受本体玻璃态增强的表面高分子橡胶态行为  

Rubbery State of Surface Polymers Enhanced by Body Glassy State

作　　者：胡文兵[1] Wen-bing Hu(School of Chemistry and Chemical Engineering,Nanjing University,Nanjing 210023)

机构地区：[1]南京大学化学化工学院,南京210023

出　　处：《高分子学报》2021年第11期1424-1426,共3页Acta Polymerica Sinica

摘　　要：表界面高分子是我们研究高分子独特物理化学性质的一个重要窗口.近日,浙江理工大学左彪课题组与国外合作者利用不相溶的离子液体液滴在聚苯乙烯平滑表面的接触边缘产生压痕,采用原子力显微镜观察了压痕的蠕变松弛随温度的变化,发现蠕变动力学在本体玻璃化温度附近不再满足时温等效原理,橡胶弹性模量平台变宽.由于高分子材料表面具有较强的分子活动能力,存在由本体向表面的分子活动能力的梯度变化.他们结合计算机分子模拟证明,低温区本体的玻璃态对表面高分子链运动具有束缚作用,导致表面高分子的橡胶态温度平台变宽.离开表面较远的玻璃态部分可起到物理交联作用,约束表面高分子链整体的活动能力,所以表面高分子在低温区表现出温度范围拓宽的橡胶态行为.这一工作的重要意义在于,这种伪缠结的物理交联作用挑战了当前人们对链的拓扑缠结网络导致线形高分子无定形本体出现橡胶态的假说.线形高分子链之间如果出现例如玻璃态冻结的物理交联作用,就可以获得有别于小分子的独特橡胶态.Surface and interface are the important windows for us to learn the unique physical chemistry of polymer materials.Recently,Professor Biao Zuo and his collaborators used atomic force microscope to observe the creep relaxation of surface wrinkle at the edge of ionic liquid droplet on the smooth surface of polystyrene.They found that in the low temperature region nearby body glass transition temperature of polystyrene,the creep relaxation could not reproduce the time-temperature superposition law as observed in the high temperature region.Since surface polymers hold relatively high mobility,there exists a mobility gradient from the surface to the body of polystyrene.They performed molecular dynamics simulations to demonstrate that the body glassy state brings constraint to the surface polymers,and it expands the modulus plateau of the rubbery states of surface polymers in the low temperature region.Leaving away from the surface,the glassy part of surface polymers plays the role of physical crosslinking,restricts the mobility of surface polymers,and thus enhances their rubbery behaviors in the low temperature region.This work challenges the current hypothesis of entanglement network,causing the rubbery state of bulk amorphous polymers.Once linear polymers make the partial frozen of the glassy states in their bulk amorphous phase for physical cross-linking,they could attain the unique rubbery states,distinguished from small molecules.

关 键 词：表界面 原子力显微镜 橡胶态 玻璃态 

分 类 号：TQ317[化学工程—高聚物工业]