Polypeptide-synthetic polymer hybrids, 2. Miscibility of poly(vinyl alcohol) with polysarcosine

Abstract

Transparent blend films were prepared from poly(vinyl alcohol) (PVA) and polysarcosine (PSA), i. e. poly(N-methylglycine). Miscibility between PVA and PSA was investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). It was revealed that PVA is miscible with PSA having a DP of 103 with contents of up to 40 wt.-%. Molecular weight dependence of the miscibility was observed, since PVA shows miscibility with PSA having a DP of 309 with contents of up to 20 wt.-%. Segmental interaction between PVA and PSA was investigated by Fourier transform infrared (FT-IR) spectroscopy. While the carbonyl stretching band of PSA appears at 1 660 cm–1, the peak maxima of the PVA/PSA blend samples were observed at 1 649–1 651 cm–1. The shift of the bands to lower wavenumbers is explained by the formation of hydrogen bonds between hydroxyl groups of PVA and the carbonyl oxygen in PSA. Furthermore, thermogravimetric (TG) analysis of the blend film proved that the thermal stability of PVA was improved by blending with PSA. The shift of the degradation temperature to a higher temperature region is discussed on the basis of hydrogen bonding interaction between the two components in the miscible state.