Free-radical Homopolymerization Research Articles

Polymerization of acrylamide in styrene containing inverse microemulsions: polymerization kinetics and polymer product composition studies

The kinetics of free-radical homopolymerization and copolymerization of acrylamide (AAm) and styrene (S) initiated by water-soluble ammonium peroxodisulfate, (APS) or by toluene-soluble dibenzoyl peroxide (DBP) in inverse microemulsion toluene/S/AOT (sodium bis(2-ethylhexyl)sulfosuccinate)/water/AAm characterized by a low volume fraction of the aqueous phase (Φaw ≈ 0.08) as a function of the concentration of S in the oil phase of the inverse microemulsion system have been studied. S strongly decreases the rate of AAm/S (co)polymerization. This is valid for both APS and DBP initiators. Kinetic measurements indicate the important role for cross-initiation of water soluble AAm growing chains and of oil soluble S analogues activated by the primary free-radicals generated from APS (or from DBP) in the dispersed water droplets (or in the continuous oil-phase) of the inverse microemulsion, respectively. With inverse microemulsions containing toluene (70.73 %)/S (2.44 %)/AOT(17.56 %)/water (7.32 %)/AAm (1.95 %), after polymerization (initiator APS, 3.04 × 10−2 mol dm−3 of water) and separation of the polymeric components, the following yields were obtained: AAm/S (co)polymer (89.20 mass%; ie 62.24 mass% of AAm structural units and 26.96 mass% of S structural units), polyacrylamide (9.4 mass%) and polystyrene (1.4 mass%). © 2000 Society of Chemical Industry

Termination Rate Coefficients of Butyl Acrylate Free-Radical Homopolymerization in Supercritical CO2 and in Bulk

Free-radical termination kinetics of butyl acrylate (BA) homopolymerization in supercritical CO2 (scCO2) and in bulk have been studied by single pulse−pulsed laser polymerization (SP−PLP) at temperatures and pressures up to 120 °C and 2500 bar, respectively. Polymerization induced by a single laser pulse is monitored via microsecond time-resolved near-infrared (NIR) spectroscopy. From individual SP−PLP experiments performed at several stages during the course of a polymerization, the ratio of termination to propagation rate coefficients, kt/kp, is obtained as a function of monomer conversion. With kp being available from pulsed laser polymerization in combination with size exclusion chromatography (PLP−SEC) experiments in both solution of scCO2 and in bulk, the kt/kp data yield individual (chain-length averaged) kt. Irrespective of polymerization pressure and temperature, kt is larger in scCO2 than in bulk polymerizations. At the highest CO2 content of 46 wt %, this enhancement amounts to about 350%. The activation volumes of kt are similar for polymerizations in scCO2 and in bulk, whereas the activation energies are clearly dissimilar: In solution of scCO2 an apparent activation energy is found which is negative. In bulk polymerization, on the other hand, EA(kt) is positive. The experimental observations indicate that thermodynamic contributions strongly affect termination rate in scCO2 solution.

On the Scaling Law for Af Type Free Radical Homopolymerization

From the equilibrium number fraction distribution for Af type free radical homopolymerization, the asymptotic distribution and polymer moments near the gel point are deduced. As a direct result of scaling transformation, a generalized scaling law which characterizes the sol-gel transition is obtained. This reveals that the curing of this type is in essence a phase transition process.

Pressure and Temperature Dependence of Butyl Acrylate Propagation Rate Coefficients in Fluid CO2

Propagation kinetics of butyl acrylate (BA) free-radical homopolymerization in fluid CO2 has been studied by the PLP−SEC (pulsed laser polymerization−size-exclusion chromatography) method at pressures between 200 and 2000 bar and temperatures between −9 and 20 °C. The CO2 content was close to 45 wt % in all experiments. As a consequence of the poor chain-transfer activity in solution of CO2, the molecular-weight distributions of the polymer samples show well-resolved PLP structures with at least two, but in most cases three, distinct inflection points. At the p and T conditions of this work, the observed propagation rate coefficients (kp) of BA in fluid carbon dioxide at CO2 contents around 45 wt % are found to be about 40% below the corresponding bulk polymerization values. The activation volume and activation energy of kp are, however, identical for bulk and solution (in CO2) free-radical BA polymerizations within experimental accuracy. The origin of the solvent influence on the propagation reaction is ...

Electron spin resonance study of the homopolymerization of aromatic bismaleimides

Maleimide homopolymerization can be initiated by the maleimide monomer without the need for added initiator. This self-initiation is believed to occur through a donor–acceptor complex formed between maleimide groups. An in-situ electron spin resonance (e.s.r.) spectroscopic technique was used to study the free-radical homopolymerization of 1,1′-(methylenedi-4,1-phenylene)bismaleimide (MDP-BMI) over a range of temperatures. Total radical concentrations were measured as a function of time at polymerization temperatures from 180 to 230°C. By analysis of the e.s.r. spectra from different maleimide monomers, MDP-BMI, N-phenylmaleimide (NPM) and 1,1′-[methylenebis-(2,6-diethyl-4,1-phenylene)] bismaleimide (MDEP-BMI), with and without free-radical initiators, it was possible to identify the e.s.r. signals due to various radical species. Unreactive diphenylmethylene radicals were observed on the polymer chains formed from MDP-BMI. Additional spectral features are present that include the signal due to the propagating radical. Maleimides containing free-radical initiator also exhibited a broad doublet signal assigned to a vinyl radical formed by hydrogen abstraction from the maleimide double bond. From comparison of the spectra of NPM and MDEP-BMI monomers, both with and without free-radical initiators, it was shown that the maleimide propagating radical gives an unusually narrow, singlet e.s.r. peak quite different from the four-line signal previously reported. © Elsevier Science Ltd.

Pressure dependence of propagation rate coefficients in free-radical homopolymerizations of methyl acrylate and dodecyl acrylate

Propagation rate coefficients (k p ) for the homopolymerization of methyl acrylate (MA) and dodecyl acrylate (DA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique at pressures between 100 and 2000 bar. The activation volumes for the propagation step, ΔV#(k p ), of MA and DA are identical within experimental accuracy, but are clearly different from the previously reported ΔV#(k p ) of methyl and dodecyl methacrylate. For both the alkyl acrylates and methacrylates a pronounced family-type behaviour of k p is seen, with k p being slightly enhanced toward larger ester size.

Pressure dependence of propagation rate coefficients in free-radical homopolymerizations of methyl acrylate and dodecyl acrylate

Pressure dependence of propagation rate coefficients in free-radical homopolymerizations of methyl acrylate and dodecyl acrylate

Pressure dependence of propagation rate coefficients in free-radical homopolymerizations of methyl acrylate and dodecyl acrylate

Propagation rate coefficients (kp) for the homopolymerization of methyl acrylate (MA) and dodecyl acrylate (DA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique at pressures between 100 and 2000 bar. The activation volumes for the propagation step, ΔV#(kp), of MA and DA are identical within experimental accuracy, but are clearly different from the previously reported ΔV#(kp) of methyl and dodecyl methacrylate. For both the alkyl acrylates and methacrylates a pronounced family-type behaviour of kp is seen, with kp being slightly enhanced toward larger ester size.

Polymers from multifunctional isocyanates 14. Alternating copolymers from isocyanato alkenes: Copolymerization of 2-propenyl isocyanate with trimethylsilyl methacrylate as electron acceptor monomer

The copolymerization of 2-propenyl isocyanate (1) with trimethylsilyl methacrylate (2) has been investigated. 1 is an electron donor monomer with little tendency to undergo homopolymerization, while 2 is an electron acceptor monomer, capable of free radical homopolymerization. Polymerization to low conversion in benzene gave copolymers with preferential incorporation of 2 and a tendency towards alternating copolymers with increasing amounts of 1 in the feed (1 : 1.13 with a 9 : 1 feed ratio of monomers 1 : 2). The glass transition temperatures of the amorphous polymers are in the range from 100–70°C, with a Tg of poly(trimethylsilyl methacrylate) being 135°C. Desilylation occurs in the presence of water, causing an exothermal reaction above the glass transition temperature probably with formation of amides, a reaction that can be used for crosslinking. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 611–616, 1998

Synthesis and characterization of amphiphilic networks obtained by copolymerization of poly(ethylene oxide) macromonomers with methylmethacrylate

Hydrogels whose elastic chains are constituted of hydrophilic Poly(ethylene oxide) (PEO) segments were obtained through free radical homopolymerization with methylmethacrylate (MMA) of α,ω-methacryloyloxy PEO macromonomers. This reaction can be conducted in water solution or in organic solvent. These networks were investigated as gels swollen to equilibrium in THF or in water. The influence of the preparation solvent on the properties of these networks was studied. The mechanical properties of the networks obtained in water are better than those of networks obtained under exactly the same conditions in organic solvents. This result can be explained by the preferential formation in water of micellar structures containing a higher concentration of polymerizable units. The influence of the concentration of the hydrophobic comonomer on the properties of these PEO networks was also examined.

A Comprehensive Simulator/Database Package for Reviewing Free-Radical Copolymerizations

1. INTRODUCTION We recently reviewed simulation of free-radical homopolymerizations in bulk and solution (Gao and Penlidis 1996). This paper, which is the second part of a series of review papers on the simulation of polymerization processes, presents a general approach to simulate free-radical copolymerizations in bulk and solution. It gives an overview of kinetic studies and simulation and modeling efforts of copolymerizations. The previously developed homopolymerization simulator (Gao and Penlidis 1996) has been further extended to simulate copolymerization in bulk and solution. The new copolymerization simulation package contains a flexible and powerful simulator, as well as a comprehensive database. It represents a further step in fulfilling the long-term goals (described in Gao and Penlidis 1996) in the development of a comprehensive simulation package for multicomponent free-radical polymerizations.

Alternating Copolymerization of 3,4-Epoxy-1-Butene and Derivatives with Maleic Anhydride

3,4-Epoxy-1-butene (I), prepared by the selective oxidation of butadiene, is an unusual difunctional monomer containing polymerizable vinyl and epoxy groups. As expected, free radical homopolymerization of I and its cyclic ketal derivatives was found to be very sluggish, as expected, for the allylic monomer structures. However, I was found to form alternating copolymers with maleic anhydride with both 1,2- and 1,5- enchainment observed. The structures of the alternating copolymers were observed to be solvent dependent with the in situ formation of cyclic ketals and their incorporation into the copolymers in polymerizations done in ketone solvents. Various cyclic ketal monomers derived from I readily formed alternating copoymers with maleic anhydride. Thermally activated self-crosslinking of these resins was observed.

Method for Determining the Kinetic Parameters in Diffusion-Controlled Free-Radical Homopolymerizations

Free-radical homopolymerizations of 2-hydroxyethyl methacrylate (HEMA) and diethylene glycol dimethacrylate (DEGDMA) photoinitiated by 2,2-dimethoxy-2-phenylacetophenone (DMPA) were studied. A nove...

A Pulsed-Laser Study of Penultimate Copolymerization Propagation Kinetics for Methyl Methacrylate/n-Butyl Acrylate

The PLP/MWD technique, based upon analysis of the molecular weight distribution (MWD) of a polymer produced by pulsed-laser polymerization (PLP), has proven to be a powerful probe for the examination of free-radical homopolymerization kinetics. The same method is applicable to the study of copolymerization propagation kinetics provided that proper calibrations are established for the measurement of copolymer MWDs, as illustrated by an examination of the methyl methacrylate (MMA)/n-butyl acrylate (nBA) system. Statistical analysis indicates that although MMA/nBA copolymer composition is well described by the terminal model, propagation kinetics are not. Like many other systems recently examined, the data are well represented by the “implicit penultimate unit effect” model of Fukuda and co-workers. However, whereas previous systems studied have propagation rates that are lower than those predicted by the terminal model, it is found that the propagation rate of MMA/nBA is greater than the terminal model predictions. The implications of these results to theoretical interpretations of the penultimate model are discussed.

A Comprehensive Simulator/Database Package for Reviewing Free-Radical Homopolymerizations

Abstract Several models have been proposed in the literature over the last two decades in order to simulate free-radical homopolymerizations. However, most of these models deal with one specific monomer system, usually under restricted polymerization conditions.

Maleic anhydride homopolymerization during melt functionalization of isotactic polypropylene

The homopolymerization of maleic anhydride was attempted at 190°C, during the melt-functionalization of polypropylene, either with or without organic peroxide using a Brabender plastograph. The free radical homopolymerization of pure maleic anhydride was also attempted either with or without organic peroxide, at 190°C, in vacuum-sealed glass vials. In all cases, free low molecular weight maleic anhydride oligomers were observed by low molecular weight size exclusion chromatography (SEC). This maleic anhydride homopolymerization tends to prove that the ceiling temperature of poly(maleic anhydride) probably lies above the previously published value of 160°C for these specific experimental conditions. © 1996 John Wiley & Sons, Inc.

Maleic anhydride homopolymerization during melt functionalization of isotactic polypropylene

The homopolymerization of maleic anhydride was attempted at 190°C, during the melt-functionalization of polypropylene, either with or without organic peroxide using a Brabender plastograph. The free radical homopolymerization of pure maleic anhydride was also attempted either with or without organic peroxide, at 190°C, in vacuum-sealed glass vials. In all cases, free low molecular weight maleic anhydride oligomers were observed by low molecular weight size exclusion chromatography (SEC). This maleic anhydride homopolymerization tends to prove that the ceiling temperature of poly(maleic anhydride) probably lies above the previously published value of 160°C for these specific experimental conditions. © 1996 John Wiley & Sons, Inc.

Hybrid Styryl-Based Polyhedral Oligomeric Silsesquioxane (Poss) Polymers

The authors have taken a unique approach to the synthesis and study of hybrid organic/inorganic materials. The method involves synthesizing nano-size inorganic P{sub 1}R{sub 7}Si{sub 8}O{sub 12} clusters which contain seven inert R groups for solubility and only one functional P group for polymerization. This strategy permits the synthesis of melt processable, linear hybrid polymers containing pendent inorganic clusters and allows one to study the effect these clusters have on chain motions and polymer properties. The synthesis of styrene-based polyhedral oligomeric silsesquioxane (POSS) macromers, their free radical homopolymerization and copolymerizations with varying amounts of 4-methylstyrene, and analysis of the effect of the pendent POSS group is presented. All of these polymers decompose under nitrogen between 365 and 400 C, and the glass transitions for these materials vary from around 110 C up to the decomposition point. Both T{sub dec} and T{sub g} increase with increasing POSS content. The shorter the spacer unit between the POSS group and the polymer chain the higher the T{sub g}. Interestingly, a slight change in the inert R groups on the POSS cluster has a large effect on the glass transition indicating that POSS-POSS interactions have an effect on chain mobility.

Free-radical homopolymerization and copolymerization of di-n-butyl itaconate

Di-n-butyl itaconate (DBI) was polymerized at 50°C in a 3 mol l −1 benzene solution using 2,2′-azobisisobutyronitrile (AIBN) as a free-radical initiator. Kinetic constants for DBI were obtained as follows: k p k 1 2 t = 0.021 mol −1 2 l 1 2 s −1 2 , 2 fk d = 3.62 × 10 −6s −1. Copolymerization reaction between DBI and methyl methacrylate (MMA), under the same experimental conditions, was carried out and the values of r DBI = 0.717 ± 0.11 and r MMA = 1.329 ± 0.09 were found for the reactivity ratios. Applying the Q—e scheme led to Q = 0.61 and e = 0.62 for DBI. Overall copolymerization rate coefficients have been analysed on the basis of terminal and penultimate effects on the propagation reaction. These parameters as well as the copolymer composition are not affected by total monomer concentration.

Semiglobal nonlinear control based on complete input—output linearization and its application to the start-up of a continuous polymerization reactor

We address the control problem of output tracking with disturbance rejection and preclusion of internal dynamics for multi-input multi-output nonlinear plants subjected to known disturbances. The closed-loop output error dynamics is required to be linear and noninteractive. Necessary and sufficient conditions for semiglobal solvability of the nonlinear control problem are given, yielding a construction of the related feedforward—feedback controller and identifying the basic information required on the measured and the assigned signals. The start-up of an open-loop unstable continuous free-radical homopolymerization reactor is considered as an application example. The solvability of the reactor control problem is characterized in terms of conditions that have direct meaning. Results are corroborated with numerical simulations.