Degradable polymers having a thermally induced shape memory can be fixed in a new, temporary shape after they have been processed into a permanent shape. They have great potential for biomedical applications, especially in the area of minimally invasive surgery. [1] One example is the insertion of a bulky medical device in a compressed temporary shape through a small surgical incision. When the implant is heated above a switching temperature (T trans ), it returns to its application-relevant permanent shape. After a given time the device degrades, and a second surgery for its removal is not necessary. [2,3] Shape-memory polymers generally consist of two components: cross-links determining the permanent shape and switching segments fixing the temporary shape at temperatures below T trans . Cross-linkage can be achieved either by physical interaction (e.g., in thermoplastic polymers) or by chemical bonds (e.g., in thermosets or photosets). In covalently cross-linked shape-memory polymer networks a maximum weight content of switching segments is possible. In constrast, thermoplastic materials must contain a sufficient amount of hard-segment-determining blocks so that a sufficient number of physical cross-links exist at temperatures above T trans . [4] The blocks that determine the switching segment may display T trans as either a melting temperature or a glass transition temperature. In biodegradable shape-memory polymers previously described as thermoplastic multiblockcopolymers [3] or photoset AB polymer networks [2,5] T trans is the melting point of crystallizable oligo(e-caprolactone) segments. Hydrogels with hydrophobic and crystallizable side chains as molecular switches also can show a thermoresponsive one-way shape-memory effect. [6] Based on noncrystallizable switching segments, completely amorphous shape-memory polymer networks having a glass transition temperature as T trans can be designed. These networks are transparent, and they should show a more

The formation of stable blood clots or hemostasis is essential to prevent major blood loss and death from excessive bleeding. However, the body's own coagulation process is not able to accomplish timely hemostasis without the assistance of hemostatic agents. For developing novel topical hemostatic agents, tissue adhesives and sealants, it is necessary to understand the coagulation process and the hemostasis mechanism of different materials. Among hemostatic materials, polysaccharides are naturally derived polymers having excellent biodegradable and biocompatible properties. This review provides an overview of polysaccharide-based hemostatic materials and agents, including their advantages and drawbacks in hemostatic applications. Furthermore, polysaccharide-based hemostatic materials with anti-microbial and healing functions are also introduced.

Thermo‐sensitive triple‐shape polymers can perform two consecutive shape changes in response to heat. These shape changes correspond to the recovery of two different deformations in reverse order, which were programmed previously at elevated temperature levels (Tmid and Thigh) by the application of external stress. Recently, an AB copolymer network was described, which surprisingly exhibited a triple‐shape effect despite being programmed with only one deformation at Thigh. Here it is explored whether a copolymer network system can be designed that enables a one‐step deformation process at ambient temperature (cold drawing) as a novel, gentle, and easy‐to‐handle triple‐shape‐creation procedure, in addition to the procedures reported to date, which generally involve deformation(s) at elevated temperature(s). A copolymer‐network system with two crystallizable polyester segments is synthesized and characterized, fulfilling two crucial criteria. These materials can be deformed at ambient temperature by cold drawing and show, even at Thigh, which is above the melting points of both switching domains, elongation at break of up to 250%. Copolymer networks with PCL contents of 75 and 50 wt% show a triple‐shape effect after cold drawing with shape‐fixity ratios between 65% and 80% and a total‐shape‐recovery ratio above 97%. Furthermore, in these copolymer networks, the triple‐shape effect can be obtained after a one‐step deformation at Thigh. Independent of the temperature at which the deformation is applied (ambient temperature or Thigh), copolymer networks that have the same compositions show similar switching temperatures and proportioning of the recovery in two steps. The two‐step programming procedure enables a triple‐shape effect in copolymer networks for an even broader range of compositions. This versatile triple‐shape‐material system based on tailored building blocks is an interesting candidate material for applications in fixation systems or disassembling systems.

Biodegradable shape-memory polymers have attracted tremendous interest as potential implant materials for minimally invasive surgery. Here, the precise control of the material's functions, for example, the switching temperature T(sw), is a particular challenge. T(sw) should be either between room and body temperature for automatically inducing the shape change upon implantation or slightly above body temperature for on demand activation. We explored whether T(sw) of amorphous polymer networks from star-shaped rac-dilactide-based macrotetrols and a diisocyanate can be controlled systematically by incorporation of p-dioxanone, diglycolide, or epsilon-caprolactone as comonomer. Thermomechanical experiments resulted that T(sw) could be adjusted between 14 and 56 degrees C by selection of comonomer type and ratio without affecting the advantageous elastic properties of the polymer networks. Furthermore, the hydrolytic degradation rate could be varied in a wide range by the content of easily hydrolyzable ester bonds, the material's hydrophilicity, and its molecular mobility.

This paper reviews the synthesis, characterization, biodegradation and usage of bioresorbable polymers based on polydepsipeptides. The ring-opening polymerization of morpholine-2,5-dione derivatives using organic Sn and enzyme lipase is discussed. The dependence of the macroscopic properties of the block copolymers on their structure is also presented. Bioresorbable polymers based on polydepsipeptides could be used as biomaterials in drug controlled release, tissue engineering scaffolding and shape-memory materials.

Hemostatic microparticles (HMs) have been widely used in surgery. To improve the comprehensive performance of HMs, multifunctional HMs named HM15 and HM15′ are prepared from starch, carboxymethyl chitosan, hyaluronic acid, and tannic acid. Herein, tannic acid is used as an effective cross‐linker. A 3D network structure for cell growth and wound repair can be formed by secondary cross‐linking. Through synergistic effect of these natural materials, the process of wound healing can be regulated controllably. HM15 and HM15′ have the ability of rapid hemostasis. Moreover, HM15′ shows excellent properties in antibacteria and wound healing acceleration. Blood clotting time treated with different HMs is shortened obviously from 436.8 s to 126 s. Compared with Celox, HM15 and HM15′ exhibited better broad spectrum antibacterial activity against both Escherichia coli and Staphylococcus aureus. Notably, the wound can be repaired rapidly by HM15′ in 14 days. These multifunctional HMs might have an important prospect in clinical application.

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