Mark J. Boerakker

ABA triblock copolymers : from controlled synthesis to controlled function

The ABA amphiphilic block copolymers, poly(hydroxyethyl methacrylate-block-methylphenylsilane-block-hydroxyethyl methacrylate) (PHEMA–PMPS–PHEMA) and poly[oligo(ethylene glycol) methyl ether methacrylate-block-methylphenylsilane-block-oligo(ethylene glycol) methyl ether methacrylate] (POEGMA–PMPS–POEGMA) were successfully synthesised via atom transfer radical polymerisation (ATRP). Macroinitiators suitable for the ATRP of oligo(ethylene glycol) methyl ether methacrylate and 2-hydroxyethyl methacrylate were synthesised from the condensation reaction of α,ω-dihalopolymethylphenylsilane and 2′-hydroxyethyl 2-bromo-2-methylpropanoate. The copolymers were characterised using 1H NMR and 13C NMR spectroscopy and molecular weight characteristics were determined using size exclusion chromatography and 1H NMR. The aggregation behaviour of some of the copolymers in water was studied using transmission and scanning electron microscopy and dynamic light scattering. These revealed the prevalent aggregate species to be micelles. Larger aggregates of 300–1000 nm diameter were also observed. The UV induced degradation of the aggregates was studied by UV-Vis spectroscopy. The thermal behaviour of selected copolymers was studied by differential scanning calorimetry and microphase separation of the two components was demonstrated.

Plastic- and liquid-crystalline architectures from dendritic receptor molecules

Host molecules with U-shaped receptor cavities have been derivatized at their convex side with two n-hydrocarbon tails (1), two first-generation (2), and two second-generation (3) monodendritic hydrocarbon tails. Although hosts 1 and 2 display plastic-crystalline behavior, evidence suggests that host 3 forms a cubic liquid-crystalline phase. In this phase, molecules of 3 are arranged in spherical supramacromolecular assemblies, in which the receptor cavities are situated in the core and the hydrocarbon tails at the periphery. The 1:1 host-guest complex of 3 with methyl 3,5dihydroxybenzoate forms a similar liquid-crystalline phase, with the guest included in the core of the assemblies.