Great lecture

ting yi dianer cuo le

听一点儿错了老师。

This already explined by professor early, it is really a very effectuive method 

Synthetic polymers

Natural polymers

very nice method to regenerate  mask

Mthods for making ploymers are:

Additional Polymerization

condensation polymerization

... Our responsibility is to preserve natural things

ionic bond

covalent bond (NaCl)

Polar(water)

Vanderwall force

Advanced Polymer Materials in Medical Supplies

Prof Yang Zhang Xi'an Jiaotong Uni.