Polymer coatings for optical fibers

BLYLER AND ALOISIO Polymer Coatings for Optical Fibers... 

The analysis of the diffusion-eontrolled features might be simplified by identifying the two types of free radieals the active and the trapped ones. Electron spin resonance speetroseopy shows that active (mobile) radicals give a 13-line spectrum and trapped (statie) radicals give a nine-line spectrum. Also, photopolymerization of a number of neat acrylate monomers used in polymer coatings for optical fiber was studied with photo DSC and with a cure monitor using a fluorescent probe. The acrylates had a functionality of one to six. It was found that conversion of monomers ranges from 40% to 100%. This, however, is depended upon functionality and structure of particular monomers. It can also be a function of the type and amount of the photoinitiator used. 

BLYLER ET AL. Polymer Materials for Optical Fiber Coating... 

GTP is a safe operation. A runaway polymerization can be quickly quenched with a protonic solvent. Since the group transfer polymerization goes to completion, no unwanted toxic monomer remains the silicone group on the living end after hydroxylation is removed as inactive siloxane. The living polymer in GTP is costlier than traditional polymerization techniques because of the stringent reaction conditions and requirements for pure and dry monomers and solvents. It can be used in fabrication of silicon chips, coating of optical fibers, etc. 

Pannell and coworkers34 described the use of poly(ferrocenylsilanes) as coatings in optical fiber gas sensors. In these devices a small change in refractive index of the polymer film results in a large change in the optical transmission of a tapered optical fiber. This is useful for remote sensing of ammonia or carbon dioxide. Polymers of type 6.20 with R/R = Me/Ph and copolymers from monomers with R/R = Me/Ph and Me/Me were found to be effective for this application. 

Nieuwenhuizen and Harteveld [92] have realized a nerve agent dosimeter gas sensor based on the strong interaction between certain metal ions and organophosphorus compounds. In this case, the sensor material contains La(III) 2-bis(carboxymethyl)amino hexadecanoic acid and different factors such as humidity, concentration and layer thickness have been studied and optimized. Using a combination of a metallic complex with a molecular-imprinted polymer, a very sensitive sensor was developed for the detection of soman, a chemical warfare agent (the detection limit was 7 ppt) [93]. The biosensing material is based on a polymer coated onto a fiber-optic probe modified with a luminescent europium detection complex. This complex was... 

The combination of molecularly imprinted polymers and europium signal transduction has proven applicable as a generic scheme to develop materials for the detection of hydrolyzed and non-hydrolyzed organophosphate containing cong>ounds such as pesticides and nerve agents. These polymers can be coated onto optical fibers and used as sensors for the detection of these species in aqueous environments. Similar functional polymers can also be used for enhancing the sensitivity and selectivity of other detection devices such as surface acoustic wave sensors. 

Other Monomer Systems. The above sections are by no means an exhaustive list of monomers that are used in free radical photopolymerizations. Diallyldiglycolcarbonate (18) has been used for many years in optical components such as lenses (51). Acrylamide (19) is used in stereolithography and to prepare holographic materials (52-54). A(-vinylpyrrolidinone (20) is copolymerized with acrylates and methacrylates for cosmetic and biomedical applications (55). Norbornene (21) is copolymerized with thiols for optical fiber coatings (56). Liquid crystal polymers (22) based on acrylates and thiol-enes are being developed to produce mirror coatings, polarizing films, and liqiud crystal displays (57,58). 

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