Photoinduced Free Radical Polymerization Research Articles

In Situ Synthesis of Oil-Based Polymer/Silver Nanocomposites by Photoinduced Electron Transfer and Free Radical Polymerization Processes

In this study, in situ synthesis of oil-based polymer–silver nanocomposites was achieved by using photoinduced free radical polymerization processes in which silver nanoparticles were formed by electron transfer reaction. An oil-based macromonomer was prepared and then copolymerized with styrene in the presence of AgNO3. Copolymerization was started with free radicals formed by photolysis of 2,2-dimethoxy-2-phenyl acetophenone and simultaneously silver nitrate was reduced to metallic silver in nanosize by electron transfer reaction. The amount of photoinitiator influenced the size of silver nanoparticles formed within the polymer films. Nanocomposite films were characterized by TEM and TGA analysis. The obtained polymer nanocomposite film was also examined in respect of surface coating material that would have an antibacterial effect against Gram-positive, Gram-negative and spore-forming bacteria. It was demonstrated that suitably coated nanocomposite samples exhibited an antibacterial effect against these bacteria.

Antibacterial Acrylamide Hydrogels Containing Silver Nanoparticles by Simultaneous Photoinduced Free Radical Polymerization and Electron Transfer Processes

AbstractAg‐nanoparticle‐containing hydrogels were successfully prepared by in situ reduction of silver nitrate in the presence of citrate molecules as stabilizing agent during photoinduced copolymerization of AAm and BAAm. Swelling‐deswelling behavior and thermal properties of the synthesized hydrogels were investigated. The interior morphology of the gels exhibit continuity, which is a common feature for hydrogel networks. Antimicrobial activities of the hydrogels were also investigated against pathogenic E. coli O157:H7, S. aureus, and non‐pathogenic E. coli K‐12, which are model microorganisms for testing bactericidal properties. The hydrogels containing well‐dispersed Ag NPs showed significant antibacterial activity.magnified image

Macroporous polymer materials: Synthesis of a new functional copolymer and its use for biological microanalysis

Macroporous materials based on a new reactive copolymer of 2-cyanoethyl methacrylate, 2-hydroxyethyl methacrylate, and ethylene glycol dimethacrylate have been prepared via photo-induced free-radical polymerization in the presence of porogeneous solvents. The effect of the composition of mixed porogenes on the porous structure of the resulting solid copolymers has been studied. A number of synthesis parameters have been optimized, namely, the concentration of initiator and the time of polymerization. As exemplified by a model biologically complementary (bioaffine) pair, the created polymer material shows promise for design of bioanalytical panels (microbiochips).

Synthesis and Characterization of One-Component Polymeric Photoinitiator by Simultaneous Double Click Reactions and Its Use in Photoinduced Free Radical Polymerization

A polystyrene copolymer (PS-B-DMAB) possessing both benzophenone and dimethylamino moieties in the side chain was synthesized by a combination of nitroxide-mediated radical polymerization (NMRP) and simultaneous double “click” reactions. First, a random copolymer of styrene (S) and chloromethylstyrene (CMS) with 32 mol % CMS content was prepared by NMRP process. Then, chloromethyl groups were converted to azide groups by reacting with NaN3 in DMF. The other two click components, namely, propargyl benzophenone (Pr-B) and propargyl 4-(dimethylamino)benzoate (Pr-DMAB), were prepared independently by the etherification and esterification reactions, respectively. Then, in the final stage, the obtained alkyne functional chromophoric (Pr-B) and hydrogen-donating (Pr-DMAB) molecules were anchored to azide-modified polystyrene (PS-N3) in one-step by “click chemistry”. The final polymer (PS-B-DMAB) and the intermediates were characterized in detail by spectral analysis and laser flash photolysis studies. The result...

Study of Optical Properties of Glass-Like Polymer Material for Blue Laser Holographic Optic Data Storage Recording

Holographic data storage is the most promising data storage technology in the next generation due to the advantages of the ultra-high data storage density and high data transfer rate. Dimensional stability of storage media and photorefraction effect of the grating are the two most important factors for holographic storage. In this study, a blue laser holographic material with low shrinkage is developed. The organic-inorganic hybrid matrix is triethoxysilylpropyl polyethyleneglycol carbamate (TSPEG) homogeneously bonded with tetraethyl orthosilicate (TEOS) prepared by sol-gel method. Diallyl phthalate pre-polymer (DAPP) and 9,10-Phenanthrenequinone (PQ) were used as a monomer and a photoinitiator, respectively. Optical data recording was performed by a blue laser source with a wavelength of 405 nm and the intensity of laser is 2 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The photoinduced free radical polymerization of DAPP in the presence of PQ can be initiated by the blue laser irradiation. The inorganic backbone limits the shrinkage resulting from the polymerization and increases the rigidity of the matrix. The shrinkage measurement shows that the blue laser holographic material with TSPEG/TEOS=0.2 (molar ratio) has very low shrinkage of about 0.145% after recording the hologram.

Synthesis and characterization of a novel water-soluble mid-chain macrophotoinitiator of polyacrylamide by Ce(IV)/HNO 3 redox system

A new water-soluble mid-chain macrophotoinitiator of polyacrylamide (PAAm) has been synthesized by redox polymerization. The polymerization of acrylamide (AAm) initiated by dihydroxy functional photoinitiator namely, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl propan-1-one (HE-HMPP), Irgacure 2959, in combination with cerium(IV) ammonium nitrate has been investigated in aqueous nitric acid. The effects of HE-HMPP, AAm, and Ce(IV) concentrations on the polymerization rate were investigated. The photodegradation and IR, 1H NMR, UV, and fluorescence spectroscopic studies revealed that polyacrylamide with desired photoinitiator functionality in the middle of the chain were obtained. This prepolymer was used in photoinduced free radical polymerization of methyl methacrylate (MMA) to produce PAAm–PMMA block copolymer.

Synthesis and characterization of a novel mid‐chain macrophotoinitiator of polyacrylonitrile by Ce(IV)/HNO3 redox system

AbstractThe polymerization of acrylonitrile initiated by cerium(IV) ammonium nitrate in combination with dihydroxy functional photoinitiator namely, 2‐hydroxy‐1‐[4‐(2‐hydroxyethoxy)phenyl]‐2‐methyl propan‐1‐one (HE‐HMPP), Irgacure 2959, has been investigated in aqueous nitric acid. A novel mid‐chain macrophotoinitiator of polyacrylonitrile (PAN) was obtained. The effects of acrylamide (AAm), HE‐HMPP, Ce(IV), and HNO3 concentrations and temperature on the polymerization rate, monomer conversion, and intrinsic viscosities were investigated. The photodegradation and IR, H NMR, UV, and fluorescence spectroscopic studies revealed that PAN with desired photoinitiator functionality in the middle of the chain was obtained. The obtained PAN was used as prepolymer for photoinduced free radical polymerization of methyl methacrylate (MMA) and AAm to produce block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5404–5413, 2008

Synthesis and Characterization of a Novel Mid-Chain Macrophotoinitiator of Poly(methyl methacrylate) by Ce(IV)/HNO3 Redox System

Dihydroxy functional photoinitiator namely, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl propan-1-one (HE-HMPP), Irgacure 2959, has been used as reducing agent in redox initiated free-radical polymerization of methyl methacrylate (MMA) in conjunction with cerium(IV) ammonium nitrate in aqueous nitric acid at 40 °C to obtain a novel mid-chain macrophotoinitiator of poly(MMA). The effects of Ce(IV), HE-HMPP, and MMA concentrations on the polymerization rate were investigated. The IR, H NMR, UV, photodegradation, and fluorescence spectroscopic studies revealed that poly(methyl methacrylate) with desired photoinitiator functionality in the polymer chain was obtained. This prepolymer was used in photoinduced free radical polymerization of acrylamide (AAm) and acrylonitrile (AN) to produce block copolymer.

In situ synthesis of gold-cross-linked poly(ethylene glycol) nanocomposites by photoinduced electron transfer and free radical polymerization processes

Gold-cross-linked poly(ethylene glycol) nanocomposites were prepared by simultaneous photoinduced electron transfer and free radical polymerization processes.

Onium Salts of Amino Acids as Co-Initiators in Photoinduced Free-Radical Polymerization

The onium salts of selected aliphatic and aromatic amino acids were investigated as electron donors in photoinduced free radical polymerization, in conjunction with either DIBF or BP as sensitizer. The laser flash photolysis experiments unmistakably documented that the free radical formation occurs via an electron transfer reaction from the amino acid salt to the chromophore triplet state. The kinetic studies clearly showed that either the DIBF or BP onium salts of selected aliphatic and aromatic sulfur-containing amino acids exhibit a significant increase in the efficiency of free-radical polymerization of TMPTA as compared to non-sulfur-containing co-initiators and that the efficiency of all tested electron donors is only slightly dependent on the cation type coupled with co-initiators tested.

Development and Evaluation of Spherical Molecularly Imprinted Polymer Beads

The majority of studies on molecularly imprinted polymers has until now been carried out on irregularly shaped particles prepared by grinding of polymer monoliths. The preparation procedures are time- and labor-consuming and produce particles of wide size distributions. To answer the need for fast and straightforward routes to spherical molecularly imprinted polymer beads, we have developed a method comprising the formation of droplets of pre-polymerization solution directly in mineral oil by vigorous mixing followed by transformation of the droplets into solid spherical beads by photoinduced free-radical polymerization. No detergents or stabilizers were required for the droplet formation. Factors influencing the bead synthesis have been investigated and are detailed here. The beads were evaluated in parallel with corresponding irregularly shaped particles prepared from polymer monoliths. Conditions for the synthesis of propranolol-imprinted poly(methacrylic acid-co-trimethylolpropane trimethacrylate) beads in the size range of 1-100 microm in almost quantitative yield are described. The beads were applied as the recognition element in a 96-well plate format radioligand assay of propranolol in human serum.

Organosilicon sulfides as co-initiators in photoinduced free radical polymerization

Three sulfur-containing silanes (organosilicon sulfides) were investigated as electron donors in photoinduced free radical polymerization, in conjunction with xanthene dye (5,7-diiodo-3-butoxy-6-fluorone, DIBF) as sensitizer. The results were compared with the nonsulfur-containing silane, N-((trimethylsilyl)methyl)aniline (K1) and thiophenoxyacetic acid (TPAA). The kinetic studies clearly showed that the DIBF-organosilicon sulfides exhibit a significant increase in the efficiency of free radical polymerization of TMPTA compared to nonsulfur-containing silane and that the efficiency of all tested electron donors is only slightly dependent on the structure of the sulfur-containing co-initiators.

Synthesis and Characterization of Novel Well‐Defined End‐Functional Macrophotoinitiator of Poly(MMA) by ATRP

A new monofunctional atom transfer radical polymerization (ATRP) initiator was synthesized by the condensation of 2‐bromopropanoyl bromide with 1‐hydroxycyclohexyl phenyl ketone (HCPK), Irgacure 184 and characterized. The ATRP of methyl methacrylate (MMA) in dry toluene at 90°C by means of this initiator in conjunction with a cuprous complex Cu(I)Cl/bipyridine (bpy) yields poly(MMA) with a photoactive alkoxy phenyl ketone end group. The gel permeation chromatography (GPC) and IR, H‐NMR, UV, and fluorescence spectroscopic studies revealed that low‐polydispersity poly(MMA) with photoinitiator functionality at the end of the chain was obtained. The obtained end‐functional PMMA macrophotoinitiator was used in photoinduced free radical polymerization of styrene (St) to produce PMMA‐b‐PSt upon irradiation via α‐cleavage of the incorporated phenyl ketone end group. This block copolymer was characterized by GPC and H‐NMR measurements.

Polymer-dispersed Liquid Crystals: Effect of Partial Matrix Fluorination on Polymer Bead-based Morphology

The morphology and electrooptical properties of polymer-dispersed liquid crystals (PDLCs) with partially fluorinated polymer matrices are investigated. Films were prepared via photo-induced free-radical polymerization of an initially isotropic solution comprised of pentafunctional (5 reactive groups) acrylate monomer and nematic liquid crystal molecules. Phase separation of discrete domains of LC is induced by the photopolymerization. The film morphologies consisted of aggregated polymeric particles dispersed throughout a continuous liquid crystal medium. Changes in morphology and electrooptical properties were observed as trifluoroethyl and hexafluoroisopropyl methacrylate were partially substituted for the multifunctional acrylate monomer. Methyl methacrylate was used in control films due to the chemical similarities to fluorinated monomers. The incorporation of fluorinated monomers resulted in better definition of the polymer bead morphology and improvement in contrast ratio, while control films displayed less pronounced changes in optical properties. Real-time transmittance monitoring and polarized optical microscopy (POM) revealed that the monofunctional monomer addition resulted in a delay of the LC phase appearence with increasing comonomer concentration. However, a LC phase appeared earlier for fluorinated systems as compared to nonfluorinated control films of similar comonomer concentration. This was interpreted as an indication of lower LC solubility in the semifluorinated polymer matrix.

POLYMERIZATION OF ACRYLAMIDE IN AQUEOUS MEDIUM INITIATED BY REDOX SYSTEM OF 4-CARBOXYBENZOPHENONE AND SULFUR-CONTAINING COMPOUNDS

A series of sulfur-containing compounds was investigated as electron donors in photoinduced free-radical polymerization, in conjunction with 4-carboxybenzophenone (CB) as sensitizer. These compounds included (phenylthio) acetic acid, ethionine, methionine, Gly-Met, Met-Gly and methionine methyl ester. The results were compared with the nonsulfur-containing compounds, alanine and triethanolamine. The best initiation yields is observed for the system CB-(phenylthio)acetic acid.

The effect of a cationic salt on the photoinitiated polymerization of methyl methacrylate

The photoinduced free radical polymerization of methyl methacrylate in the presence of benzophenone and thiophenoxyacetic acid were investigated. It has been observed that adding of diphenyliodoniumhexafluorophosphate (Ph 2I +PF 6) salt increased the rate of polymerization and molecular weight of polymer.

Photoinitiierte Polymerisation mit Dialkoxythiocarbonyldisulfiden – eine Polymerisationsreaktion mit Primärradikalabbruch

Photoinitiated Polymerization with Dialkoxy Thiocarbonyl Disulfides – a Polymerization Reaction with Primary Radical TerminationThe photoinduced free radical polymerization of methyl methacrylate (MMA) and some other vinyl monomers using dialkoxy thiocarbonyl disulfides (1–4) as photoinitiators was studied. The photolysis of these initiators leads to cleavage of the SS bond, which was determined by spin trapping experiments with phenyl tert‐butyl nitrone. No evidence was found for a further thermal decomposition of the primary alkoxy thiocarbonyl sulfide radicals (R·) at room temperature. In the absence of scavengers the primary radicals react back exclusively to the initial compounds, due to a strong cage effect. By means of UV spectroscopic measurements and in the presence of MMA the quantum yields of the initiator decomposition were detected to be 0.8. The polymerization of acrylic and methacrylic derivatives can be initiated by the R·, contrary to the situation with fumarates and maleates. The mechanism of MMA polymerization depends on the light intensity absorbed by the initiators. At high intensities the combination of primary and polymer radicals terminates the chain reaction. This follows from the measured monomer exponent of α = 2, the light intensity exponent of β = 0,2 and the number of thiocarbonyl end groups of 2 in the polymers isolated. Contrary to this, in the low intensity region the experimental data obey the ideal kinetic equation. Kinetic modelling gives evidence for an interaction of the monomer with the cage radicals.