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Nonisothermal crystallizations of polycaprolactone (PCL) in the presence of poly(vinyl chloride) (PVC) at a cooling rate of 0.5 °C/min from 90 to 30 °C under supercritical CO2 at a constant pressure 304 atm were investigated. DSC and SAXS data found that the nonisothermal crystallizations of the PCL/PVC blends under supercritical CO2 resulted in decrease in thickness of the crystalline layers in the lamellar stacks. These nonisothermal supercritical CO2 treatments also generated a morphological heterogeneity with size (13.8 nm for pure PCL) larger than the long period (12.1 nm) of the lamellar stacks. The size of this heterogeneity was slightly enhanced from 13.8 nm for pure PCL to 15.2 and 16.3 nm for the blends containing 10 and 25 wt % PVC, respectively.

We systematically studied the effects of composition and crystallization temperature (Tc) on the morphological patterns of poly(vinylidene fluoride) (PVDF)/poly(vinyl acetate) (PVAc) blends by means of small angle X-Ray scattering (SAXS). The absolute intensity was measured so that the morphological structures can be resolved from the intensity perturbation. The scattering intensity associated with the PVDF lamellar stacks was strongly enhanced upon blending with PVAc. This was due to the presence of amorphous PVAc in the interlamellar regions that enhanced the electron density contrast between the crystalline and amorphous layers. Except for an intermediate Tc of 110°C where the systems attained the maximum crystal growth rate, partial extralamellar segregation of PVAc became prevalent when the PVAc composition exceeded 20 or 30 wt%. Even crystallization at as low as 20°C (where the diluent mobility was expected to be sluggish) produced a large extent of extralamellar segregation due to slow crystal growth. The results suggested that the crystal growth kinetics has dominated over the diluent mobility in controlling the average distance of diluent segregation in PVDF/PVAc with the prescribed molecular weight combination.

Polyester based polyurethanes were synthesized from a low molecular weight polyester (Mn∼2000) and 4,4′-methylene bis(phenyl isocyanate) (MDI) with butanediol as a chain extender and glycerol as crosslinker. The polyester was synthesized from adipic acid and glycol, a mixture of 1,6-hexanediol and 1,2-propanediol. The effect of the crosslinker content on the phase segregation of soft- and hard-segments was studied by DSC (differential scanning calorimetry) and SAXS (small angle X-ray scattering). The introducing of triol functional group into the hard segments increased the aggregation of hard segments through crosslink covalent bonds. Owing to highly steric hindrance, the presence of tri-ol crosslinker in the hard segments decreased the aggregation of hard segments through hydrogen bonding. The phase segregation of soft- and hard-segments is thus due to the aggregation of hard-segments through crosslinked covalent bonds and H-bonding.