Controlled free radical polymerization has been used to synthesize binary and ternary gradient copolymers of various gradient strength. In these systems, the exact details of the sequence differ from chain to chain but on average are tuned in a sensitive manner based on the semi-batch nature of the polymerization. Like A-B block copolymers, gradient copolymers can undergo nanophase separation. However, because there are no pure A or pure B blocks within a gradient copolymer chain, the nanophase separation in copolymers with a linear gradient leads to a sinusoidal composition profile within bulk gradient copolymers. This unusual composition profile at the nanolevel results in behavior and properties that cannot be achieved with block or random copolymers, including glass transition breadth exceeding 100 K. In to glass transition behavior and its implications for damping applications, results of recent and ongoing research will be discussed related to unusual temperature dependent phase behavior rarely seen in block copolymers but more easily achieved because of the additional variable of gradient sequence. The superiority of gradient copolymers over block copolymers as interfacial agents will also be discussed. Examples will be provided in the field of blend compatibilziation resulting, in some cases, in dispersed phase domains averaging ~100 nm in diameter.

Advantages of gradient sequencing in copolymers for unusual, tunable properties, phase behavior, and application as an interfacial agent in polymer blends

246th National Meeting (2013)

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