Journal of Polymer Science Part B: Polymer Physics, Vol.43, No.9, 1076-1089, 2005
Hydrogen-bonding, crystallinity, and morphological properties of poly(silicic acid)/waterborne polyurethane nanocomposites
Unique nanocomposites consisting of poly(silicic acid) nanoparticles (PNs) and waterborne polyurethane (WPU) were prepared. The aliphatic WPU prepared in this study was end-capped with a silanol group, which could react with PNs via a sol-gel process. PNs were modified with phenyltrimethoxysilane (PTMS) and 3-(trimethoxysilyl)propyl ester (TMPE) and then blended with WPU. The structure-property relationships were examined. Solid-state Si-29 NMR spectra of WPU showed that structures T-1, T-2, and T-3 of WPU decreased and structures Q(3) and Q(4) of PN/WPU nanocomposites increased gradually. When the PN concentration increased to 10 wt %, PN/WPU nanocomposites exhibited the maximum fraction of hydrogen-bonded carbonyl groups. In the PTMS-PN and TMPE-PN systems, the fraction of hydrogen-bonded carbonyl groups fluctuated stably when the concentrations of PTMS-PN and TMPS-PN exceeded 5 wt %. The X-ray diffraction results revealed that alpha-form, gamma-form, or triclinic crystallization could be found in the WPU matrix. A differential scanning calorimetry spectrum showed that the crystalline structure of the hard segment of WPU was influenced by the nanoparticle concentration. The degrees of crystallinity were 88% for the PN/WPU nanocomposites, 41% for the PTMS-PN/WPU nanocomposites, and 54% for the TMPE-PN/WPU nanocomposites when the PN, PTMS-PN, and TMPE-PN concentrations were 5 wt %. (c) 2005 Wiley Periodicals, Inc.