Water-soluble Initiator Research Articles

Controlled radical emulsion polymerization of polystyrene

In this paper, a new water-soluble initiator system, 2-bromopropane/CuSO4/sodium ascorbate, was used as the initiator for emulsion polymerization. Radical emulsion poly- merization of styrene was successfully carried out at 80 °C by using sodium dodecylbenzenesulfonate as the emulsifier. The 2-bromopropane/CuSO4/sodium ascorbate-initiated emulsion polymerization shows the controlled free-radical polymeriza- tion features with linear growth of molecular weight. Polysty- rene with a relatively high molecular weight and a narrow molecular weight distribution can be synthesized by this method. On the other hand, stable polystyrene latex can be obtained, and the size of the polystyrene latex increased with the increase in monomer conversion.

Synthesis and surface properties of PDMS-containing latexes by emulsion polymerization using AIBN as the initiator

In this article, a series of PBMA-g-PDMS latexes with high polydimethylsiloxane (PDMS) content up to 60wt% were prepared by emulsion copolymerization of extremely hydrophobic PDMS-macromonomers (PDMS-M) and n-butyl methacrylate (BMA). High yields of PDMS-containing latex particles were obtained and the PDMS-Ms were fully incorporated into the acrylic backbone by using 2,2′-azobisisobutyronitrile (AIBN) as the initiator and sodium dodecyl sulfate (SDS) as the surfactant. The key of successfully incorporating the PDMS segment to the acrylic polymer was the use of the oil-soluble initiator, AIBN, via a miniemulsion mechanism during which no transport of hydrophobic PDMS-Ms through the aqueous phase was needed. Use of a water-soluble initiator like potassium persulfate (KPS) led to particle flocculation and unsuccessful incorporation of PDMS-M in the latex particle. The particle diameter of prepared latexes was 60–170nm, with the polydispersity index (PDI) of 0.1–0.3. All the prepared latexes were very stable, as indicated by the ζ-potential of around −80mV. DSC and GPC results confirmed that PDMS was chemically linked to the PBMA backbone. The advancing water contact angles (CA) on the films from the PBMA-g-PDMS latexes were above 100°, and the receding water CA reached as high as 94°, indicating the film surface was significantly enriched in PDMS. The surface activity of the PDMS-g-PBMA copolymer was further demonstrated by the high water CA on the film from a blend of the copolymer latex and a conventional acrylic latex.

Polymer-Based Protein Engineering Can Rationally Tune Enzyme Activity, pH-Dependence, and Stability

The attachment of inert polymers, such as polyethylene glycol, to proteins has driven the emergence of a multibillion dollar biotechnology industry. In all cases, proteins have been stabilized or altered by covalently coupling the pre-existing polymer to the surface of the protein. This approach is inherently limited by a lack of exquisite control of polymer architecture, site and density of attachment. Using a novel water-soluble atom transfer radical polymerization initiator, we have grown temperature- and pH-responsive polymers from the surface of a model protein, the enzyme chymotrypsin. Poly(2-(dimethylamino)ethyl methacrylate) changes in conformation with altered temperature and pH. Growing the polymer from the surface of chymotrypsin we were able to demonstrate that changes in temperature or pH can change predictably the conformation of the polymer surrounding the enzyme, which in turn enabled the rational tailoring of enzyme activity and stability. Using what we now term "Polymer-Based Protein Engineering", we have increased the activity and stability of chymotrypsin by an order of magnitude at pHs where the enzyme is usually inactive or unstable.

Atom transfer radical emulsion polymerization (emulsion ATRP) of styrene with water-soluble initiator

This study presents styrene emulsion polymerization initiated in aqueous media through an atom transfer radical polymerization (ATRP) mechanism. The water-soluble initiator employed in this process has been synthesized by our team by reacting diethanolamine with α-bromoisobutyryl bromide. The complexation of CuBr was realized by using a bicomponent complexation system comprised of 2,2′-bipyridine and N,N,N′,N′,N″-pentamethyldiethylenetriamine. The initiator ratio influence on the obtained emulsion was studied. The obtained latexes and polymer particles have been characterized by dynamic light scattering, scanning electron microscopy, and gel permeation chromatography.

Phase Transfer Catalyzed Polymerization of Styrene and Graft Copolymerization of Styrene onto Gelatin

The use of tetrabutylammonium bromide (TBAB), as phase transfer catalyst during polymerization of styrene in the presence of water-soluble radical initiator, potassium persulfate (KPS), and graft copolymerization of styrene onto gelatin, a water soluble polymer, using a water-insoluble radical initiator, benzoyl peroxide (BPO), has been explored in a water-benzene biphasic system. The percentage conversion (Pc) of styrene to polystyrene and percent grafting (Pg) of styrene onto gelatin was studied as a function of various reaction parameters. Under optimum reaction conditions, maximum Pc (76%) was obtained at [KPS] = 12.9 × 10−4 moles/L, [Sty] = 4.3 ×10−3 moles/L, and maximum Pg (87%) was obtained at [BPO] = 4.6× 10−4 moles/L, [Sty] = 13.88 × 10−3 moles/L using [PTC] = 2.89 × 10−4 moles/Lin 10 mL each of water and benzene in 120 min at 60 °C. The graft copolymer, Gel-g-poly(Sty), was characterized by IR, Thermogravimetric Analysis, Scanning Electron Microscopy and swelling behaviour in different solvents. Metal uptake and degradation studies of the grafted sample were also carried out. The grafted sample showed maximum uptake for Cu2+ (88%), Ni2+ (80%) and Fe2+ (50%). Degradation studies of Gel-g-poly(Sty) were carried out by soil burial test and UV radiations. Photo-degradation showed better degradation (5.26% wt. loss) in 32 h of exposure to UV radiations as compared to soil burial degradation (8.46% wt. loss) in 30 days. Gelatin-styrene graft copolymers can thus be used as bio- and photo-degradable materials for environmental management.

A Novel Embed Fluorescence Method for Monitoring the Change from Emulsion Polymeriztion to Microemulsion Polymerization

In this paper, we present a novel embed fluorescence method that allows one to monitor the change from emulsion polymerization to microemulsion polymerization with low monomer contents. The microemulsion polymerization of methyl methacrylate (MMA) was investigated using N-(2-anthracene) methacrylamide (AnMA) as the probe whose fluorescence emission intensity was proportional to the conversion of MMA into the polymer.In this research, the trace amount of AnMA unit looked like embed in the MMA chain. In a solution containing 3wt% of MMA with respect to water, with the anionic surfactant of sodium dodecyl sulphate (SDS) and water-soluble initiator of potassium persulfate (KPS), the process of changing from emulsion to microemulsion has been monitored. By contrast, with the non-ionic surfactant of polyoxyethylene (20) oleyl ether (Brij98) or water-insoluble initiator of 2,2′-azobis(isobutyronitrile) (AIBN), the process of changing from emulsion to microemulsion also have been monitored.

Novel potentially biocompatible nanoporous hydrogel based on poly ((2-dimethylaminoethyl) methacrylate) grafted onto salep: synthesis, swelling behavior and drug release study

A novel potentially biocompatible nanoporous hydrogel was synthesized via crosslinking graft copolymerization of (2-dimethylaminoethyl) methacrylate (DMA) monomer onto salep backbones. Methylenebisacrylamide (MBA) and ammonium persulfate (APS) were applied as water-soluble crosslinker and initiator, respectively. To investigate the structure of the obtained hydrogel, fourier transforms infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM) were used. Swelling behavior of the obtained hydrogel at different temperatures and pH media was investigated and it was found that the synthesized hydrogel has a high sensitivity to pH. The swelling first increased and then decreased with increasing pH from 2 to 12 at 37 °C and the maximum water absorbency was observed at pH = 8. Swelling reversibility of the hydrogel at pH 2.0 and 8.0 was examined to show the pH sensitivity and smartness of hydrogel. Lastly, the potential use of this hydrogel for the loading and releasing of tetracycline hydrochloride (TH) as a model drug was examined. The results showed that 95 % of TH was released at pH 8 after 4 h at 37 °C which were best fitted with Korsmeyer kinetic model.

Synthesis of polyalkylacrylate nanolatexes by microemulsion polymerization method

The paper concerns with the radical polymerization of [octadecyl acrylate (ODA), isooctyl acrylate (iso-OA) and α-olefins 1-Octene (n-O)]. These microemulsions were stabilized by sodium dodecyl sulfate (SDS) and initiated by water-soluble initiator potassium persulfate (KPS). The nanolatex particle sizes were determined by transmission electron microscope (TEM). They were situated between 10 and 100nm. The microstructures were confirmed by FT-IR and molecular weights determined by Gel permeation chromatography (GPC). The obtained M. wt. were (≈70×103, 101×103 and 153×103g/mol). The polydispersity, molecular weights, and particle sizes were discussed in the light of micelle formation and shape of the alkyl group via emulsion polymerization.

Small-Angle Neutron Scattering Study on Specific Polymerization Loci Induced by Copolymerization of Polymerizable Surfactant and Styrene during Miniemulsion Polymerization

We have investigated the origin of a specific polymerization loci that yielded copolymer particles with a bimodal gel permeation chromatographic profile in the early stage of miniemulsion polymerization of styrene (St) with the polymerizable surfactant N-n-dodecyl-N-2-methacryloyloxyethyl-N,N-dimethylammonium bromide (C12DMAEMA). The formation of particles by miniemulsion polymerization using C12DMAEMA was investigated as a function of the polymerization time (tp) and was compared with that using the nonpolymerizable surfactant cetyltrimethylammonium bromide (CTAB). St was miniemulsified with C12DMAEMA or CTAB and was polymerized with either a water-soluble initiator, 2,2′-azobis(2-amidinopropane) dihydrochloride (V50), or an oil-soluble initiator, 2,2′-azobis(isobutyronitrile) (AIBN), at 60 °C in the presence of polystyrene (PSt) as a hydrophobe. Gel permeation chromatography (GPC) and elemental analysis indirectly predicted two different polymerization loci in the St/C12DMAEMA/V50 polymerization system....

Preparation of micron-sized, monodisperse nonspherical polymeric particles with a variety of shapes via seeded dispersion polymerization initiated by ammonium persulfate

In this work, the preparation of nonspherical particles via seeded dispersion polymerization of styrene in the presence of various methacrylic seed particles initiated by ammonium persulfate (APS) as a water soluble initiator in the methanol/water media using poly(vinyl pyrrolidone) as a dispersant was discussed. It was observed that in the presence of poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-butyl methacrylate) (Pn-BMA), and poly(2-ethylhexyl methacrylate) seed particles, particles with velvet-like surface, unique uneven surface, bead-like shape, and void-containing anomalous shape can be produced, respectively. Moreover, the effect of various polymerization conditions such as dispersant and initiator concentration, methanol/water weight ratio, and styrene/Pn-BMA seed particle weight ratio on the shapes of the obtained Pn-BMA/PS composite particles was studied. The experimental results showed that seeded dispersion polymerization initiated by APS is expected as a novel method for the production of polymeric particles with a variety of nonspherical shapes.

Polymerization kinetics and reactivity of alternative initiators systems for use in light-activated dental resins

ObjectivesThe purpose of this study was to evaluate the reactivity and polymerization kinetics behavior of a model dental adhesive resin with water-soluble initiator systems. MethodsA monomer blend based on Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin, which was polymerized using a thioxanthone type (QTX) as a photoinitiator. Binary and ternary photoinitiator systems were formulated using 1mol% of each initiator. The co-initiators used in this study were ethyl 4-dimethylaminobenzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), 1,3-diethyl-2-thiobarbituric acid (BARB), p-toluenesulfinic acid and sodium salt hydrate (SULF). Absorption spectra of the initiators were measured using a UV–Vis spectrophotometer, and the photon absorption energy (PAE) was calculated. The binary system camphorquinone (CQ)/amine was used as a reference group (control). Twelve groups were tested in triplicate. Fourier-transform infrared spectroscopy (FTIR) was used to investigate the polymerization reaction during the photoactivation period to obtain the degree of conversion (DC) and maximum polymerization rate (Rpmax) profile of the model resin. ResultsIn the analyzed absorption profiles, the absorption spectrum of QTX is almost entirely localized in the UV region, whereas that of CQ is in the visible range. With respect to binary systems, CQ+EDAB exhibited higher DC and Rpmax values. In formulations that contained ternary initiator systems, the group CQ+QTX+EDAB was the only one of the investigated experimental groups that exhibited an Rpmax value greater than that of CQ+EDAB. The groups QTX+EDAB+DPIHFP and QTX+DPIHFP+SULF exhibited values similar to those of CQ+EDAB with respect to the final DC; however, they also exhibited lower reactivity. SignificanceWater-soluble initiator systems should be considered as alternatives to the widely used CQ/amine system in dentin adhesive formulations.

Photo-sensitive hydrogels for three-dimensional laser microfabrication in the presence of whole organisms

Hydrogels are polymeric materials with water contents similar to that of soft tissues. Due to their biomimetic properties, they have been extensively used in various biomedical applications including cell encapsulation for tissue engineering. The utilization of photopolymers provides a possibility for the temporal and spatial controlling of hydrogel cross-links. We produced three-dimensional (3-D) hydrogel scaffolds by means of the two-photon polymerization (2PP) technique. Using a highly efficient water-soluble initiator, photopolymers with up to 80 wt.% water were processed with high precision and reproducibility at a writing speed of 10 mm/s. The biocompatibility of the applied materials was verified using Caenorhabditis elegans as living test organisms. Furthermore, these living organisms were successfully embedded within a 200×200×35 μm³ hydrogel scaffold. As most biologic tissues exhibit a window of transparency at the wavelength of the applied femtosecond laser, it is suggested that 2PP is promising for an in situ approach. Our results demonstrate the feasibility of and potential for bio-fabricating 3-D tissue constructs in the micrometre-range via near-infrared lasers in direct contact with a living organism.

Drying Mechanism of Poly(N-isopropylacrylamide) Microgel Dispersions

The drying mechanism of poly(N-isopropylacrylamide) (pNIPAm) microgel dispersions was investigated. The microgels were synthesized by temperature-programmed aqueous free radical precipitation polymerization using NIPAm, N,N'-methylenebis(acrylamide), and water-soluble initiator. Drying processes of the microgel dispersions were observed with a digital camera and an optical microscope, and the resultant dried structures were observed by scanning electron microscopy. We found that the presence of the microgels changed the behavior of the drying process of water. In particular, the microgels were adsorbed at the air/water interface selectively within a few minutes irrespective of the microgel concentration. The relationship between the drying mechanism and structure of the resultant microgel thin film has been clarified by changing the microgel concentration of the dispersions.

Polymerization of ethyl methacrylate under the influence of ultrasound assisted a new multi-site phase-transfer catalyst system – A kinetic study

The kinetics of multi-site phase-transfer catalyzed free radical polymerisation of ethyl methacrylate (EMA) using potassium peroxy disulphate (PDS) as a water soluble initiator and newly synthesized 1,4-dihexadecylpyrazine-1,4-diium dibromide as multi-site phase-transfer catalyst (MPTC) has been investigated in ethyl acetate/water two phase system at constant temperature 55±1°C under nitrogen atmosphere and ultrasound irradiation conditions. The rate of polymerization increases with an increase in concentrations of EMA, PDS and MPTC. The order with respect to monomer, initiator and MPTC were found to be 1.03, 0.52 and 0.53, respectively. Based on the observed results a suitable mechanism has been proposed to account for the experimental observations and its significance was discussed.

Aqueous free-radical polymerization of PEGMEMA macromer: kinetic studies via an on-line 1H NMR technique

Free-radical polymerization of polyethylene glycol methyl ether methacrylate macromer (PEGMEMA) was studied in aqueous media and in the presence of potassium persulfate (KPS) as water soluble initiator. An on-line nuclear magnetic resonance (NMR) method was applied to record the reaction data and determine the monomer conversion at various times during the polymerization reaction progress. 1H NMR spectrum of reaction mixture containing monomer, initiator and resultant polymer was continuously recorded in NMR instrument with the increase of reaction time. By processing the obtained data from NMR spectrum, the rate equation can be derived and reaction order can be determined with regard to monomer and initiator concentration. In other words, to determine the order of polymerization with regard to the concentration of reactants in free-radical polymerization of PEGMEMA, macromer samples with different amounts of monomer and KPS were prepared and polymerized at 50 °C. Orders of reaction with respect to monomer and initiator molar concentrations were equal to 1.025 and 0.480, respectively. The obtained values for reaction orders in this study were consistent with the classical kinetic rate equation in which the dependency of polymerization rate (Rp) on monomer and initiator concentrations was equal to 1 and 0.5, respectively. To measure polymerization activation energy (Ea), the effect of reaction temperature on the polymerization rate was investigated and Ea = 37.08 kJ/mol was obtained at the temperature range of 40–50 °C.

Ultrasound assisted polymerization of N-vinyl imidazole under phase-transfer catalysis condition – A kinetic study

The kinetics of phase-transfer catalyzed radical polymerization of N-vinyl imidazole (NVI) using potassium peroxy disulfate (PDS) as water soluble initiator and tetraoctylammonium chloride (TOAC) as PTC has been investigated in ethyl acetate/water two phase system assisted by ultrasound irradiation at constant temperature 60+1°C under nitrogen atmosphere. and. The rate of polymerization increases with an increase in concentrations of NVI, PTC and PDS. The order with respect to [NVI], [PTC], and [PDS] were found to be 1.01, 1.03 and 0.52 respectively. Based on the observed results a suitable mechanism has been proposed to account for the experimental observations followed by a discussion on its significance.

Flavonoids preservation and release by methacrylic acid-grafted (N-vinyl-pyrrolidone)

Context: Flavonoids preservation and release.Objective: Synthesis of a polymeric material able to prevent thermal and photo degradation of a flavonoid model compound, such as (+)-catechin, and suitable for a controlled/sustained delivery of this molecule in gastro-intestinal simulating fluids.Materials and methods: Methacrylic acid (MAA) was grafted onto poly(N-vinyl-pyrrolidone) (PVP) by a free radical grafting procedure involving a single-step reaction at room temperature. For this purpose, hydrogen peroxide/ascorbic acid redox pair was employed as water-soluble and biocompatible initiator system.Results and discussion: FT-IR spectra confirmed the insertion of MAA onto the polymeric chain. Stability studies, performed under various conditions, such as freeze–thaw cycles, exposure to strong light, thermal stability studies under constant humidity and with light protection at different temperatures, showed the preservative properties of the polymeric material towards flavonoids. Furthermore, the biocompatibility was highlighted by Hen’s Egg Test-Chorioallantoic Membrane assay and in vitro release studies demonstrated the possibility to employ PVP-MAA copolymer as a device for gastro-intestinal release of flavonoids.Conclusion: The coupling of good preservative properties together with biocompatibility and the usefulness as carrier in controlled release make this kind of material very interesting from an industrial point of view for different applications in food, pharmaceutical, and cosmetic fields.

Synthesis of micron-sized polymeric particles in soap-free emulsion polymerization using oil-soluble initiators and electrolytes

Soap-free emulsion polymerization of styrene using oil-soluble initiators and electrolytes was investigated to synthesize micron-sized polystyrene particles. It was clear that an oil-soluble initiator, such as AIBN, worked like a water-soluble initiator in soap-free emulsion polymerization of styrene to prepare monodispersed particles with negative charges, probably because of the polarization of the electron-attractive functional groups decomposed from the initiators and the pi electron cloud of benzene in a styrene monomer. The addition of an electrolyte enabled secondary particles to effectively promote hetero-coagulation for particle growth by reduction of an electrical double layer and prevention of self-growth. Changing the concentration and type of electrolyte enabled us to control the size up to 12 μm in soap-free emulsion polymerization of styrene using AIBN. Conventionally, organic solvents and surfactants have been used to prepare micron-sized polymeric particles, but this method enabled the synthesis of micron-sized polymeric particles in water using electrolytes without surfactants.

Homopolymerization of N-vinylamides in the presence of water-soluble initiators and preparation of polyelectrolytes from the polymerization products

Homopolymerization of vinylformamide and N-methyl-N-vinylacetamide in water in the presence of 2,2′-azobis(2-methylpropanediamine) dihydrochloride and of the hydrogen peroxide-ammonium hydroxide system was examined. Hydrolysis of polyvinylformamide, poly-N-methyl-N-vinylacetamide, and poly-N-vinylacetamide with hydrochloric acid at 100°C was studied.

Ultrasound assisted free radical polymerization of glycidyl methacrylate by a new disite phase-transfer catalyst system: A kinetic study

The kinetics of multi-site phase-transfer catalyzed free radical polymerisation of glycidyl methacrylate (GMA) using potassium peroxy disulphate (PDS) as water soluble initiator and newly synthesized 1,4-dihexadecylpyrazine-1,4-diium dibromide as multi-site phase-transfer catalyst (MPTC) has been investigated in ethyl acetate/water two phase system at constant temperature 65±1°C under nitrogen atmosphere and ultrasound irradiation conditions. The rate of polymerization increases with an increase in concentrations of GMA, PDS and MPTC. The order with respect to monomer, initiator and MPTC were found to be 1.0, 0.5 and 1.0, respectively. The comparative study reveals that the Rp of GMA determined in the presence of PTC combined with ultrasound has shown more enhancements in the activity than PTC alone. Based on the observed results a suitable mechanism has been proposed to account for the experimental observations and its significance was discussed.