College Park, Maryland      June 6 - 10 , 2004

M2-B3 (11:15 AM): The Impact of the Molecular Structure of a Compatibilizer on the Interfacial Structure of Compatibilized Polymeric Interfaces

R. Mehta, S. Kamath, C.P. O Brien, M. Lay, M.D. Dadmun (University of Tennessee)

This talk will discuss results by our group that has centered on understanding the optimal modification of polymeric biphasic interfaces to improve their strength. Monte Carlo simulation and experimental studies indicate that copolymeric interfacial modifiers that are blocky copolymers improve the strength of polymer/polymer interfaces most effectively. This result is interpreted to indicate that these copolymers most effectively entangle with the homopolymers by the formation of doubly bound loops at the soft interface.

Additionally, neutron reflectivity has been completed to correlate this mechanical data to the structure of the copolymer/homopolymer interfaces. More specifically, the depth profiles of trilayer thin films that consist of a layer of deuterated poly(methyl methacrylate), a layer of a protonated styrene/methyl methacrylate copolymer, and a top layer of deuterated polystyrene were determined using neutron reflectivity for various copolymer architectures, ranging from alternating to random to diblock copolymers. The depth profile and interfacial characteristics of this trilayer indicate that the specific sequence distribution of the copolymer dramatically impacts the ability of that copolymer to extend into the polymer and entangle. The data demonstrate that, for a given molecular weight and copolymer composition, the pentablock and triblock copolymers create the broadest interfaces between the copolymer and homopolymer, while random and alternating copolymers produce the narrowest. This trend agrees with the mechanical testing data and will be discussed.

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