Effect of ester group bulkiness of polyacrylates on miscibility with poly(vinyl acetate)

摘要

BACKGROUND: The miscibility of poly(vinyl acetate) (PVAc) with a series of polyacrylates, namely poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(butyl acrylate) (PBA), with ester chains of varying bulkiness was studied from both qualitative and quantitative points of view. RESULTS: The evidence from thermal (differential scanning calorimetry) and Fourier transform infrared analyses demonstrates that the miscibility of PVAc with the polyacrylates is rapidly reduced on increasing the bulkiness of their ester chains. Miscibility is quantitatively discussed in the framework of the corresponding states theory applying the approximate Patterson form. For this reason the characteristic values of volume, temperature and pressure were preliminarily evaluated both experimentally, through dilatometric measurements, and by calculations. At the same time, calorimetric measurements allowed the evaluation of the enthalpies of mixing of the components. CONCLUSION: The conclusions reached with this approach are that polar interactions are active among the repeat units of the blend components, but the intensities of these forces are progressively reduced by the shielding of the apolar groups of the polyacrylates. The steric hindrance of the hydrocarbon groups shields the interactions of the polar groups of PVAc with the COOR moieties of the acrylates, so that the miscibility progressively decreases from PMA to PEA to PBA.