Nonlinear changes in specific volume. A route to resolve an entropy crisis

The volume difference in Poly(4-methyl-1-pentane), P4M1P, is discussed as a function of both pressure and temperature. Variation in intensity on cooling at a fixed pressure of 32 MPa showed that intensity decreases sharply during the initial stages of cooling, followed by a more gradual decrease toward a minimum. It was observed that at higher pressures, when the crystallization occurs, the expansion upon crystallization, is similar to ice/water. The results show that by controlling the molecular architecture of the polymer with respect to the side group nonlinearity in specific volume behavior of the liquid can be generated , which in combination with a high specific volume of the crystal, allows the existence of reentrant behavior.