Strengthened, recyclable shape memory rubber films with a rigid filler nano-capillary network
The universal strategy for designing commodity rubbers to obtain high mechanical performances mainly relies on two aspects: either a developed crosslink network or an effective filler-reinforcing system. However, recycling of rubbers cannot bypass them. In this paper, strengthened and recyclable shape memory carboxylated styrene-butadiene rubber (XSBR)/carboxymethyl chitosan (CMCS) films are prepared by concentrating a mixture of XSBR latex and CMCS solution. During this process, the CMCS was regenerated due to water evaporation and synchronously entangled with XSBR chains, which constructed a mutually physical crosslink network via hydrogen bonding. With the increasing content of CMCS, regenerated CMCS changed its morphology from typical nanoparticles to nano-fibrils. When the CMCS content exceeded 10 wt%, a rigid CMCS nano-capillary network was formed in the films, constructing a special “reinforced concrete structure”. This rigid CMCS nano-capillary network significantly improves the mechanical properties of the XSBR/CMCS films. At the same time, due to the capillary network running through the whole film, the XSBR could be recycled by soaking films in water without any retained CMCS. Furthermore, our XSBR/CMCS films exhibited impressive shape memory behavior in a coincidental temperature range which is quite suitable for designing a smart medical device for the human body, e.g. a band-aid for bone fracture.