Methacrylic acid-triggered phase transition behavior of thermosensitive hydroxypropylcellulose

Methacrylic acid (MAA)-triggered phase transition of thermosensitive hydroxypropyl cellulose (HPC) was studied. The phase transition temperature of 0.1 wt.% HPC aqueous solutions was dramatically reduced from 41 °C to 8 °C as the MAA concentration increased from 0 wt.% to 4 wt.%. The sharp decrease of HPC phase transition temperature triggered by MAA may be attributed to strong hydrogen bonding between MAA and HPC. It may be proposed that the hydrogen bonding of MAA with HPC restricts the interaction of water with HPC and so reduces the solubility of HPC in water and improves the hydrophobic association of HPC. Furthermore, MAA attaching on HPC polymer chains was polymerized to form surfactant-free PMAA nanogels around ambient temperature when HPC collapsed forming PMAA nanogels. Effect of MAA concentration and polymerization temperature on the size and size distribution of PMAA nanogels was investigated.