1.1.8　Ladder Polymers

As the name suggests（顾名思义），a ladder polymer（梯形聚合物）consists of linear molecules in which two skeletal strands（骨架主链）are linked together in a regular sequence（序列）by crosslinking units，as illustrated diagramatically（图解地）in Figure 1.5.In practice，aromatic rings（芳环）may constitute the linking units.As might be expected（可以预料的），ladder polymers have a more rigid（刚性的）molecular structure than conventional linear polymers，and they are often much less soluble.However，they frequently display very good thermal stability（热稳定性），because the decrease of molecular weight must be preceded（在……之前发生）by the cleavage（断裂）of two bonds at each cleavage site.

Figure 1.5　Ladder polymer

（参见本章二维码：1-2 聚合物按结构分类）