Students Present Posters at National ACS, Spring 2008
The Waldow group had two students, Christopher Hamre and Nicole Grant, present posters at the Spring 2008 ACS meeting in New Orleans. The abstracts are presented below.
1) Christopher Hamre, Graduated 12/2007 
CHED 729 - Bicontinuous microemulsion study of ternary polymer blends using dynamic light scattering
Christopher J. Hamre, hamrecj@plu.edu and Dean A. Waldow, waldowda@plu.edu, Department of Chemistry, Pacific Lutheran University, 1010 122nd Street S, Tacoma, WA 98447
High temperature dynamic light scattering (DLS) and cloud point measurements were used to study polymer blends composed of polystyrene (PS), polybutadiene (PB), and a PS-PB diblock copolymer. The copolymer acts as a surfactant potentially leading to the formation of a bicontinuous microemulsion (BME). Measurements as a function of scattering angle were taken over a temperature range of 180°C to 75°C. Intensity autocorrelation functions for all polymer compositions were fit using a double exponential function and were combined with zero-shear viscosities to determine dynamic correlation lengths. Two distinct density fluctuations were observed. The dynamic correlation lengths from the fast mode for the binary and 4% diblock blends diverge near their cloud point temperatures as the samples phase separate. The 8%, 10%, and 12% diblock blends have dynamic correlation lengths that do not diverge when temperature is lowered suggesting the presence of a BME similar to research presented in the literature.
ACCEPTED
Abstract ID#: 1165997
2) Nicole Grant, To graduate 5/2008
CHED 710 - Influence of diblock copolymer composition on the phase behavior of a polymer blend studied by cloud point measurements
Nicole D. Grant, grantnd@plu.edu and Dean A. Waldow, waldowda@plu.edu, Department of Chemistry, Pacific Lutheran University, 1010 122nd Street S, Tacoma, WA 98447
Anionic polymerization was used to synthesize polystyrene (PS) / polybutadiene (PB) diblock copolymers with a range of compositions. These diblock compositions ranged from 20/80 to 80/20 in terms of styrene and butadiene monomer content. These diblocks were used to evaluate the influence of diblock copolymer composition on the phase behavior of a PS/PB blend. The phase boundaries were analyzed using cloud point measurements as a function of diblock content. The results of this research are consistent with the predictions of a theoretical model by Jacek Dudowicz et al. (Macromolecules 1995, 28, 2276). Their results suggest that if a diblock copolymer with a 50/50 PS/PB composition is added to a binary blend, it will lower the critical temperature. Whereas a diblock copolymer with a distribution which is further away from an equal distribution, such as an 80/20 PS/PB composition, will raise the critical temperature.
ACCEPTED
Abstract ID#: 1166074