Yes. Polymers can be registered as single-type structures, but as multi-component compounds as well. In order to register as single structures, you can just simply draw structures then click on the Repeating Group tool on the toolbar, select the atoms you want to be included and set the repeat pattern. For more info click here

Registering as multi-component compounds polymers can be stored with its monomer units, that are created by stripping the "leaving groups" (configurable) from the monomers. More details can be found here. 
The molecular weight and molecular formula of polymers cannot be calculated.  Polymers can be stored with its monomer units, that are created by stripping the "leaving groups" (configurable) from the monomers. More details can be found here.