Applications of Sonochemistry(SC)
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Polymer and Biomaterial applications The effects of ultrasound on polymers (giant molecules formed by the coupling of small molecules-monomers) have been thoroughly studied over the past 30 years. The controlled cleavage of polymers in solutions irradiated with ultrasound has been examined in detail. Polymer degradation produces chains of smaller lengths with relatively uniform molecular weight distributions, with cleavage occurring primarily in the center of the polymer chain. Several mechanisms have been proposed for this sonochemical cleavage, which is usually described as a mechanical breakage of the chains induced by shock waves or solvent flow created by cavitation during the ultrasonic irradiation of liquids. This polymer fragmentation has been used by G. J. Price at the University of Bath to synthesize block copolymers of various sorts. Block copolymers are long chain polymers with two different, but linked, parts. As an analogy, imagine a train made up in front by passenger cars and in back by freight cars. In this fashion, block copolymers can do double-duty in their properties. Peter Kruus at Carleton University, Ottawa, reported the use of ultrasound to initiate polymerization in solutions of various monomers. Applications of ultrasound to the synthesis of biomaterials are under rapid development. While the chemical effects of ultrasound on aqueous solutions have been studied for many years, the development of aqueous sonochemistry for biomaterials synthesis is very recent. The area of protein microencapsulation has proved especially interesting. Microencapsulation, the enclosing of materials in capsules a few micrometers in size, has diverse important applications; these include uses with dyes, flavors and fragrances, as drug delivery systems, and as medical diagnostic agents.
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