Environment-adaptable PAM/CMC semi-IPN hydrogels microspheres with high latent heat achieved through dual locking water strategy

Polyacrylamide (PAM) hydrogel is easy to prepare and has been widely used in industrial and biomedical fields. But its mechanical properties and environmental adaptability are very poor. In this work, by introducing carboxymethyl cellulose (CMC) into the PAM crosslink network, a semi-interpenetrating (semi-IPN) network structure was constructed to improve the mechanical properties of PAM hydrogels. PAM/CMC hydrogel microspheres (HMPs) with semi-IPN structure were successfully prepared by in-situ precipitation droplet crosslinking polymerization (PDIC). On this basis, a double locking water strategy was proposed and achieved: firstly, lithium chloride (LiCl) was introduced into PAM/CMC hydrogel to retain the internal water; secondly, the PAM/CMC HMPs were coated with single layer graphene oxide (GO) to restrain the loss of free water on the HMPs surfaces. The morphology, the state of water in HMPs, the compression performance, phase transition behavior and heat transfer performance of the GO coated PAM/CMC/LiCl HMPs (GO@HMPs) were further studied. The experimental results showed that the CMC could effectively improve the compression performance of PAM HMPs, and the PAM/CMC HMPs had also good compression recovery performance. The anti-dehydration performance of PAM/CMC HMPs was effectively improved by the double locking water strategy. The latent heat of GO@HMPs was higher than that of the current commercial phase change microsphere materials. The GO@HMPs had excellent heat absorption ability and were expected to be used in infrared stealth and thermal camouflage fields.