Microcapsule having temperature-dependent permeability profile

Abstract

The microcapsules of the invention are comprised of crystallizable polymers which are preferably side-chain crystallizable polymers or cross-linked, side-chain crystallizable polymers having a specific first order transition point or 'melt' temperature. The polymers are caused to form microcapsules and thereby encapsulate one or more compounds generally referred to herein as an active ingredient such as a herbicide, insecticide, fungicide, or fertilizer. The polymer of the microcapsule surrounds the active ingredient separating it from the outside environment. Crystallizable polymers used herein have temperature-dependent permeabilities with respect to a given component such that this component is kept out of contact with the active ingredient at a temperature below a given first order transition point and (due to increased permeability) is allowed to contact the active ingredient at a temperature at or above the transition point. The permeability of the polymer is not only temperature-dependent but reversible. The microcapsules are less than 200 microns in median diameter, more generally less than 100 microns in median diameter and preferably less than 50 microns in median diameter. By varying the polymer and reactants used in the formation of the microcapsules, the release rate and timing of the release of active ingredient from the microcapsule can be temperature controlled to obtain the various objects, advantages and features of the present invention.