Methacrylate System Research Articles

Monomer concentration effect on the phase behavior of poly(propyl acrylate) and poly(propyl methacrylate) with supercritical CO2 and C2H4

Experimental cloud-point data to temperature of 186 °C and pressure of ~2,500 bar are presented for ternary mixtures of poly(propyl acrylate)(PPA)-CO2-propyl acrylate (PA) PPA-C2H4-PA and poly(propyl methacrylate) (PPMA)-CO2-propyl methacrylate (PMA) systems. Cloud-point pressures of PPA-CO2-PA system were measured in the temperature range of 32 °C to 175 dgC and to pressures as high as 2,070 bar with PA concentrations of 0.0, 5.0, 11.7 and 30.4 wt%. Adding 34.1 wt% PA to the PPA-CO2 mixture significantly changes the phase behavior. This system changes the pressure-temperature slope of the phase behavior curves from U-LCST region to LCST region as the PA concentration increases. Cloud-point data to 170 °C and 1,400 bar are presented for PPA-C2H4-PA mixtures and with PA concentration of 0.0, 5.7, 15.5 and 22.2 wt%. The cloud-point curve of PPA-C2H4 system shows relatively flat at 730 bar for temperatures between 41 and 150 °C. With 15.5 and 22.2 wt% PA the cloud-point curve exhibits a positive slope that extends to 35 °C and ~180 bar. Also, the ternary PPMA-CO2-PMA system was measured below 186 °C and 2,484 bar, and with cosolvent of 5.2-20.1 wt%. PPMA does not dissolve in pure CO2 to 233 °C and 2,500 bar. Also, when 41.5 wt% PMA is added to the PPMA-CO2 solution, the cloud-point curve shows the typical appearance of a lower critical solution temperature (LCST) boundary.

Acrylic-phosphate glasses composites as self-curing controlled delivery systems of antibiotics.

New antibiotic delivery systems based on self-hardening methyl methacrylate (MMA)/polymethyl methacrylate (PMMA) systems and phosphate glasses (PG) in the system P(2)O(5)-CaO-Na(2)O have been developed. Self-curing formulations were prepared by mixing the solid component containing PMMA beads, different proportions of PG (30-70 wt %) and vancomycin (5 wt %) as antibiotic, with the liquid component made of MMA monomer. Dough and setting times increased with the content of PG but peak temperature decreased to values well below to guarantee the chemical stability of the antibiotic drug, gentamicin or vancomycin. Mechanical properties of the PMMA/PG composites were evaluated in compression test giving rise to values of compressive strength in the range of 100 MPa. The release of vancomycin was analyzed in vitro by immersion of samples in phosphate buffer of pH=7.4. Release profiles were influenced by the content of PG present in the cement. An initial burst of drug release was observed in all cases. The composites with 70 wt % PG released nearly the total amount of drug loaded in a period of 45 days, and those containing 60 wt % PG released the 70% of the vancomycin in the same period of time. However, either the control of the composite with 30 wt % PG released only the 30% of the drug in 10-15 days. The surface of the drug-loaded composites before and after release experiments was analyzed by ESEM. The deposition of some aggregates at certain points of the surface was detected for the specimens immersed in buffer phosphate after 45 days. This material was characterized by FTIR and Raman spectroscopy as an amorphous phosphate formed by calcium ortho and pyrophosphates, and indicates an interaction between the hydrated layer at the place of the glass and the surrounding medium.

Film formation from cationic electropaint systems containing resins with different glass transition temperature

Some phenomena in the deposition process of electropainting have not been well elucidated till now. In this paper, to investigate an influence of glass transition temperature ( T g) on film formation, the deposited film was observed with an atomic force microscope and the electrochemistry was investigated, using two kinds of cationic acrylate resin with different T g (methyl methacrylate system (MMAs): T g=70°C, and methyl acrylate system (MAs): T g=5°C). Electrodeposition was performed under constant voltage or current condition. At constant voltage, the deposition behavior in the two resin systems differed extremely. The MMAs, the resin with high T g, produced a high resistance film. The MAs, the resin with low T g, was deposited forming a film at a voltage lower than 20 V. At constant current, the film formation did not result in a rise in voltage. It behaved like a conductive film. When the resin with high T g was used, particulate deposits were observed by AFM even in the induction period. The resin with low T g formed flat deposits. These results suggest that paint deposition is initiated once electrolysis of water starts. In addition, there are two types of film formation on the cationic electropainting: high resistance film formation for the resin with high T g, and ion-permeable film formation for the resin with low T g. In both cases, film growth occurs at the film/bulk solution interface.

Polymerization of Cationic Surfactant Films in Microemulsions

Properties of microemulsion phases containing mixtures of polymerizable surfactants, single-chain 11-(methacryloyloxy)undecyltrimethylammonium bromide, and double-chain dodecyl-(11-(methacryloyloxy)undecyl)trimethylammonium bromide, and their acrylate analogues have been studied. SANS has shown how film composition, in terms of single-chain surfmer, can be used as a control variable to optimize phase behavior and physicochemical properties of these multi-component systems. A direct comparison between methacrylate and acrylate systems has shown how surfactant molecular structure can influence microemulsion structure; with methacrylates spherical droplets are formed, whereas with the acrylate analogues there is a transition to cylinders. Free-radical polymerization yield partially encapsulated aqueous domains with retention of parent structure.

Release of recombinant human bone morphogenetic protein-2 from heterocyclic methacrylate polymer systems

The release of recombinant human bone morphogenetic protein-2 (rhBMP-2) from three room temperature polymerising methacrylate systems has been studied. These all contained poly(ethyl methacrylate) powder, but the monomer liquids comprised, respectively, tetrahydrofurfuryl methacrylate (THFM), 90/10 THFM/hydroxyethyl methacrylate (HEMA), and 70/30 THFM/HEMA. In all cases, rhBMP-2 was released, but the addition of 10% HEMA accelerated release (a nine-fold increase in diffusion coefficient); a further increase to 30% HEMA had no additional effect. For most of the release process, a diffusion process operated, although the early stages were not well defined. At the end of the 15 day period, the release, respectively, for the PEM/THFM, PEM:90/10 THFM/HEMA and PEM:70/30 THFM/HEMA systems was 596, 878 and 923 ng (i.e. up to 92% of the rhBMP-2 added).

Propagation Rate Coefficients of Acrylate−Methacrylate Free-Radical Bulk Copolymerizations

Copolymerization propagation rate coefficients, kp,copo, have been measured for the binary systems methyl acrylate (MA)−dodecyl methacrylate (DMA), butyl acrylate (BA)−methyl methacrylate (MMA), dodecyl acrylate (DA)−DMA, and DA−MMA at 40 °C and 1000 bar by the pulsed laser polymerization (PLP)−size-exclusion chromatography (SEC) technique. These acrylate−methacrylate systems are interesting because of the significant difference, by more than 1 order of magnitude, between the homopropagation rate coefficients of the two families. Reactivity ratios, ri, are determined from monomer feed compositions and the NMR spectroscopically measured copolymer compositions. The resulting ri values for the four acrylate−methacrylate copolymerizations agree within experimental accuracy. Moreover, these ri data are surprisingly close to reactivity ratio data estimated from individual addition rate coefficients to MA and MMA, respectively, of appropriate small (meth)acrylate-type free radicals. Such addition rate coefficien...

3, 4-Dichlorobenzyl methacrylate and ethyl methacrylate system: monomer reactivity ratios and determination of thermodynamic properties at infinite dilution by using inverse gas chromatography

Copolymers with various contents of 3,4-dichlorobenzyl methacrylate (BzMA) and ethyl methacrylate (EMA) were prepared in 1,4-dioxane solution using 2,2′-azobisisobutyronitrile (AIBN) as initiator at 60°C. The copolymer compositions were determined by 1H NMR analysis. The monomer reactivity ratios were calculated by both Fineman–Ross, and Kelen–Tüdös methods. The monomer reactivity ratios were found to be r BMA=0.521±0.019, r EMA=0.847±0.221 (Kelen–Tüdös) and r BMA=0.677±0.008, r EMA=1.117±0.209 (Fineman–Ross). The FT-IR, 13C NMR spectra of the copolymers have been discussed. In all other samples thermal degradation proceeded in a single step. A slight increase in thermal stability of the copolymers was observed with increase in BzMA content. Some thermodynamic quantities such as the specific retention volumes, V g 0, weight fraction activity coefficients of solute probes at infinite dilution, Ω 1 ∞, Flory–Huggins intereaction parameters, χ 12 ∞, between polymers and solvents, the partial molar free energy, Δ G 1 ∞ the partial molar heat of mixing, Δ H 1 ∞, at infinite dilution were determined from the interactions of poly(BzMA- co-EMA) with alcohols, ketones, acetates, aromatics and n-alkanes by inverse gas chromatography method at 130–150°C. All probes are non-solvent for poly(BzMA- co-EMA) (7:93%) and poly(BzMA- co-EMA) (87:13%) at 130–150°C.

The significance of chain length dependent termination in cross-linking polymerizations

Evidence is presented in support of the existence of chain length dependent termination in cross-linking free radical polymerizations. Photopolymerizations of multifunctional methacrylates and acrylates were examined, and the difference in the inherent chain transfer characteristics of these systems provided a means for studying the effect of kinetic chain length on the polymerization behavior. The kinetic chain length was varied in each system by changing the initiation rate (Ri) and via the addition of a chain transfer agent (1-dodecanethiol). Changing Ri in the methacrylate systems led to a non-classical dependence of the rate of polymerization on Ri similar to that observed in linear polymerizations that exhibit chain length dependent termination. Additionally, incorporation of a chain transfer agent into the polymerization system, even at very low concentrations (0.1wt%), had a dramatic effect on the methacrylate polymerization kinetics. As expected, because of their predisposition to chain transfer, the acrylate systems were minimally affected by changes in Ri and the addition of chain transfer agent.

Photoinitiated cross-linking of a thiol–methacrylate system

The photoinitiated thiol–ene cross-linking of a dimethacrylate polyether of Bisphenol A and pentaerythritol tetrakis 2-mercaptopropionate was studied in the presence of 2,2-dimethyl-2-hydroxy acetophenone (Darocur 1173). Two complementary techniques were used: photocalorimetry and real-time infrared spectroscopy. In the first part, the kinetic reaction was characterized by a stoichiometric mixture in reactive functions. The influence of temperature, photoinitiator concentration and ultraviolet (UV) light intensity was investigated. The results mainly show that the methacrylate homopolymerization is faster than the thiol–ene addition so that the reaction is usually stopped because of the complete consumption of the methacrylate double bonds. A theoretical approach has allowed us to determine a transfer constant of 0.26. Moreover, an increase in the autoacceleration rate was observed in the presence of the thiol monomer. In the second part, the molar fraction of methacrylate double bonds and thiol functions was changed to determine the effect on the kinetic reaction and the glass transition temperature of the final material.

Studies on the preparation of stable and high solid content emulsifier‐free latexes and characterization of the obtained copolymers for MMA/BA system with the addition of AHPS

3-Allyloxy-2-hydroxyl-propanesulfonic (AHPS) salt was synthesized and used as a hydrophilic comonomer for the methyl methacrylate (MMA) and n-butyl acrylate (BA) emulsifier-free emulsion copolymerization system to obtain latices of stable and high-solid content. Properties of the latices, such as flow behavior, stability, and final diameter of the latex particles were studied. In addition, physical properties of the obtained copolymers, such as glass transition temperature (Tg), stress–strain behavior, and water resistance were investigated. With the addition of AHPS, the latices of stable and high-solid content (as high as 60%) were prepared. Flow of the latices follows the law of the Bingham body. The final diameter of the latex particles is 0.3–0.5 μm in diameter, which is larger than that of the conventional latex particles and decreases with the increase of AHPS and potassium persulfate (KPS) concentration. All the copolymers are atactic polymers, showed as single Tg on dynamic mechanical analysis spectrum. Compared with the copolymers that were prepared by surfactant emulsion polymerization, tensile strength, as well as water resistance is greatly improved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 21–28, 2001

Chlorhexidine release from room temperature polymerising methacrylate systems

A series of different methacrylate monomers (with either 1 or 2.5% dimethyl- p-toluidine, DMPT) was gelled with poly(ethyl methacrylate) powder (containing benzoyl peroxide) thus forming a room temperature curing system. When doped with 5.625% chlorhexidine diacetate the release from the tetrahydrofurfuryl methacrylate-based samples was considerably greater than that from other methacrylate monomers. This seems to be due to the formation of channels in the polymer. Nuclear magnetic resonance spectroscopy, of solutions that the samples were immersed in, showed chlorhexidine was indeed being released from the polymer. It also showed that doping the polymer with chlorhexidine hindered the polymerisation, resulting in a higher level of residual monomer and low molecular weight components being leached from the polymer. The DMPT also affected the polymerisation with greater leaching from the 2.5% DMPT sample.

The effect of two hydrophilic monomers on the water uptake of a heterocyclic methacrylate system

The room temperature polymerising system poly(ethyl methacrylate) (PEM)/tetrahydrofurfuryl methcrylate (THFM) has been modified by replacing some of the THFM by hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (HPM), respectively. In both cases, the equilibrium uptake of the parent system is reduced substantially, in spite of the hydrophilic nature of these monomers. The effect is less with HPM. Corresponding to these decreases in uptake are substantial increases in the diffusion coefficients. This points to changes from a cluster-dominated process, to a more continuum-based process in the dual monomer systems. Addition of chicken serum albumin to these systems increases water uptake. At higher levels of HEMA addition, there is a substantial increase in polymerisation exotherm.

Free radical grafting onto cellulose in homogeneous conditions. 2. Modified cellulose–methyl methacrylate system

The homogeneous grafting of methyl methacrylate (MMA) onto methacrylate-modified cellulose (CEMA) was achieved by a two-step process at three different temperatures ( T p) in the range 40–70°C. Grafting yield (GP%) and grafting efficiency (GE%) were determined and related to the conditions of synthesis. The role of various reaction parameters on GP% and GE% (namely, reaction temperature and time, cellulose degree of substitution (DS), molar ratios of MMA to methacrylate pendant groups (–MA) and of MMA to initiator) was evaluated. Molecular weights of grafted chains and of PMMA homopolymer were determined at the chosen T p and compared to each other. The average number of grafts per cellulose molecule ( n g) was calculated and, together with the molecular weight data of the grafted chains, utilized to interpret the experimental trend of GP% vs. T p. On the basis of the above results, interesting perspectives of the homogeneous grafting method were outlined.

UV radiation curing of surface coatings based on ENR-cycloaliphatic diepoxide-glycidyl methacrylate system by cationic photoinitiators-optimization of process variables through response surface methodology

This paper reports on the results of the ultraviolet curing of surface coatings based on cycloaliphatic diepoxide-epoxidized natural rubber (ENR)-glycidyl methacrylate (GMA) system with a cationic photoinitiator. The results reported in our earlier publication1 showed that ENR acts as a toughening agent for the otherwise brittle epoxy resin, and that GMA functions as a crosslinking agent in the system and promotes adhesion between the elastomeric domain and the resin matrix. In this paper, the results of the effect of operating variables on the properties of the cured film are reported. Response surface methodology (RSM) was employed to collect data and to establish the functional relationships between operating variables and performance characteristics of the cured coatings. The data are represented in three-dimensional response surface plots. These plots not only enable the interpretation of results, but also allow the determination of the optimum treatment combinations required to maximize the properties of the surface coatings.

Effect of Polymerization Temperature and Cross-Linker Concentration on Reaction Diffusion Controlled Termination

The effects of temperature and cross-linking agent concentration on reaction diffusion controlled termination have been determined for several loosely cross-linked acrylate and methacrylate systems. The systems studied were 10/90 DEGDA/sBA (10 mol % diethylene glycol diacrylate, 90 mol % sec-butyl acrylate), 1/99/40 DEGDMA/HEMA/PEG400 (1 wt % diethylene glycol dimethacrylate, 99 wt % 2-hydroxyethyl methacrylate diluted with poly(ethylene glycol) 400 to 40 wt %), and 10/90 DEGDMA/OcMA (10 wt % DEGDMA, 90 wt % n-octyl methacrylate.) The effect of increased cross-linking agent concentration is to decrease the reaction diffusion parameter (R), defined as kt/kp[M], until a plateau is reached. The reaction diffusion parameter was found to increase as the polymerization temperature is increased above Tg for the methacrylate systems. However, as the temperature is decreased below the Tg for loosely cross-linked systems, R was found to also increase. This phenomenon is not readily predicted using current theory, and thus it is proposed that chain transfer to monomer becomes an important means of radical mobility in loosely cross-linked systems below the Tg. These results enhance the current understanding of reaction diffusion controlled termination, particularly in cross-linked systems.

Potential bootstrap effect and phase separation of reaction solutions

The phase separation in monomer–copolymer solutions was studied for styrene–acrylonitrile, styrene–butyl methacrylate and styrene–methyl methacrylate systems in order to find conditions to stimulate a bootstrap effect in radical copolymerization. There was phase separation at T sep< T cop and a bootstrap effect for the styrene–acrylonitrile and styrene–butyl methacrylate system, but no effects for the styrene–methyl methacrylate system. Both the data on the phase separation and the excess free energy of the monomer mixing (Δ G ex) are needed to explain the dependence of the bootstrap effect on the temperature of the styrene–butyl methacrylate copolymerization. Temperature had a large influence on the copolymer inhomogeneity in the copolymerization of styrene with butyl methacrylate in this study.

The effect of solvation on thermal decomposition of 2,2'-azoisobutyronitrile in the acrylonitrile/methyl methacrylate system

The effect of solvation on thermal decomposition of 2,2'-azoisobutyronitrile in the acrylonitrile/methyl methacrylate system

Reversible Cobalt−Carbon Bond Formation in Catalytic Chain Transfer Polymerization

The reversible bond formation between cobalt(II) catalytic chain transfer agents and propagating radicals was studied using electron paramagnetic resonance and conventional kinetic measurements. It was found that this reversible cobalt−carbon bond formation has no significant effect on the catalytic chain transfer polymerization of methyl methacrylate but does affect the polymerization behavior of styrene. In both systems significant induction periods are observed which seem to disappear in the methyl methacrylate system but persist in the styrene system upon decreasing the initial concentration of the cobalt(II) complex. The overall rates of polymerizations are found to be readily described by “classical” free-radical polymerization kinetics, including a chain-length-dependent average termination rate coefficient. Furthermore, in contrast to the situation observed in methyl methacrylate polymerization where constant molecular weights are produced over the entire conversion range, it was found that the molecular weight in styrene increases with conversion until a constant molecular weight is obtained which is given by the Mayo equation. The kinetic behavior and the molecular weight evolution could simply be modeled by a reaction scheme providing a constant radical concentration and the presence of a chain transfer agent.

Phase behavior and modeling of the poly(methyl methacrylate)–CO 2–methyl methacrylate system

Cloud-point data for the system poly(methyl methacrylate) (PMMA)–CO 2–methyl methacrylate (MMA) are measured in the temperature range of 26 to 170°C, to pressures as high as 2500 bar, and with cosolvent concentrations of 10.4, 28.9, and 48.4 wt.%. PMMA does not dissolve in pure CO 2 to 255°C and 2550 bar. The cloud-point curve for the PMMA–CO 2–10.4 wt.% MMA system exhibits a negative slope that reaches 2500 bar at 105°C. With 28.9 wt.% MMA the cloud-point curve remains relatively flat at ∼900 bar for temperatures between 25 and 170°C. With 48.4 wt.% MMA the cloud-point curve exhibits a positive slope that extends to 20°C and ∼100 bar. Pressure-composition isotherms are also reported for the CO 2–MMA system at 40.0, 80.0, 105.5°C. This system exhibits type-I phase behavior with a continuous mixture–critical curve. The Peng–Robinson (PR) and SAFT equations of state model the CO 2–MMA data reasonably well without any binary interaction parameters, although the PR equation provides a better representation of the mixture-critical region. It is not possible to obtain even a qualitative fit of the PMMA–MMA–CO 2 data with the SAFT equation of state. The SAFT model qualitatively shows that the cloud-point pressure decreases with increasing MMA concentration and that the cloud-point curve exhibits a positive slope for very high concentrations of MMA in solution.

Modeling Insight into the Diffusion-Limited Cause of the Gel Effect in Free Radical Polymerization

The molecular-level cause of the gel effect in free radical polymerization, associated with a decrease in the termination rate parameter with increasing conversion, is studied by experimental and modeling approaches. The predictive Vrentas−Duda free volume theory serves as a basis for modeling as it handles quantitatively the temperature and polymer concentration dependencies of monomer diffusion. The polymer concentration (c) dependencies of various diffusional processes fit an expression of the form [Dm(c)/Dm(0)]ξx,m, where Dm is the monomer diffusion coefficient and ξx,m expresses the power-law dependence of the diffusional process of interest (x) relative to that of monomer (m). Relevant values of ξx,m vary from ∼ 0.8 for segmental mobility, to ∼1−2 or 3 for oligomeric diffusion, to ∼ 3.0−3.5 for unentangled polymer diffusion, and to ∼ 9.5−10 for entangled polymer diffusion. If the very high conversion regime, where issues unrelated to the origin of the gel effect add unnecessary complications, is avoided, the modeling of conversion−time data requires only that the polymer concentration dependence of the termination reaction, caused by a diffusional process cited above, must be taken into account. Comparison of ξx,m values needed to fit various methyl methacrylate conversion−time data (values of 1.1−5.0 were required, increasing with increasing molecular weight of the polymer produced) with those needed for different diffusion types indicates that termination is governed by diffusion of the shortest radical chains present in significant number. In contrast to some “short−long” termination theories that commonly distinguish “short” and “long” as unentangled and entangled, this study finds that entanglements are irrelevant in distinguishing “short” from “long”. Styrene polymerizations yield ξx,m values substantially below 1. This is ascribed to chain transfer, supported by the fact that methyl methacrylate systems with chain transfer agent show similar suppressed gel effect behavior. The very low ξx,m values result in part from the reduced polymer concentration dependence of kt associated with the highly mobile short radical chains obtained in chain transfer reactions. While systems with significant chain transfer must be studied further, this modeling approach should serve as a robust basis for a more complete description of termination under various conditions.