Preparation of hollow poly(divinyl benzene) particles with multiple holes in the shell by microsuspension polymerization with the SaPSeP method

Hollow polymer particles with multiple holes in the shell were prepared by aqueous microsuspension polymerization of micrometer-sized, monodisperse divinylbenzene/n-hexadecane droplets in the presence of sodium dodecyl sulfate (SDS) at concentrations above 4 mM utilizing the Self-assembling Phase-Separated Polymer (SaPSeP) method developed by the authors. The total surface area of the holes per particle increased with an increase in the SDS concentration. At [SDS] = 10 mM, “flower-like” non-spherical particles were formed. Part CCCXV of series “Studies on Suspension and Emulsion”     

Fluorescence Investigations of Oxygen‐Doped Simple Amine Compared with Fluorescent PAMAM Dendrimer

Blue emission of oxygen‐doped tertiary amine (triethylamine), a key unit of fluorescent poly(amido amine) dendrimer, was demonstrated. It was found that the fluorescence intensity could be further enhanced if the tertiary amines locate densely in the dendrimer interior as the branching sites. Moreover, a solvatochromic phenol blue, instead of oxygen, is able to induce the blue fluorescence of the tertiary amino‐branching sites based on a guaranteed host‐guest complexation of phenol blue molecules and dendrimer interior.

     

Preparation of multihollow polystyrene particles by seeded emulsion polymerization using seed particles with incorporated nonionic emulsifier: effect of temperature

Seeded emulsion polymerizations of styrene using polystyrene (PS) seed particles with incorporated nonionic emulsifier were carried out at 40 and 70 °C to investigate the influence of temperature during the polymerization process including the swelling step of the seed particles with monomer on the formation of multihollow PS particles. An increase in the temperature during the polymerization process caused an increase in the rate of coalescence (i.e., the degree of coalescence at any given time) of the small water domains in the inside. After the coalescence proceeded excessively, the water domains were eventually discharged from the particles to the medium, resulting in nonhollow particles. The results show that it is important for the preparation of the multihollow PS particles to control the coalescence of a lot of small water domains inside the seed particles with the incorporated nonionic emulsifier, and strongly support the formation mechanism previously proposed. Part CCCXX of the series “Studies on Suspension and Emulsion”.     

Multifunctional carbon-coated magnetic sensing graphene oxide-cyclodextrin nanohybrid for potential cancer theranosis

Journal of Nanoparticle Research - Over the last years, an environmentally friendly and economically efficient way of nanoparticle production has been found in the biosynthesis of metal...     

Mechanofluorochromism of carbazole-type D–π–A fluorescent dyes

We have newly designed and synthesized unsymmetrical carbazole-type D–π–A fluorescent dyes. The dyes show a bathochromic shift-type mechanofluorochromism (MFC): grinding of as-recrystallized dyes induces a bathochromic shift of fluorescent color and the fluorescent color is recovered by heating or exposure to solvent vapor. In order to clarify the MFC mechanism for the carbazole-type D–π–A fluorescent dyes, time-resolved fluorescence spectroscopy, X-ray powder diffractometry, single-crystal X-ray structural analysis, IR spectroscopy, and differential scanning calorimetry are performed before and after grinding of the solids. On the basis of experimental results and semi-empirical molecular orbital calculations (AM1 and INDO/S), we have revealed that the MFC is attributed to a reversible switching between crystalline and amorphous states with changes of intermolecular hydrogen bonding and π–π interaction.     

Influence of peak inspiratory flow rates and pressure drops on inhalation performance of dry powder inhalers

The aim of this study was to reveal the relationship between human inspiratory flow patterns and the concomitant drops in pressure in different inhalation devices, and the influence of the devices on inhalation performance. As a model formulation for inhalers, a physically mixed dry powder composed of salbutamol sulfate and coarse lactose monohydrate was selected. The drops in pressure at 28.3?L/min of three inhalation devices, Single-type, Dual-type, and Reverse-type, was 1.0, 5.1, and 8.7?kPa, respectively. Measurements of human inspiratory patterns revealed that although the least resistant device (Single) had large inter- and intra-individual variation of peak flow rate (PFR), the coefficients of variation of PFR of the three devices were almost the same. In tests with a human inspiratory flow simulator in vitro, inhalation performance was higher, but the variation in inhalation performance in the range of human flow patterns was wider, for the more resistant device. To minimize the intra- and inter-individual variation in inhalation performance for the model formulation in this study, a formulation design that allows active pharmaceutical ingredient to detach from the carrier with a lower inhalation flow rate is needed.     

Preparation of cationic nanoparticles by the particle dissolution method from submicron-sized,styrene-butyl acrylate-dimethylaminoethyl methacrylate terpolymer particles

Cationic nanoparticles were prepared from submicron-sized styrene-butyl acrylate-dimethylaminoethyl methacrylate terpolymer (59.2/20.8/20.0, molar ratio) particles in a polyoxyethylene nonylphenylether nonionic emulsifier aqueous solution at pH 2.0 above 150 °C.     

Coenzyme models. 15. A polymeric model system for the NADH-dependent dehydrogenase enzymes

Copolymers of 4-vinylpyridine (4-VP) and N-(p-vinylbenzyl)-1,4-dihydronicotinamide (VNicH) were synthesized, and a carbonyl substrate (benzil) was reduced to alcohol in an aqueous ethanol solution in the absence and presence of metal ions (Zn²⁺ and Ni²⁺) as part of a model study of NADH-dependent enzymes. The reduction rates by VNicH in polymers were four to seven times greater than that of the corresponding monomeric analog (N-benzyl-1,4-dihydronicotinamide). Added metal ions catalyzed the reduction by VNicH-29 (VNicH content, 29 mole%) but inhibited the reduction by VNicH-9 (VNicH content, 9 mole%). It was suggested that metal catalysis occurs only when metal ions are bound closely near the dihydronicotinamide moiety.     

The viscoelasticity of spinnable solutions of alkyltrimethylammonium salicylates

The viscoelasticity has been measured for aqueous solutions of tetradecyl-and hexadecyltrimethylammonium salicylates (C₁₄TASal, C₁₆TASal). The aqueous solutions of C₁₄TASal without salt displayed the gel-like behavior at 10.0×10^–2 g cm^–3, but those more dilute than 3.2×10^–2 g cm^–3 presented the viscoelasticity similar to that of a Maxwell liquid. The Maxwell-like behavior was converted to the polymer-like one on the addition of (0.1–0.2) M NaBr or (0.02–0.2) M NaSal. The gel-like viscoelasticity can be connected with the spinnability of cohesive fracture failure, and the Maxwell-like and polymer-like viscoelasticities are concerned with the spinnability of ductile failure. The gel-like and Maxwell-like viscoelasticities originate in the pseudo-network formed by the pseudo-linkages between rodlike micelles, while the polymer-like viscoelasticity is caused by the entanglement of long rodlike micelles in semidilute and concentrated solutions. The aqueous solutions of C₁₆TASal behaved very similar to those of C₁₄TASal.     

Synthesis and electrochromic properties of a new family of methacrylate polymers containing pendant oligothiophenes

A new family of methacrylate polymers containing pendant terthiophene, quaterthiophene, quinquethiophene, and sexithiophene was synthesized by the radical polymerization of the corresponding methacrylate monomers, and the electrochemical and electrochromic properties were investigated. The anodic oxidation of these polymers in the presence of tetra‐n‐butylammonium perchlorate as a supporting electrolyte produced radical‐cation salts of pendant oligothiophenes with ClO as a dopant. The electrochemically oxidized polymers had partially crosslinked structures resulting from the coupling reaction of pendant oligothiophene radical cations, the extent of crosslinking significantly decreasing with the increasing conjugation length of the pendant oligothiophenes. Comparative spectroelectrochemical studies of the monomers in solution and the polymers as solid films showed that π‐dimer formation of oligothiophene radical cations took place more readily for the polymer films than for the monomers in solution. This new family of methacrylate polymers containing pendant oligothiophenes constitutes a new class of potential electrochromic materials, undergoing reversible, clear color changes on electrochemical oxidation and reduction. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2471–2484, 2003