Synthesis of photochromic diarylethene polymers for a write-by-light/erase-by-heat recording system

A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with functional properties of photocoloration, photostability of the colored state, and thermal erasion by heating was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching above 150 °C in solution and in the solid state as well as the performance of the monomeric diarylethene chromophore. In addition, the colored state has a high photostability under visible room light. The diarylethene homopolymer had a glass transition temperature (T_g) as high as polystyrene. The copolymer of 1a with N-1-adamantylmaleimide exhibited extremely high T_g above 200 °C with keeping the photofunctional performance. Such photochromic polymer and copolymers with high T_g can be potentially applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.     

Radical polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate,a dimer of methyl acrylate,as a polymerizable α-substituted acrylate

Polymerization and copolymerization of methyl α-(2-carbomethoxyethyl)acrylate (MMEA), which is known as a dimer of methyl acrylate, were studied in relation to steric hindrance-assisted polymerization. The propagating polymer radical from MMEA was detected as a five-line spectrum and quantified by ESR spectroscopy during the bulk polymerization at 40–80°C. The absolute rate constants of propagation and termination (κ_p and κ_t) for MMEA at 60°C (κ_p = 19 L/mol s and κ_t = 5.1 × 10⁵ L/mol s) were evaluated using the concentration of the propagating radical at the steady state. The balance of the propagation and termination rates allows polymer formation from MMEA. The polymerization rate of MMEA at 60°C was less than that of MMA by a factor of about 4 at a constant monomer concentration. Although no influence of ceiling temperature was observed at a temperature ranging from 40 to 70°C, addition-fragmentation in competition with propagation reduced the molecular weight of the polymer. The content of the unsaturated end group was estimated to be 0.1% at 60°C to the total amount of the monomer units consisting of the main chain. MMEA exhibited reactivities almost similar to those of MMA toward polymer radicals. It is concluded that MMEA is one of the polymerizable acrylates bearing a substituted alkyl group as an α-substituent. Characterization of poly(MMEA) was also carried out. © 1996 John Wiley & Sons, Inc.     

Plasmonic Enhancement of a Photocycloreversion Reaction of a Diarylethene Derivative Using Individually Dispersed Silver Nanoparticles

The fabrication of silver nanoparticles covered with polymers with a well‐defined core–shell structure and the quantitative evaluation of the plasmonic enhancement effect on a photochemical reaction in the vicinity of these silver nanoparticles individually dispersed in a medium are described. The photocycloreversion reaction of a diarylethene polymer in the vicinity of silver nanoparticles was enhanced by 2–6 times relative to the reaction without the nanoparticles. The promotion of the photocycloreversion reaction is due to enhancement of the electromagnetic field near the surface of the silver core.     

A statistical theory of excitable membranes. Nonlinear force-flux relation and fluctuation

A statistical theory of an excitable membrane is proposed under the assumptions that the membrane is composed of an ensemble of a number of active patches, and that the flip-flop transition of an active patch is governed by the dissipative interaction caused by an electric eddy current. By the method of expanding the master equation in the system size together with the Gaussian approximation, the time course of an excitation and the steady N-shaped relation between current and voltage are derived from the ensemble theory of open systems. The fluctuation of electric current under a fixed voltage becomes anomalously large in the marginal state at the threshold potential. The fluctuation associated with an action potential increases sharply at the jump-up transition, but it is not so large at the flip-back catastrophe. The fluctuation-dissipation relation at the steady state of the membrane system is discussed on the basis of a variational principle.This study was supported partly by a grant from the Ministry of Education, Japan.     

Targeted Gene Delivery via PEI Complexed with an Antibody

Stable carriers are required for gene delivery. The use of polyethyleneimine (PEI) has been researched extensively; however, it is not suitable for targeted gene delivery to specific cells. To provide a targeting ability of the specific antibody to PEI, two repeats of Fc-binding domain of protein G (C2) were utilized. The constructed protein containing C2 could bind to a specific antibody and form a larger complex with plasmid DNA/PEI complex. The specific antibody to cell surface protein was bound to the complex through the use of C2 domain, and it was added to cells. As the result, the efficient expression of delivered reporter gene could be realized.