Following our recent report that it is possible to purify and cut SWNTs by using a saw-edged homogenizer in a monochlorobenzene (MCB) solution of polymethylmethacrylate (PMMA) [Appl. Phys. A 71 (2000) 451], we report here our investigation of the effect of PMMA and MCB on the purification and cutting of SWNTs by thermogravimetric analyses. Our results show that MCB helps the a-C aggregation states to homogenize during the ultrasonic treatment. The PMMA helps to make bundles of SWNTs thinner and accelerates both the cutting and damaging of them.