Biodegradable SMPs

In accordance with a concept derived from the SBS/PCL blend, Wang et al. developed a series of novel biodegradable SMP blends consisting of... 

Block copolymers based on hard segments of crystallizable poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate) (PHBV) and switching segments of hyperbranched three-arm poly(3-caprolactone) were proposed by Xue et al. (2010) as biodegradable SMPs for fast, self-deploying stents. Those containing copolymer with 25 wt% PHBV demonstrated almost complete self-expansion at 37°C within just 25 s, which is much faster than current self-deployable stents. 

Biodegradable polymers play a prominent role in the family of SMPs. This is due to their biodegradabdity because in many of the medical applications the related devices with SM function (e.g., sutures, catheters, stents) should be present only temporarily in the human body. The other, not less important, aspect is that the switch temperature for shape programming (Tf.j. g) can well be matched with that of the body. 

Next we shall give an overview on SMP systems which are composed fully or partly from biodegradable polyesters. To give a comprehensive review is beyond our intention owing to large body of the related works available both in the open and patent literatures. On the other hand, the reader will get a structured overview of the basic strategies followed to tailor the structure and performance of SMPs in order to meet the requirements of given applications. 

Copolymerization is the most widely used technique to control and tune the biodegradability of polymers. Copolymerization thus widens the potential of SMPs for their biomedical applications. 

The group of Nagata incorporated UV-curable moieties directly into the main chain of the related polymers [41-43]. Thus, photocurable, biodegradable multiblock SMPs were prepared by polycondensation from PCL diol, PEG, and 5-cinnamoyloxyisophthalic acid [41]. The latter compounds acted as UV cross-linker without any photoinitiator. The semicrystalline photosets exhibited Tg----60 C, and in the range 35-47°C. Both and R values were... 

Biodegradable polyester SMPs are mostly used in and developed for applications in the human body. That is the reason many R D works addressed the adjustment of related to or Tg, respectively, to the body temperature. The... 

---