Earl G. Melby

An Attempt to Adapt Superacid Chemistry for “Living” Carbenium Ion Polymerizations

Abstract The discovery that carbocations can be stabilized in super acid media, e.g., SbF5-SO2, etc., raises the possibility of “living” carbenium ion polymerization. Polymerization experiments with isobutylene and styrene carried out at high acid concentrations and in the virtual absence of nucleophile, i.e., under conditions conducive for living polymerization, failed to indicate a linear conversion vs molecular weight relationship and/or block copolymer formation. Additional model experiments with 2,4,4-trimethyl-1-pentene substantiate our conclusions that “living” carbocation polymerizations are unlikely to be produced by superacid chemistry.

Block and Bigraft copolymers by Carbocation Polymerizaation

Abstract The recent observation that the rate of methylation of t-BuCl by Me3Al is several orders faster than that of t-bubr, Which in turn is much faster than that of t-BuI, Provides the basis of a new synthetic method for the preparation of block and bigraft copolymers. This presentation concerns the synthesis and characterization of the first well-defined block and bigraft copolymers produced by the carbenium ion mechanisum i. e., poly(styrene-b-isobutylene), poly[(ethylene-co-propylence)-gStyrence-g-α-methylstyrence)]. The synthesis of the block copolymers involved three key steps: 1)the synthesis of a chlorobrominated alkane initiator, 2) the selective initiation of styrence polymerization by the chlorobrominated alkane in conjunction with alkylayuminum halide under conditions of no chain transfer, and 3)selective initiation of isobutylence polymerization by the polystyrence-Br in conjuction with alkylaluminum halide. Selective solubility, DSC, and GPC data indicate pure block copolymer. The effect o...

Glass-reinforced Thermosetting Polyester Molding: Materials and Processing

Fiber reinforcement of plastics is used primarily to increase strength, stiffness and reduce thermal expansion, thus providing materials more like and competitive with metals. Leading examples for the benefits so obtained are sheet molding compound (SMC) and bulk molding compound (BMC) prepared from glass fibers and thermosetting unsaturated polyesters. These compounds can provide not only high strength and stiffness but also high heat resistance, high impact strength, smooth surfaces, zero mold shrinkage, easier than thermoplastic processing with substantially lower required molding pressures and, finally, low cost per unit volume. Representative properties are shown in Table 1 for typical compounds intended primarily for exterior automotive body parts, the highest volume application of these materials.