GOALI: Balanced Surfactants for Self-Assembly of Highly Immiscible Polymers

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Nitash Balsara - University of California - Berkeley David Lohse - ExxonMobil GOALI: Balanced Surfactants for Self-Assembly of Highly Immiscible Polymers Intellectual Merit of Proposed Activity The objective of the proposed work is to build a library of surfactants for controlling the self-assembly in mixtures of highly immiscible polymers. This will enable the creation of newnanostructured polymer materials. It may also enable reusing commingled polymeric waste. The approach represents a departure from the large body of previous experimental and theoretical work in this field which relied on the surfactancy of A-B copolymers for organizing mixtures of A and B homopolymers. It is now recognized that these types of copolymers can only organize interfaces if the homopolymers are weakly immiscible. The surfactant that will be used in the research is a balanced A-C block copolymer. The notion of balance is adapted from the literature on surfactancy in aqueous systems. Nonionic surfactants with balanced hydrophobic and hydrophilic character have been successful in creating nanoscale organization in oil/water mixture in spite of their high degree of incompatibility. The reseserch deals with the application of this principle to polymers. Experiments will be conducted on mixtures of highly immiscible polyolefins, polybutene (PB) and polyisobutylene (PIB). Polybutene-block-ethylenebutene copolymer (PB-EB) copolymer will serve as the surfactant. This system was chosen on the basis of the temperature dependence of the PB/EB and PIB/EB Flory-Huggins interaction parameters. It is expected that the balancing of PIB-philic and PIB-phobic tendencies of the surfactant will lead to the rich varieties of phase behaviors that have, thus far, only been identified in aqueous mixtures. The principle of balance that is being developed is, however, perfectly general, and can be applied to a wide variety of polymer blends. Model polymers required for this study will be synthesized by anionic and cationic polymerization. Self-assembly will be studied by small angle neutron scattering at the National Institute of Standards and Technology (NIST), light scattering, and electron microscopy. Broader Impact of Proposed Activity and GOALI mechanism The student working on this project will be jointly advised by the PI (at UC Berkeley) and co-PI (at ExxonMobil). The student will spend about 6 weeks every year, working at the ExxonMobil Corporate Research Labs in Annandale, NJ. All of the expenses associated with the visit (lodging, travel, lab supplies, etc.) will be paid by ExxonMobil. The framework for this collaboration has already been established: the PhD student spent 2 weeks this past summer at ExxonMobil, learning about polymer synthesis, and obtaining safety training and clearances to work in the ExxonMobil Labs. Exposure to an industrial research lab will add a new dimension to the student's education. Since the project will involve several visits to the NIST, the student will learn about the functioning of government laboratories. The materials and samples that will be synthesized and characterized will be used in teaching courses on both thermodynamics and polymer science at Berkeley, and at other institutions such as NIST.