Cross-Polarization Magic-Angle Spinning 13C Nuclear Magnetic Resonance Study of the Homogeneity of Some Photopolymerized Acrylic Networks

Abstract

A theoretical analysis of relaxation processes has been used in the qualitative interpretation of carbon-resolved, proton Tlp data obtained at 100.56 MHz for three solid polyacrylate networks made by photopolymerization of the polyol acrylate monomers poly(ethylene glycol) diacrylate (PEGA), trimethylolpropane triacrylate (TMPTA), and dipentaerythritol pentaacrylate (DPHPA). This analysis permits an estimate of the spin diffusion rates between different chemical species. Such rates are strongly dependent on spatial proximity and hence are applicable to the determination of the homogeneity of the networks. Proton Tip's in networks are not quite averaged to a single value by spin diffusion like in polymer blends, indicating there is extensive intermixing of TMPTA and DPHPA in forming the network. Proton Tip experiments are sufficiently sensitive to distinguish between a TMPTADPHPA network and PEGA homopolymer. When glass fibers are present in the network, they act like a spin diffusion medium, producing an increase in the rates of relaxation for all three components of the network.

Photopolymerization of Polyfunctional Acrylates and Methacrylate Mixtures: Characterization of Polymeric Networks by a Combination of Fluorescence Spectroscopy and Solid State Nuclear Magnetic Resonance

“…18 As we previously reported, these values are strongly dependent on the homogeneity of the networks. 18 Closer values imply a more homogeneous network with the compounds in closer, more intimate contact.…”

“…18 As we previously reported, these values are strongly dependent on the homogeneity of the networks. 18 Closer values imply a more homogeneous network with the compounds in closer, more intimate contact. A clear phase separation has been reported previously as occurring in a polymer formed by the photopolymerization of a mixture of the triacrylate TMPTA, the pentacrylate DPHPA, and the long chain poly(ethylene glycol diacrylate) PEGA 400.…”

“…If the rate of spin diffusion is small compared to the difference in the relaxation rates (large domains/small diffusion constant), the components of the network retain their relaxation behavior. Different T 1 ρ values are determined for the components of the network, and it is concluded that a phase separation between the components of the network has occurred . So, by determining the rates of spin diffusion of all components that are incorporated in a photoformed polymer, one can determine whether the network is homogeneous or whether a phase separation has occurred and monomers are incorporated in spatially separated networks.…”

Characterization of network structure in radiation-cured resins of polyfunctional acrylic ester and N-vinylpyrrolidone by MALDI-MS combined with supercritical methanolysis

“…However, it is not an easy task to analyze cured resins even using advanced spectroscopic method such as high-resolution NMR due to their insoluble nature. Although solid-state NMR has been successfully utilized to study the heterogeneity of network structures in photo-cured resins, 4,5 this technique is not necessarily suitable for characterizing microstructures in the rigidly cross-linked resins mainly because of insufficient resolution.…”

Evaluation of molecular weight of original epoxy acrylates in UV-cured resins by pyrolysis-gas chromatography in the presence of organic alkali

“…However, it is not an easy task to analyze cross-linked UV-cured resins even using advanced spectroscopic method such as high-resolution NMR because of their insoluble nature. Although solid-state NMR has been successfully utilized to study the heterogeneity of network structures in photo-cured resins [4,5], this technique is not necessarily suitable for practical applications mainly because of insufficient resolution. On the other hand, Haken et al attempted to characterize cross-linked dimethacrylates of bisphenol A diglycidyl ethers by gas and liquid chromatography combined with off-line acid and alkali fusion.…”