A "by-productless" cellulose foaming agent for use in imidazolium ionic liquids

Cellulose foams, or sponges, are produced from solutions in ionic liquids by the aqueous acid mediated decomposition of 1-alkyl-3-methylimidazolium-2-carboxylates, where the alkyl group and acid may be selected such that the by-product is the ionic liquid solvent: a by-productless foaming.     

Layer-by-layer deposition of polyelectrolyte macroinitiators for enhanced initiator density in surface-initiated ATRP

The layer-by-layer (L-b-L) deposition of oppositely charged polyelectrolytic macroinitiators has been demonstrated on planar silica substrates. The build-up of the macroinitiator multilayers was monitored by ellipsometry (up to 21 layers) and dual polarization interferometry (up to 17 layers) and good agreement was found between these techniques. The increase in L-b-L thickness was approximately linear, with an average thickness of 2.3 A per layer of deposited macroinitiator. Surface-initiated ATRP of a model nonionic methacrylic monomer, 2-hydroxyethyl methacrylate (HEMA) in a 1:1 methanol/water mixture was conducted at ambient temperature. Increasing the number of macroinitiator layers led to a significant increase in PHEMA brush thickness up to 110 nm, which is attributed to the greater surface grafting density. PHEMA brush thicknesses obtained after 22 h showed a linear dependence on the number of layers of deposited macro-initiator, with all layers exhibiting near-identical growth kinetics. X-ray photoelectron spectroscopy was used to monitor L-b-L assembly and also to confirm PHEMA growth. This technique indicated the loss of small counterions from the multilayers during L-b-L deposition and confirmed an increase in the surface density of bromoester initiator groups as the number of deposited macroinitiator layers was increased. For 17 macroinitiator layers, the bromoester initiator density is estimated to be approximately 4.9 +/- 0.2 nm (-2) from the DPI data. This is comparable to that calculated for ATRP initiator monolayers obtained by either thiol or silane chemistry. Ellipsometry suggested that the macroinitiator multilayers were weakly hydrated prior to the in situ HEMA polymerization. AFM studies indicated that the PHEMA brushes had appreciable surface roughness, but this roughness became negligible compared to the brush thickness with increasing macroinitiator layers.     

Synthesis of sterically stabilized polystyrene latex particles using cationic block copolymers and macromonomers and their application as stimulus-responsive particulate emulsifiers for oil-in-water emulsions

2-(Dimethylamino)ethyl methacrylate (DMA) was block copolymerized with methyl methacrylate (MMA) using group transfer polymerization to give four AB diblock, ABA triblock, and BAB triblock copolymers of low polydispersity (Mw/Mn < 1.20). In addition, a near-monodisperse styrene-functionalized DMA-based macromonomer was synthesized via oxyanionic polymerization using a potassium 4-vinylbenzyl alcoholate initiator. These five well-defined, tertiary amine methacrylate-based copolymers were evaluated as steric stabilizers for the synthesis of polystyrene latexes via emulsion and dispersion polymerization. The most efficient steric stabilizers proved to be the DMA-MMA diblock copolymer and the DMA-based macromonomer. The polystyrene latexes were characterized in terms of their particle size and morphology, stabilizer content, surface charge, and surface activity using dynamic light scattering, scanning electron microscopy, 1H NMR spectroscopy, aqueous electrophoresis measurements, and surface tensiometry, respectively. The pH-dependent surface activity exhibited by selected latexes suggests potential applications as stimulus-responsive particulate emulsifiers for oil-in-water emulsions.     

Use of sterically-stabilised polystyrene latex particles as a pH-responsive particulate emulsifier to prepare surfactant-free oil-in-water emulsions

A pH-responsive, sterically-stabilised polystyrene latex is used as a particulate emulsifier for oil-in-water emulsions; demulsification occurs rapidly on lowering the solution pH and the original emulsion can be reformed on pH cycling.