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This article reviews the degradability of chemically synthesized bioelastomers, mainly designed for soft tissue repair. These bioelastomers involve biodegradable polyurethanes, polyphosphazenes, linear and crosslinked poly(ether/ester)s, poly(ε-caprolactone) copolymers, poly(1,3-trimethylene carbonate) and their copolymers, poly(polyol sebacate)s, poly(diol-citrates) and poly(ester amide)s. The in vitro and in vivo degradation mechanisms and impact factors influencing degradation behaviors are discussed. In addition, the molecular designs, synthesis methods, structure properties, mechanical properties, biocompatibility and potential applications of these bioelastomers were also presented.

In this study, a soft and thermoplastic starch with an improved ageing-resistant property was prepared by melt blending method for a biodegradable biomaterial. The glycerol content varies from 30 to 60 wt %. The aging temperature and humidity of the glycerol-plasticized thermoplastic starch (GTPS) was 378C and 50 6 5 RH %, respectively. The retrogradation was characterized by X-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR), and the stressstrain mechanical properties. The XRD results suggest that high content of glycerol promotes the formation of single helix structure of V-type, but inhibits double helix structure of B-type. Changing of the tan d, storage modules (E 0 ), and the glass transition temperatures as a function of glycerol content and ageing time was detected by DMTA. FTIR result shows that the shifting speed of the peak of hydroxyl group stretching fell as the glycerol content increased. The glycerol content has no obvious effect on the mechanical properties when it is high enough.Results from all characterizations demonstrate that the ageing speed is closely relative to the plasticizers content. The higher content of glycerol possesses an obviously inhibitory effect on the ageing.

A thermoplastic poly(glycerol sebacate) elastomer (TMPGS), prepared by a two-step method for the first time, is characterized in the present work. First, non-crosslinked poly(glycerol sebacate) (PGS) prepolymers at the 1 : 1 molar ratio of glycerol to sebacic acid were synthesized through a condensation reaction. Second, TMPGSs were achieved through prepolymers that continued to react after the addition of more sebacic acid at a total molar ratio of 2 : 2.5 (glycerol/sebacic acid). The swelling experiments demonstrated that its crosslinking density was low and that it was composed of sol and gel. Compared with our previous results, the content of sol decreased but still reached >60%. Differential scanning calorimetry (DSC) studies demonstrated that TMPGS was crystallizable and had a glass transition temperature below À208C, but at close to 378C, its state altered and became almost amorphous. It was explained that both the semi-interpenetrated polymer networks composed of sol and gel and the crystal regions imparted thermoplasticity to the elastomer. Finally, the in vitro degradation tests illuminated the degradation characteristic of TMPGS in 378C phosphate buffered saline solution (pH ¼ 7.4).

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ABSTRACT:We studied the condensing reaction of sebacic acid and glycerol and prepared biodegradable elastomers. Swelling experiments proved that the elastomers were crosslinked polyesters consisting of both insoluble parts (gel) and soluble parts (sol), but the content of sol was higher than gel. X-ray diffraction analysis showed that some ordered and crystallized structures existed in most of the elastomers. Differential scanning calorimetry measurement showed that there were both crystal regions and amorphous regions with low glass-transition temperatures in the products, which indicated the elastomers had a microphase separation structure. The elastomers exhibited thermal processing abilities, such as mold-shaping performance, and a certain elasticity, and hydroxyl, carboxyl, and ester groups in the molecular chains endowed the elastomers with good biodegradation abilities. Furthermore, by altering the molar ratio of the reactants, we were able to adjust the mechanical properties, biodegradable performance, and so on of the elastomers. Glycerol and polymers containing sebacic acid have been approved for biological medical uses by the U.S. Food and Drug Administration, so the elastomers we prepared would have broad application in medical fields such as implants and drug-delivery systems.