Method of cross-linking poly(ethylene oxide) and poly[oxymethylene-oligo(oxyethylene)] with ultraviolet radiation

Abstract

Poly(ethylene oxide) (PEO) and poly[oxymethylene-oligo(oxyethylene)](PEM) disks are cross-linked by exposure to UV radiation. The rate of formation of cross-links is greatly enhanced by the presence of benzophenone, and an average cross-link density of up to 6 mol% of ethoxy units can be obtained after irradiation. The highly cross-linked polymers are insoluble in water or organic solvents and show improved physical properties for handling and the formation of free-standing films. Dynamic modulus measurements and polymer swelling are employed to characterize the polymers. Dynamic modulus measurements show that, upon irradiation, PEO and PEM become cross-linked elastomeric solids.

What is claimed is: 
     
       1. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] comprising the following steps: (a) dissolving said poly[oxymethylene-oligo(oxyethylene)] in a sufficient amount of polar organic solvent to form a solution;   (b) casting said solution to form a film;   (c) cutting said film to a predetermined thickness;   (d) drying the film; and   (e) irradiating said film with Ultraviolet radiation in a wavelength range   from about 190-350 nm for a predetermined amount of time.   
     
     
       2. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 1 wherein said polar organic solvent is selected from the group consisting of: acetone; acetonitrile; chloroform; and dimethyl sulfoxide. 
     
     
       3. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 1 wherein said drying is at about 60° C. in vacuo. 
     
     
       4. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 1 wherein said wavelength is about 254 nm. 
     
     
       5. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 1 further comprising the step of rotating said film 180° at one-half said predetermined time in step (e) to promote even exposure to the Ultraviolet wavelength. 
     
     
       6. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 1 further comprising the step of adding a predetermined amount of a photoinitiator between step (a) and step (b). 
     
     
       7. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 6 wherein said photoinitiator is selected from the group consisting of: benzophenone; 1,2 dibenzoylbenzene; 1,3 dibenzoylbenzene; 1,4 dibenzoylbenzene; and trans,trans dibenzylidene acetone. 
     
     
       8. A method of cross-linking poly[oxymethylene-oligo(oxyethylene)] as claimed in claim 6 further comprising the step of washing said film after the irradiation with a polar organic solvent to remove the photoinitiator. 
     
     
       9. A method of cross-linking poly(ethylene oxide) comprising the following steps: (a) dissolving said poly(ethylene oxide) in a sufficient amount of polar organic solvent to form a solution;   (b) casting said solution to form a film;   (b) cutting said film to a predetermined thickness;   (c) further drying said film;   (d) irradiating the film with Ultraviolet radiation in the wavelength range from about 190-350 nm for a predetermined amount of time.   
     
     
       10. A method of cross-linking poly(ethylene oxide) as claimed in claim 9 wherein said polar organic solvent is selected from the group consisting of: acetone; acetonitrile; chloroform; and dimethyl sulfoxide. 
     
     
       11. A method of cross-linking poly(ethylene oxide) as claimed in claim 9 wherein said drying is at about 60° C. in vacuo. 
     
     
       12. A method of cross-linking poly(ethylene oxide) as claimed in claim 9 wherein said wavelength is about 254 nm. 
     
     
       13. A method of cross-linking poly(ethylene oxide) as claimed in claim 9 further comprising the step of rotating said film 180° at one-half said predetermined time in step (e) to promote even exposure to the Ultraviolet wavelength. 
     
     
       14. A method of cross-linking poly(ethylene oxide) as claimed in claim 9 further comprising the steps of mixing with the dissolved poly(ethylene oxide)a predetermined amount of photoinitiator under essentially dark conditions to avoid chain scission in the poly(ethylene oxide). 
     
     
       15. A method of cross-linking poly(ethylene oxide) as claimed in claim 14 wherein said photoinitiator is selected from the group consisting of: benzophenone; 1,2 dibenzoylbenzene; 1,3 dibenzoylbenzene; 1,4 dibenzoylbenzene; or trans, trans dibenzylidene acetone. 
     
     
       16. A method of cross-linking poly(ethylene oxide) as claimed in claim 14 further comprising the step of washing said film after the irradiation with a polar organic solvent to remove the photoinitiator.