Preparation and characterization of polypropylene/mesoporous silica nanocomposites with confined polypropylene

Polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospecific propylene polymerization with Ti-MCM-41/Al(i-C₄H₉)₃ catalyst. The cross polarization/magic angle spinning (CP/MAS) ¹³C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti-MCM-41 in the nanocomposites, as measured by N₂ adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti-MCM-41. Alkali treatment followed by extraction with o-dichlorobenzene allows us to extract the confined PP out of the Ti-MCM-41 mesopores. Although the PP/Ti-MCM-41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (M_w) and molecular weight distribution (M_w/M_n) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti-MCM-41 mesopores (M_w = 200,000–450,000, M_w/M_n = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003     

Investigation of the crystal structure and the structural and magnetic properties of SrCu2(PO4)2

SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) A, b = 15.36918(14) A, and c = 10.37036(10) A. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1...Cu2 = 3.256 A. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1-O...O-Cu2 and Cu2-O...O-Cu2 super-superexchange paths with Cu1...Cu2 = 5.861 A and Cu2...Cu2 = 5.251 A, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1-Cu2-Cu2-Cu1 with -2J(1)/kB = 82.4 K for Cu1-Cu2 and -2J(2)/k(B) = 59 K for Cu2-Cu2. A spin gap deduced from this model (Delta/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Delta/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.     

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.Part CII of the series Studies on Suspension and Emulsion.     

Glass transition temperature of polyurethane foams derived from lignin by controlled reaction rate

Sodium ligninosulfonate (LS)-based polyurethane (PU) foams were prepared using three kinds of ethylene glycols, diethylene glycol, triethylene glycol or polyethylene glycol. Two kinds of industrial NaLS, acid-based and alkaline-based NaLS, were mixed with various ratios, and foaming reactions were controlled. Mixing, cream, and rise time were used as an index of foaming reaction. Mixing time was defined as the time interval from adding isocyanate to detection of evolved heat under stirring, cream time as the time interval from termination of stirring to starting of foaming, and rise time as the time interval from starting to completion of foaming. The above reaction time increased with increasing amount of acid base NaLS content in polyols. Apparent density, compression strength and compression modulus of PU foams linearly increased with reaction time. Thermal decomposition temperature was measured by thermogravimetry and glass transition temperature by differential scanning calorimetry. Glass transition temperature can be controlled in a temperature range from 310 to 390 K by changing the mixing rate of two kinds of LS and molecular mass of ethylene glycols. It was found that mechanical and thermal properties of PU foams are controllable through the foaming reaction rate using two kinds of industrial lignin.     

Optical Polymer Having a High Refractive Index and High Abbe Number Prepared by Radical Polymerization Using 2,5-BiS(2-Thia-3-Butenyl)-1,4-Dithiane

Abstract

Novel poly(vinylsulfide)s were prepared by addition polymerization using 2,5-bis(2-thia-3-butenyl)-1,4-dithiane (TBD) with a radical initiator for an optical polymer having a high refractive index (n_D) and Abbe number (v). Homopolymerization of TBD (72.9% conversion) and copolymerization with acrylonitrile or acrylates having nonpolar groups (50.4–81.3% conversion according to the comonomers used) in a limited composition range yielded hard and transparent polymers suitable for application in optics. The methacrylates used yielded no polymeric product as a result of the copolymerization. The obtained polymers had T_g, n_D and v ranging between 41.0–124.0°C, 1.678–1.546 and 34.1–43.8, respectively, except that poly(TBD) did not exhibit T_g below 200°C, and it had the highest n_D Most of the polymers have higher n_D and v than those of other conventional optical polymers and moreover, their values are comparable to those of flint glasses. The copolymerizability of TBD and the group contribution to n_D and v are discussed based on the Q-e scheme and on the Lorentz-Lorenz equation, respectively. This work shows that TBD serves as a useful material for the preparation of polymers having high n_D and v along with a T_g of more than 100°C, and that the polymers thus obtained are promising optical materials.

     

Regioselective Alkylation of Thiazolylsulfonamides: Direct and Efficient Synthesis of 3‐Alkylthiazolidene Derivatives

Various N‐3‐alkylated thiazolidenesulfonamide derivatives were efficiently prepared by the direct endo‐selective alkylation of thiazolylsulfonamides. The effects of different bases and solvents were investigated, and the NaH–THF combination was found to be the most effective at conferring high yields and endo‐selectivity.     

Thermal oxidative degradation of additive-free polypropylene pellets investigated by multichannel Fourier-transform chemiluminescence spectroscopy

Thermal oxidative degradation of additive-free polypropylene pellets heated isothermally in dry air at 150 and 180 °C (below and above the melting point of 163 °C) was investigated by multichannel Fourier-transform chemiluminescence spectroscopy. The initial peak wavelength of chemiluminescence emission at 490 nm remained constant during the early stages of thermal degradation, but new emissions developed with time in the red spectral region over an extended oxidation period. The time-dependent luminescence spectra were deconvoluted into three emission bands by least-squares fitting using Gaussian curves. We concluded that at least three groups of luminescent species (luminophores), having different conjugation lengths, were generated by thermal oxidation over extended periods and show luminescence around 490, 660, and 740 nm.     

Inclusional association as studied by the drying dissipative structure. Part 2. Drying pattern of n-alkyltrimethylammonium bromide

Macro- and microscopic drying patterns were observed on a cover glass and a watch glass during the course of dryness of aqueous solutions of a series of n-alkyltrimethylammonium bromides (alkyl: n-decyl, n-dodecyl, n-tetradecyl, and n-hexadecyl). The broad rings formed at the outside edges of the macroscopic patterns. Size of the initial liquid on the substrates, d _i, that of the final broad ring, d _f, and the ratio, d _f/d _i, changed as the surfactant concentration changed, and there appeared a bending point in each curve, which was found to correspond to the critical micelle concentration (cmc) of the surfactant. The cmc values evaluated from the d _i, d _f, and d _f/d _i values agreed well with the reference values reported previously. Cooperative drying processes of the convection, sedimentation, and solidification were supported. Microscopic drying patterns such as rod-like, dendritic, and granule-like patterns were observed, and they changed as a function of the carbon number of the alkyl groups, surfactant concentration, and the distance from the center of the pattern.