A novel dendritic polyisophthalate with 12 naphthyl groups at the chain ends was synthesized from 5-hydroxyisophthalic acid as an AB 2 monomer, 1,3,5-benzenetricarbonyl trichloride as an 'initiator core' molecule, and b-naphthol as an endcapping reagent, via a stepwise growth process. An average molecular weight of 2860 g mol À1 , and a refractive index of 1.618 at 650 nm were obtained by gel permeation chromatography and ellipsometry, respectively. A photopolymerizable recording dry film incorporating this dendrimer as a polymeric binder was used for holographic recording. Diffraction gratings with diffraction efficiency exceeding 80%, together with a modulation index of 10 À2 were obtained.

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A hyperbranched (meth)acrylated poly-(amine ester) (HPAE-2-A) was synthesized by the modification of the hydroxyl end groups of the second generation of a hyperbranched poly(amine ester) with acryloyl chloride and methacrylic anhydride. The photopolymerization kinetics were investigated with photo-differential scanning calorimetry and Fourier transform infrared. The properties of HPAE-2-A, including the dynamic viscosity, pendulum hardness, and shrinkage, were also studied in comparison with those of a hyperbranched methacrylated poly(amine ester) (HPAE-2-MA) prepared in the laboratory and tradi-tional epoxy acrylate and epoxy methacrylate. HPAE-2-A polymerized rapidly under UV irradiation in the presence of a photoinitiator and had a higher final conversion of double bonds. The thermomechanical properties of UV-cured HPAE-2-MA films were compared with those of EB-cured films measured with a dynamic mechanical thermal analyzer.

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ABSTRACT:The influences of the irradiation temperature, comonomer content, sample thickness, and photoinitiator concentration on the polymerization kinetics of hyperbranched acrylated aromatic polyester (HAAPE) were investigated with photo-differential scanning calorimetry and IR measurements. The maximum photopolymerization rate increased with the temperature rising up to 110°C but decreased beyond 110°C. An activation energy of 16 kJ mol Ϫ1for the photopolymerization was obtained below 110°C from an Arrhenius plot, but it was negative beyond 120°C. A remarkable synergistic effect between HAAPE and the comonomer trimethylolpropane triacrylate with a molar fraction of around 0.4 was observed from a photopolymerization kinetic study of the resins. The final unsaturation conversion in an ultraviolet-cured film decreased with the sample thickness, and this became more remarkable as the photoinitiator concentration increased.