Solvent Effects on Kinetics of 2-Hydroxyethyl Methacrylate Semibatch Radical Copolymerization

Abstract

Radical copolymerizations of 2-hydroxyethyl methacrylate (HEMA) with n-butyl methacrylate (BMA) and n-butyl acrylate (BA) were carried out in xylene, DMF, and n-butanol solutions. Solvent effects on copolymerization propagation kinetics were investigated using pulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) as well as proton NMR, while starved-feed higher temperature semibatch reactions were carried out in different solutions to simulate industrial production. Solvent choice, through its influence on hydrogen bonding of HEMA monomer, has a significant impact on the copolymer composition and propagation rate coefficient and thus influences the semibatch polymerization behavior of BMA/HEMA, as previously found for the styrene/HEMA system. The presence of HEMA leads to increased polymer molecular weight, a result attributed to branching reactions involving dimethacrylate impurity. Although H-bonding (and solvent choice) influences BA/HEMA kinetics, its relative effect is negligible on semibatch operation under the conditions studied.

Modeling of Semibatch Solution Radical Copolymerization of Butyl Methacrylate and 2‐Hydroxyethyl Acrylate

“…More recently, the copolymerization of HEA with both BMA and BA has been systematically studied, with similar solvent‐dependent shifts in composition observed . In addition, the relative levels of solvent and free monomer have been shown to influence the rate of backbiting during HEA (co)polymerization, and a small amount of ethylene glycol dimethacrylate (EGDMA) impurity contained in HEMA was hypothesized to be the cause of a large increase in polymer MMs produced under semibatch conditions for ST/HEMA and BMA/HEMA, but not BA/HEMA …”

“…The reactor was charged with 129 g (or 220 g in case of the larger reactor) of solvent and then heated to reaction temperature under nitrogen inert gas atmosphere. The feed reservoir was charged with 239 g (or 408 g in case of the larger reactor) of monomer solution with controlled composition before adding 2 mol% of TBPA relative to the monomer content, as reported elsewhere . The reaction mixture was then fed over 6 h into the reactor to achieve a final polymer content of 65 wt%, assuming 100% monomer conversion.…”

“…GC‐samples were diluted (1/300 w/w ratio) in acetone and analyzed using a Varian CP‐3800 GC setup. The system consists of a CP‐8410 autosampler, CP‐117 isothermal split/splitless injector (with a 9:1 split), 30M chrompack capillary column (CP‐Sil 8 CB), oven and flame ionization detector (FID) for quantitative analysis of residual monomers based upon external calibration, as reported in a previous study . SEC samples, prepared in tetrahydrofuran (THF), were analyzed with a WATERS 2960 separation module with a WATERS 410 differential refractometer (DRI) and a Wyatt Instruments Dawn EOS 690 nm laser photometer multiangle light scattering (LS) detector.…”

“…The BMA/HEA semibatch copolymerization behavior (i.e., free monomer profiles and polymer molar mass averages and distributions) is compared to that of the previously studied and modeled BMA/BA system . It will be shown that as well as considering the influence of the functional comonomer on the kinetics, it is necessary to select appropriate conditions so that a single phase solution is maintained, as HEA homopolymers are gel‐like polymers with limited solubility in solvents with reduced polarity such as xylenes . Thus, in addition to development and verification of the model, experimental limitations such as maximum HEA content are considered.…”

Solvent Effects on Acrylate kp in Organic Media?—A Systematic PLP–SEC Study

“…Free radical polymerization (FRP) is-in academia as well as in industry-usually carried out in the presence of a solvent. In organic media, solvent effects on the propagation reaction are usually regarded to be negligible, as long as they do not disrupt H-bonding, [1][2][3][4][5][6] or the solvent is an ionic liquid. [6][7][8][9] Recently, we employed the pulsed laser polymerization-size exclusion chromatography (PLP-SEC) method to investigate the FRP propagation behavior of linear and branched alkyl (meth)acrylates and identifi ed several global trends, such as the steady, linear increase of the propagation rate coeffi cient, k p , for linear alkyl (meth) acrylates with the increasing number of C-atoms in their The Arrhenius parameters of the propagation rate coeffi cient, k p , are determined employing high-frequency pulsed laser polymerization-size exclusion chromatography (PLP-SEC) for the homologous series of fi ve linear alkyl acrylates (i.e., methyl acrylate (MA), butyl acrylate (BA), dodecyl acrylate (DA), stearyl acrylate (SA), and behenyl acrylate (BeA)) in 1 M solution in butyl acetate (BuAc) as well as in toluene.…”