A Study of the Use of Novel Self-Ordering Functionalized Polymers to Control Crystal Growth
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0923-V05-09
A Study of the Use of Novel Self-Ordering Functionalized Polymers to Control Crystal Growth Brigid R. Heywood1, and Adam C. D. Ovens1,2 1 Chemistry, Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom 2 Chemistry, Keele University, Keele, ST5 5BG, United Kingdom ABSTRACT In this research, the ability of a series of novel oligomeric organic species to control the nucleation and growth of inorganic crystals was investigated. The issues under consideration were (i) the relative hydrophobicity which might be programmed into a polymer; (ii) the impact of metal binding, or bridging on polymer activity in crystallization; (iii) the mode of polymer self organisation. An homologous series of alkyl-substituted, sulfonated calixarenes were used to probe these issues. The ability of a metal cation to either bridge adjacent calix[4]arenes, or to adsorb into the molecular cavity, impacted the interaction of these molecules with nascent crystals. Selective and specific adsorption behaviours were revealed by the expression of smooth, well defined faces in crystal equilibrium morphology. When the relative hydrophobicity was high (increased molecular weight of alkyl-substituent), these compounds segregated at the gas/liquid interface and, as a consequence of cation-induced ordering, induced the oriented nucleation of crystals. This study has revealed that, in addition to polymer-crystal epitaxial relationships, a tuneable range of chemical characteristics can be programmed into polymeric substrates which are used to control nucleation and growth. INTRODUCTION The growth of crystals remains a topic of interest despite the fact that many of the parameters for the controlled synthetic crystallization of both organic and inorganic materials (e.g. supersaturation, aggregation control, solvent effects, etc.) have been resolved. Recently, much attention has been directed to the study of crystal growth in biological systems [1,2]. In this case the crystallization products are crystals engineered to express unique forms and habits; which are linked to their bio-function [3,4]. For example, the biogenic magnetite/greigite present in magnetotactic bacteria exhibit unusual crystal morphologies; each crystal is preferentially elongated along a growth axis which runs parallel to the easy axis of magnetization [5,6]. The nacre of molluscs, which serves both mechanical and physio-regulatory functions, is assembled from an ordered array of close packed {110} twinned aragonite crystals, with normal growth suppressed along the [001] direction [7]. The study of macromolecules isolated from mineralized tissues has yielded much information about their chemical identities, and their ability to affect the crystallization of inorganic minerals [5,8,9]. However, the fact that the structural integrity of such reagents is often compromised during the isolation procedures; coupled with the destruction of any spatial and temporal association(s) with other bio-matrix components, offers a challenge to any study of their direct role in
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