STUDIES ON THE INITIATION MECHANISM OF ORGANIC PEROXIDE AND N-METHACRYLOYLOXYETHYL-N-METHYL ANILINE IN METHYL METHACRYLATE POLYMERIZATION

The initiation mechanism of methyl methacrylate (MMA) polymerization by organic peroxide and polymerizable aromatic tertiary amine such as N-methacryloyloxyethyl-N-methyl aniline (MEMA) binary system has been studied. The kinetics of polymerization of MMA and the ESR spectra of organic peroxide/MEMA system were determined. Based on the ESR study and the end-group analysis by UV spectra of the polymer formed, the initiation mechanism is proposed.

GRAFT POLYMERIZATION OF ACRYLAMIDE ONTO HOMOPOLYMER OF 5-METHYL-5-HEXEN-2, 4-DIONE INITIATED BY CERIC ION

The homopolymerization of 5-methyl-5-hexen-2,4-dione (methacryloylacetone, MAA), a vinyl monomer having beta-diketone group, was carried out in the presence of benzophenone (BP)/N, N-dimenthyl-4-toluidine (DMT) system. Graft polymerization of acrylamide initiated by eerie ion onto the homopolymer film was investigated and the mechanism of the grafting reaction was proposed on the basis of ESR study. The grafted copolymer was characterized by means of grafting percentage, water absorption, XPS spectra and scanning electron photomicrographs.

STUDIES ON ORGANIC PEROXIDE/N, NDI(2-α-METHYL-ACRYLOYLOXY PROPYL)-PARA-TOLUIDINE BINARY SYSTEMS

The polymerization of methyl methacrylate (MMA) initiated by organic peroxide and polymerizable aromatic tertiary amine such as N, N-di (2-α-methylacryloyloxy propyl)-p-toluidine (MP)_2PT binary system has been studied. It was found that the (MP)_2PT promotes MMA polymerization, and the kinetics of MMA polymerization fits the radical polymerization rate equation. Based on the ESR studies and the end-group analysis the initiation mechanism is proposed.

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N, N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

Acrylamide polymerization initiated with a redox initiation system consisting of eerie ion and ethyl N,N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was found that the polymerization rate equation is in good agreement with that of a redox initiated polymerization, and the overall activation energy of the polymerization was determined to be 25.2 kJ.mol(-1). Accordingly, the system belongs to a redox initiator. The initiation mechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies. Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with eerie ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate (BE) to form PAN-b-PBA block copolymer.

Grafting of 4-Vinyl Pyridine onto Nylon-6 Initiated by Redox System

The graft copolymerization of 4-vinyl pyridine （4VP） onto nylon-6 （PA6） was studied by using potassium diperiodatonickelate（IV） （DPN）-PA6 redox system in alkaline medium. The structures of graft copolymers were confirmed by Fourier transfer infrared spectroscopy （FTIR） and X-ray diffraction. The properties of graft copolymers were investigated by thermogravimetric analysis （TGA）. A mechanism was proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, the ratio of 4VP to PA6, pH as well as reaction temperature and time were investigated. Graft copolymers with high grafting efficiency （〉95%） were obtained, which indicated that DPN-PA6 redox system is an efficient initiator for this graft copolymerization. The quaternized PA6-g-P4VP （QPAVP） was proved to be an excellent adsorbent to heavy metal ions.

A thioxanthone-based photocaged superbase for highly effective free radical photopolymerization

Thioxanthone-based N-phthalimidoamino acid ammonium salt（thioxanthen-DBU） as a photocaged base was synthesized and characterized. The photochemical properties and initiation mechanism were analyzed. It was found that the compound absorbs over the UV and visible region with relatively high absorption coefficients. Furthermore, the covalent binding of N-phthalimidoamino acid and type II chromophores（thioxanthone, TX） remarkably improved the photoreactivity. Specifically, in combination with a benzoyl peroxide initiator, thioxanthen-DBU was able to initiate the amine-mediated redox photopolymerization of trimethylol propane triacrylate（TMPTA）, and an excellent photopolymerization profile was obtained.

CuSO_4 -CATALYZED SELF-INITIATED RADICAL POLYMERIZATION OF 2-(N,N- DIMETHYLAMINO)ETHYL METHACRYLATE AS AN INTRINSICALLY REDUCING INIMER

Since tertiary amines （Cα-H） can be oxidized by peroxides and transition metal cations in high oxidation states into Ca2＋ radicals to initiate vinylic polymerizations of methacrylates, Cu2＋ and 2-（N,N-dimethylamino）ethyl methacrylate （DMAEMA） form a polymerizable redox initiating pair, in which DMAEMA serves as an intrinsically reducing inimer. CuSOa-catalyzed aqueous self-initiated radical polymerizations of DMAEMA were successfully performed at ambient temperature via a continuous Cu2＋-tertiary amine redox initiation based on catalyst regeneration in the presence of O2. The polymerization kinetics was monitored by gas chromatography and the structure of PDMAEMA was characterized by gel- permeation chromatography, nuclear magnetic resonance spectroscopy, laser light scattering and online intrinsic-viscosity analysis. Both the monomer conversion and the molecular weight of PDMAEMA increase with the reaction while the molecular weight distribution maintains rather broad, as the Cu2＋-DMAEMA redox-initiation leads to linear PDMAEMA chains with terminal methacryloxyl moieties, and the Cu2＋-PDMAEMA redox-initiation results in branched chains. The branched topology forms and develops only for the high-MW components of the PDMAEMA. Our results provide a facile strategy to prepare branched polymers from such commercially available intrinsically reducing inimers using a negligible concentration of regenerative air-stable catalysts.