A method of cleaning a fouled or a scaled RO or NF membrane surface with a solution containing one or more thermo-responsive polymers is disclosed. More specifically, the method comprises: treating the membrane surface in a membrane separation system with a solution containing one or more TRP, wherein said TRP is soluble in said solution and at least an effective amount of said TRP diffuses into a foulant layer on said membrane surface; making insoluble said TRP diffused into said foulant layer; optionally, rinsing the membrane.