6 cm the fibers are collected by the same method as described in example 1 the purpose of the present example is to provide a polymer fiber of pbo and kevlar except that in the step a the pbo is replaced by the mixture of pbo and kevlar to afford the polymer solution the other processing conditions are the same as in example 1 to provide a pbo kevlar nano fiber the purpose of the present example is to provide a polymer fiber of pbo and silk except that in the step a the pbo is replaced by the mixture of pbo and silk to afford the polymer solution the other processing conditions are the same as in example 1 to provide a pbo silk nano fiber the purpose of the present example is to provide a polymer fiber of pbo and pla poly lactic acid except that in the step a the pbo is replaced by the mixture of pbo and pla to afford the polymer solution the other processing conditions are the same as in example 1 to provide a pbo pla nano fiber the purpose of the present example is to provide a polymer fiber of pbo and chitosan except that in the step a the pbo is replaced by the mixture of pbo and chitosan to afford the polymer solution the other processing conditions are the same as in.