title: Photoinduced smart, self-healing polymer sealant for photovoltaics.
abstract: Polyisobutylene (PIB)-based polymer networks potentially useful as smart coatings for photovoltaic devices have been developed. Low molecular weight coumarin functional triarm star PIB was synthesized via a single step SN2 reaction of bromoallyl functional triarm star PIB with 4-methylumbelliferone or umbelliferone in the presence of sodium hydride. Quantitative end functionality was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. UVA (λmax = 365 nm) induced reversible photodimerization of the coumarin moieties resulted in cross-linked elastomeric films exhibiting self-healing behavior. The extent of photodimerization/photoscission was monitored by UV-vis spectroscopy. The low oxygen (1.9 × 10(-16) mol m m(-2) s(-1) Pa(-1)) and moisture (46 × 10(-16) mol m m(-2) s(-1) Pa(-1)) permeability of the cross-linked polymer films suggest excellent barrier properties of the cross-linked polymer films. The self-healing process was studied by atomic force microscopy (AFM). For this, mechanical cuts were introduced in the cross-linked PIB films through micromachining with an AFM tip and the rate of healing induced by UV, sunlight, or both was followed by taking AFM images of the film at different time intervals during the repair process.
authors.affiliation: Department of Chemistry, University of Massachusetts Lowell , One University Avenue, Lowell, Massachusetts 01854, United States.
authors.forename: Sanjib
authors.initials: S
authors.lastname: Banerjee
authors.forename: Ranjan
authors.initials: R
authors.lastname: Tripathy
authors.forename: David
authors.initials: D
authors.lastname: Cozzens
authors.forename: Tibor
authors.initials: T
authors.lastname: Nagy
authors.forename: Sandor
authors.initials: S
authors.lastname: Keki
authors.forename: Miklos
authors.initials: M
authors.lastname: Zsuga
authors.forename: Rudolf
authors.initials: R
authors.lastname: Faust
keywords: functional coatings; photochemistry; photovoltaic devices; polyisobutylene; self-healing