Polystyrene having high degree of expandability, and formulation having a highly-expandable polymer therein

A polystyrene polymer as well as an expandable polystyrene formulation comprises a polystyrene polymer having a particular molecular weight distribution. The polymer itself exhibits a polydispersity of from about 1 to less than 2.0, a weight average molecular weight of greater than about 200,000 to about 300,000, and an Mz:Mn of from about 2 to less than about 3.0. Furthermore, the polystyrene polymer is branched to from 0 to less than 5 weight percent. The expandable polystyrene formulation comprises a polystyrene polymer exhibiting a polydispersity of from about 1.0 to less than 2.5, a weight average molecular weight of from greater than about 180,000 to about 300,000, an Mz:Mn of from about 2 to about 4.5. The polystyrene polymer is present in an amount of from about 94.5 weight percent to about 98 weight percent, based on the total weight of the formulation, and the polystyrene polymer is branched to from 0 to less than 5 weight percent. The formulation further comprises a blowing agent, wherein the blowing agent is present in an amount of from about 2 weight percent to less than 5.5 weight percent, wherein the blowing agent is a hydrocarbon which is gaseous or liquid at standard temperature and pressure, does not dissolve the styrene polymer, and boils below the softening point of the polymer.