Proposed mechanism of the influence of the molecular weight of OVAm and PVAm on the silica network formation during the gelation process. (Diameter of PVAm chains is much larger than shown)

Contexts in source publication

Context 1

... solution of tetraethoxysilane (TEOS), water, and 0.1 M HCl was mixed with a 1.0 % solution of OVAm or PVAm in water 9) . In the case of PVAm (M n 5 000 -400 000), the solutions immediately become opaque and the polymer precipitates. Obviously, the large coils of the high-molecular-weight PVAm form agglomerate, interfering with the gel formation (Fig. ...

Context 2

... for 48 h brittle, transparent, yellowish, and glassy materials were obtained. When the OVAm content in the reaction system is higher than 0.033 %, a significant acceleration of the gel formation process was observed. It is suggested that a small portion of OVAm catalyzes the gelation process because of the presence of free primary amine functions (Fig. 6). The influence of amino-group-containing catalysts on the gel formation process of silica was recently reported 10,11,12) . The proposed mechanisms involve the reaction of primary amino groups with silanol groups. For the IR spectroscopic proof of the formation of hydrogen bonds between primary amino groups of OVAm and silica gel 11) ...