聚丙烯酸的单分子应力-应变行为

利用原子力显微镜的一种新方法 单分子力谱技术 研究了聚丙烯酸单链的弹性性质，得到了聚丙烯酸链的拉力与拉伸曲线．其拉力与拉伸曲线可以通过修改的Ｌａｎｇｅｖｉｎ方程进行较好地拟合．结果表明聚丙烯酸链的弹性性质与长度线性成比例，聚丙烯酸链具有相同的Ｋｕｈｎ长度（０６４±００５ｎｍ）和链段弹性系数（１３０００±２０００ｐＮ／ｎｍ），充分表明我们位伸的是聚丙烯酸的单链，所测得的拉力 拉伸行为是聚丙烯酸单链的弹性行为

MECHANICAL PROPERTIES OF SINGLE POLY(ARYLIC ACID) CHAIN STUDIED BY ATOMIC FORCE MICROSCOPY--SINGLE MOLECULE FORCE SPECTROSCOPY ON POLY(ACRYLIC ACID)

The mechanical properties of polyacrylic acid is investigated on the molecular scale by using of an atomic force microscopy. Polyacrylic acid was adsorbed onto the glass substrate, then picked up at one point of the chain with an AFM tip and stretched. The elongation of individual molecules was recorded as a function of the applied load.In the force curves of PAA,the monotonically rising forces with the elongation of the polymer chain is observed.After normalization according to their contour lengths,all of the force curves can be superimposed together,no difference can be found,indicating that the mechanical properties of polyacrylic acid scale linearly with their lengths.The force extension curve can be modeled by a modified Langevin Function.It is found that all of the poly(acrylic acid) chains have the same Kuhn length (064±005 nm) and same segment elasticiy (13000±2000 pN/nm). Both the experimental results and fit results clearly indicate that single polyacrylic acid chain is stretched and nanomechanical properties of single poly(acrylic acid) chain is measured.