The next step involved the grafting of HEMA by absorbed AIBN on the surface of PAN, making the surface to be coated with hydrophilic domains of HEMA.

• 第二阶段再利用超临界二氧化碳把亲水性单体带至高分子表面上，进行自由基接枝反应，令亲水性单体接枝在高分子表面上，形成亲水性区域。