Architectural Effects in the Phase Formation and Miscibility of SCLCPs Prepared by ATRP

University Of Akron, Akron OH

Investigators

Abstract

In contrast to polymers based on conventional, non-mesogenic monomers, the effect of architecture on the properties of side-chain liquid crystalline polymers (SCLCPs) has barely been investigated. The synthesis of cyclic and branched SCPCPs is proposed in order to determine if high degrees of branching hinders the ability of the polymer to form a liquid crystalline phase, and in order to investigate whether or not the presence of a long mesogenic side chain in every repeat unit influences any of their solution and solid-state properties, such that the SCLCPs might appear to have greater branching than their nominal values. In particular, an ideal architecture is sought for generating SCLCPs with exceptionally fluid mesophases, such that either new applications can be identified or in order to compete with LMMLCs for applications that would benefit from the structural integrity of a polymer. These different architectures are also needed to investigate the source of the broad phase transitions often exhibited by SCLCPs synthesized by non-living polymerizations. New chemistry is proposed to synthesize the first cyclic polyacrylates and the first hyperbranched polyacrylates that are chemically analogous to linear polyacrylates; the hyperbranched polymers will contain an ester group attached to every other carbon atom along the polymer backbone, with a non-initiator-containing alkylester attached as a free side chain. All of the proposed architectures are new to the field of SCLCPs. The solution behavior of the polymers will be investigated by light scattering measurements and GPC as a function of molecular weight. The thermotropic behavior of the homopolymers will be determined as a function of molecular weight and extent of branching by DSC, polarized optical microscopy and possibly X-ray diffraction. Polarized optical microscopy will also be used to qualitatively determine how the extent of branching affects the polymers' dynamics, which will be correlated with the 13C-NMR T1C spin-lattice relaxation times of specific carbons within the mesogen, spacer, branch points and/or polymer backbone of each architecture. The spatial distribution of the components of the architectural blends will be characterized by magnetic resonance imaging. The proposed research is a multidisciplinary project that will train graduate students and postdoctoral researchers, including at least two women, in organic, polymer and physical chemistry. Undergraduate students may contribute through an REU summer supplement during summer months, with mentoring by the graduate students. All participants will present their work routinely at group meetings and ACS and Gordon conferences. Students and postdoctoral researchers will learn how to use Schlenk line synthetic techniques, and how to use NMR, GPC, DSC, polarized optical microscopy and light scattering in order to characterize their polymers, precursors and blends. Those students working on the chain transfer study will also learn how to use a high vacuum line for their kinetic measurements. This work may also contribute to improving the infrastructure of the University of Akron through the acquisition of an NMR imaging instrument if the university instrument proposal is successful.