Polymeric photoinitiators bearing side-chain acyldiphenylphosphinoxide moieties for uv surface coatings

Polymeric photoinitiators bearing side-chain acyldiphenylphosphinoxide moieties have been prepared by reacting poly(methacryloyl chloride) and methacryloyl chloride/methyl methacrylate copolymers with methoxydiphenylphosphine. The activity of the above polymeric systems has been checked in the UV curing of both clear and pigmented coating formulations and compared with that of the low molecular weight analog pivaloyldiphenyl-phosphinoxide. The stability to light and to different hydrolitic conditions of the polymeric photoinitiators with respect to pivaloyldiphenylphosphinoxide has also been tested. The data concerning activity and stability are discussed in terms of structural features of the above systems. © 1993 John Wiley & Sons, Inc.     

Commissioning of the NPDGamma Detector Array: Counting Statistics in Current Mode Operation and Parity Violation in the Capture of Cold Neutrons on B4C and 27Al

The NPDGamma γ-ray detector has been built to measure, with high accuracy, the size of the small parity-violating asymmetry in the angular distribution of gamma rays from the capture of polarized cold neutrons by protons. The high cold neutron flux at the Los Alamos Neutron Scattering Center (LANSCE) spallation neutron source and control of systematic errors require the use of current mode detection with vacuum photodiodes and low-noise solid-state preamplifiers. We show that the detector array operates at counting statistics and that the asymmetries due to B₄C and ²⁷Al are zero to with- in 2 × 10⁻⁶ and 7 × 10⁻⁷, respectively. Boron and aluminum are used throughout the experiment. The results presented here are preliminary.     

Novel polymeric photoinitiators bearing side-chain α-aminoacetophenone moieties for ultraviolet-curable pigmented coatings

New polymeric photoinitiators with pendant α-aminoacetophenone moieties, such as the homopolymers of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-methacryloyloxypropyl)]aminopropan-1-one and of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-methacryloyloxypropyl)]aminobutan-1-one have been prepared and fully characterized. Their photoinitiation activity has been also checked in the ultraviolet cure of a standard acrylic mixture, under irradiation over 380 nm, thus simulating the absorption conditions of a TiO₂-pigmented coating formulation. The results have been compared with those found by using the corresponding low-molecular-weight structural models, purposely synthesized. The activity data obtained are discussed and related to the structural requirements of the above systems. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2237–2246, 1997     

Copolymeric systems bearing side-chain thioxanthone and α-aminoacetophenone moieties as photoinitiators for ultraviolet-curable pigmented coatings

Copolymers of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-meth-acryloyloxy propyl)]aminopropan-1-one and of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methyl-N-(3-methacryloyloxypropyl)]aminobutan-1-one with 1-[(2-methacryloyloxy)ethoxycarbonyl]thioxanthone were prepared and structurally characterized. The above systems were also checked in the ultraviolet cure of an acrylic mixture upon irradiation over 380 nm, thus simulating the conditions of a TiO₂-pigmented formulation. The curing results were compared with those obtained in the presence of the mixtures of the corresponding homopolymers as well as of their low-molecular-weight models. The copolymeric systems display synergistic effects of activity with respect to the structural models but show lower photoinitiation efficiency against the homopolymers mixtures. These data are discussed and interpreted in terms of structural requirements and photochemical mechanistic aspects of the above systems. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2247–2258, 1997     

Optically active polymers containing side-chain benzophenone chromophores

Optically active copolymers of (—)menthyl acrylate (MtA) with 4-hydroxybenzophenone acrylate (ABP) have been prepared by radical initiation. Reactivity ratios, mean sequence lengths and the statistical distribution of the sequence lengths of both co-units have been evaluated. Chiroptical properties of the copolymers indicate that a chiral perturbation of side-chain benzophenone chromophores occurs, due to the dissymetric arrangement of the macromolecules. C.d. data in the spectral region connected with the nåπ°1 electronic transition of benzophenone chromophore, combined with statistical distribution of sequence lengths of monomeric units in the macromolecules suggest that the observed ellipticity is essentially due to the isolated ABP units, inserted in blocks of chiral MtA units.     

Synthesis of Polystyrene-Bound Organotin Derivatives as Intermediates for the Production of Hybrid Materials

Polystyrenes bearing tricyclohexylstannyl moieties with different stereoregularities, molecular weights, and chemical composition have been prepared and characterized through two synthetic routes. The suitability of the products obtained to be used as intermediate derivatives in the synthesis of the corresponding organotin trichlorides, precursors to organic–inorganic hybrid materials, has been investigated.