Hydroxypropyl methylcellulose-poly (methacrylic acid) (HPMC-PMAA) nanogels were synthesized at different pH using HPMC as a template without surfactant in an aqueous solution, which was based on the phase transition behavior of HPMC induced by MAA at various pH. MAA at pH = 6.0 caused the phase transition of HPMC aqueous solution to occur at a lower temperature than that without MAA, and it continuously went down upon the decrease of pH for MAA, whose pKa is 5.5. This is attributed to the hydrogen bonding effect at pH < pKa being stronger than the salt effect when pH > pKa between HPMC and MAA. HPMC-PMAA nanogels were synthesized without surfactant at pH < 4.0, and it showed a most rapid rate to prepare nanogels when pH is 4.0. The synthesis of PMAA-HPMC nanogels without surfactant is environmentally friendly and is expected to provide a new method to synthesize novel hybrid nanomaterials. [ABSTRACT FROM AUTHOR]