Polymerization Of 2-hydroxyethyl Methacrylate Research Articles

Synthesis-Morphology-Mechanical Properties Relationships Of Polymer-Silica Nanocomposite Hybrid Materials

ABSTRACTTwo types of polymer-silica nanocomposites have been prepared by undergoing free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) either in the presence of HEMA-functionalized SiO2 nanoparticles (Type 1) or during the simultaneous in situ growing of the silica phase through the acid-catalyzed sol-gel polymerization of tetraethoxysilane (TEOS) (Type 2). Relationships between synthesis, morphology and mechanical properties are discussed mainly on the basis of solid state 29Si nuclear magnetic resonance spectroscopy (NMR), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA).

Resorbable polyacrylic hydrogels derived from vitamin E and their application in the healing of tendons.

A hydrogel containing vitamin E (alpha-tocopherol) was prepared by free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) and alpha-tocopheryl methacrylate (VEMA), the latter being synthesized previously to its use. The hydrogel containing 20 wt % of VEMA showed equilibrium water content in the range of those of hydrogel networks, at any pH. The swelling of the hydrogel followed Fick's law, indicating that sorption of water molecules is controlled by diffusion, although the values of diffusion coefficients for the VEMA-containing hydrogel were lower than those of poly-HEMA in any medium. Surface characterization of the VEMA-containing hydrogel revealed a decrease in the surface energy of solid owing to a decrease of the polar component mainly. The application of finely powdered xerogel of HEMA-VEMA copolymer bearing 20 wt % of the vitamin E derivative gave a very fast and positive response showing an activated regeneration capacity, probably due to the stimulation of the cellular proliferation or the more plausible effect, the cellular protection associated to the antioxidant properties of the vitamin E residue.

Polymerization under Magnetic Field. Part 9. Polymerization of 2-Hydroxyethyl Methacrylate by Benzoyl Peroxide

A systematic investigation of the influence of Magnetic Field on polymerization and copolymerization has been carried out on 2-hydroxyethyl methacrylate under UV-irradiation using benzoyl peroxide as initiator.

Photoinitiated vinyl polymerization by safranine T/triethanolamine in aqueous solution

The photolysis of safranine T in the presence of triethanolamine has been used as a source of free radicals in the polymerization of 2-hydroxyethyl methacrylate in aqueous solution. The polymerization rate was measured at several amine and dye concentrations. Flash photolysis studies of safranine in basic aqueous solutions indicate that the photoinitiation proceeds by the amine radicals formed in the interaction of the unprotonated form of the dye triplet with the hydroxyl amine. Primary radical termination does not play a significant role.

Preparation of micron-size monodisperse poly(2-hydroxyethyl methacrylate) particles by dispersion polymerization

Dispersion polymerization of 2-hydroxyethyl methacrylate using four categories of polymeric stabilizers in a mixture of good and poor solvents was performed to produce polymeric particles. The stabilizers employed were methyl methacrylate and styrene homopolymers, methacryloyl-terminated poly(methyl methacrylate) and polystyrene macromonomers, an amphiphilic poly(methyl methacrylate-co-methacrylic acid-graft-styrene), and polybutadiene derivatives containing reactive vinyl groups. Dispersion copolymerization with a small amount of the macromonomer gave micron-size particles with relatively narrow size distribution. The amphiphilic graft copolymer and the polybutadiene derivatives also afforded monodisperse particles. The mixed ratio between good and poor solvents greatly affected the particle size and size distribution. © 1996 John Wiley & Sons, Inc.

Laser Flash Photolysis Study of the Photoinitiator System Safranine T-Aliphatic Amines for Vinyl Polymerization

The polymerization of 2-hydroxyethyl methacrylate, in a methanol solution, proceeds efficiently using the photoinitiator safranine T in the presence of tertiary aliphatic amines. Polymerization rates were measured at several amine concentrations. These values increase with the amine concentration, reaching a maximum, and further amine addition slowly reduces the polymerization rate. The quenching of the dye excited states by amines was analyzed by static fluorescence and laser flash photolysis. The excited singlet quenching involves a charge-transfer process with rate constants near the diffusional limit. Flash photolysis studies of safranine in the presence of amines, in a methanol solution, yield the triplet species 3 SH + and 3 S + and the unprotonated semireduced radical

Effects of water and carboxylic acid monomer on polymerization of HEMA in the presence of N-phenylglycine

Objectives. This research was designed to study the effect of water or carboxylic acid monomer on the polymerization of 2-hydroxyethyl methacrylate (HEMA) in order to understand the bonding mechanism of dentin bonding systems using N-phenylglycine (NPG). Methods. The polymerization of HEMA in the presence of NPG was studied by adding various amounts of water and/or 4-(2-methacryloyloxyethoxycarbonyl) phthalic acid (4-MET) and evaluated using differential scanning calorimetry (DSC). Results. The addition of water promoted the polymerization of HEMA. Polymerization was further promoted through the addition of 4-MET as a carboxylic acid monomer. Polymerization was promoted at the molar ratio of 4-MET to NPG of 1.0–7.0. Significance. Moisture on the surface could contribute to improving bond strength in dentin bonding systems using NPG by promoting polymerization at the dentin interface.

Hydrophilic sponges based on 2‐hydroxyethyl methacrylate. I. effect of monomer mixture composition on the pore size

AbstractA large number of hydrophilic sponges were prepared by polymerisation of 2‐hydroxyethyl methacrylate in variable concentrations of water (60‐90% wt) in the initial monomer mixture. Concentration and type of crosslinking agents (ethylene dimethacrylate (EDMA) and hexamethylene dimethacrylate (HDMA)) and concentration of redox initiators were also changed. All sponges were examined in cross‐section by conventional and environmental scanning electron microscopy. Micrographs indicated that, in order to obtain sponges with characteristics appropriate for biomedical use (e.g. pores larger than 10 μm), the minimum water concentration was 75% wt with EDMA as a crosslinking agent, or 70% wt with HDMA, for contents of crosslinking agents and initiator less than 1% wt. Micrographs also showed that higher contents of crosslinking agents or initiator led to larger pores. In high concentrations of water, this effect was less evident. Microscopic details confirmed the crucial role of the phase separation during polymerisation.

Graft copolymer emulsions of sodium alginate with hydroxyallsyl methacrylates for microencapsulation

A hybrid material with interesting capsule forming properties has been prepared by γ-initiated polymerization of hydroxyethyl methacrylate (HEMA) or other acrylic monomers in the presence of aqueous sodium alginate. For example, an aqueous solution of HEMA (1 wt%) and sodium alginate (1 wt%) was irradiated in a γ-source at a dose of 0.15 MR, to produce a stable emulsion which coalesced in the form of a homogeneous precipitate when added to 0.1 M CaCI 2. Polymerization of HEMA was presumed to be initiated by free radicals generated in the alginate by γ-irradiation. The emulsion consisted largely of polyHEMA homopolymer stabilized by an alginate-polyacrylate graft (or block) copolymer of highly branched and ill-defined character, which acts as surfactant to prevent coagulation of the emulsion. Erythrocytes were encapsulated in such an emulsion by extrusion of cell/copolymer emulsion mixture into HEPES buffered CaCI 2 (10 mM Ca). Cells appeared intact and functional after encapsulation. By SEM it appeared that the capsule wall consisted of microspheres of polyHEMA on the inner and outer surfaces held together by the alginate. Furthermore the capsule did not contain the internal meshwork, characteristic of calcium alginate homopolymer gels. Although much remains to be learned about these materials, the combination of the easy gelling characteristics of the alginate with the range of desirable properties (e.g. biocompatibility) afforded by the acrylic monomers may have a significant impact on the development of cell microencapsulation technology.

Activation of radical polymerization by microwaves—I. Polymerization of 2-hydroxyethyl methacrylate

2-Hydroxyethylmethacrylate (HEMA) in bulk without any radical initiator is treated with a polarized microwave beam (2.45 GHz) inside a wave guide at various electrical powers ( P 0). The fluid monomer polymerizes finally to form a solid material. The various steps of the reaction of polymerization are described through study of the variation with time of the temperature of the sample and of the part ( P u) of the electrical power ( P 0) degraded in the polymerizable medium because of dielectric loss.

Immobilization of Streptomyces phaeochromogenes cells at a high concentration by radiation-induced polymerization of glass-forming monomers

Characteristics of Streptomyces phaeochromogenes cells immobilized by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperatures were studied. It was found that very high concentrations of cells could be trapped effectively on the surface of the polymer matrix. Glucose isomerase activity of immobilized cells increased with increasing cell concentration. No cell leakage from the matrix was observed with repeated use, even at very high cell concentration and low monomer concentrations. The Km value of immobilized cells decreased with increasing cell concentration and with decreasing monomer concentration; it was close to that of intact cells.

Immobilization of enzymes by radiation-induced polymerization of glass-forming monomers. double entrapping of enzymes in the presence of various additives

Immobilization of enzymes by a double entrapping method was investigated, α-Amylase was trapped by radiation-induced low temperature polymerization of 2-hydroxyethyl methacrylate after being absorbed by various inorganic additives. Drierite showed the most remarkable effect by increased enzymatic activity and decreased activity loss in batch enzyme reactions. Double entrapping of cellulase was tried by preparing an entangled mixture of enzyme and various natural polymers as additives and then polymerizing with the monomeric system at low temperatures. The composite, including enzyme-additive mixture prepared by coprecipitating and coevaporating methods, showed a considerable enhancing effect on enzymatic activity and durability in batch enzyme reactions.

Radiation‐induced polymerization of glass‐forming systems. I. Effect of temperature on the initial polymerization rate

AbstractRadiation‐induced polymerization of hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) was investigated. HEMA and GMA formed a stable supercooled or glassy phase by themselves at low temperatures. It was found that the initial polymerization rate was proportional to ca.0.5 power of the dose rate in the region of relatively high temperatures and the dose rate exponent changed sharply to 1.0 at a temperature Tr, at which the viscosity of monomeric systems reached ca. 103 cP as the temperature decreased. Moreover, a maximum in the polymerization rate–temperature curve occurred at Tv. It was deduced that the polymerization mechanism changed from the stationary to the nonstationary at Tv. The temperature at which a minimum of the polymerization rate occurred could be calculated kinetically considering the viscosity dependency of termination rate, and it agreed well with that obtained experimentally. It was deduced that occurrence of the minimum polymerization rate above Tv was attributable mainly to the decrease in termination rate due to diffusion control.

Radiation‐induced polymerization of glass‐forming systems. II. Effect of temperature on the polymerization rate at higher conversion

AbstractThe effect of temperature and conversion on the polymerization rate at higher conversion was investigated with regard to the γ‐ray‐induced polymerization of hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) in the supercooled phase. The polymerization rate changed from acceleration to depression at various conversions, depending on the polymerization temperature. It was found that Tv at which the viscosity of the system became ca. 103 cpoise influenced the shape of the polymerization time–conversion curve. The experimentally obtained conversion reflection point in the polymerization time–conversion curve agreed with the conversion where the polymerization temperature is the same as the calculated Tv of the system. When the polymerization temperature was lower than Tv of the monomer, no acceleration of the polymerization occurred. When the polymerization temperature was higher than Tv of the polymer, no depression of the polymerization rate was observed. The effect of temperature on the saturated conversion (final conversion) was also examined in terms of Tg of the polymerization system. The experimentally obtained saturated conversion agreed with the conversion where the polymerization temperature is the same as the calculated Tg of the system.