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A series of linear polyaryloxysilanes having various combinations of methyl, phenyl, vinyl, and allyl substituents was synthesized by melt-condensing , '-biphenol and dianilinosilanes. These soluble thermo-

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A novel system has been developed for the slow release of pesticides with advantages of being more practical and less costly than materials currently used. Thermoplastic polymers and copolymers of glycolic and lactic acid are employed as the slow-release encapsulating agent. These polymers degrade to natural materials that are harmless to the environment and, in doing so, slowly release encapsulated herbicides or pesticides. The total polymer and pesticide package is easy to fabricate and offers the potential of effectively controlling the runoff of agricultural chemicals into streams while maintaining an effective dose.There is need for the development of safe and effective controlled release formulations of pesticides. Experience to date suggests that such formulations could make it possible to use smaller amounts of pesticides and perhaps even improve performance efficiency. Technology of this kind would also be (of value in making pesticides safe in the environment.Aliphatic polyesters have been known for some time to have excellent physical properties, but are sensitive to moisture (Sorenson and Campbell, 1961). More recent investigations have centered on poly(1actic acid), PLA, and poly(glyco1ic acid), PGA, for use in absorbable sutures and prosthetic devices t Frazza and Schmitt, 1971; Meclicui Worid News, 1971). Our own investigations indicate that the polyesters of glycolic and lactic acids biodegrade via hydrolysis, a conclusion supported by other workers (Kulkarni et al., 19il). The degradation products apparently are lactic and glycolic acids, CO2, and water, all of which are, of course? harmless. The degradation time is of the order of two or tjix months, depending upon environment, chemical composition, and geometry of the polymer devices. Poly(glyco1ic acid) has been approved by FDA for use in absorbable sutures and has become an item of commerce.A series of announcements (Chem. Week, 1970, 1972a, 1972b Chem. Eng. News, 1972) has indicated the interest in slow-release systems for preventing the runoff of agricultural chemicals. Most of these systems use synthetic high polymers as the encapsulating agent, or carrier, for the pesticides. These polymers are typically synthetic rubbers, polyamides. and other polymers with unknown metabolic fates in soil, an important point in view of the increasingly tough stance taken by EPA and FDA. Presumably, these agencies will require some sort of "impact statements" on this use of polymeric materials. In addition. some of the above-cited encapsulating materials are thermosets, and the release of herbicide is dependent upon their diffusion through surface pores in the polymer matrix. The fabrication of such devices is more difficult and expensive than the use of a thermoplastic in which the pesticide is simply mixed in the molten polymer and fabricated by routine plastic molding operations. In addition. almost all of the polymers currently used as encapsulating matrices for pesticide have extremely long lifetimes in normal exterior environments and, depending o...

synopsisA three-component catalytic system has been discovered, which successfully polymerizes a-phenylethylisonitrile to high polymer ( D P = 200-900) and also polymerizes n-hexylisonitrile. The catalyst componqnts ate a strong acid, a free-radical source, and a heterophase and are all necessary in this system. The use of a liquid medium in which the polymer is insoluble promotes the rate of polymerization and total yield. Poly-(a-phenylethylisonitrile), formed from monomer in a presence of oxygen and finely ground glass coated with sulfuric acid, can itself serve, in the presence of monomer and oxygen, a s a catalyst for this polymerization. Preparative details and discussion of these synthesis factors are given.