Synthesis and rheological properties of hydrophobically modified poly(vinyl alcohol)

A novel series of water-soluble hydrophobically modified poly(vinyl alcohol) (HMPVA) with various hydrophobe contents was prepared by grafting poly(vinyl alcohol) (PVA) using 1-dodecanol and toluene-2,4-diisocyanate as hydrophobic monomer and coupling agent, respectively. The chemical structure of HMPVA was analyzed by Fourier Transform Infrared Spectrometer (FTIR) and H-1 NMR. Rheological properties of the aqueous solutions also confirmed the incorporation of hydrophobic groups into PVA. In dilute concentration regime, HMPVAs exhibited lower intrinsic viscosity than PVA, suggesting that HMPVA molecules were more shrunken. While the aqueous solution viscosity was enhanced due to hydrophobic modification at a high concentration, and HMPVAs with higher hydrophobe contents exhibited lager values of apparent viscosities. Over a frequency range of 1 to 10(2) rad/s, the dynamic storage modulus of PVA solution was smaller than the dynamic loss modulus whereas the dynamic storage modulus of HMPVAs solutions was greater than the dynamic loss modulus, indicating the evolution of viscoelastic solid properties in HMPVAs solutions. The yield stress of PVA was nearly zero whereas that of HMPVAs represented positive values, implying that networks were present in HMPVAs solutions.