Dispersing graphene in hydroxypropyl cellulose by utilizing its lcst behavior

A novel method for producing graphene/hydroxypropyl cellulose (HPC) composite with a fine dispersion of graphene is established. The thermoresponsive HPC, with low a critical solution temperature (LCST) behavior, becomes self-associated into nanospheres when its homogeneous solution is heated to a temperature higher than the LCST. The formed nanospheres of HPC can then "clamp" graphene layers and get them finely dispersed in solution and in the polymer matrix. Incorporating graphene via this method can largely prevent graphene from agglomeration. Compared with the conventional casting method, the proposed LCST method can further enhance the electrical conductivity of HPC/graphene composites by 2-3 orders of magnitude. The percolation threshold value of RGO loading is as low as 0.11 vol%. Graphene layers are "sandwiched" into the nanospheres of hydroxypropyl cellulose (HPC) during its conformational transition. Via this method, the dispersion of graphene is manipulated well and the electrical conductivity of the HPC/graphene composites is enhanced further by 2-3 orders of magnitude, compared with the casting method.