Pursuit of reinitiation efficiency of resonance‐stabilized monomeric allyl radical generated via “degradative monomer chain transfer” in allyl polymerization

For a deeper understanding of allyl polymerization mechanism, the reinitiation efficiency of resonance‐stabilized monomeric allyl radical was pursued because in allyl polymerization it is commonly conceived that the monomeric allyl radical generated via the allylic hydrogen abstraction of growing polymer radical from monomer, i.e., “degradative monomer chain transfer,” has much less tendency to initiate a new polymer chain and, therefore, this monomer chain transfer is essentially a termination reaction. Based on the renewed allyl polymerization mechanism in our preceding article, the monomer chain transfer constant in the polymerization of allyl benzoate was estimated to be 2.7 × 10^?2 at 80 °C under the polymerization condition, where the coupling termination reaction of growing polymer radical with allyl radical was negligible and, concurrently, the reinitiation reaction of allyl radical was enhanced significantly. The reinitiation efficiencies of monomeric allyl radical were pursued by the dead‐end polymerizations of allyl benzoate at 80, 105, and 130 °C using a small amount of initiators; they increased remarkably with raised temperature. Thus, the enhanced reinitiation reactivity of allyl radical at an elevated temperature could bias the well‐known degradative monomer chain transfer characteristic of allyl polymerization toward the chain transfer in common vinyl polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Memristive operations demonstrated by gap-type atomic switches

We demonstrate memristive operations using gap-type Ag₂S atomic switches, in which the growth and shrinkage of an Ag protrusion are controlled by using solid-electrochemical reactions. In addition to conventional memristive operations such as those proposed and demonstrated by resistive random-access memories (ReRAMs) using metal oxide compounds, gap-type Ag₂S atomic switches also show new types of memristive operations by storing information from input signals without changing their output until a sufficient number of signals are inputted. The new types of memristive operations resemble the learning process seen in neuroplasticity, where changes occur in the organization of the human brain as a result of experience.     

Ring-opening polymerization of nitrogen– and phosphorus-containing monomers: Polymerization mechanism and polymer properties

The first part of this paper describes cationic polymerizations of cyclic imino ethers, 2-oxazolines and 5,6-dihydro–4H–1,3–oxazines, which proceed via cyclic onium propagating species or via covalently bonded alkyl halide species. In an extreme case, both ionic and covalent species are present in equilibrium and propagate concurrently. The propagation rate constants due to the respective species were determined. A poly(cyclic imino ether) becomes hydrophilic or lipophilic dependent on the substituent of the monomer. Based on this principle, various types of nonionic polymer surfactants have been prepared, e.g., diblock and triblock copolymers, graft copolymers, and surfactants having one 2-oxazoline chain. The second part is concerned with ring-opening polymerizations of new eight cyclic trivalent phosphorus monomers. These polymerizations produced phosphorus-containing functional polymers such as a chelating resin. ³¹P NMR analyses of polymerization of cyclic phosphinite monomers led to propose a new mechanism of “Electrophilic Ring-Opening Polymerization”.     

Bisthiol-Assisted Multilayers' Self-Assembly of Gold Nanoparticles: Synthesis,Characterization, Size Control and Electrocatalytic Applications

The layer-by-layer (LBL) approach has been utilized to self-assemble multilayers films of citrate-stabilized gold nanoparticles (AuNPs) on polycrystalline gold (poly-Au) substrates. 1,4-benzenedimethanethiol (BDMT) was used as a cross linker to bind every two successive AuNPs layers. The transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques were employed to confirm the existence of the alternative layers of AuNPs and BDMT in the self-assembled multilayers film. The AuNPs modified poly-Au electrode showed a significant electrocatalysis towards the reduction of oxygen (a positive potential shift of about 100 mV was observed in the reduction peak potential compared to that obtained at the bare poly-Au electrode). The AuNPs tend to aggregate during their assembling to different extent which markedly depends on the substrate geometry and roughness. An effort was dedicated to understand and control the aggregation phenomenon.     

Functional polymers based on high hydrophilicity of poly(2-methyl-2-oxazoline)

Polymers of the family of 2-substituted 2-oxazolines have the general structure of poly(N-acylethylenimine), whose hydrophilic/lipophilic properties vary according to the substituent, i.e., the acyl group of the polymer. Of special interest is the polymer of 2-methyl-substituted monomer, which has a strong affinity for water. Another useful feature of the 2-oxazoline family is the fact that its polymerization reaction is quite clean without disturbance by chain transfer and termination. On the basis of the above characteristics, three kinds of novel materials of functional polymers have been explored:

• 1. Non-ionic polymeric surfactants.
• 2. Non-ionic hydrogels.
• 3. Block copolymer with silica gel: Organic/inorganic polymers hybrids.