William C. Pike

Benzocyclobutenes as styrene monomer scavengers and molecular weight “stabilizers” in atactic and syndiotactic polystyrenes

Syndiotactic polystyrene (SPS) is a semicrystalline polymer with a melting point of 270°C. At processing temperatures of 300°C or higher, SPS begins to decompose with loss of molecular weight and the formation of styrene monomer. Under these conditions, atactic polystyrene also decomposes. One approach to controlling this generation and buildup of styrene and the molecular weight loss during processing is to add a compound that will react with styrene and/or with the polymer decomposition products at the processing conditions. This report describes the use of three benzocyclobutene (BCB) compounds (ethylene bis-BCB, divinyl disiloxane bis-BCB, and a copolymer of styrene and 4-vinyl BCB) during SPS and atactic polystyrene processing. The conclusions are: 1. BCB moieties, when extruded with SPS at the 2 wt % level, caused a substantial decrease in residual styrene compared with a control SPS; 2. BCB compounds, when extruded with SPS, resulted in high molecular weight fractions. The result with the divinyl disiloxane bis-BCB was especially dramatic; and 3. BCB functionalized materials may find utility as additives in SPS during processing to minimize loss of molecular weight and buildup of styrene.