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Controlled radical polymerization initiated by stable radical terminated polytetrahydrofuran

Abstract Block copolymers of tetrahydrofuran and styrene were prepared by using stable free radical polymerization (SFRP) of styrene with 2,2,6,6-tetramethyl-1-piperidinyl-1-oxy (TEMPO) terminated polytetrahydrofuran (PTHF). For this purpose azo containing PTHFs were prepared and reacted with TEMPO.

Bifunctional Initiators. III. Photochemical Synthesis of Block Copolymers of Styrene and Methyl Methacrylate with the Aid of Azo-benzoin Initiators

Abstract Block copolymers of styrene and methyl methacrylate were prepared by means of azo-benzoin initiators. In the first stage, prepolymers were synthesized by using these initiators. Photoactive prepolymers containing benzoin end groups were employed in the second stage for block copolymerization. The block copolymer structure was elucidated by means of extraction by appropriate solvents, GPC analysis, and IR and NMR spectral measurements. Mechanisms for initiation and possible termination for systems involving benzoin-type initiators are discussed in the light of results from studies of composition of the block copolymerization mixture. Structure and efficiency of the formation of the block copolymers depend greatly on both the relative reactivities of the photochemically derived radicals and the termination mode of polymerization.

Synthesis of conducting PPy/pTHF copolymers

Living polytetrahydrofuran (pTHF) was terminated with the potassium salt of pyrrole to yield polymers with pyrrole end groups. Copolymerization of THF and pyrrole with short and long pTHF segments was achieved by constant potential electrolysis. Syntheses of the block copolymers were performed using tetrabutylammonium tetrafluoroborate, sodium perchlorate, and sodium p-toluenesulfonate as the supporting electrolytes. Characterization of the block copolymers were based on scanning electron microscopy, differential scanning calorimetry, thermal gravimetry analysis, cyclic voltammetry, and FTIR studies. No significant effect of the chain length on the properties of the copolymers was observed; however, use of different dopants resulted in different thermal and electrochemical behaviors, surface morphologies, and conductivities.

Photoinitiated cationic polymerization using a novel phenacyl anilinium salt

Abstract A novel phenacyl anilinium salt, N-phenacyl, N,N-dimethylanilinium hexafluoroantimonate, (PDA), has been synthesized and used as photoinitiator for cationic polymerization of cyclohexene oxide (CHO), butyl vinyl ether (BVE) and N-vinyl carbazol (NVC). Plausible mechanism of the photoinitiation involves the decay of the excited PDA with both heterolytic and homolytic cleavages of carbon–nitrogen bond. Thus, phenacylium cations formed directly or subsequent intermolecular electron transfer, respectively, initiate the polymerization.

Immobilization of glucose oxidase in polypyrrole/polytetrahydrofuran graft copolymers

Glucose oxidase (GOD) was immobilized in four different conducting polymer matrices, namely: polypyrrole, (PPy), poly(pyrrole-graft-polytetrahydrofuran), (1) and (3); and poly(pyrrole-graft-polystyrene/polytetrahydrofuran), (2). The kinetic parameters V(max) and K(m), and the optimum temperature were determined for both immobilized and native enzymes. The effect of electrolysis time and several supporting electrolytes, p-toluenesulfonic acid, p-toluene sulfonic acid (PTSA), sodium p-toluene sulfonate, sodium p-toluene sulfonate (NaPTS), and sodium dodecyl sulfate, sodium dodecyl sulfate (SDS), on enzyme immobilization were investigated. The high K(m) value (59.9 mM) of enzyme immobilized in PPy was decreased via immobilization in graft copolymer matrices of pyrrole. V(max), which was 2.25 mM/min for pure PPy, was found as 4.71 mM/min for compound (3).

BIFUNCTIONAL INITIATORS : SYNTHESIS, CHARACTERIZATION, AND INITIATOR PROPERTIES OF AZO-BENZOIN INITIATORS

Abstract Two new azo-benzoin initiators were synthesized by the condensation of 4,4′-azo-bis-(4-cyanopentanoic acid chloride) (ACPC) with benzoin (B) and α-methylolbenzoin methyl ether. The initiator structures were confirmed by IR and NMR spectroscopy. The kinetics of the bulk polymerization of styrene initiated by the azo benzoin initiator, obtained from ACPC and B, was investigated and the kinetic parameters evaluated. The initiation of polymerization of styrene by means of azo-benzoin initiators yields polymers with terminal photoactive benzoin groups.

Preparation of hyperbranched polyester polyol-based urethane acrylates and applications on UV-curable wood coatings

In the present study, hyperbranched urethane acrylates (UA/HB-PEs) were synthesized by modifying the hydroxyl groups of hyperbranched polyester polyols (HB-PEs). The structure of oligomers were characterized by FTIR and 1H NMR spectroscopic techniques. Formulations containing UA/HB-PEs, reactive diluents, and photoinitiator were applied onto wood substrates and successfully polymerized under UV-irradiation. The coating performances and thermal properties of UV-cured films were evaluated. The studies on film characteristics reveal that the incorporation of UA/HB-PE afforded coatings with good adhesion and high gloss properties. It is observed that UV-cured coatings originated from [2,2-bis(4-β-hydroxyethoxy) phenyl propane] (HB-HEPA)- and [2,2-bis(4-β-hydroxyethoxy) phenyl 6F propane] (HB-HEPFA)-based oligomers possessed better surface and mechanical properties.

Benzophenone based addition fragmentation agent for photoinitiated cationic polymerization

Abstract Photoactive allyl ammonium salt (BPEA) containing benzophenone moiety in the structure was synthesized and characterized. Its capability to act as a self-initiating addition fragmentation agent in the photoinitiated cationic polymerization of oxiranes such as cyclohexene oxide and vinyl monomers such as butylvinyl ether was investigated. These monomers turned out to be polymerizable in the presence of BPEA provided free radicals are generated photochemically at λ>300 nm by hydrogen abstraction of excited benzophenone moiety. Accordingly, a free radical adds to the carbon–carbon double bond of a ground state BPEA and fragmentation of the adduct radical results in the formation of reactive ammonium radical cation which is essentially responsible for the initiation.

Photoinitiated polymerization of ethyl cyanoacrylate by phosphonium salts

The photoinitiated polymerization of ethyl cyanoacrylate (ECA) by benzyl triphenylphosphonium hexafluoroantimonate (BP+) and (anthracen-9-ylmethyl)triphenylphosphonium hexafluoroantimonate (MAP+) was studied. Zwitterionic and free radical mechanisms which involved homolytic and heterolytic decomposition of the phosphonium salts are discussed. The anthracene-sensitized photopolymerization of ECA was also demonstrated. Die photoinitiierte Polymerisation von Cyanacrylsaureethylester (ECA) mit Benzyltriphenylphosphoniumhexafluorantimonat (BP+) und (Anthracen-9-ylmethyl)triphenylphosphoniumhexafluorantimonat (MAP+) als Photoinitiatoren wurde untersucht. Ein zwitterionischer sowie ein radikalischer Mechanisms, einschlieslich der homolytischen und heterolytischen Zersetzung der Phosphoniumsalze, werden diskutiert. Die mit Anthracen initiierte Photopolymerisation von ECA wurde ebenfalls untersucht

CONDUCTING MULTIPHASE BLOCK COPOLYMERS OF POLYPYRROLE WITH POLYTETRAHYDROFURAN AND POLYTETRAHYDROFURAN-b-POLYSTYRENE

Living bifunctional azo-polytetrahydrofuran (azo-PTHF) was terminated with pyrrolyl potassium salt to yield a polymer with electrochemically active functional end groups. This polymer is further used to synthesize polytetrahydrofuran-polystyrene (PTHF-b-PS-b-PTHF) block copolymer. These polymers are electrochemically blocked with polypyrrole using constant potential electrolysis (PPy/Azo-PTHF and PPy/PTHF-b-PS-b-PTHF). Two different solvent-electrolyte pairs were used during electrolysis. Characterizations of pristine and the blocked copolpolymers are based on Cyclic Voltammetry (CV), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermal Gravimetry Analysis (TGA), Scanning Electron Microscope (SEM) Nuclear Magnetic Resonance Spectroscopy (NMR) and Gel Permeation Chromatography (GPC). Conductivities were measured using a four-probe technique.