the current major way of making nanofibers is electrospinning . however , the minimum fiber diameter is limited to be about 300 - 500 nm , which is not compliant with the physical definition of nano structures . futher , the productivity is relatively low . this invention provides a method for manufacturing a nano - sized di - block polymer including at least a hard - segment polymer and a soft - segment polymer . first , a sample containing the hard - segment polymer , the soft - segment polymer , and a catalyst is dissolved in a first solvent . then the dissolved sample is cast on substrate , and then the first solvent to is removed form a dried sample . finally , the nano - sized di - block polymer is formed by crew - cutting .