Acoustic source localization in anisotropic plates

The conventional triangulation technique cannot locate the acoustic source in an anisotropic plate because this technique requires the wave speed to be independent of the propagation direction which is not the case for an anisotropic plate. All methods proposed so far for source localization in anisotropic plates require either the knowledge of the direction dependent velocity profile or a dense array of sensors. In this paper for the first time a technique is proposed to locate the acoustic source in large anisotropic plates with the help of only six sensors without knowing the direction dependent velocity profile in the plate. Experimental results show that the proposed technique works for both isotropic and anisotropic structures. For isotropic plates the required number of sensors can be reduced from 6 to 4.     

A generalised approach for active control of structural–interior global noise: Practical implementation

The experimental validation of a generalised approach to the sensing of orthogonal contributors to the global error (acoustic potential energy) within a coupled structural–acoustic cavity is presented. The goal is the measurement and control of the global error without any knowledge of the structural dynamics of the noise source, based on an acoustic centric decomposition approach that is applicable to any noise source. Two sensing approaches are attempted, structural and acoustic sensing, to measure the global error within the coupled enclosure. Once estimates of the global error are obtained, minimisation with an adaptive feedforward controller is implemented. The level of achieved attenuation in the global error is compared. The achieved level of attenuation is also compared to the maximum level of attenuation of the global error that can be achieved based on the disturbance/secondary source arrangement. The maximum level of attenuation is evaluated from experimental data, rather than pure theoretical methods.     

Preparation and photoluminescence characteristics of polysiloxane pendant tris(2,2′-bipyridine)ruthenium (II) complex

Polysiloxanes containing pendant tris(2,2′-bipyridine)ruthenium(II) complex (Ru(bpy)3²⁺) were prepared by reaction of polysiloxane-pendant 2,2′-bipyridine (PSiO-bpy) with cis-Ru(bpy)₂Cl₂. In methanol solution, the polymer pendant Ru(bpy)3²⁺ showed absorption maximum at 456nm and emission maximum at around 609nm, both of which are shifted to longer wavelength than the monomeric Ru(bpy)₃²⁺. The lifetime τ₀ of the excited polymer complex with low Ru(bpy)3²⁺ content was almost the same as that of the monomeric one in methanol (830ns), but τ₀ of the polymer with higher complex content was shorter because of a concentration quenching. In a solid state, τ₀ was much shorter (306–503ns) than that in a methanol solution contrary to the conventional polymeric system. Higher complex content in the polymer film caused higher glass transition temperature (Tg), but shorter τ₀. These results indicate concentration quenching in the polymer film. The excited polymer pendant Ru(bpy)3²⁺ was quenched by oxygen, and the relative emission intensity followed the Stern-Volmer equation. In a methanol solution the quenching rate constant (k_q) was the same order of magnitude as the monomeric complex, and independent of the complex content in the polymer. In a film, k_q was higher for the polymer with higher complex content.     

Noncovalent Modification of Cycloparaphenylene by Catenane Formation Using an Active Metal Template Strategy**

The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2′-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C−H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions.     

Nonthrombogenic polymers - designs and evaluation

New nonthrombogenic polymers were designed with attention to the surface of biological membranes, that is, the surface was completely covered with phospholipids adsorbed from plasma. The polymers with phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine polymers, could interact with phospholipids in plasma selectively and strongly. The adsorbed phospholipids on the polymer surface were concentrated, organized each other and then formed a self-assembled biomimetic membrane surface. The surface showed excellent resistance for both protein adsorption and blood cell adhesion.     

Highly stereospecific protonation of stereoregular living PMMA anions with several alcohols

Living and highly isotactic poly(methyl methacrylate) (PMMA) anion (M̄n = 2.5 × 10³) prepared with t-C₄H₉MgBr as an initiator was protonated with phenol in toluene at −78°C. The reaction was stereospecific toward meso addition, and the meso/racemo ratio at the chain-end of the resultant polymer was 89/11. Addition of 1,4-dioxane to the living isotactic PMMA anion in toluene at −78°C remarkably reduced the viscosity of the system, and protonation of the PMMA anion with phenol in the presence of 1,4-dioxane enhanced the meso-specificity to 94%. On the other hand, the protonation reaction of the living syndiotactic PMMA anion (M̄n = 2.5 × 10³), which was generated by t-C₄H₉Li/(n-C₄H₉)₃Al in toluene at −93°C, with t-butanol was found to be 97% racemo-specific. These highly stereospecific protonation reactions of the stereoregular PMMA anions were in contrast to the protonation of the anions with methanol or benzyl alcohol which was almost non-stereospecific.     

Stereocomplex formation of isotactic poly(methyl methacrylate) with a wide variety of syndiotactic polymethacrylates

Syndiotactic (st–) polymers of methacrylates with primary and secondary ester groups, prepared by the syndiotactic-specific living polymerization with t-C₄H₉Li/R₃Al, were found to form stereocomplexes with isotactic (it–) poly(methyl methacrylate) (PMMA) by annealing in the solid state or by mixing in certain solvents such as acetone and toluene. Melting points of the complexes depend on the structure of the ester group and can be changed in a wide range of temperature. st–Polymers of tertiary esters did not form the complex. Effects of anneal conditions, molecular weight, and tacticity on the melting point of the complex were studied in some detail for the combination of st–poly(benzyl methacrylate) and it–PMMA. st–Random copolymers of MMA with several alkyl methacrylates also formed stereocomplexes with it–PMMA, whose melting point could be changed continuously by changing the composition in a certain range of temperature. st–Block copolymers of PMMA and poly(benzyl methacrylate) formed stereocomplexes with it–PMMA which showed two melting points, provided the block lengths are long enough for the two types of the com plexes to form independently. Stereoblock PMMA, it–PMMA–block–st–PMMA, and stereoblock copolymer, it–PMMA–block–st–poly(butyl methacrylate), were found to form stereocomplexes more easily than the corresponding mixtures. The stereoregular uniform PMMAs were used for elucidating the process of stereocomplex formation and its stoichiometry by means of gelpermeation chromatography (GPC). The preliminary results clearly indicated that the complexation occurs mainly in 1:1 stoichiometry in the beginning, while a small fraction of 1:2 (it–: st–) complex was also formed concomitantly. By similar GPC experiments using a series of uniform PMMAs, the minimum length of PMMA chains for the complex formation was found to be in the range of degrees of polymerization from 42 to 46.     

Synthesis and Mechanical Properties of Polypropylene-based Polymer Hybrids via Controlled Radical Polymerization

Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.