Papers by Keyword: Spiropyran

Abstract: Mechanorphore-based Poly (glycidyl methacrylate) was synthesized by atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) in bulk by using spiropyran-based initiator, CuCl in combination with N,N,N’,N’’,N’’-pentamethyldiethylenetriamine (PMDETA) as catalyst. The resultant polymer was characterized by gel permeation chromatography (GPC) and ¹H NMR spectroscopy. The relative molecular mass of PGMA can be changed by polymerization time. The resultant polymers have controlled molecular weight and low polydispersity. The present synthetic strategy provides a convenient and efficient method to synthesize mechanophore-linked PGMA which can be ulteriorly crosslinked to form thermosetting polymer networks.

Abstract: Spiropyrans are among the most promising organic photochromic dyes. However, spiropyrans are very sensitive dyes and there are many independent factors that can affect the performance of these dyes. The effect of substituent on the optical absorption spectra, fading kinetic, and also the dye stability of spiropyrans in diphenyl ether by UV irradiation has been investigated. The 6-nitro BIPS displayed greater absorbance intensity of 0.740% at 600nm compared to 8-ethoxy-6-nitro BIPS of 0.651% at 620nm. Furthermore, 6-nitro BIPS is less stable as it has higher rate constant of 0.1003s^-1 and thus lower half-life time (50% decay of the photochromic effect) of 6.9s, in contrast to 8-ethoxy-6-nitro BIPS of 0.0594s^-1 and 11.7s respectively.

Abstract: This paper demonstrated the photochromic behavior of two novel spiropyran functionalized dendrigraft polybutadiene with linear-comb and star-comb architectures (LC-PB-Sp and SC-PB-Sp, respectively). LC-PB-Sp and SC-PB-Sp were synthesized via the combination of anionic polymerization and click chemistry methodology. The photochromic behavior was investigated based on UV-Vis spectroscopy. The results showed that the coloring speed was in an order of v (Sp) >v (SC-PB-Sp) >v (LC-PB-Sp), while the discoloration speed exhibited in an order of v (SC-PB-Sp) >v (LC-PB-Sp) >v (Sp), suggesting that the nonpolar dendritic PB matrices tended to stabilize the nonpolar closed form of spiropyran. Furthermore, the retrieval rate of SC-PB-Sp was much faster than its corresponding LC-PB-Sp due to its more compact structure.

Abstract: In order to elucidate the mechanism of photochromism and spectrum properties observed for spiropyran, the model complexes of spiropyran, in which different substituent and structure are key factors, have been optimized by using ab initio and hybrid DFT programs. The primary relationship between the substituent species and structure and photochromism was given by simulation calculation.

Abstract: Spiropyran photochromic compounds can be switched using light exposure between a non-polar spiro form (SP) and a zwitterionic merocyanine form (MC) that is subject to protonation (MC-H+). It has recently been demonstrated by Walsh et al. that, under acidic conditions, electroosmotic flow (EOF) generated in vinyl based spiropyran monoliths can be modulated using light irradiation [1]. In this paper, we report a spiropyran-modified acrylate based monolith which is particularly sensitive to protonation in the MC form, producing a positively charged surface that converts to the unpolar SP form by exposure to white light. When the MC-H+ form is dominant, it produces a charged surface which enables a relatively high flow rate (up to 1.6 μl/min) to be generated under electroosmotic conditions. Upon exposure to white light, the concentration of MC-H+ decreases due to the photo-conversion to the uncharged SP form, with up to 20% reduction of the EOF. The process is reversible, and removal of the light source results in a flow increase back to the original rate. The ability to alter flow rates in micro-fluidic channels using light has very significant implications, as it could dramatically simplify the manner in which micro-flow systems are controlled.