Simultaneous poly(vinyl acetate)/silica networks. Influence of crosslinking agents

The modification of the rate or formation of interpenetrant simultaneous in organic-organic (SIPIN) networks of poly(vinyl acetate) (PVAc)-SiO2 was stu died. The P(VAc) network was formed by radical polymerization with benzoyl peroxide in the presence of a crosslinked monomer, diethylen glycol bis mal eate. SiO2 network was obtained by sol-gel reaction of tetraethoxysilane (T EOS) catalyzed by radical polymerizable acids: maleic acid (MA) and acrylic acid (AA). The reaction medium was the ethylic alcohol-water mixture. The formation rate of SIPIN depends on the ratio of initial organic over aqueou s phases in case of catalysis by MA. The gelling times for MA are higher th an those for AA. This behavior inversely proportional to the acid strength is assigned to the selective interaction of the acids with the hydrocarbona ted or aqueous zone of initial systems. Crotonic acid (CrA) is partitioned in the hydrocarbonate zone where TEOS also lies. The glass transition tempe rature of organic network, P(VAc), increases with the increase of crosslink ing agent concentration. It is higher in the network prepared in presence o f MA owing to the higher number of hydrogen bonds induced by COOH.