fig. 1. SMP based self-tightening suture for wound closure. The photos from left to right show the shrinkage and tightening of the suture with temperature increase. Reproduced from Ref. 3 wit

15、h permission.Benefited in no small part to the potential for biomedical uses, the SMPfield has undergone explosive growth within the last decade. Along the way, many SMP systems and innovative non-biomedical applications have emerged. Since 2000s, a number of excellent reviews have been published th

16、at cover the general aspects of SMPs 6, 7, 8, 9, 10 and 11, SMP composites 12 and 13, biomedical applications 4 and 5, and non-biomedical applications 14 and 15.On the other hand, recent progresses in the last five years in the SMP field have significantly challenged the conventional view of polymer SME. As such, the intent of the current paper is not to provide an extensive review of the SMP research. Instead, the focus is on h