Construction of polymer skeletons with radiation‐scissile groups at predetermined sites

Polymers that can be cleaved at predetermined sites by ionizing radiations have been synthesized by incorporating benzylic esters into their skeletons. Secondary electrons generated by ionizing radiations are captured by the benzylic esters to dissociate into benzylic radicals and carboxyl anions, so that the polymer skeletons are cleaved at predetermined sites. The γ‐irradiation of a three‐armed star polymer, 1,2,4‐tri‐(2‐polystyrene‐2‐methyl‐propyonyloxymethyl)‐benzene, results in the selective scission of the arms, and the resultant radicals neither combine with each other nor graft to the other polymer skeletons to give larger polymer molecules. The irradiation of poly(methyl methacrylate) crosslinked with 4‐methacryloyloxybenzyl methacrylate results in the selective scission at the crosslinking sites with high radiation‐chemical efficiency of 8.5 scissions per 100 eV radiation energy absorbed. These results indicate that the incorporation of benzylic esters into polymer skeletons opens a new way of constructing radiation resists with high sensitivity to ionizing radiations and high resistivity to plasma etching. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1945–1953, 2008     

Fabrication and characterization of poly(butylene succinate)‐grafted carbon fiber/poly(L‐lactide) nanocomposites

A new poly(butylene succinate) (PBS)‐grafted vapor grown carbon fiber (VGCF)/poly(L ‐lactide) (PLLA) nanocomposites were successfully prepared by an in situ condensation reaction between PBS (M_w = 6,000) and surface oxidized VGCF, followed by direct melt mixing technique, and their mechanical and thermal properties were evaluated. Fourier transform infrared spectroscopy and scanning electron microscopy studies indicate a chemical interaction between the PBS and the surface of VGCF. It was found that the maximum tensile strength and modulus of PBS‐grafted VGCF/PLLA nanocomposites were 135 MPa (27% increase relative to neat PLLA) and 4,400 MPa (29% increase relative to neat PLLA), respectively. The results indicate that significant improvement in the mechanical properties can be accomplished by optimizing the surface modification conditions for VGCF. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4433–4441, 2008     

Determination of prednisolone and prednisone in plasma by liquid chromatography with fluorescence detection

After a single-step extraction from plasma (250 μl) with dichloromethane, the drugs and dexamethasone (internal standard) are oxidized by copper(II) acetate to the corresponding glyoxal and converted into the fluorescent quinoxalines by reaction with 1,2-diamino-4,5-methylenedioxybenzene. The quinoxalines are separated within 55 min by reversed-phase liquid chromatography with isocratic elution. The detection limits for prednisolone and prednisone added to plasma are 3 ng ml^?1 in plasma (signal-to-noise ratio=3).     

A dynamic correlation function for amorphous solids

A report is given of a new inelastic neutron scattering measurement for vitreous SiO₂ made with a high energy resolution and a wide and continuous range of momentum transfer. The use of a real-space correlation function in the interpretation of the Q-dependence of the scattering function is investigated.     

Pulsed neutron scattering on molten Bi + BiI3 mixtures

The differential cross-sections for neutron scattering on liquid Bi-I alloys with six compositions have been measured by time-of-flight neutron diffractometry on the electron linac. The concentration dependences of the nearest neighbour distance of Bi-I or Bi-Bi and the second nearest neighbour distance of I-I or Bi-Bi reveal a tendency towards preference of like nearest neighbours Bi-Bi or formation of clusters consisting of Bi species above the liquidus temperature near the composition corresponding to BiI (i.e., 50 at% Bi). The metal-nonmetal transition, quite well documented for the system, may originate from concentration fluctuations with preferred Bi-Bi coordination.     

Development of a headspace GC/MS analysis for carbonyl compounds (aldehydes and ketones) in household products after derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine.

Carbonyl compounds (aldehydes and ketones) are suspected to be among the chemical compounds responsible for Sick Building Syndrome and Multiple Chemical Sensitivities. A headspace gas chromatography/mass spectrometry (GC/MS) analysis for these compounds was developed using derivatization of the compounds into volatile derivatives with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA). For GC/MS detection, two ionization modes including electron impact ionization (EI) and negative chemical ionization (NCI) were compared. The NCI mode seemed to be better because of its higher selectivity and sensitivity. This headspace GC/MS (NCI mode) was employed as analysis for aldehydes and ketones in materials (fiber products, adhesives, and printed materials). Formaldehyde was detected in the range of N.D. (not detected) to 39 microg/g; acetaldehyde, N.D. to 4.1 microg/g; propionaldehyde, N.D. to 1.0 microg/g; n-butyraldehyde, N.D. to 0.10 microg/g; and acetone, N.D. to 3.1 microg/g in the samples analyzed.     

On the Polar Decomposition of the Product of Two Operators and Its Applications

Let T = U|T| and S = V|S| be the polar decompositions. In this paper, we shall obtain the polar decomposition of TS as TS = UWV|TS|, where |T||S^*| = W||T||S^*|| is the polar decomposition. Next, we shall show that TS = UV|TS| is the polar decomposition if and only if |T| commutes with |S^*|. Lastly, we shall apply this result to binormal and centered operators. We shall obtain characterizations of these operator classes from the viewpoint of the polar decomposition.     

On discontinuity and tail behaviours of the integrated density of states for nested pre-fractals

We consider a general finitely ramified fractal set called a nested fractal which is determined byN number of similitudes. Basic properties of the integrated density of statesN (x) for the discrete Laplacian on the associated nested prefractal are investigated. In particulard N is shown to be purely discontinuous ifM, whereM is the number of branches of the inverse of the rational function involved in the spectral decimation method due to Rammal-Toulouse. Sierpinski gaskets and the modified Koch curve are special examples.