Cross-sections for deuteron photo-disintegration from 139 to 832 MeV

The cross-sections for deuteron photo-disintegration have been measured at nine c.m. angles from 37 to 143 degrees. The minimum and maximum photon energies have been 139 and 832 MeV respectively. The results are in agreement with earlier data above 300 MeV, but are significantly larger below 200 MeV, the discrepancies being up to 50% at the lowest energies measured.     

Influence of Coulomb-excited vibrations on a nuclear Josephson effect

The transfer of nucleonic Cooper pairs during the scattering of two superfluid nuclei just below the Coulomb barrier is discussed microscopically. Break-up of pairs, especially by Coulomb excitation of vibrational states, and competition from other channels reduce the transfer probability.     

Dye distribution in fluorescent-labeled latex prepared by emulsion polymerization

Emulsion polymerizations were used for preparing fluorescent-labeled polymers. The labeled polymers were analyzed by gel permeation chromatography (GPC) using both fluorescence (FL) and refractive index (RI) as detectors. The uniformity of polymer labeling was measured by the ratio between FL and RI signals, calculated by a computer software, on the basis of each GPC chromatogram. It was found that in emulsion polymerizations, the semicontinuous process can produce a more homogenous dye distribution in the host polymer molecules than the batch method. Uniform labeling of a polymer with various dyes can be achieved by the semi-continuous process. However, experimental conditions for polymerization, such as initiator concentration and the presence of surfactant or chain transfer agent, may influence the uniformity of dye distribution. © 1994 John Wiley & Sons, Inc.     

Continuous and Segmented Semiconducting Fiber-like Nanostructures with Spatially Selective Functionalization by Living Crystallization-Driven Self-Assembly

Fiber-like π-conjugated nanostructures are important components of flexible organic electronic and optoelectronic devices. To broaden the range of potential applications, one needs to control not only the length of these nanostructures, but the introduction of diverse functionality with spatially selective control. Here we report the synthesis of a crystalline-coil block copolymer of oligo(p-phenylenevinylene)-b-poly(2-vinylpyridine) (OPV₅-b-P2VP₄₄), in which the basicity and coordinating/chelating ability of the P2VP segment provide a landscape for the incorporation of a variety of functional inorganic NPs. Through a self-seeding strategy, we were able to prepare monodisperse fiber-like micelles of OPV₅-b-P2VP₄₄ with lengths ranging from 50 to 800 nm. Significantly, the exposed two ends of OPV core of these fiber-like micelles remained active toward further epitaxial deposition of OPV₅-b-PNIPAM₄₉ and OPV₅-b-P2VP₄₄ to generate uniform A-B-A and B-A-B-A-B segmented block comicelles with tunable lengths for each block. The P2VP domains in these (co-)micelles can be selectively decorated with inorganic and polymeric nanoparticles as well as metal oxide coatings, to afford hybrid fiber-like nanostructures. This work provides a versatile strategy toward the fabrication of narrow length dispersity continuous and segmented π-conjugated OPV-containing fiber-like micelles with the capacity to be decorated in a spatially selective way with varying functionalities.     

Effect of chain architecture on the phase transition of star and cyclic poly(N‐isopropylacrylamide) in water

The heat‐induced phase transition of aqueous solutions of Poly(N‐isopropylacrylamide) (PNIPAM) in water is examined for a four‐arm PNIPAM star (s‐PNIPAM), a cyclic PNIPAM (c‐PNIPAM), and their linear counterparts (l‐PNIPAM) in the case of polymers (1.0 g L^?1) of 12,700 g mol^?1 < M_n < 14,700 g mol^?1. Investigations by turbidity, high‐sensitivity differential scanning calorimetry (HS‐DSC), and light scattering (LS) indicate that the polymer architecture has a strong effect on the cloud point (T_c: decrease for s‐PNIPAM; increase for c‐PNIPAM), the phase transition enthalpy change (ΔH decrease for s‐PNIPAM and c‐PNIPAM), and the hydrodynamic radius of the aggregates formed above T_c (R_H: c‐PNIPAM < s‐PNIPAM < l‐PNIPAM). The properties of s‐PNIPAM are compared with those of previously reported PNIPAM star polymers (3 to 52 arms). The overall observations are described in terms of the arm molecular weight and the local chain density in the vicinity of the core of the star, by analogy with the model developed for PNIPAM brushes on nanoparticles or planar surfaces. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2059–2068.