Surface induced selective delamination of amphiphilic ABA block copolymer thin films

This is the result of an ongoing collaboration with Dr. N. Sommerdijk’s Biomaterials group at the University of Eindhoven (the Netherlands) and illustrates the close collaboration that exists in pursuing the design and application of novel polymeric materials between the two groups. This details work on a physical phenomenon (selective delamination) and key materials (amphiphilic block copolymers) that have subsequently been applied in the design of novel biomaterials. These results have appeared in a larger body of work including Advanced Materials, Angewandtie Chemie International Edition and the Journal of Materials Chemistry

ABA triblock copolymers: from controlled synthesis to controlled function

The ABA amphiphilic block copolymers, poly(hydroxyethyl methacrylate-hlock-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 alpha,omega-dihalopolymethylphenylsilane and 2'-hydroxyethyl 2-bromo-2-methylpropanoate. The copolymers were characterised using H-1 NMR and C-13 NMR spectroscopy and molecular weight characteristics were determined using size exclusion chromatography and H-1 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

The synthesis of methacrylate amphiphilic diblock and triblock copolymers by copper mediated atom transfer radical polymerisation

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ABA Amphiphilic block copolymers with comb-like segments from ATRP: Self-assembly in aqueous and electrolyte solutions

Amphiphilic block copolymers (BCs) can self-organize into various aggregates morphologies in solution where the solvent is selective for one of the blocks. The size and the shape of these various molecular assemblies depends on the balance of hydrophilic and hydrophobic regions of the block copolymer. Among these aggregates, vesicles, which have been considered as powerful nanocarriers, are especially interesting for their applications in the design of drug delivery systems. Here we report preliminary results of our studies into the self-assembly behaviour in aqueous dispersions of poly[olig(ethylene glycol methyl ether)]-block-polystyrene-block-[olig(ethylene glycol methyl ether)] (POEGMA-PS-POEGMA) prepared by atom transfer radical polymerisation techniques (ATRP) for different hydrophilic:hydrophobic weight ratios between the blocks. Size and morphology of the aggregates were analysed by TEM and dynamic light scattering. The effects of two salts, NaCl and CaBr2 on the aggregation behaviour were studied and fluorescence measurements were also carried out in order to determine the critical aggregation concentration (c.a.c.) and to exhibit the encapsulation of a fluorescent probe

Synthesis of poly[dimethylsiloxane-block- oligo(ethylene glycol)methyl ether methacrylate]: an amphiphilic copolymer with a comb-like block

AB amphiphilic comb-like block copolymers of poly(oligo[ethylene glycol] methyl ether methacrylate) and polydimethylsiloxane were synthesised with a methodology based on atom transfer radical polymerization (ATRP). The anionic ring opening polymerisation of hexamethylcyclotrisiloxane followed by reaction with 3-(chlorodimethylsilyl) propyl 2-bromo-2-methylpropanoate propyldimethylchlorosilane gave suitable macroinitiators for the ATRP of oligo[ethylene glycol] methyl ether methacrylate. The latter synthetic procedure was optimised by performing a number of syntheses varying the reaction solvent, catalytic complex and the temperature used. Copolymers with relatively high polydispersity indices (Mw/Mn>1.3) could be synthesised at room temperature by employing a Cu(I)Br:N,N,N?,N?,N?-pentamethyldiethylenetriamine complex in n-propanol with Cu(II)Br. The optimum reaction conditions employed a Cu(I)Cl:N-(n-propyl)-2-pyridyl(methanimine) complex with an n-propanol/water mixture or toluene as solvent at 90 °C. This gave block copolymers of the desired molecular weights and polydispersity indices of less than 1.1. The block copolymers were characterised with 1H NMR and 13C NMR spectroscopy and size exclusion chromatography

The synthesis and self-assembly of ABA amphiphilic block copolymers containing styrene and oligo(ethylene glycol) methyl ether methacrylate in dilute aqueous solutions: Elevated cloud point temperatures for thermoresponsive micelles

A series of ABA amphiphilic triblock copolymers possessing polystyrene (PS) central hydrophobic blocks, one group with “short” PS blocks (DP = 54–86) and one with “long” PS blocks (DP = 183–204) were synthesized by atom transfer radical polymerization. The outer hydrophilic blocks were various lengths of poly(oligoethylene glycol methyl ether) methacrylate, a comb-like polymer. The critical aggregation concentrations were recorded for certain block copolymer samples and were found to be in the range circa 10?9 mol L?1 for short PS blocks and circa 10?12 mol L?1 for long PS blocks. Dilute aqueous solutions were analyzed by transmission electron microscopy (TEM) and demonstrated that the short PS block copolymers formed spherical micelles and the long PS block copolymers formed predominantly spherical micelles with smaller proportions of cylindrical and Y-branched cylindrical micelles. Dynamic light scattering analysis results agreed with the TEM observations demonstrating variations in micelle size with PS and POEGMA chain length: the hydrodynamic diameters (DH) of the shorter PS block copolymer micelles increased with increasing POEGMA block lengths while maintaining similar PS micellar core diameters (DC); in contrast the values of DH and DC for the longer PS block copolymer micelles decreased. Surface-pressure isotherms were recorded for two of the samples and these indicated close packing of a short PS block copolymer at the air–water interface. The aggregate solutions were demonstrated to be stable over a 38-day period with no change in aggregate size or noticeable precipitation. The cloud point temperatures of certain block copolymer aggregate solutions were measured and found to be in the range 76–93 °C; significantly these were ?11 °C higher in temperature than those of POEGMA homopolymer samples with similar chain lengths. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7739–7756, 200