Professor Sperling was world-renowned for research on interpenetrating polymer networks and their ability to serve as effective damping materials for acoustic and vibrational noise. Here, we discuss two strategies that we have developed to prepare polymerics that undergo nanophase separation but with broad interphase regions leading to glass transition temperature (Tg) response over extraordinarily broad temperature ranges. Such materials exhibit excellent broad-temperature-range damping properties. The first strategy was developed in our group a decade ago and involves the synthesis of gradient copolymers by nitroxide-mediated polymerization (NMP). By employing (NMP) with two monomers for which the associated homopolymers possess strikingly different Tgs and are moderately incompatible, it is possible to synthesize high molecular weight copolymers with quasi-linear gradients along the chain lengths that lead to continuous glass transition breadths as large as 100 K as measured by DSC. These broad glass transitions result from the gradient copolymers undergoing nanophase separation but with a sinusoidal composition profile with a period of several tens of nanometers. The Tg breadth reflects the glass transition responses of all compositions present in the nanophase-separated sample. Dynamic mechanical analysis of such gradient copolymers demonstrates that temperature range over which good damping character is obtained (tan delta &gt; 0.30) can exceed 60 K. We are currently doing research on polyhydroxyurethanes (PHUs) with poly(tetramethylene oxide) (PTMO)-based soft segments which undergo nanophase separation and have developed the first PHUs that exhibit thermoplastic elastomer properties. Unlike polyurethanes which exhibt nanophase separation with narrow interphase, PHUs with PTMO-base soft segments exhibit nanophase separation with broad interphase because of hydrogen bonding between hard-segment hydroxyl groups and soft-segment ether oxygens which competes with interurethane group hydrogen bonding. We have been able to produce PHUs with excellent damping characteristics of temperature ranges exceeding 80 K. The exact temperatures exhibiting good damping can be easily tuned in both gradient copolymers and PHUs by the content of the high Tg materials in the copolymers or PHUs and the selection of the high and low Tg component species.

Nanophase-separated gradient copolymers and polyhydroxyurethanes with unusually broad interphases leading to excellent damping properties over extraordinarily broad temperature ranges

254th National Meeting (2017)

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