An important process for making a new class of polymeric material is called microcellular plastics invented at the Massachusetts Institute of Technology. Many researches for microcellular plastics have been done in various ways and fields. But a research for the polymer which has previous history has not been tried yet. In this paper, weight gain of $CO_2$ was measured in a polymer matrix which had previous history and no history. In each case, experimental data for solubility and diffusivity was shown. A model for $CO_2$ solution process in molecular range was made. The conclusion of this paper is that the previous history has an effect on diffusivity but not solubility and the previous history made by $CO_2$ in supercritical state makes diffusivity of $CO_2$ larger.