Open Access. Powered by Scholars. Published by Universities.®
- Publication
Articles 1 - 2 of 2
Full-Text Articles in Engineering
Consequences Of Block Number On The Order-Disorder Transition And Viscoelastic Properties Of Linear (Ab)N Multiblock Copolymers, Lifeng Wu, Eric W. Cochran, Timothy P. Lodge, Frank S. Bates
Consequences Of Block Number On The Order-Disorder Transition And Viscoelastic Properties Of Linear (Ab)N Multiblock Copolymers, Lifeng Wu, Eric W. Cochran, Timothy P. Lodge, Frank S. Bates
Eric W. Cochran
The effect of block number on the order-disorder transition (ODT) and viscoelastic properties were studied for linear (AB) n multiblock copolymers. A series of symmetric poly(styrene-b-isoprene) n multiblocks ((SI) n, n = 1-10) were synthesized by anionic polymerization, and their order-disorder transition temperatures (T ODT) were located using dynamic mechanical spectroscopy. As n increases, T ODT approaches an asymptotic value, consistent with random phase approximation calculations. A systematic difference between the experimental and theoretical results is attributable to the effects of fluctuations, independent of the number of blocks. Addition of up to 20 vol % of a nonselective solvent depresses …
Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
We studied the ultrafast laser-induced coherent phonon oscillation in prismatic shaped gold nanoparticles assembled in monolayer periodic arrays by using the nanosphere lithographic technique. The amplitude and phase of the oscillation observed by ultrafast pump−probe transient spectroscopy is monitored as the wavelength of the dipolar surface plasmon absorption decreases. At a certain wavelength, the oscillation could not be observed. As the monitoring wavelength decreases further, the sign of the amplitude changes. From the wavelength at which the oscillation is not detected, the dependence of the absorption maxima on the size of the nanoparticles, the changes in the nanoparticle size are …