Abstract: A stimulus-responsive formulation of stimulus-responsive polymer particles in aqueous composition has a rheology-stimulus profile (e.g. rheology-temperature) whereby it exhibits certain rheological behaviours over a range of temperatures, which is controllable by copolymerising a stimulus-responsive polymer-forming monomer, such as N-isopropylacrylamide, with a certain proportion of second monomer having weak acid functionality (such as acrylic acid) to form the stimulus-responsive microgel particles of the formulation and by addition of a base to the formulation to neutralise a portion but not all of the weak acid functionality. Thus a stimulus-responsive formulation may be controlled to exhibit gel-to-liquid-to-gel like behaviour with increasing temperature.

Abstract: A method of making a polymeric compound, comprising discrete particles responsive to an external stimulus, that is resistant to aggregation in high-shear fields, which includes the addition of a polymerization initiator to a reaction mixture comprising a monomer corresponding to the polymeric compound, wherein the method comprises the portion-wise addition of aliquots of a cross-linking agent to the reaction mixture, wherein an aliquot of the cross-linking agent is added to the reaction mixture both before the addition of the polymerization initiator and after the polymerization has progressed substantially to completion. The polymer particles are largely immune to the effects of transient shear rates at least as high as 106 s?1, whilst maintaining their thermal responsiveness and being present at moderate concentration. The structural and chemical modifications brought by the delayed portion-wise addition of the cross-linking agent allow an improvement in stability in a high-shear field.