Study on miscibility of PEO and PCL in blends with PHB by solution viscometry

Viscometric studies were carried out for polymer-blend solutions in chloroform, i.e. for solutions of two polymers in a common solvent. Polymer blends comprised poly(3-hydroxy butyrate) (PHB) in combination with poly(ethylene oxide) (PEO) and poly(ε-caprolactone) (PCL), respectively. Experimental results obey the Huggins equation to an excellent approximation in the concentration range studied. Intrinsic viscosities vary linearly with blend composition to a good approximation. Huggins coefficients display generally nonlinear dependencies on blend composition. Positive deviations from perfect behaviour are attributed to attractions between different chain molecules or miscibility of the constituents. The viscometric study demonstrates that PEO is miscible with PHB, whereas PCL is immiscible.