Very flexible polymers such as polyethylene will mainly re-enter the lamellae at adjacent sites when slowly crystallized whereas fast cooling will result in some random re-entry (at a distant location). Another small portion of the chain ends remains in the amorphous phase or enters another neighboring lamella. In many other cases, polymer crystal growth with adjacent re-entry is either not possible or very unlikely. For example, polymers with a very stiff backbone such as PEEK or PES are incapable of adjacent re-entry as these polymers cannot bend over a short distances, and hence, can only re-enter the crystal several stems away from the exit point, whereas very stiff polymers such as liquid crystals will predominantly enter other crystals and/or a large portion of the chains will remain in the amorphous phase.Many polymers are not linear but include a certain degree of long or short chain branching which will effect the structure and degree of crystallinity. For example, short branches such as butyl, hexyl and octyl, which are purposefully introduced in linear low density polyethylene (LLDPE), reduce the overall crystallinity and the size of the spherulites whereas long branches can undergo side-chain crystallization. Branching also increases the amorphous portion in the spherulites because side chains disrupt/impede lamellar growth.