Regine Stockmann

Multi-responsive (diethylene glycol)methyl ether methacrylate (DEGMA)-based copolymer systems

Multi-responsive (diethylene glycol) methyl ether methacrylate–methacrylic acid (DEGMA–MAA) copolymers were synthesised for the first time via RAFT polymerisation, and the structure–activity interplay of statistical and block copolymers in solution was compared. In addition to MAA, DEGMA was also copolymerised with 2-(dimethylamino)ethyl methacrylate (DMAEMA) to generate two sets of well-defined weakly acidic or weakly basic copolymers, respectively. The temperature, pH and salt-responsive properties of all polymers was determined via UV-visible spectroscopy and dynamic light scattering, and their solution structures as a function of temperature were visualised via electron microscopy. Results from this study indicate that the DEGMA–MAA statistical and block copolymers display similar stimuli-responsive property trends to the well-characterised DEGMA–DMAEMA copolymers, and show similar lower critical solution temperature (LCST) modulations and aggregate structures in water.

Forward Osmosis: A Novel Membrane Separation Technology of Relevance to Food and Related Industries

Forward osmosis (FO) is an emerging membrane technology that enables the concentration of liquid streams through the removal of water across a semipermeable membrane driven by the osmotic pressure difference between the liquid feed stream and a draw solution across the membrane. Similar to other membrane-based concentration processes, including reverse osmosis (RO) and nanofiltration, FO is a nonthermal concentration process with minimal impact on the sensorial and nutritional quality of food products. However, FO has several advantages over pressure-driven membrane processes such as RO that make it commercially attractive. These include the following: (1) FO does not require external hydraulic pressure for operation and hence has potential for significant energy saving; (2) FO has lower membrane fouling propensity as the solids are not compressed against the membrane; and (3) unlike RO, FO can potentially be used to achieve the concentration factors typical of evaporation. This chapter discusses FO and its application in food concentration. The studies to date indicate that FO is an economically feasible alternative to evaporation for liquid food concentration. The development of membranes with improved mass transfer performance and economically recoverable draw solutes suitable for food application will further improve the prospect of widespread commercial application of FO in the concentration of food streams.

Temperature-responsive methacrylamide polyampholytes

A series of methacrylamide-based polyampholytes were synthesised for the first time and their temperature responsive properties investigated. N-[3-(Dimethylamino)propyl]methacrylamide (DMAPMAm) and methacrylic acid (MAA) were copolymerised in equimolar amounts along with N-(tert-butyl)methacrylamide (tBMAm) via RAFT polymerisation, forming a series of polymers with varying tBMAm content. A variety of solvents were assessed to determine the optimal conditions for synthesis. The solution properties of the resultant polymers were then determined via turbidimetry and NMR. Results from this study show that tBMAm was an effective modulator of TCP events when it was present in levels of 16% or more of the total monomers in the polymer chain. Below this threshold, polymers displayed properties akin to traditional polyampholytes due to the antipolyelectrolyte effect. Above this level however, the polymers displayed properties analogous to other temperature-responsive polymer systems. Interestingly changes in both pH and addition of salt led to an increase in the polymer cloud points, and in some cases loss of thermoresponsivity entirely, despite the high level of anionic and cationic charges present in the side chains.