Near-infrared (NIR) light-triggered shape memory polymers are expected to have a more promising prospect in biomedical applications compared with traditional heat-triggered shape memory polymers. In this work, a new kind of polyurethane with NIR light-triggered shape memory property was prepared by using polycaprolactone (PCL), polydopamine nanoparticles (PDANPs), hexamethylene diisocyanate (HDI), and 1,4-butanediol (BDO). The synthesized PCL–PDA polyurethanes, especially when the weight content of PDANPs was 0.17%, showed excellent mechanical properties because the PDANPs were well-dispersed in polyurethanes by the chain extension reaction. Moreover, it also showed an NIR light-triggered rapid shape recovery because of the photothermal effect of polydopamine. The in vitro and in vivo tests showed that the PCL–PDA polyurethane would not inhibit cell proliferation nor induce a strong host inflammatory response, revealing the non-cytotoxicity and good biocompatibility of the material. In addition, the PCL–PDA polyurethane exhibited excellent in vivo NIR light-triggered shape memory performance under an 808 nm laser with low intensity (0.33 W cm–2), which was harmless to the human skin. These results demonstrated the potential of the PCL–PDA polyurethane in biomedical implant applications.

A series of four-armed poly(D,L-lactide)-block-poly(D-lactide) (4-DL-D) copolymers were synthesized by ring-opening polymerization. By fixing the poly(D,L-lactide) (PDLLA) block length (1 kg mol −1 ) and changing the poly(D-lactide) (PDLA) block length (M n,PDLA = 0, 0.5, 1.1, 1.3, 1.8 and 2.6 kg mol −1 ), the crystallization and alkaline degradation of the PLLA/4-DL-D blends were investigated. The four-armed PDLLA core of the copolymer inhibited the crystallization of PLLA, while the outer PDLA block could affect the crystallization differently when its length changed. If M n,PDLA was 0 or 0.5 kg mol −1 , the crystallization of PLLA in the PLLA/4-DL-D blend was retarded markedly and the degradation rate of the blend films was much faster than that of neat PLLA film. Interestingly, when M n,PDLA was 1.1 kg mol −1 or higher, stereocomplex (SC) crystallites with different morphologies were formed, and the degradation rate of the PLLA/4-DL-D blend decreased gradually with increasing M n,PDLA . In the PLLA/4-DL-D1.1 blend, the SC crystallites acted as nucleators for PLLA homocrystallites, while in the PLLA/4-DL-D1.3 blend, small isolated SC crystallites were observed inside the PLLA homospherulites. When M n,PDLA was 1.8 or 2.6 kg mol −1 , a network structure of SC crystallites was formed and the degradation resistance of the films was markedly enhanced. A possible isothermal crystallization mechanism was proposed for the PLLA/4-DL-D blends, and the relationship between the crystallization state and degradation behavior was explored. This work revealed that the crystallization state, which was controlled by the PDLA block length, had a significant effect on the degradation behavior of PLLA/4-DL-D blend films.

Nanomedicine based tumor targeting therapy has emerged as a promising strategy to overcome the lack of specificity of conventional chemotherapeutic agents. The “passive” targeting caused by tumor EPR effect and...

Four-armed poly(ε-caprolactone)-block-poly(d-lactide) (4-C-D) copolymers with different poly(d-lactide) (PDLA) block lengths (Mn,PDLAs) were synthesized by sequential ring-opening polymerization (ROP). The formation of stereocomplex (SC) crystallites in the 80/20 poly(l-lactide) (PLLA)/4-C-D blends were investigated with the change of Mn,PDLA from 0.5 to 1.5 kg/mol. It was found that the crystallization and alkaline degradation of the blends were profoundly affected by the formed SC crystallites. The PLLA/4-C-D0.5 blend had the lowest crystallization rate of the three blends, and it was difficult to see spherulites in this blend by polarized optical microscopy (POM) observation after isothermal crystallization at 140 °C for 4 h. Meanwhile, when Mn,PDLA was 1 kg/mol or 1.5 kg/mol, SC crystallites could be formed in the PLLA/4-C-D blend and acted as nucleators for the crystallization of PLLA homo-crystals. However, the overall crystallization rates of the two blends were still lower than that of the neat PLLA. In the PLLA/4-C-D1.5 blend, the Raman results showed that small isolated SC spherulites were trapped inside the big PLLA homo-spherulites during isothermal crystallization. The degradation rate of the PLLA/4-C-D blend decreased when Mn,PDLA increased from 0.5 to 1.5 kg/mol, and the degradation morphologies had a close relationship with the crystallization state of the blends. This work revealed the gradual formation of SC crystallites with the increase in Mn,PDLA in the PLLA/4-C-D blends and its significant effect on the crystallization and degradation behaviors of the blend films.

No abstract