Photo-Responsive Microencapsulation Materials, Compositions and Methods of Use Thereof

Abstract

Photoactivatable prepolymers and methods of use thereof are disclosed for microencapsulation of a substantially water-insoluble material within a nonporous shell. As provided herein, the microencapsulated material is released with no more than a slow release rate. Upon exposure of the nonporous shell to light, the nonporous shell is converted into a porous shell having an increased release rate for the microencapsulated material.

1 .- 18 . (canceled) 
     
     
         19 . A method for producing microcapsules comprising a substantially water-insoluble liquid material within a non-porous, light-sensitive shell, wherein the non-porous shell is characterized by a release rate of the liquid material in the absence of light of less than lppm/minute, wherein exposure to light converts the nonporous shell into a porous shell characterized by a release rate of the liquid material of from 1 to at least 100 ppm/minute, the method comprising the steps of:
 (a) providing an organic solution comprising said liquid material and an etherified photoactivatable-based prepolymer or mixture of photoactivatable and nonphotoactive-based prepolymers dissolved therein;   (b) creating an emulsion of said organic solution in a continuous phase aqueous solution comprising water and a surface-active agent, wherein said emulsion comprises discrete droplets of said organic solution dispersed in said continuous phase aqueous solution, there being formed thereby an interface between the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and   (c) causing in situ self-condensation and curing of said prepolymers in the organic phase of said discrete droplets adjacent to said interface by catalysis using heat, pH, or a chemical or free radical initiator for a time sufficient to allow substantial completion of in situ condensation of said prepolymers, thereby converting the liquid droplets of said organic solution to microcapsules comprising a solid nonpermeable polymer shell that encloses said liquid material.   
     
     
         20 . A method according to  claim 19 , wherein from about 1% to about 100% of the prepolymer of step (a) are photoactivatable prepolymers. 
     
     
         21 . A method according to  claim 19 , wherein the photoactivatable prepolymer is a benzoin derivative. 
     
     
         22 . A method according to  claim 19 , wherein the photoactivatable prepolymer is an o-nitrobenzoyl derivative, an alpha-keto ester, a benzophenone, a benzyl alcohol, a phenacyl ester, a fluorenecarboxylate, an arylamine, a cinnamyl ester, or a vinylsilane, or combination thereof. 
     
     
         23 . A method according to any of  claim 19 , wherein the prepolymer of step (a) comprises from about 1% to about 70% of the organic solution on a weight basis 
     
     
         24 . A method according to any of  claim 19 , wherein the droplets of the dispersion formed in step (b) are from about 0.5 microns to about 4000 microns in diameter. 
     
     
         25 . A method according to any of  claim 19 , wherein the in situ self-condensation in step (c) is performed at a pH of between about 1.0 and about 12.0. 
     
     
         26 . A method according to any of  claim 19 , wherein the in situ self-condensation in step (c) is performed at a temperature between about 10 degrees C. and about 100 degrees C. 
     
     
         27 . A method according to  claim 19 , wherein said organic solution contains a wall-modifying agent which serves to modify the character of the microcapsule polymeric wall by varying its permeability to the core material. 
     
     
         28 . A method according to  claim 19 , wherein the liquid material comprises a fragrance, a flavor, a drug, an herbicide or a pesticide. 
     
     
         29 . A method according to  claim 19 , wherein the liquid material comprises a plurality of substantially water-insoluble compounds that are fragrances, flavorings, drugs, herbicides or pesticides. 
     
     
         30 . A microcapsule comprising a substantially water-insoluble liquid material within a non-porous, light-sensitive shell, wherein the non-porous shell is characterized by a release rate of the liquid material in the absence of light of less than lppm/minute, wherein exposure to light converts the nonporous shell into a porous shell characterized by a release rate of the liquid material of from 1 to 100 ppm/minute, wherein the shell comprises a combination of non-photoactivatable and photoactivatable polymers. 
     
     
         31 . A mixture of photoactivatable and non-photoactive prepolymers for use in the method of claim  1 , wherein the photoreactive prepolymer is a o-nitrobenzoyl derivative, an alpha-keto ester, a benzophenone, a benzyl alcohol, a phenacyl ester, a fluorenecarboxylate, an arylamine, a cinnamyl ester, or a vinylsilane, or combination thereof. 
     
     
         32 . A photoactivatable prepolymer of claim  1  having the formula (I): 
       
         
           
           
               
               
           
         
       
       wherein
 R 1  and R 2  are independently hydrogen, alkyl, aryl, alkoxy, substituted alkoxy, hydroxy, amino or carboxy or substituted carboxy, wherein both R 1  and R 2  are capable of reactions to form polymers and preferably contain hydroxy, amino, carboxy, sulfhydryl or phosphoryl moieties; R 3  group is hydrogen, alkoxy, alkyl, aryl, or substituted alkoxy; and R 4  is aryl or substituted aryl. 
 
     
     
         33 . A mixture according to  claim 31  further comprising a solvent, a polymerization catalyst, a wall-modifying agent or a light adsorbing additive.