Amphphilic alternating molecular brushes can be seen as arrays of amphiphilic block copolymers joined at the junction point between the hydrophobic block and the hydrophilic block. Although there is extensive literature describing phase behaviour and self-assembly of amphiphlic block copolymers in selective solvents, there are remarkably few publications on the behaviour of the molecular brushes.
In this study we made use of the strongly alternating tendency of N-substituted maleimides and para-substituted styrene. As hydrophobic component, we synthesized a series of N-alkylmaleimides with chain lengths varying from C₁₀ to C₂₂. For the hydrophilic component we converted 4-vinyl benzyl chloride to a macromonomer with monomethoxy poly(ethylene glycol) with degrees of polymerization 11, 15 and 21.
Molecular brushes were synthesized via alternating conventional radical copolymerization of a maleimide and a styrene macromonomer. After chemical characterization of the molecular brushes, their self-assembly in water as a selective solvent was studied. The main emphasis in the study was on the nature of the common (organic) solvent and on the rate of transfer into the aqueous environment. SEM and conflocal flourescence microscopy were used as the prime techniques to determine to morphology of the molecular brushes after self-assembly.
Various highly branched morphologies were observed, but some systems exhibited a highly reproducible complex morphology (Figure 1). The influence of the various parameters on morphology development will be discussed.

Figure 1. Example of self-assembly of an amphiphilic alternating molecular brush in water.

Bert Klumperman

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