New soybean oil-styrene-divinylbenzene thermosetting copolymers. I. Synthesis and characterization

The cationic copolymerization of regular soybean oil, low-saturation soybea n oil (LoSatSoy oil), or conjugated LoSatSoy oil with styrene and divinylbe nzene initiated by boron trifluoride diethyl etherate (BF3. OEt2) or relate d modified initiators provides viable polymers ranging from soft rubbers to hard, tough, or brittle plastics. The gelation time of the reaction varies from 1 x 10(2) to 2 x 10(5) s at room temperature. The yields of bulk poly mers are essentially quantitative. The amount of crosslinked polymer remain ing after Soxhlet extraction ranges from 80 to 92%, depending on the stoich iometry and the type of oil used. Proton nuclear magnetic resonance spectro scopy and Soxhlet extraction data indicate that the structure of the result ing bulk polymer is a crosslinked polymer network interpenetrated with some linear or less-crosslinked triglyceride oil-styrene-divinylbenzene copolym ers, a small amount of low molecular weight free oil, and minor amounts of initiator fragments. The bulk polymers possess glass-transition temperature s ranging from approximately 0 to 105 degreesC, which are comparable to tho se of commercially available rubbery materials and conventional plastics. T hermogravimetric analysis (TGA) indicates that these copolymers are thermal ly stable under 200 degreesC, with temperatures at 10% weight loss in air ( T-10) ranging from 312 to 434 degreesC, and temperatures at 50% weight loss in air (T-50) ranging from 445 to 480 degreesC. Of the various polymeric m aterials, the conjugated LoSatSoy oil polymers have the highest glass-trans ition temperatures (T-g) and thermal stabilities (T-10). The preceding prop erties that suggest that these soybean oil polymers may prove useful where petroleum-based polymeric materials have found widespread utility. (C) 2001 John Wiley & Sons, Inc.